Effect of climate change on humic substances and associated impacts on the quality of surface water and groundwater: A review

Calcium-organic matter fouling in nanofiltration: Synchrotron-based X-ray fluorescence and absorption near-edge structure spectroscopy for speciation

Calcium (Ca)-enhanced organic matter (OM) fouling of nanofiltration (NF) membranes leads to reduced flux during desalination and requires frequent cleaning. Fouling mechanisms are not fully understood, which limits the development of targeted fouling control methods. This study employed synchrotron-based X-ray fluorescence (XRF) and X-ray absorption near-edge structure (XANES) spectroscopy to quantify the spatial distribution and mass of Ca deposition as well as changes in the Ca coordination environment characteristic of specific fouling mechanisms, respectively. Bench-scale filtration experiments were performed using feed solutions containing Ca and ten different types of organic matter (OM), as well as the common scalants, calcium carbonate (CaCO3) and calcium sulfate (CaSO4). Osmotic backwash (OB) was performed at regular intervals for fouling control. Ca-OM aggregation resulted in greater flux decline and lower flux recovery during OB than Ca conditioning of membranes followed by filtration of feed solution with OM. Linear combination fitting (LCF) of XANES absorption spectra from fouled membranes indicated that Ca-OM aggregation preferentially occurred for OM types that exhibited both high carboxylic group and negative charge density. Consequently, these OM types exhibited greater deposition of Ca and TOC on the membrane surface when compared to other OM types. For the coexistence of scalants and OM, Ca speciation within the fouling layer was characteristic of both Ca bound to the membrane (i.e. potential bridging, charge screening) as well as Ca-OM aggregation and deposition mechanisms, while a range of crystal polymorphs were observed to occur simultaneously. XRF and XANES represent powerful tools for the elucidation of NF fouling mechanisms by quantification of Ca deposition as well as Ca speciation. Fouling control methods should target OM types with high carboxyl group density and negative charge to neutralize or eliminate interactions with Ca.

Proposal of novel Predicted No Effect Concentrations (PNEC) for metals in freshwater using Species Sensitivity Distribution for different taxonomic groups

Water pollution by metals and metalloids promotes toxic effects to aquatic biota especially in mining regions. Environmental legislation applied to protect aquatic life from the toxicity of metals relies on the definition of protective values (PVs) for each compound. Among methods used to define PVs, Species Sensitivity Distribution (SSD) curves enable the derivation of the Predicted No Effect concentration (PNEC). In this context, this is one of the first studies to propose the construction of acute and chronic split SSD curves built separately for three groups of freshwater organisms (algae, invertebrates and fish) to derive PNEC values for the 14 metals most commonly observed in iron ore mining tailings. Data used to construct split SSD curves were derived from the USEPA ECOTOX knowledgebase and EnviroTox databases and segregated according to the freshwater organism group and as "acute" or "chronic" toxicity. Then, split SSD curves were built using a minimum of nine species for each group to determine the hazardous concentration to 5% of species (HC5) and PNEC values for each group. Once PNEC were derived, a framework was proposed to calculate the Bioavailabity Factor (BioF) used to adjust values for local bioavailability conditions considering water quality characteristics in different regions. The lowest acute PNEC were observed for algae and invertebrates and corresponded to Silver (Ag). Nearly half of calculated PNEC were below current PVs in practice in Brazil, United States (US), United Kingdom (UK), Canada and European Union (EU). Results reinforce the pertinence of: (i) splitting SSD curves to define PVs for metals; and (ii) taking bioavailability into consideration to correct PNEC for local conditions. In addition, outcomes suggest that it is critical to rethink PVs related to metals for aquatic life protection, mainly in Brazil and Minas Gerais state, a region known for extensive mining activity. Finally, PNEC values obtained in this study may be used for ecological risk assessment studies, especially in areas affected by mining and other activities that result in pollution by metals and metalloids, such as Brazil.

A review on the recovery of humic substances from anaerobic digestate of sludge as a potential fertilizer: Quantification, efficiency and interaction with pollutants

This study reviewed the recovery of humic substances (HS) from anaerobic digestate of sludge as a potential fertilizer, focusing on the quantification of HS, the efficiency of HS recovery, and its interaction with pollutants. The potential pitfalls of current misunderstanding for HS quantification in sludge were pointed out. HS present in sludge showed potential to be used as a fertilizer, which solubilized insoluble phosphates for enhanced soil fertility. Pretreatment prior to anaerobic sludge digestion and composting of anaerobic digestate of sludge (ADS) improved the amount of HS in anaerobic digestate. But the amount of HS extracted from the retentate of ADS was much lower than the level required for the common HS fertilizer. Therefore, an additional concentration was required to process the retentate of ADS into HS liquid fertilizer. The quinone moieties in HS accepted electrons from anaerobic microbial respiration and their role in the degradation of organic pollutants were summarized. By binding with HS, the speciation of metals in sludge was changed from water-soluble and exchangeable to organic- and sulfide-bound fractions. Future research should focus on the novel application of machine learning for quantifying HS within sludge, offering a practical approach to interpret complex fluorescence data and enhance understanding of HS characteristics and distribution. Further studies should explore the application of hydrothermal humification to enhance HS content in ADS, offering an energy-efficient method for rapid fertilization in sustainable agriculture. This study offers a window into HS recovery from ADS.

Assessing microclimatic influences in Colombo metropolitan area (CMA) amidst global climate change: a comprehensive study from 1980 to 2022

Climate change has become an emerging topic, leading to widespread damage. However, when considering climate, attention is drawn to various scales, and urban microclimate has emerged as a trending subject due to its direct relevance to human living environments. Among the microclimatic factors, temperature and precipitation are utilized in order to identify trends. The identification of changes in precipitation and temperature from ground stations poses difficulties due to the lack of well-distributed stations; thus, satellite-based products are gaining popularity. The satellite products were validated against ground data, following which time-series and spatial analyses were conducted. The rainfall anomaly index, seasonality index, heat wave magnitude index, and mean temperature differ in the Colombo Metropolitan Area compared to the entire country. Each index is calculated decadal-wise to identify trends. By utilizing four climate indices, the analysis endeavors to investigate the microclimate identification in Colombo Metropolitan Area compared to its surrounding areas such as the Western Province and the entire country. This study aids local authorities in mitigating climate change by enhancing city resilience. These findings underscore the importance of understanding and addressing the impacts of climate change on temperature extremes to mitigate potential adverse effects on human activities and the environment. Understanding the specific reasons for spatial changes in rainfall anomalies often necessitates extensive climate modeling and data analysis.

Reactive Nitrogen Species Generated from Far-UVC Photolysis of Nitrate Contribute to Pesticide Degradation and Nitrogenous Byproduct Formation

Climate change has resulted in increased use of pesticides and fertilizers in agriculture, leading to elevated pesticide and nitrate levels in aquatic ecosystems that receive agricultural runoff. In this study, we demonstrate that far-UVC (UV222) photolysis of nitrate rapidly degrades four pesticides in surface water, with a degradation rate constant 37.1-144.75 times higher than that achieved by UV254 photolysis of nitrate. The improved pesticide degradation is due not only to the enhanced direct photolysis by UV222 compared to UV254 but also to the increased generation of hydroxyl radicals (HO•) and reactive nitrogen species (e.g., NO2• and ONOO-) in the UV222/nitrate process. We determined the innate quantum yields of nitrate photolysis at 222 nm and incorporated these values into a kinetic model, allowing for the accurate prediction of nitrate photodecay and reactive species generation. While reactive nitrogen species predominantly contribute to pesticide degradation in the UV222/nitrate process, they also lead to the formation of nitration byproducts. Using stable isotope-labeled nitrate (15NO3-) combined with mass spectrometry, we confirmed that the nitration byproducts are formed from the reactive nitrogen species generated from nitrate photolysis. Additionally, we demonstrate that the UV222/nitrate process increases the formation potential of highly toxic nitrogenous chlorinated products (e.g., trichloronitromethane) during postchlorination in real surface water.

