A water quality management strategy for regionally protected water through health risk assessment and spatial distribution of heavy metal pollution in 3 marine reserves

Role of phosphate in microalgal-bacterial symbiosis system treating wastewater containing heavy metals

Phosphorus is one of the important factors to successfully establish the microalgal-bacterial symbiosis (MABS) system. The migration and transformation of phosphorus can occur in various ways, and the effects of phosphate on the MABS system facing environmental impacts like heavy metal stress are often ignored. This study investigated the roles of phosphate on the response of the MABS system to zinc ion (Zn2+). The results showed that the pollutant removal effect in the MABS system was significantly reduced, and microbial growth and activity were inhibited with the presence of Zn2+. When phosphate and Zn2+ coexisted, the inhibition effects of pollutants removal and microbial growth rate were mitigated compared to that of only with the presence of Zn2+, with the increasing rates of 28.3% for total nitrogen removal, 48.9% for chemical oxygen demand removal, 78.3% for chlorophyll-a concentration, and 13.3% for volatile suspended solids concentration. When phosphate was subsequently supplemented in the MABS system after adding Zn2+, both pollutants removal efficiency and microbial growth and activity were not recovered. Thus, the inhibition effect of Zn2+ on the MABS system was irreversible. Further analysis showed that Zn2+ preferentially combined with phosphate could form chemical precipitate, which reduced the fixation of MABS system for Zn2+ through extracellular adsorption and intracellular uptake. Under Zn2+ stress, the succession of microbial communities occurred, and Parachlorella was more tolerant to Zn2+. This study revealed the comprehensive response mechanism of the co-effects of phosphate and Zn2+ on the MABS system, and provided some insights for the MABS system treating wastewater containing heavy metals, as well as migration and transformation of heavy metals in aquatic ecosystems.

Spatio-seasonal patterns and sources of major ions in the Longjiang River catchment, Southern China

River water quality is closely related to the major ion sources and hydrological conditions. However, there is a limited cognition about the geochemical sources and the seasonal variations of major ions. Thus, in this study, a total of 90 water samples were collected from the Longjiang River and its three tributaries in the dry and wet seasons. The samples were analyzed, including major ion concentrations and physicochemical parameters. Statistical analysis, such as correlation analysis and principal component analysis (PCA), was employed to investigate the spatial and seasonal variations in major ion composition and their respective sources. Our study revealed that the predominant major ions in the studied samples are Ca2+, Mg2+, HCO - 3, and SO2 - 4. Most of ions exhibited notable spatial disparities attributable to variations in geological settings and human activities. Regions characterized by igneous rock outcrops tend to exhibit higher levels of K+ and Na+, while areas with higher population densities in the middle and downstream segments show elevated concentrations of Cl-, NO - 3, SO2 - 4, Na+, and K+. The observed peak SO2 - 4 levels may be attributed to active mining operations. Most parameters displayed higher values in flood season than those in dry season due to dilution effects. Stoichiometric analysis indicated that carbonate weathering inputs contribute to over 85% of the mean total cation concentrations in the water, followed by contributions from silicates, atmospheric deposition, and anthropogenic inputs. On the whole, although the water quality remains non-polluted and is suitable for drinking and irrigation purposes, the enrichment of SO2 - 4 and NO - 3 may contribute to water eutrophication. Caution is warranted during the dry season due to reduced water flow resulting from dam interceptions and limited dilution capacity, potentially leading to elevated pollutant concentrations. Taken together, our results provided a scientific basis for water quality managements of monsoon rivers.

Source identification of sedimentary organic carbon in coastal wetlands of the western Bohai Sea