Effect of physicochemical parameters on the occurrence of per- and polyfluoroalkyl substances (PFAS) in aquatic environment

Perfluoroalkyl substances (PFAS) and their distribution in aquatic environments have been studied extensively, but more information is needed to link these occurrences to their physicochemical characteristics. Understanding how these parameters influence PFAS can help predict their fate, mobility, and occurrences in water. This study reviewed the influence of physicochemical parameters on the occurrences of PFAS in aquatic environment using the relevant keywords to retrieve articles from databases spanning mostly between 2017 and 2024. The result suggests that high pH, turbidity, and dissolved oxygen, give high concentration of PFAS, while high electrical conductivity, temperature and salinity give low PFAS concentration in the water. Therefore, monitoring and safeguarding the aquatic bodies for human and environmental safety is imperative. Future studies should include the effects of the physicochemical properties on PFAS occurrences in the natural environment and focus on an organism's distinctive characteristics to comprehend the bioaccumulation and biomagnification of PFAS in them and environmental matrices.

The role of dissolved organic carbon in Great Smoky Mountains National Park streams impacted by long-term acid deposition

Following reductions in acid deposition in the Great Smoky Mountains National Park (GRSM) since the 2000s, many streams remain acidic and the role of organic acids (OA-) remains unknown due to limited OA- data. This study investigated dissolved organic carbon (DOC) concentrations as a surrogate for OA- across GRSM and its relationships with watershed characteristics, seasons, flow, and stream chemistry. Baseflow water samples were collected from seven watersheds for 2 years and stormflow samples from three watersheds for 1 year. During baseflow, DOC concentrations ranged from < 0.04 to 2.29 mg L-1 with watershed medians between 0.61 and 1.00 mg L-1. Stormflow DOC concentrations ranged from 1.36 to 5.66 mg L-1. During the summer, median DOC concentrations were about twice that of the other three seasons. Stream DOC concentrations decreased with increasing elevation during baseflow but increased with increasing elevation during stormflow. Considering high elevations historically received greater acid deposition, this gradient between baseflow and stormflow suggests higher elevation streams are more impacted by OA-. Based on an OA-/DOC acidity model, it was estimated that during baseflow OA- was a minor contributor to stream acidity, in the order of 5.3 μeq L-1, however stormflow OA- was estimated at 52.5 μeq L-1, contributing to nearly half of stream acidity. Baseflow DOC was significantly correlated with pH and Ca2+, suggesting stream acidification/recovery is governed by base cations and Ca2+ availability. Furthermore, this study provides essential data for future research to evaluate stream DOC trends during acidification recovery and changes in biogeochemical processes.

Characterization of natural and anthropogenic dissolved organic matter in the yangtze river basin using FT-ICR MS

Dissolved organic matter (DOM) is a complex mixture that plays a crucial role in global carbon cycling and climate dynamics. Understanding the chemical composition of DOM is crucial for studying its biogeochemical behavior. However, identifying individual DOM molecules is challenging. Here, using ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry and an in-house database, we developed a framework to investigate DOM characteristics in natural water. Through the developed approach, we successfully identified thousands of individual DOM molecules in the water bodies of the Yangtze River Basin. For the first time, the proportions of natural and anthropogenic organics within DOM were revealed. In total, 9006 unambiguous molecular formulas were assigned to DOM in the Yangtze River Basin. The proportions of CHNO and CHOS compounds increased from upstream to downstream regions. Moreover, 1099 DOM compounds were tentatively identified, with 85 % being endogenous organics and 15 % being exogenous organics. Notably, lipids and pharmaceuticals and personal care products were the most frequently detected endogenous and exogenous compounds. The spatial variation of the identified DOM indicated anthropogenic discharges considerably increased both the number and abundance of DOM in the downstream Yangtze River Basin. This study highlighted the importance of anthropogenic impacts on DOM in water.

Revealing the impact of wildfires on groundwater quality: Insights from Sierra de la Culebra (Spain)

Wildfires induce changes in soil and vegetation composition, significantly impacting the hydrological cycle and altering future runoff and infiltration patterns. Ash residue on the ground can infiltrate the subsoil along with water, leading to modifications in groundwater hydrochemistry. Climate change and summer heatwaves can create favourable conditions for severe wildfires, such as the one that occurred in Zamora, Spain, in 2022. Fourteen simultaneous points of origin across various locations in Zamora triggered the worst environmental disaster in this province, as well as the largest fire recorded in the history of Spain. Following the severe wildfires in Sierra de la Culebra, Zamora, groundwater samples were obtained to compare the hydrochemistry with pre-fire background data spanning several years. A general decline in pH across all sampling points was observed, most notably at Z1, likely due to its very high permeability and leaching of organic acids from burned vegetation. Increases in major ions such as SO42- and NO3- were detected at Z1-2, while HCO3- levels decreased, indicating possible oxidation of soil organic matter and the introduction of wildfire-derived organic acids into the groundwater system. Elevated concentrations of Na+, K+, Mg2+, and Ca2+ were observed at Z3, suggesting possible ash residue infiltration. Despite the severity of the wildfires, the results indicate that there were no significant long-lasting impacts on groundwater quality overall. This finding suggests that the groundwater systems in the study area are resilient to such environmental catastrophes.

Drinking water QMRA and decision-making: Sensitivity of risk to common independence assumptions about model inputs

When assessing risk posed by waterborne pathogens in drinking water, it is common to use Monte Carlo simulations in Quantitative Microbial Risk Assessment (QMRA). This method accounts for the variables that affect risk and their different values in a given system. A common underlying assumption in such analyses is that all random variables are independent (i.e., one is not associated in any way with another). Although the independence assumption simplifies the analysis, it is not always correct. For example, treatment efficiency can depend on microbial concentrations if changes in microbial concentrations either affect treatment themselves or are associated with water quality changes that affect treatment (e.g., during/after climate shocks like extreme precipitation events or wildfires). Notably, the effects of erroneous assumptions of independence in QMRA have not been widely discussed. Due to the implications of drinking water safety decisions on public health protection, it is critical that risk models accurately reflect the context being studied to meaningfully support decision-making. This work illustrates how dependence between pathogen concentration and either treatment efficiency or water consumption can impact risk estimates using hypothetical scenarios of relevance to drinking water QMRA. It is shown that the mean and variance of risk estimates can change substantially with different degrees of correlation. Data from a water supply system in Calgary, Canada are also used to illustrate the effect of dependence on risk. Recognizing the difficulty of obtaining data to empirically assess dependence, a framework to guide evaluation of the effect of dependence is presented to enhance support for decision making. This work emphasizes the importance of acknowledging and discussing assumptions implicit to models.

A machine learning approach to investigate the impact of land use land cover (LULC) changes on groundwater quality, health risks and ecological risks through GIS and response surface methodology (RSM)

Groundwater resources are enormously affected by land use land cover (LULC) dynamics caused by increasing urbanisation, agricultural and household discharge as a result of global population growth. This study investigates the impact of decadal LULC changes in groundwater quality, human and ecological health from 2009 to 2021 in a diverse landscape, West Bengal, India. Using groundwater quality data from 479 wells in 2009 and 734 well in 2021, a recently proposed Water Pollution Index (WPI) was computed, and its geospatial distribution by a machine learning-based 'Empirical Bayesian Kriging' (EBK) tool manifested a decline in water quality since the number of excellent water category decreased from 30.5% to 28% and polluted water increased from 44% to 45%. ANOVA and Friedman tests revealed statistically significant differences (p < 0.0001) in year-wise water quality parameters as well as group comparisons for both years. Landsat 7 and 8 satellite images were used to classify the LULC types applying machine learning tools for both years, and were coupled with response surface methodology (RSM) for the first time, which revealed that the alteration of groundwater quality were attributed to LULC changes, e.g. WPI showed a positive correlation with built-up areas, village-vegetation cover, agricultural lands, and a negative correlation with surface water, barren lands, and forest cover. Expansion in built-up areas by 0.7%, and village-vegetation orchards by 2.3%, accompanied by a reduction in surface water coverage by 0.6%, and 2.4% in croplands caused a 1.5% drop in excellent water and 1% increase in polluted water category. However, ecological risks through the ecological risk index (ERI) exhibited a lower risk in 2021 attributed to reduced high-risk potential zones. This study highlights the potentiality in linking LULC and water quality changes using some advanced statistical tools like GIS and RSM for better management of water quality and landscape ecology.

Disinfection by-product formation potential in response to variability in dissolved organic matter and nutrient inputs: Insights from a mesocosm study

Changes in rainfall patterns driven by climate change affect the transport of dissolved organic matter (DOM) and nutrients through runoff to freshwater systems. This presents challenges for drinking water providers. DOM, which is a heterogeneous mix of organic molecules, serves as a critical precursor for disinfection by-products (DBPs) which are associated with adverse health effects. Predicting DBP formation is complex due to changes in DOM concentration and composition in source waters, intensified by altered rainfall frequency and intensity. We employed a novel mesocosm approach to investigate the response of DBP precursors to variability in DOM composition and inorganic nutrients, such as nitrogen and phosphorus, export to lakes. Three distinct pulse event scenarios, mimicking extreme, intermittent, and continuous runoff were studied. Simultaneous experiments were conducted at two boreal lakes with distinct DOM composition, as reflected in their color (brown and clear lakes), and bromide content, using standardized methods. Results showed primarily site-specific changes in DBP precursors, some heavily influenced by runoff variability. Intermittent and daily pulse events in the clear-water mesocosms exhibited higher haloacetonitriles (HANs) formation potential linked to freshly produced protein-like DOM enhanced by light availability. In contrast, trihalomethanes (THMs), associated with humic-like DOM, showed no significant differences between pulse events in the brown-water mesocosms. Elevated bromide concentration in the clear mesocosms critically influenced THMs speciation and concentrations. These findings contribute to understanding how changing precipitation patterns impact the dynamics of DBP formation, thereby offering insights for monitoring the mobilization and alterations of DBP precursors within catchment areas and lake ecosystems.

Trihalomethanes in global drinking water: Distributions, risk assessments, and attributable disease burden of bladder cancer

This study aimed to assess the global spatiotemporal variations of trihalomethanes (THMs) in drinking water, evaluate their cancer and non-cancer risks, and THM-attributable bladder cancer burden. THM concentrations in drinking water around fifty years on a global scale were integrated. Health risks were assessed using Monte Carlo simulations and attributable bladder cancer burden was estimated by comparative risk assessment methodology. The results showed that global mean THM concentrations in drinking water significantly decreased from 78.37 μg/L (1973-1983) to 51.99 μg/L (1984-2004) and to 21.90 μg/L (after 2004). The lifestage-integrative cancer risk and hazard index of THMs through all exposure pathways were acceptable with the average level of 6.45 × 10-5 and 7.63 × 10-2, respectively. The global attributable disability adjusted of life years (DALYs) and the age-standardized DALYs rate (ASDR) dropped by 16% and 56% from 1990-1994 to 2015-2019, respectively. A big decline in the attributable ASDR was observed in the United Kingdom (62%) and the United States (27%), while China experienced a nearly 3-fold increase due to the expanded water supply coverage and increased life expectancy. However, China also benefited from the spread of chlorination, which helped reduce nearly 90% of unsafe-water-caused mortality from 1998 to 2018.

Removal of strontium by nanofiltration: Role of complexation and speciation of strontium with organic matter

Strontium (Sr) removal from water is required because excessive naturally occurring Sr exposure is hazardous to human health. Climate and seasonal changes cause water quality variations, in particular quality and quantity of organic matter (OM) and pH, and such variations affect Sr removal by nanofiltration (NF). The mechanisms for such variations are not clear and thus OM complexation and speciation require attention. Sr removal by NF was investigated with emphasis on the role of OM (type and concentration) and pH (2-12) on possible removal mechanisms, specifically size and/or charge exclusion as well as solute-solute interactions. The filtration results show that the addition of various OM (10 types) and an increase of OM concentration (2-100 mgC.L-1) increased Sr removal by 10-15%. The Sr-OM interaction was enhanced with increasing OM concentration, implying enhanced size exclusion via Sr-OM interaction as the main mechanism. Such interactions were quantified by asymmetric flow field-flow fractionation (FFFF) coupled with an inductively coupled plasma mass spectrometer (ICP-MS). Both extremely low and high pH increased Sr removal due to the enhanced charge exclusion and Sr-OM interactions. This work elucidated and verified the mechanism of OM and pH on Sr removal by NF membranes.

Pore size distribution and Al oxide content significantly regulated the effects of humic acid on perfluorooctanoic acid transport in natural soils

The ubiquity of dissolved organic matter (DOM) makes it encounter the released perfluorooctanoic acid (PFOA) in subsurface environment. However, the effect of DOM (e.g., humic acid, HA) on PFOA transport in soils and the critical influencing factors and mechanisms remain obscure. Column experiments were conducted to explore PFOA transport with the presence of different concentrations of HA in three types of soils and two types of Al oxide coated sand. Results revealed soil properties significantly regulate the effects of HA on PFOA transport, for which pore size distribution, minerals content (e.g., Al oxide) and pH were critical influencing soil-properties. For soil with large mesopore volume, pore blockage caused by HA controlled the effect of HA on PFOA transport. Large mesopore volume significantly alleviated pore blockage of HA, and led to insignificant effects of HA on PFOA transport. For soil exhibited minimum mesopore volume, Al oxide content and pH dominated the effect of HA on PFOA transport. Results from Al oxide coated sand (low mesopore volume) columns further proved that higher Al oxide content and lower pH caused more significant facilitating effect of HA on PFOA transport via site competition. Results highlighted the importance of considering pore size distribution and Al oxide content when assessing PFOA mobility capacity with co-transport with DOM in soils.

The impacts of climate change on groundwater quality: A review

Groundwater has been known as the second largest freshwater storage in the world, following surface water. Over the years, groundwater has already been under overwhelming pressure to satisfy human needs for artificial activities around the world. Meanwhile, the most noticeable footprint of human activities is the impact of climate change. Climate change has the potential to change the physical and chemical properties of groundwater, thereby affecting its ecological functions. This study summarizes existing research affiliated with the possible effects of a changing climate on the quality of groundwater, including changes in water availability, increased salinity and pollution from extreme weather events, and the potentiality of seawater intrusion into coastal aquifers. Previous works dealing with groundwater-induced responses to the climate system and climate impacts on groundwater quality through natural and anthropogenic processes have been reviewed. The climate-induced changes in groundwater quality including pH, dissolved oxygen level, salinity, and concentrations of organic and inorganic compounds were assessed. Some future research directions are proposed, including exploring the potential changes in the occurrences and fate of micropollutants in groundwater, examining the relationship between the increase of microcystin in groundwater and climate change, studying the changes in the stability of metals and metal complexation, and completing studies across different regional climate regions.

The bioreduction of U(VI) and Pu(IV): Experimental and thermodynamic studies

The experimental and thermodynamic bioreduction of U(VI)aq and Pu(IV)am was studied in order to more accurately predict their transport velocities in groundwater and assess the contamination risks to the associated environments. The results obtained in this study emphasize the impact of carbonate-calcium and humic acids at 7.1 and anoxic solutions on the rate and extent of U(VI)aq and Pu(IV)am bioreduction by Shewanella putrefaciens. We found that the bioreduction rate of U(VI)aq became slow in the presence of NaHCO3/CaCl2. The more negative standard redox potentials of the ternary complexes of U(VI)-Ca2+-CO32- accounted for the decreased rate of bioreduction, e.g., [Formula: see text]  = -0.6797 V ≪ [Formula: see text]  = 0.3862 V. The bioreduction of Pu(IV)am seemed feasible, while humic acids accepted the adequate extracellular electrons secreted by S. putrefaciens, and the redox potential of Eh(HAox/HAred) was lower than Eh(PuO2(am)/Pu3+), e.g., Eh(HAox/HAred) ≦ Eh(PuO2(am)/Pu3+) if humic acids accepted ≧ 7.952 × 10-7 mol of electrons. The standard redox potentials, Eho(PuO2(am)/Pu3+) = 0.9295 V ≫ [Formula: see text]  = -0.6797 V, cannot explain the reduction extent of Pu(IV)am (8.9%), which is notably smaller than that of U(VI)aq (74.9%). In fact, the redox potential of Pu(IV)am was distinctly negative under the experimental conditions of trace-level Pu(IV)am (∼2.8 × 10-9 mol/L Pu(IV) if Pu(IV)am was completely dissolved), e.g., Eh(PuO2(am)/Pu3+) = -0.1590 V (α(Pu3+) = 10-10 mol/L, pH = 7.1). Therefore, the chemical factor of Pu3+ activity, leading to a rapid drop in Eh(PuO2(am)/Pu3+) at trace-level Pu(IV)am, was responsible for the relatively small reduction extent of Pu(IV)am.