Coastal wetlands play a vital role in mitigating climate change, yet the characteristics of buried organic carbon (OC) and carbon cycling are limited due to difficulties in assessing the composition of OC from different sources (allochthonous vs. autochthonous). In this study, we analyzed the total organic carbon (TOC) to total nitrogen (TN) ratio (C/N), stable carbon isotope (δ13C) composition, and n-alkane content to distinguish different sources of OC in the surface sediments of the coastal wetlands on the western coast of the Bohai Sea. The coupling of the C/N ratio with δ13C and n-alkane biomarkers has been proved to be an effective tool for revealing OC sources. The three end-member Bayesian mixing model based on coupling C/N ratios with δ13C showed that the sedimentary OC was dominated by the contribution of terrestrial particulate organic matter (POM), followed by freshwater algae and marine phytoplankton, with relative contributions of 47 ± 21 %, 41 ± 18 % and 12 ± 17 %, respectively. The relative contributions of terrestrial plants, aquatic macrophytes and marine phytoplankton assessed by n-alkanes were 56 ± 8 %, 35 ± 9 % and 9 ± 5 % in the study area, respectively. The relatively high salinity levels and strong hydrodynamic conditions of the Beidagang Reservoir led to higher terrestrial plants source and lower aquatic macrophytes source than these of Qilihai Reservoir based on the assessment of n-alkanes. Both methods showed that sedimentary OC was mainly derived from terrestrial sources (plant-dominated), suggesting that vegetation plays a crucial role in storing carbon in coastal wetlands, thus, the coastal vegetation management needs to be strengthened in the future. Our findings provide insights into the origins and dynamics of OC in coastal wetlands on the western coast of the Bohai Sea and a significant scientific basis for future monitoring of the blue carbon budget balance in coastal wetlands.

Trace metals in commercial seafood products (canned, pickled and smoked): Comparison, exposure and health risk assessment

This study used inductively coupled plasma and mass spectrometry, followed by microwave digestion, to assess the concentration of six trace metals (Cr, Ni, As, Cd, Hg, and Pb) in three canned products (tuna in oil [TIO], sardine in oil [SIO], and mackerel in oil [MIO]), two pickled products (prawn pickle [PP] and fish pickle [FP]), and one smoked product (masmin) collected from Tuticorin market, southern India. Trace metal (TM) levels in canned, pickled, and smoked fish varied from 0.01 to 1.48, 0.009 to 0.94, and 0.08 to 4.13 mg/kg, respectively. The concentration of TMs in the seafood was observed in the following order: As > Cr > Pb > Ni > Cd > Hg. Regarding their accumulation in the seafood products, masmin showed the highest levels followed by SIO, MIO, TIO, FP, and PP. The results revealed that smoked products showed higher TM concentrations, followed by canned and pickled products. The level of TMs in seafood products was below the maximum residue limit set by the European Commission (EC/1881/2006) and the Food Safety and Standards Authority of India (FSSAI). Risk assessment for consumer health implied that the evaluated target hazard quotient (THQ < 1), hazard index (HI < 1), and target cancer risk (TCR < 1.E-04) values did not exceed their guideline values and did not cause non-carcinogenic and carcinogenic health impacts through seafood product consumption. The pollution index (Pi) values of TMs in seafood products ranged from 0.01 to 0.7, with As and Cd showing the lowest and highest values, which were below 0.7, indicating their safety for consumption. The metal pollution index (MPI) for TMs in seafood ranged from 9.E-05 to 0.007, with the lowest and highest values associated with PP and TIO products. The MPI value for seafood products was below 1, signifying low TMs accumulation, suggesting the safety of seafood for consumption. The maximum seafood meal consumption limit (CRmm) was calculated, showing that adults can safely consume > 16 meals/month without chronic or acute toxicity. The results of this study suggest that the accumulation of TMs in the analyzed seafood product was below the health guidelines and pollution index values, making it suitable for smooth domestic and international export as well as safe consumption.

Source apportionment of heavy metal(loid)s in sediments of a typical karst mountain drinking-water reservoir and the associated risk assessment based on chemical speciations