Measurement of haloacetic acids in human urine samples from six megacities of China using a refined detection method

Haloacetic acids (HAAs) are common disinfection by-products in chlorine disinfected water. Humans are extensively exposed to them. However, nationwide biomonitoring data were not available for any country. This study developed a labor-efficient and sensitive method for the detection of urinary HAAs, including trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA), and conducted an exposure assessment in a Chinese population. A total of 850 first-morning-void urine samples were collected from adults in six megacities in China: Wuhan (central), Lanzhou (northwest), Chengdu (southwest), Taiyuan (north), Shanghai (east), and Dalian (northeast). Each participant (n = 425) provided a pair of urine samples during the warm (September to October 2018) and cold (December 2018 to January 2019) seasons. The detection method achieved good retention of the target analytes using a Fluoro-Phenyl column and excellent selectivity using in-source fragmentation ions as precursor ions in multiple reaction monitoring. The detection rate of urinary TCAA in Chinese populations was high (78.5%) but varied among different regions (54.0% to 98.0%). DCAA was rarely detected (<10%). The overall median value of specific gravity adjusted TCAA concentrations was 5.70 μg/L in the warm season and 3.87 μg/L in the cold season, respectively. Higher urinary TCAA concentrations were more likely to occur in Wuhan (Yangtze River Basin), urban areas, and during the warm season. The upstream region of the Yangtze River Basin (Chengdu) typically has lower TCAA concentrations. TCAA formation in coastal cities such as Shanghai and Dalian may be impacted by seawater intrusion. Estimated daily intakes of TCAA were lower than its chronic reference dose of 20 μg/kg-bw/day. This detection method can be applied to future biomonitoring of urinary HAAs. More attention should be paid to the highly exposed subgroups when exploring the health effects of long-term TCAA exposure.

Super-wetting and self-cleaning polyvinyl alcohol/sodium alginate nanofiber membrane decorated with MIL-88A(Fe) for efficient oil/water emulsion separation and dye degradation

Membrane separation is considered an effective approach to water purification. Nevertheless, membrane fouling dramatically decreases the separation efficiency and lifetime of membranes, thus limiting its further development and application. Herein, a multifunctional self-cleaning MIL-88A(Fe) decorated polyvinyl alcohol/sodium alginate (MIL-88A(Fe)@PVA-SA) nanofiber membrane was prepared by electrospinning and in-situ growth methods for the separation of oil/water emulsions and photo-Fenton degradation of dyes. The membrane possesses superhydrophilicity with a water contact angle (WCA) of 0° and superoleophobicity with underwater oil contact angle (UCA) of 161.7°, and exhibits superior separation efficiency (>99.5 %) and permeation flux (1140-2455 L/m2/h) for different oil/water emulsions. Moreover, the membrane exhibited an outstanding photo-Fenton performance under visible light, with degradation efficiencies (~99.9 %) towards methylene blue (MB) and reactive red 24 (RR24) within 90 min. Importantly, the membrane can be easily regenerated by simple rinsing and photo-Fenton self-cleaning treatment. In this study, MIL-88A(Fe)@PVA-SA nanofiber membrane has a promising application in dye removal and oil/water separation, providing a new idea to develop novel membrane materials.

Rethinking terrestrial dissolved organic matter in dam reservoirs before mixing: Linking photodegradation and biodegradation and the phenanthrene binding behavior

With the increased construction of dam reservoirs and the demand for water security, terrestrial dissolved organic matter (DOM) has received attention because of its role in regulating water quality, ecological functions, and the fate and transport of pollutants in dam reservoirs. This study investigated the transformations of soil DOM and vegetation DOM of dam reservoirs following photodegradation and biodegradation before conservative mixing, as well as the resultant effects on phenanthrene binding. Based on the results, terrestrial DOM could undergo transformation via photodegradation and biodegradation before conservative mixing in dam reservoirs. Although both processes resulted in substantial decreases in DOM concentrations, the changes in chromophoric DOM and fluorescent DOM depended on the original DOM sources. Furthermore, the photodegradation of terrestrial DOM resulted in more pronounced photobleaching than photomineralization. In addition, photodegradation of terrestrial DOM resulted in the generation of DOM-derived by-products with low molecular weight and low aromaticity, whereas the biodegradation of terrestrial DOM resulted in DOM-derived by-products with low molecular weight and high aromaticity. Subsequently, the photodegradation and biodegradation of terrestrial DOM substantially enhanced the binding affinity of phenanthrene. Soil DOM is prior to vegetation DOM when predicting the ecological risk of HOCs. These results indicate that the terrestrial DOM in dam reservoirs should be reconsidered before conservative mixing. Further studies on the coupling effects of both biogeochemical processes, as well as on the relative contributions of soil DOM and vegetation DOM after transformation to the aquatic DOM in dam reservoirs, are required. This study provides information on the environmental effects of dam construction from the perspective of biogeochemical processes.

A Temporal Graph Model to Predict Chemical Transformations in Complex Dissolved Organic Matter

Dissolved organic matter (DOM) is a complex mixture of thousands of natural molecules that undergo constant transformation in the environment, such as sunlight induced photochemical reactions. Despite molecular level resolution from ultrahigh resolution mass spectrometry (UHRMS), trends of mass peak intensities are currently the only way to follow photochemically induced molecular changes in DOM. Many real-world relationships and temporal processes can be intuitively modeled using graph data structures (networks). Graphs enhance the potential and value of AI applications by adding context and interconnections allowing the uncovering of hidden or unknown relationships in data sets. We use a temporal graph model and link prediction to identify transformations of DOM molecules in a photo-oxidation experiment. Our link prediction algorithm simultaneously considers educt removal and product formation for molecules linked by predefined transformation units (oxidation, decarboxylation, etc.). The transformations are further weighted by the extent of intensity change and clustered on the graph structure to identify groups of similar reactivity. The temporal graph is capable of identifying relevant molecules subject to similar reactions and enabling to study their time course. Our approach overcomes previous data evaluation limitations for mechanistic studies of DOM and leverages the potential of temporal graphs to study DOM reactivity by UHRMS.

Potential interaction mechanisms between PAHs and glomalin related-soil protein (GRSP)

Glomalin-related soil protein (GRSP) has gained widespread attention because of its benefits to carbon sequestration, improving soil quality and fixing heavy metals. However, studies on how GRSP affects the environmental fate of organic contaminants are scarce. In this study, different types of GRSPs were isolated from forest soils and characterized to study the binding of GRSPs and PAHs under different environmental conditions. The results indicated that GRSPs contain abundant functional groups (such as -NH, -COOH, and CO) and material composition, like humic acid, proteins, and lipids. For the tested GRSPs, EE-GRSP has lower DOC, SUVA₂₆₀ and SUVA₂₈₀ values, as well as higher E2/E3 values, indicating that EE-GRSP has lower hydrophobicity and molecular weight. These properties can lead to strong interactions between GRSP and PAHs, especially with benzopyrene, which has a high K_ow and K_sw and a large molecular size, with binding constants ranging from 16,119 to 163,697 L kg^-1. Furthermore, low pH (pH = 3) and temperature (15 °C) could increase GRSP's aggregation, enhance the GRSP binding ability with PAHs, whose binding constants were 11,595 and 5067.3 L kg^-1. Therefore, the binding between GRSP and PAHs may lead to changes in the fate of PAHs in the soil and affect the environmental risk of PAHs. The results presented here will deepen our understanding of the environmental function of GRSPs and provide a theoretical basis to further elucidate the mechanisms of GRSPs and organic pollutants.

Water quality of The Gambia River: A prospective drinking water supply

Drinking water in The Gambia is mostly derived from boreholes that could potentially be contaminated. The Gambia River, a major river in West Africa that covers 12 % of the country's area, could be more exploited for drinking water supply. During the dry season, the total dissolved solids (TDS), ranging from 0.02 to 33 g/L in The Gambia River, decreases with the distance to the river mouth with no major inorganic contamination. The freshwater (<0.8 g/L TDS) starts from Jasobo at approximately 120 km from the river mouth and extends by about 350 km to the eastern border of The Gambia. With a dissolved organic carbon (DOC) ranging from 2 to 15 mgC/L, the natural organic matter (NOM) of The Gambia River was characterised by 40-60 % humic substances of paedogenic origin. With such characteristics, unknown disinfection by-products could be formed if chemical disinfection, such as chlorination, was implemented during treatment. Out of 103 types of micropollutants, 21 were detected (4 pesticides, 10 pharmaceuticals, 7 per- and polyfluoroalkyl substances (PFAS)) with concentrations ranging from 0.1 to 1500 ng/L. Pesticides, bisphenol A and PFAS concentrations were below the stricter EU guidelines set for drinking water. These were mainly confined to the urban area of high population density near the river mouth, while the quality of the freshwater region of low population density was surprisingly pristine. These results indicate that The Gambia River, especially in its upper regions, would be well suited as a drinking water supply when using decentralised ultrafiltration treatment for the removal of turbidity, as well as, depending on pore size, to a certain extent microorganisms and DOC.

A new strategy for treating Pb2+ and Zn2+ pollution with industrial waste derivatives Humin

Metal pollution caused by industrial waste accumulation is a long-term and far-reaching problem. Humin (HM), as a highly condensed organic component insoluble in alkaline or water solution, is often discarded as humic acid industrial waste. However, the abundant active functional groups in HM reported by some researches make it possible for HM to remove metals. In this study, a waste reuse strategy was proposed to reduce the pressure of industrial metal pollution on the environment. HM was obtained from lignite waste residue. Scanning electron microscopy, energy spectrum and Fourier infrared spectroscopy, combined with the adsorption models were employed to reveal the mechanism of HM adsorption. The results showed that HM had multiple adsorption mechanism and high biological stability. The adsorption capacity of HM to Zn²⁺ and Pb²⁺ were 194.88 mg/g and 289.59 mg/g respectively. HM adsorbed Zn²⁺ mainly by physical multilayer adsorption. And the adsorption of Pb²⁺ by HM was mainly a monolayer chemical reaction, which depended on its active functional groups and the exchange of valence electrons. Notably, HM could simultaneously remove Pb²⁺ and Zn²⁺ and almost did not affect its original adsorption capacity to single ions. These results will provide a new strategy for the treatment of metal pollution in the future and alleviate the pressure of multiple metal pollution of the environment.

Anthropogenic, Carbon-Reinforced Soil as a Living Engineered Material

In recent years, the simple synthesis of artificial humic substances (A-HS) by alkaline hydrothermal processing of waste biomass was described. This A-HS was shown to support water and mineral binding, to change soil structure, to avoid fertilizer mineralization, and to support plant growth. Many of the observed macroscopic effects could, however, not be directly related to the minute amounts of A-HS which have been added, and an A-HS stimulated microbiome was found to be the key for understanding. In this review, we describe such anthropogenic soil in the language of the modern concept of living engineered materials and identify natural and artificial HS as the enabler to set up the interactive microbial system along the interfaces of the mineral grains. In that, old chemical concepts as surface activity, redox mediation, and pH buffering are the base of the system structure build-up and the complex self-adaptability of biological systems. The resulting chemical/biological hybrid system has the potential to address world problems as soil fertility, nutrition of a growing world population, and climate change.

Response mechanism of sediment organic matter of plateau lakes in cold and arid regions to climate change: a case study of Hulun Lake, China

Lake organic matter is one of the important forms of terrestrial carbon, and its sedimentary evolution is affected by many factors such as climate and sources. However, few studies have been conducted on the feedback mechanism of the sedimentary evolution of organic matter to climate change in cold and arid lakes. Historical variations and compositions of sources of the sediment organic matter (SOM) of Hulun Lake, a typical lake in the cold and arid region of China, were studied by multiple methods. The interactions and fee7dback mechanisms between the sedimentary evolution of SOM and climate change, and compositions of SOM source change, were also discussed. Overall, the characteristic indexes of the SOM, including total organic carbon (TOC), carbon stable isotope (δ¹³C), carbon to nitrogen ratio (C/N), and fluorescence intensity (FI) of the protein-like component in water extractable organic matter (WEOM), showed obvious and uniform characteristics of periodical changes. The indexes were relatively stable before 1920, and fluctuated from 1920 to 1979. Since the 1980s, values of TOC, δ¹³C, and FI of the protein-like component in WEOM has increased, while C/N decreased. The absolute dominant contribution of terrestrial source to the SOM had changed, and the relative average contribution rate of autochthonous source increased from 17.6% before 1920 to 36.9% after 2000. The increase of temperature, strong evaporation concentration effect, and change of compositions of SOM sources are the important driving factors of the sedimentary evolution of organic matter in Hulun Lake.

Fluorescence characteristics and source analysis of DOM in groundwater during the wet season in the CKDu zone of North Central Province, Sri Lanka

The dissolved organic matter (DOM) should be purified for safe drinking water due to disinfection by-products (DBPs) produced by disinfectants reaction with DOM. Current research on groundwater in the chronic kidney disease with unknown etiology (CKDu) zone of the North Central Province (NCP) in Sri Lanka has focused mainly on aquatic chemistry, with limited attention paid to the spatial distribution, compositional sources and factors of DOM. Therefore, the structure, composition, source and spatial distribution of the DOM of two kinds of groundwater samples collected from dug well and tube well in the NCP during the wet season were determined, compared and analyzed by analytical tools such as parallel factor analysis (PARAFAC). Results show that the average concentrations of TOC in these two groundwater samples are generally higher than 5.0 mg/L, and the concentration of TOC in the groundwater of the shallow weathered aquifer is higher than that of the deep hard rock aquifer, while its distribution of the two aquifers are on contrary. The DOM in the dug well has three types and four components, including humus-like component C1 (33.36%) and C2 (38.60%), protein-like component C3 (13.09%) and heterogeneous organic component C4 (14.95%). In the tube well, two types and two components of the DOM are determined, including humus-like component CⅠ (69.80%) widely existing in natural water and soluble microbial by-product CⅡ (30.20%) produced by microbial community activities. In the dug well, DOM is mainly exogenous input, the higher ion concentration in water affected the fluorescence intensity of humus and protein components. And in the tube well, DOM has obvious endogenous characteristics, and higher pH value may inhibit the production of protein like fluorescent substances to a certain extent.

Differences in the composition, source, and stability of suspended particulate matter and sediment organic matter in Hulun Lake, China

The occurrence, migration, transformation, and stability of sediment (SOM) and suspended particulate (SPOM) organic matters have important effects on the environmental behaviors of carbon, nitrogen, phosphorus, and other pollutants in a water environment. The content, composition, fluorescence characteristics, source, and stability of SOM and SPOM in Hulun Lake, a typical lake in cold and arid region of China, were compared by sequential extraction, three-dimensional fluorescence spectroscopy, parallel factor technique, carbon-nitrogen ratio, and stable carbon isotope. Contents of SOM and SPOM in north and west were higher than those in east and south. The average content of SPOM (24.70 ± 4.63 g/kg) was slightly higher than that of SOM (23.04 ± 10.27 g/kg), but the difference was not significant. Humin was the dominant component in SOM and SPOM, accounting for 73.7% and 61.2%, respectively. Humus was the main fluorescence component of water-extractable organic matter in SOM and SPOM, accounting for 79.9% and 70.4%, respectively, of the total fluorescence intensity. SOM and SPOM were derived from terrestrial sources with a relative contribution rate of about 70%. SPOM was more influenced by autochthonous sources and had a significantly lower humification degree and stability than SOM. Effects of climate changes on migration, transformation, stability, and bioavailability of organic matters and endogenous pollutants closely related to organic matters in lakes of cold and arid regions should be paid attention in the future.

Sources, characteristics, and in situ degradation of dissolved organic matters: A case study of a drinking water reservoir located in a cold-temperate forest

Dissolved organic matter (DOM) plays a pivotal role in the biogeochemical cycles of elements and the regulation of forest ecosystem functions. However, studies on the regional and seasonal characteristics of DOM in cold-temperate montane forests are still not comprehensive. In this study, samples of water, soil, and sediment from different sites in the forest drainage basin were collected, and their DOM was characterized by an excitation-emission matrix and parallel factor analysis (EEM-PARAFAC). The results showed that terrestrial-sourced humic-like substances were the dominant DOM in the studied reservoir and inflowing rivers. The quality and quantity of DOM exhibited spatiotemporal variations with the influence of terrain and monsoonal precipitation. The average concentration of dissolved organic carbon (DOC) in the wet season was 11.62 mg/L, which was higher than that in the dry season (8.18 mg/L). Higher humification index (HIX) values were observed in the wet season and upstream water than in the dry season and reservoir water. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was used to further develop a molecular-level understanding of the in situ degradation process of DOM. The results indicated that photodegradation rather than biodegradation may play a dominant role in the in situ degradation of terrestrial-sourced humic-like substances under natural conditions. The biodegradability of DOM was enhanced after the in situ degradation process. Additionally, a significant decrease in the precursors of disinfectant byproducts in DOM was observed after in situ degradation. To our knowledge, this is the first study of the sources, characteristics, and in situ degradation of DOM in a reservoir in a cold-temperate forest. These findings help better understand the quality, quantity, and biogeochemical process of DOM in the studied reservoir and may contribute to the selection of drinking water treatment technologies for water supply.