As important place for water storage and supply, drinking-water reservoirs in karst mountain areas play a key role in ensuring human well-being, and its water quality safety has attracted much attention. Source apportionment and ecological risks of heavy metal(loid)s in sediments of drinking-water reservoir are important for water security, public health, and regional water resources management, especially in karst mountain areas where water resources are scarce. To expound the accumulation, potential ecological risks, and sources of heavy metal(loid)s in a drinking-water reservoir in Northwest Guizhou, China, the surface sediments were collected and analyzed based on the combined use of the geo-accumulation index (Igeo), sequential extraction (BCR), ratios of secondary phase and primary phase (RSP), risk assessment code (RAC), modified potential ecological risk index (MRI), as well as the positive matrix factorization methods. The results indicated that the accumulation of Cd in sediments was obvious, with approximately 61.9% of the samples showing moderate to high accumulation levels, followed by Pb, Cu, Ni, and Zn, whereas the As and Cr were at low levels. A large proportion of BCR-extracted acid extractable and reducible fraction were found in Cd (72.5%) and Pb (40.3%), suggesting high bioavailability. The combined results of RSP, RAC, and MRI showed that Cd was the major pollutant in sediments with high potential ecological risk, while the risk of other elements was low. Source apportionment results of heavy metal(loid)s indicated that Cd (75.76%) and Zn (23.1%) mainly originated from agricultural activities; As (69.82%), Cr (50.05%), Cu (33.47%), and Ni (31.87%) were associated with domestic sources related to residents' lives; Cu (52.36%), Ni (44.57%), Cr (34.33%), As (26.51%), Pb (24.77%), and Zn (23.80%) primarily came from natural geological sources; and Pb (47.56%), Zn (22.46%) and Cr (13.92%) might be introduced by mixed sources of traffic and domestic. The contribution ratios of the four sources were 18.41%, 36.67%, 29.48%, and 15.44%, respectively. Overall, priority control factors for pollution in relation to agricultural sources included Cd, while domestic sources are primarily associated with As. It is crucial to place special emphasis on the impacts of human activities when formulating pollution prevention and control measures. The results of this study can provide valuable reference and insights for water resources management and pollution prevention and control strategies in karst mountainous areas.

Multivariate analysis of trace elements in starry sturgeon (Acipenser stellatus) spine in different areas of the Caspian Sea

Sturgeons are one of the most valuable species in the Caspian Sea. There, habitation of the seabed and feeding on benthic organisms makes this species a good indicator of trace element status. Thus, we aimed to determine the concentrations of 31 trace elements in the pectoral fin spine of starry sturgeons, and to evaluate the relationships between the different chemical elements. For this, a total of 40 starry sturgeons were obtained in a repopulation programme from the coastal waters north and south of the Caspian Sea. First, we used a multivariate analysis of variance to establish the differences between zones. Later, to assess relationships between trace elements, we used principal component analysis and cluster analysis. In general, the concentration of many trace elements did not vary between zones. However, some elements, including mercury or arsenic, were found in the north areas at higher concentrations.

Evaluating Groundwater Quality in the Asante Akyem Central District of Ghana

Groundwater is the primary water supply source for many people living on the surface of the earth. They depend on this valuable resource for their daily needs. But this natural resource is continuously being threatened by both natural and anthropogenic activities. Therefore, continuous monitoring and assessment of the water quality of this resource is important to keep check of the effects of water contaminants especially on human health. This study assessed the levels of Fe, Cd, Mn, and Hg in hand-dug wells at 4 communities (Ahyiayem, Odumasi Zongo, Apeboaso, and Kwaakyewaso) in the Asante Akyem Central District of Ghana and evaluated its sources and potential health risk associated with their exposure. These communities are known for illegal small-scale mining. The analysis also included other water quality parameters such as pH, nitrate, potassium, sodium, total hardness, calcium hardness, Phosphate, chloride, and total dissolved solids. From the research, there was no carcinogenic health risk to the communities concerning Fe, Mn, and Hg through ingestion and dermal contact because the hazard quotients and health hazard indices recorded in both adults and children were below one (<1). However, from the research, Cd exhibited carcinogenic health risk because its Cancer risk (CR) index exceeded 10-6 for both adults and children. This implies that there is a risk of cancer infection from ingesting water from the hand-dug wells in the study areas. According to the analysis of the Water Quality Index (WQI), the wells at Ahyiayem, Apeboaso, and Kwaakyewaso recorded indexes that were between 15 and 50, signifying that the hand-dug wells in these communities are safe for human consumption. However, about 90% of the wells at Odumasi Zongo recorded WQI values that were between 80 and 320. This means the hand-dug wells at Odumasi Zongo are highly polluted and not safe for human consumption.