Influence of DOM and microbes on Fe biogeochemistry at a riverbank filtration site

Riverbank filtration (RBF) constitutes an important part of the water cycle, which involves active natural filtration leading to pollution of river water being intercepted and retained. The RBF has the function of water purification, but retention of exogenous pollutants in the RBF system complicates biogeochemical processes due to the presence of primary active components. In this study, we verified the essential role of microbial mediation during the interactions between primary Fe minerals in the RBF system and dissolved organic matter (DOM) in river water based on lab-scale experiments. The results demonstrated that DOM from infiltration of river water increased the amount of iron (Fe) released from the sediment in RBF, leading to an increase in Fe concentration in groundwater by higher than one order of magnitude. In particular, the existence of Fe bacteria even made this effect more thorough and more complex. Abiotic reduction was shown to play a more significant role in increasing Fe release than microbe-mediated reduction. Increasing the amount of Fe released could change the distribution of Fe minerals at the sediment surface, thereby affecting the structure of the microbial community in the RBF system and decreasing the DOM concentration in the groundwater. Moreover, As and Mn were found to behave in a similar manner as Fe due to their close biochemical properties when interacting with primary minerals in sediment. This study not only provides mechanistic insight into the higher Fe concentrations encountered in the groundwater of nearby rivers but also has important practical implications for developing nature-based technologies for water pollution control and environmental remediation.

Two constructed wetlands within a Mediterranean natural park immersed in an agrolandscape reduce most heavy metal water concentrations and dampen the majority of pesticide presence

The water concentrations of 12 heavy and other metals/metalloids were analyzed seasonally along two horizontal-flow constructed wetlands (CWs) (Tancat Mília-TM and Tancat l'Illa-TLI) located within the Mediterranean Albufera de València Natural Park during 2020-2021. A wide-scope screening of pesticides present in waters was also performed. The two CWs were created to improve water quality and increase biodiversity. They currently receive effluent waters from two different tertiary-treatment wastewater plants, and the water flows along the CWs before being discharged into the main lagoon and a smaller lagoon in TM and TLI, respectively. TLI manages to reduce (Mn) or maintain the concentration of most of the studied elements (Zn, Ni, Hg, Cr, Fe Cd, Cu) at the same level as outside (67%). Only Al, Pb, B, and As remain at a higher concentration. TM also reduces Zn and Cu and keeps the concentration of Cr, Cd, and Hg (representing 42%). Al, Pb, B, and As remain at higher concentrations, as in TLI, but Ni, Fe, and Mn are also at higher concentrations. Although both CWs vary in their ability to remove elements, no risks to human health or the environment have been detected due to the low metal concentration in their outlets, all of them (except Hg) below the legal limits for environmental quality in the European Union. With the detection of 71 compounds in water in each CW area (26 herbicides, 26 insecticides, and 19 fungicides in TLI, and 29 herbicides, 23 insecticides, and 19 fungicides in TM), we also provide evidence of the impact of pesticides, which depends on the application method (helicopter, tractor), originated from areas with high agricultural pressure (chiefly rice crops) on systems (mainly TM) created to preserve biodiversity. Nevertheless, both systems provide crucial environmental services in water quality in this agrolandscape.

Humic Lake Exhibits Higher Microbial Functional Gene Diversity and Weaker Gene Interaction Efficiency than a Common Alkaline Lake

Humic lakes (HLs) are special water bodies (high organic matter content, low pH, and low transparency) that are important sources of major greenhouse gases. The knowledge about microbial functional potentials and the interactions among different genes in HL water has been scarcely understood. In this study, we used 16S rRNA gene sequencing and the GeoChip 5.0 to investigate microbial community compositions and functional gene structures in an HL and a reference weakly alkaline lake (RAL). The HL microbial communities showed distinct compositions and functional gene structures than those in the RAL. The functional gene diversity was significantly higher in the HL than in the RAL. Specifically, higher gene relative intensities in carbon and nitrogen fixations, the degradation of various types of carbon, methane oxidation and methanogenesis, ammonification, denitrification, and assimilatory N reduction were observed in the HL samples. By contrast, the metabolic potentials of microorganisms involved in dissimilatory N reduction, phosphorus degradation, and sulfur oxidation were weaker in the HL than in the RAL. Despite higher functional gene diversity, the interaction efficiency among genes (reflected by network geodesic distance and clustering coefficient) might be reduced in the HL. Different functional microbes may develop less interdependent relationships in acquiring nutrients given the high resource availability in the HL. Overall, the enhanced microbial metabolic potentials and less efficient functional interactions might have great consequences on nutrient cycling and greenhouse gas emissions in the HL ecosystem.

The role of humic substances in sediment phosphorus release in northern lakes

In northern lakes, which are often stained and productive, the impacts of dissolved organic carbon (DOC) on sediment phosphorus (P) release are largely unexplored. Here we elucidated the factors behind experimentally-derived sediment release rates of P by diffusion (DF) in four Finnish lakes with a range of colour. Next, we extended our analysis to a larger set of northern lakes for further insights regarding possible implications of organic substances on sediment P release. The significant correlation between pore-water soluble reactive P and dissolved iron, and a positive effect of iron-bound sedimentary P (Fe-P) on DF supports the classic paradigm of redox-dependent P release in the four Finnish lakes studied. Nevertheless, the P release from Fe-P may be inhibited by humic substances, as we observed lower Fe-P and negative DF in two humic rich lakes (high DOC). The analysis of a larger set of northern lakes supported the negative effect of humic substances on P release rate (RR) determined by in situ P increases. In this dataset, DOC correlated positively with water colour and negatively with RR. Furthermore, multiple stepwise regression analysis selected sediment total P and organic matter content in sediments (LOI) as the best predictors of RR, similar to a previously published model by Nürnberg (1988). While the model predictions (RR_pred) were correlated to RR in the present study, they tended to overestimate RR that was determined in closed experimental systems. The inhibiting effects of humic substances on RR may be manifested in both internal P loading and primary production.

Groundwater quality and human health risk assessment in selected coastal and floodplain areas of Bangladesh

Groundwater aquifers are a common source of drinking water in Bangladesh. However, groundwater contamination is a major public health concern across the country. This research aims to examine the groundwater quality and health concerns using a random sampling process. Multivariate statistical and health risk analyses of elements were performed to determine the source of contaminants and their effects on human health. A total of 24 parameters were analyzed, where Na⁺, NH₄⁺, K⁺, Mg²⁺, F^-, NO₃^-, Mn, Fe, Se, U, and As concentrations were found to be high in different sampling points compared to the Department of Environment of Bangladesh (DoE), and the World Health Organization (WHO) groundwater quality standards. Principal Component Analysis (PCA) and Cluster Analysis (CA) identified the dominant and potential sources of contaminants in the groundwater aquifer, including geogenic, salinity intrusion, industrial, and agricultural. The results of the degree of contamination level (C_d) and the heavy metal pollution index (HPI) showed that 28% and 12% of the sampling points had high levels of heavy metal contamination, indicating a high risk for human health issues. Cr concentrations were found to have a higher carcinogenic (cancer) risk than As and Cd concentrations. Hazard quotient (HQ) and hazard index (HI) scores expressed the hazardous status and possible chronic effects in the context of individual sampling points. For both child and adults, 44% and 36% of the sampling points had a high HI score, indicating the possibility of long-term health risks for local populations.

Humic acids alleviate the toxicity of reduced graphene oxide modified by nanosized palladium in microalgae

The use of graphene-family materials modified by nanosized palladium (Pd/GFMs) has intensified rapidly in various fields; however, the effects of environmental factors (e.g., natural organic matter (NOM)) on the transformation and ecotoxicity of Pd/GFMs remain largely unknown. In this study, reduced graphene oxide modified by nanosized Pd (Pd/rGO) was incubated with humic acid (HA) under light irradiation for 56 d to explore the effects of NOM on the physicochemical transformations (e.g., defects, surface charges and dispersity) and biological toxicity (e.g., growth inhibition, oxidative stress and ultrastructural damage on algae cells) of Pd/GFMs. The results revealed that HA increased the defects and dispersity of Pd/rGO. Growth inhibition, damage to cellular ultrastructures, and oxidative stress in microalgae cells were induced by Pd/rGO, and corresponding defense responses (e.g., superoxide dismutase, peroxidase and glutathione) were activated. HA diminished the above defense responses in microalgae triggered by Pd/rGO by regulating GSH metabolism and the alanine biosynthesis pathway. In the presence of HA, cell wall damage (i.e., hole formation) caused by exposure to Pd/rGO was restored, and the plasmolysis area was reduced by 28.6 %. In addition, growth inhibition, lipid peroxidation, loss of mitochondrial membrane potential and ROS formation induced by 1.0 mg/L MoS₂NPs were decreased by 1.4-65.6 %, 13.9-26.1 %, 21.8-58.3 % and 9.6-16.1 %, respectively. These findings highlight the need to consider the effects of HA on the environmental transformation and biological toxicity of Pd/GFMs, which presents significant implications for the management of Pd/GFMs.

A review of the global climate change impacts, adaptation, and sustainable mitigation measures

Climate change is a long-lasting change in the weather arrays across tropics to polls. It is a global threat that has embarked on to put stress on various sectors. This study is aimed to conceptually engineer how climate variability is deteriorating the sustainability of diverse sectors worldwide. Specifically, the agricultural sector's vulnerability is a globally concerning scenario, as sufficient production and food supplies are threatened due to irreversible weather fluctuations. In turn, it is challenging the global feeding patterns, particularly in countries with agriculture as an integral part of their economy and total productivity. Climate change has also put the integrity and survival of many species at stake due to shifts in optimum temperature ranges, thereby accelerating biodiversity loss by progressively changing the ecosystem structures. Climate variations increase the likelihood of particular food and waterborne and vector-borne diseases, and a recent example is a coronavirus pandemic. Climate change also accelerates the enigma of antimicrobial resistance, another threat to human health due to the increasing incidence of resistant pathogenic infections. Besides, the global tourism industry is devastated as climate change impacts unfavorable tourism spots. The methodology investigates hypothetical scenarios of climate variability and attempts to describe the quality of evidence to facilitate readers' careful, critical engagement. Secondary data is used to identify sustainability issues such as environmental, social, and economic viability. To better understand the problem, gathered the information in this report from various media outlets, research agencies, policy papers, newspapers, and other sources. This review is a sectorial assessment of climate change mitigation and adaptation approaches worldwide in the aforementioned sectors and the associated economic costs. According to the findings, government involvement is necessary for the country's long-term development through strict accountability of resources and regulations implemented in the past to generate cutting-edge climate policy. Therefore, mitigating the impacts of climate change must be of the utmost importance, and hence, this global threat requires global commitment to address its dreadful implications to ensure global sustenance.

Divergences of soil carbon turnover and regulation in alpine steppes and meadows on the Tibetan Plateau

The grasslands of the Tibetan Plateau store approximately 2.5% of global soil organic carbon (SOC) and considerable soil inorganic carbon (SIC) and have the potential to become a vast carbon source or sink as climate change progresses. However, the soil carbon (C) sequestration mechanisms that occur across large-scale natural gradients remain unclear. Here, humic substances (HS) were utilized to trace soil C turnover at 0-20 cm, and we compared divergences among three main grassland types (alpine meadow, alpine steppe, and artificial plantation) using structural equation modeling (SEM). The results showed that the alpine meadows sequestered the most soil C (63.99 ± 4.41 g kg^-1 SOC and 4.11 ± 0.63 g kg^-1 SIC), sequestering 2-3 times more than the alpine steppe ecosystems (19.78 ± 1.98 g kg^-1 SOC and 9.21 ± 0.66 g kg^-1 SIC). The alpine steppe and artificial plantation regions have strong C sink potential due to their low C/N ratios (P < 0.05). Importantly, SIC played an important role in the alpine steppes, accounting for nearly 26-37% of soil C. The ratios of recalcitrant HS to SOC were estimated as 46.50%, 65.09%, and 78.17% in the alpine meadow, alpine steppe, and artificial plantation ecosystems, respectively, indicating that SOC in the alpine meadow was the most sensitive to climate change. Fulvic acid (FA) accounted for 50.86% of SOC in the 0-20-cm interval, contributing most to the formation of SOC in all vegetation types. In addition, in contrast to climatic controls on soil C turnover in the alpine meadow, climate conditions rarely controlled C turnover in the alpine steppe. Moreover, sand and silt were the main soil minerals involved in C turnover in alpine meadow and alpine steppe ecosystems, respectively. Our study improves understanding of the mechanism by which soil C sinks form on the Tibetan Plateau under warming and wetting conditions.

Viability of a practical multicyclic sorption-based water harvester with improved water yield

Sorption-based atmospheric water harvesting (SAWH) has emerged as an attractive way to relieve water scarcity. However, the daily water yield of currently reported SAWH devices remains low to satisfy the rising demand for drinking water. The sorption and desorption kinetics, long-term stability and especially facile scaling-fabrication of adsorbents and scaled-up device implementation have become the bottleneck to such large-scale SAWH application. To overcome these challenges, an air-cooled SAWH device was fabricated to investigate its atmospheric water harvesting (AWH) performance under real island climate and its feasibility of multicyclic operation. Under monocyclic operation, the device demonstrated the superior water productivity as much as 3.9 kg day^-1, or 0.39 kg_water kg_adsorbent^-1 day^-1, at 31 °C and 70% RH, with a thermal efficiency of 25.4% (desorption at 94 °C). The SAWH device demonstrated successful water production through 2 adsorption-desorption cycles within one day, with increased thermal efficiency to as high as 32.2% and increased water harvesting performance up to 0.42 kg_water kg_adsorbent^-1 day^-1 by 20-90%. This is the first demonstration in multicyclic SAWH at large scales, holding the promise of large-scale and practical water supply in island areas while opening up new applications such as indoor dehumidification.

Assessment of Land Use Land Cover Changes and Future Predictions Using CA-ANN Simulation for Selangor, Malaysia

Land use land cover (LULC) has altered dramatically because of anthropogenic activities, particularly in places where climate change and population growth are severe. The geographic information system (GIS) and remote sensing are widely used techniques for monitoring LULC changes. This study aimed to assess the LULC changes and predict future trends in Selangor, Malaysia. The satellite images from 1991–2021 were classified to develop LULC maps using support vector machine (SVM) classification in ArcGIS. The image classification was based on six different LULC classes, i.e., (i) water, (ii) developed, (iii) barren, (iv) forest, (v) agriculture, and (vi) wetlands. The resulting LULC maps illustrated the area changes from 1991 to 2021 in different classes, where developed, barren, and water lands increased by 15.54%, 1.95%, and 0.53%, respectively. However, agricultural, forest, and wetlands decreased by 3.07%, 14.01%, and 0.94%, respectively. The cellular automata-artificial neural network (CA-ANN) technique was used to predict the LULC changes from 2031–2051. The percentage of correctness for the simulation was 82.43%, and overall kappa value was 0.72. The prediction maps from 2031–2051 illustrated decreasing trends in (i) agricultural by 3.73%, (ii) forest by 1.09%, (iii) barren by 0.21%, (iv) wetlands by 0.06%, and (v) water by 0.04% and increasing trends in (vi) developed by 5.12%. The outcomes of this study provide crucial knowledge that may help in developing future sustainable planning and management, as well as assist authorities in making informed decisions to improve environmental and ecological conditions.

Base Flow Variation and Attribution Analysis Based on the Budyko Theory in the Weihe River Basin

The composition and change of runoff are closely related to climate change and human activities. To design effective watershed water resources management measures, there is a need for a clear understanding of the impact of climate change and human activities on baseflow and surface runoff. The purpose of this essay is to quantify their impact on the annual total stream flow, surface runoff, and base flow in the Weihe River Basin (WRB) using a two-stage annual precipitation partitioning method, wherein the surface runoff and base flow are separated from the measured total flow by using a one-parameter digital filter method for which the common filter parameter value is 0.925. The stream flow records were split into two periods: 1960–1970 (pre-change period) and 1971–2005 (post-change period) based on the hydrological breakpoints detected. We found that climate change and human activities have different impacts on base flow and surface runoff. We attributed the decrease in surface runoff due to climate change accounting for 76–78%, while we determined that human activities were responsible to the decrease in base flow accounting for 59–73% of the total observed change. We concluded that both climate change and human beings contributed to the hydrologic change through different hydrological processes: climate change dominated the surface runoff change, while human influences controlled the base flow change. To achieve the expected goals of ecological restoration, appropriate measures must be taken by watershed management in the WRB to mitigate the likely impacts of climate change on water hydrology.