Evaluation of heavy metals contamination in cereals, vegetables and fruits with probabilistic health hazard in a highly polluted megacity

Heavy metals (HMs) contamination in foodstuffs could pose serious health issues for public health and humans are continually exposed to HMs through the consumption of cereals, fruits, and vegetables. The present study was conducted to assess 11 HMs in foodstuffs to investigate pollution levels and health risks to children and adults. The mean contents of Cd, Cr, Cu, Ni, Zn, Fe, Pb, Co, As, Mn and Ba in foodstuffs were 0.69, 2.73, 10.56, 6.60, 14.50, 9.63, 2.75, 0.50, 0.94, 15.39 and 0.43 mg/kg, respectively and the concentration of Cd, Cr, Cu, Ni and Pb were higher than maximum permissible concentrations (MPCs) showing that these foods may be contaminated with metals and constitute a danger to consumers. Vegetables had relatively higher metal contents followed by cereals and fruits. The average value of the Nemerrow composite pollution index (NCPI) for cereals, fruits, and vegetables were 3.99, 6.53, and 11.34, respectively indicating cereal and fruits were moderately contaminated whereas vegetables were heavily contaminated by the studied metals. The total estimated daily and weekly intakes for all studied metals were higher than the maximum tolerable daily intake (MTDI) and provisional tolerance weekly intake (PTWI) recommended by FAO/WHO. The target hazard quotients and hazard index of all studied metals exceeded the standard limit for adults and children suggesting significant non-carcinogenic health hazards. The total cancer risk value of Cd, Cr, Ni, Pb, and As from food intake exceeded the threshold range (1.0E-04), suggesting potential carcinogenic risks. Based on practical and sensible evaluation techniques, the current work will assist policymakers in controlling metal contamination in foodstuffs.

Spatio-temporal variability and potential health risks assessment of heavy metals in the surface water of Awash basin, Ethiopia

Increasing urbanization and industrialization are impacting on water quality globally. In the Awash River basin, Ethiopia, these drivers are impacting on water quality with further impacts created due to changes in water management releasing geogenic contaminants. The resulting water quality has potential to cause significant ecological and human health impacts. The physicochemical and heavy metals saptio-temporal variability and their associated risks to human health and ecology were assessed across twenty sampling stations in the Awash River basin. Over twenty-two physicochemical and ten heavy metals parameters were analyzed using different instruments including inductively coupled plasma mass spectrometer (ICP-MS). Elevated levels of heavy metals (As, V, Mo, Mn, and Fe) were detected in the surface water, surpassing the drinking water quality standards set by the World Health Organization (WHO). Seasonal variation was evident with peak concentration of As, Ni, Hg, and Cr were recorded in the dry season. A water quality index, hazard quotient, hazard index, heavy metal pollution index and heavy metal evaluation index were formulated to assess the potential risks to both human health and the environment. The highest values of heavy metal pollution index (HPI) above the threshold (>100) were observed in stations at Lake Beseka with HPI values ranged from 105 to 177. Similarly, the highest values of the heavy metals evaluation index (HEI) were observed in stations situated at cluster 3. The evaluation of health risk that is not related to cancer through hazard quotient demonstrated that in the case of both dermal and ingestion contact, cluster C3 > C1 > C4 > C2 and C3 > C4 > C2 > C1 were observed in children and adults, respectively. Overall, measures to reduce potential pollution risks must be taken in accordance with the standards in the river basin. Nevertheless, further research on the toxicity of heavy metals that pose risks to human health is also necessary.

Trace elements in surface sediments from Xinyanggang River of Jiangsu Province, China: Spatial distribution, risk assessment and source appointment

The Xinyanggang River in Yancheng City, one of the essential rivers entering the Yellow sea, has imported abundant pollutants to the coast of Jiangsu Province. Trace elements (Cr, Ni, Cu, Zn, As, Rb, Sr, Mo, Pb, Th, U, Sc, Ga, Se, Zr, Nb, and Sn) in surface sediments in the Xinyanggang River were measured to analyze the spatial distribution, risk assessment, and source appointment. The results showed that the parts of 17 trace elements presented high average values in river sediments, such as Zr (309.19 mg/kg), Sr (182.72 mg/kg), Zn (77.67 mg/kg), and Cr (70.63 mg/kg). Compared with some coastal rivers, the Xinyanggang River was polluted by certain trace elements, such as Cr, Zn, and As. Based on the analysis of the enrichment factor (EF), the contamination factor (CF), the pollution load index (PLI), and the geoaccumulation index (I_geo), trace elements in sediments showed unpolluted to moderate contamination and mild to moderate enrichment. Among them, Zn, Pb, and Sn were highly polluted. The multivariate analysis, the principal component analysis-multiple linear regression (APCS-MLR) model, and the Unmix model identified four contributing trace element sources. Cr, Th, U, Se, Zr, and Nb originated from manufacturing industries and hydrodynamic transport erosion. Ni, Rb, Sc, and Ga were attributed to natural source. Cu, Zn, Mo, Pb, and Sn were contributed from mixed sources including industrial wastewater and transportation emissions. As and Sr were associated mainly with mixed sources of agriculture and combustion. These four sources of metals accounted for 22.5 %, 5.7 %, 15.3 %, and 11.1 % by using the APCS-MLR model, whereas 22.9 %, 39.7 %, 17.5 %, and 19.9 % by using the Unmix model, respectively.

Hazardous toxic metal(loid)s in top- and deep-soils during the transformation of aquaculture ponds restored to farmland

The pollution risks due to the soil migration of toxic metal(loid)s (TMs) are a greatly hazard to ecological environment as well as animal and human health. Previous studies have primarily focused on surface contamination while deep soil layers often contain dangerous levels of TMs. We used restored wheat and rice farmlands from aquaculture ponds as a case study to examine the ecological risk and distribution of TMs in soil profiles. The elements Cu, Zn, Cr, Cd, Hg and As were markedly enriched in the 60-180 cm soil layers of restored farmland, and their concentrations decreased in the several depths as follows: 120-180 cm > 60-120 cm > 0-60 cm. Concentrations of TMs were 9.5-128 % greater in the restored farmlands relative to farmlands not exposed to aquaculture practices. Cadmium and mercury were the most serious contaminants and increased the overall ecological risk. The subsoil of wheat farming system had the highest pollution risk versus the restored rice farmland at 60-120 cm due to elevated levels of Cu, Zn and Pb. Toxic metal(loid)s might be derived from natural sources in deep soil of conventional farmland whereas aquaculture practices were found to constitute the major contribution in the subsoil of restored farmland. Our results indicated that the TMs that were buried in deep soil layers migrated upward and were a significant pollution risk. Urgent actions should be taken to identify and alleviate the contamination sources of these deep soils in addition to the conventional leaching and migration processes of surface contaminants.

Spatial Distribution, Source Analysis and Health Risk Study of Heavy Metals in the Liujiang River Basin in Different Seasons

Three high-frequency sampling and monitoring experiments were performed at the Lutang and Luowei transects of the Liujiang River entrance and at the southeast exit of the Liuzhou during 2019 for the purpose of assessing physico-chemical variables and human health hazards of water heavy metals in different rainfall processes. There were significant seasonal variations in concentrations of 11 heavy metals and most variables showed higher levels during the dry season. The distribution of heavy metals in the Liuzhou area varied significantly by region. Pollution source analysis indicated distinct seasons of wetness and dryness. The dry season is dominated by anthropogenic activities, while the wet season is dominated by natural processes. The results of hazard quotient (HQ) and carcinogenic risk (CR) analysis showed that the health risk of non-carcinogenic heavy metals in the wet season is slightly higher than that in the dry season. Seasonal changes in carcinogenic risk are the opposite; this is due to the combined influence of natural and human activities on the concentration of heavy metals in the river. Among them, Al was the most important pollutant causing non-carcinogenic, with As being a significant contributor to carcinogenic health risk. Spatially, the downstream Luowei transect has a high health risk in both the dry and rainy seasons, probably due to the fact that the Luowei transect is located within a major industrial area in the study area. There are some input points for industrial effluent discharge in the area. Therefore, high-frequency monitoring is essential to analyze and reduce the heavy metal concentrations in the Liujiang River during dry and wet seasons in order to protect the health of the residents in the area.