Alleviation of Ultrafiltration Membrane Fouling by ClO2 Pre-Oxidation: Fouling Mechanism and Interface Characteristics

In order to alleviate membrane fouling and improve removal efficiency, a series of pretreatment technologies were applied to the ultrafiltration process. In this study, ClO₂ was used as a pre-oxidation strategy for the ultrafiltration (UF) process. Humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA) were used as three typical organic model foulants, and the mixture of the three substances was used as a representation of simulated natural water. The dosages of ClO₂ were 0.5, 1, 2, 4, and 8 mg/L, with 90 min pre-oxidation. The results showed that ClO₂ pre-oxidation at low doses (1–2 mg/L) could alleviate the membrane flux decline caused by humus, polysaccharides, and simulated natural water, but had a limited alleviating effect on the irreversible resistance of the membrane. The interfacial free energy analysis showed that the interaction force between the membrane and the simulated natural water was also repulsive after the pre-oxidation, indicating that ClO₂ pre-oxidation was an effective way to alleviate cake layer fouling by reducing the interaction between the foulant and the membrane. In addition, ClO₂ oxidation activated the hidden functional groups in the raw water, resulting in an increase in the fluorescence value of humic analogs, but had a good removal effect on the fluorescence intensity of BSA. Furthermore, the membrane fouling fitting model showed that ClO₂, at a low dose (1 mg/L), could change the mechanism of membrane fouling induced by simulated natural water from standard blocking and cake layer blocking to critical blocking. Overall, ClO₂ pre-oxidation was an efficient pretreatment strategy for UF membrane fouling alleviation, especially for the fouling control of HA and SA at low dosages.

Enhanced arsenic migration in tailings soil with the addition of humic acid, fulvic acid and thiol-modified humic acid

Humus is an important parameter to affect the environmental fate of arsenic (As) in tailing soil. According to the batch and column experiment, the effects of humus (HS) including humic acid (HA), fulvic acid (FA) on the As release and basic properties of soil were studied in the soil from a mining region. In addition, HA was modified by 3-mercaptopropyltrimethoxysilane (3-MPTS) with different sulfur content (S%) to improve the release capacity of As. The results indicated that HS could destroy the binding of As with Fe, Mn, Al and Ca without affecting the basic properties of tailings soil, thus achieving the co-release of As and associated metals. Besides, the As release capacity of FA (25.47 %) was slightly higher than that of HA (21.90 %). The ability of thiol-modified HAs to release As from tailings soil after being modified with different S% of 3-MPTS was significantly improved, of which 2 % had the best treatment. The thiol groups (-SH) reached 45.00 % of total S. With the increase of S%, the surface thoil content, aromatization degree and total reduction capacity (TRC) of HA increased. The study demonstrated that HS and thiol-modified HA could promote the migration of As and could advance the treatment of heavy metal contaminated tailing soil.

The influence of the physicochemical properties of sediment on the content and ecotoxicity of trace elements in bottom sediments

The sorption mechanisms of the trace elements in bottom sediment are not fully understood. The study aim was to analyse the effect sorption capacity of bottom sediments on the content of trace elements and the bottom sediment ecotoxicity. The study found higher content of trace elements caused higher potential toxicity of bottom sediments. However, the PCA analysis indicated that ecotoxicity to Heterocypris incongruens was not related to the trace element content in the sediments. It was found that some of the physicochemical properties of bottom sediments determine the behavior of the test organism. The study revealed a strong relationships between the properties of bottom sediments and trace element sorption, which results from significant differences in the carbonate and organic matter contents. The obtained relationships showed a significant role in trace element sorption of negatively dissociating functional groups (carboxyl, phenolic, alcohol, and carbonyl groups) of Cha, Cfa, Cnh and DOC fraction and of clay minerals. Positive correlation between the metal content and the volume of ultramicropores, cryptopores and residual pores suggest that these pore groups contain reactive sites capable of effective element sorption. In contrast, larger pores turned out to be of marginal importance in trace elements sorption, probably participating only in their migration within the bottom sediment structure. An understanding of the above factors will provide comprehensive information on the fate of trace elements in aquatic systems.

Effects of temperature and microorganism densities on disinfection by-product formation

This study investigated the role of microorganisms on the correlation between temperature changes and disinfection by-product formation in natural waters. Climate changes have resulted in an increase in the global surface temperature. Studies have revealed that increases in temperature may change the composition of dissolved organic matter (DOM), which may contain major disinfection by-product (DBP) precursors. This change in the DOM composition may affect DBP formation after conventional water treatment processes. Understanding the role of microorganisms in DOM composition as well as DBP formation and speciation is critical for controlling DBP formation. In this study, laboratory stimulatory experiments were conducted on water samples from various sources, at various temperatures, and with various microbial concentrations. The results revealed a decreasing trend of dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), and haloacetic acid formation potential (HAAFP) at high temperature incubations irrespective of microbial concentrates. This result may be attributed to the fact that microorganism activities or concentrations in water increase at higher temperatures, which may result in higher DOC consumption and lower DBP formation. Water samples spiked with bacteria concentrates exhibited higher THMFP or HAAFP reduction than did samples without bacteria concentrates. A higher biomass in water may contribute to a higher consumption of DOC and consequently lower DBP formation potentials, especially at high incubation temperatures.

Evapotranspiration Trends and Interactions in Light of the Anthropogenic Footprint and the Climate Crisis: A Review

Evapotranspiration (ET) is a parameter of major importance participating in both hydrological cycle and surface energy balance. Trends of ET are discussed along with the dependence of evaporation to key environmental variables. The evaporation paradox can be approached via natural phenomena aggravated by anthropogenic impact. ET appears as one of the most affected parameters by human activities. Complex hydrological processes are governed by local environmental conditions thus generalizations are difficult. However, in some settings, common hydrological interactions could be detected. Mediterranean climate regions (MCRs) appear vulnerability to the foreseen increase in ET, aggravated by precipitation shifting and air temperature warming, whereas in tropical forests its role is rather beneficial. ET determines groundwater level and quality. Groundwater level appeared to be a robust predictor of annual ET for peatlands in Southeast Asia. In semi-arid to arid areas, increases in ET have implications on water availability and soil salinization. ET-changes after a wildfire can be substantial for groundwater recharge if a canopy-loss threshold is surpassed. Those consequences are site-specific. Post-fire ET rebound seems climate and fire-severity-dependent. Overall, this qualitative structured review sets the foundations for interdisciplinary researchers and water managers to deploy ET as a means to address challenging environmental issues such as water availability.

Molecular properties of the Humeome of two calcareous grassland soils as revealed by GC/qTOF-MS and NMR spectroscopy

A Humeomic fractionation revealed the humus molecular composition of two uncropped calcareous soils of Northern France and differentiated the soils Humeome by extracting humic components first unbound to the organo-mineral matrix and then liberated from their progressively stronger intermolecular and intramolecular ester and ether linkages. We separated organo- (ORG1-3) and water-soluble (AQU2 and AQU4) fractions, a final extractable fraction (RESOM) and soil residues. Organo-soluble fractions were studied by GC coupled with high-resolution mass spectrometry (GC/qTOF-MS), all fractions underwent mono- and two-dimensional liquid-state NMR (except for the iron-rich AQU4 fraction), while solid-state ¹³C-CPMAS-NMR spectroscopy analyzed soil residues. The Calcaric Leptosol (A) showed a larger mass extraction than the Calcaric Cambisol (B), and a greater cumulative C and N content in its Humeome. Both soils showed the greatest weight yield for AQU4 fraction, followed by ORG2, RESOM, ORG1, AQU2, and ORG3. ORG2 was the most differentiating fraction between the two soils for both compound concentration and diversity, showing a larger C content for soil A than for soil B and a different distribution in aromatic compounds, fatty acids, and dicarboxylic acids. No significant differences between soils were found for ORG 3, suggesting similar processes of OM stabilization for its recalcitrant components, mostly hydrophobic esters of alkanoic, hydroxy, and aromatic acids with linear alkanols. We confirmed that Humeomic fractionation coupled to advanced analytical instrumentations enabled a detailed molecular characterization of the soil Humeome and differentiated between the two calcareous grassland soils and the other soils previously subjected to Humeomics.