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

Environmental impact of COVID-19 imposed lockdown (2020) and the new normal condition (2021) on two different beaches of India (Ghoghla beach, Diu and Somnath beach, Veraval) were compared with the pre-lockdown era, 2013. The lockdown phase favored the natural restoration of the beaches and showed infinitesimal values of the parameters tested when compared with the pre-lockdown regime. However, the new normal situation in 2021 opened up the accessibility of these beaches to the tourists and pilgrims resulting in significant changes of water quality. The release of diluted sewage mixed with freshwater from the Somnath town to the sea has led to the drastic change in beach water quality. The mean cadmium concentration increased drastically in beach waters (Ghoghla: 1.35, 0.28 and 7.09 μg/L; Somnath: 0.45, 0.28 and 0.58 μg/L) during pre-to-post lockdown, respectively. However, post-lockdown resulted in the rise of toxic heavy metals in the sediments of Somnath beach but Ghoghla beach remained to be pristine which may be due to the Blue Flagship status. The total number of marine bacteria was higher during 2013 and 2021 when compared during lockdown describing greater human interventions. For instance, Vibrio spp. count in Ghoghla beach water during pre-lockdown phase was 7733 CFU/mL and this value reduced to 70 and 5 CFU/mL in the lockdown and post-lockdown phases. Interestingly, the diversity of planktonic and benthic components showed a different trend from pre-to-post lockdown due to significant change in the inorganic nutrients and metal bioaccumulation. To our knowledge, this will be the first comprehensive assessment to report the environmental and ecological health of Ghoghla beach and Somnath beach during the pre-to-post lockdown.

A suitable organic fertilizer substitution ratio could improve maize yield and soil fertility with low pollution risk

Organic fertilizer substitution (OFS) is an effective strategy for reducing the chemical fertilizer usage; however, the effects of different OFS ratios (OFSRs) on maize yield, soil fertility, and heavy metal pollution risk are still unclear. Therefore, determining a suitable OFSR is important. Through the pot experiment, no fertilizer (CK) and organic fertilizer substituting 0% (CF, chemical fertilizer alone), 8% (OF8), 16% (OF16), and 24% (OF24) of the chemical N fertilizer were set to investigate the effects of different OFSRs on maize growth and yield, soil properties (available nutrients, carbon fractions, and carbon pool indices), and nutrients and heavy metals in grain and soil. The results showed that OF8, OF16, and OF24 improved soil fertility by increasing soil organic carbon (SOC, by 10.05-16.26%) and its fractions, most middle- and micro-nutrients content, and carbon pool management index (CPMI, by 17.45-30.31%) compared with CF, while improving grain nutritional quality. However, they increased heavy metals content in grain and soil and their Nemerow comprehensive pollution index (NCPI, by 4.06-16.56% in grain and 2.55-5.57% in soil) but did not cause pollution. Among them, throughout the growth period, only OF8 treatment increased soil available nitrogen (AN), phosphorus (AP), and potassium (AK) content by 3.04-11.15%, 7.11-8.05%, and 0.12-6.05%, respectively, compared with CF, which thus significantly promoted maize growth and increased yield (by 35.65%); the NCPI of grain and soil was however lower than that OF16 and OF24. In conclusion, substitution ratio of 8% was considered ideal for promoting maize growth, improving yield and soil fertility, with a low pollution risk. The results of this study would aid in guiding the scientific application of OFS technology to agricultural production, thereby contributing to resource utilization of organic waste and sustainable agricultural development.

Contamination level, source identification and health risk assessment of potentially toxic elements in drinking water sources of mining and non-mining areas of Khyber Pakhtunkhwa, Pakistan

Accelerated mining activities have increased water contamination with potentially toxic elements (PTEs) and their associated human health risk in developing countries. The current study investigated the distribution of PTEs, their potential sources and health risk assessment in both ground and surface water sources in mining and non-mining areas of Khyber Pakhtunkhwa, Pakistan. Water samples (n = 150) were taken from selected sites and were analyzed for six PTEs (Ni, Cr, Zn, Cu, Pb and Mn). Among PTEs, Cr showed a high mean concentration (497) μg L^-1, followed by Zn (414) μg L^-1 in the mining area, while Zn showed the lowest mean value (4.44) μg L^-1 in non-mining areas. Elevated concentrations of Ni, Cr and a moderate level of Pb in ground and surface water of Mohmand District exceeded the permissible limits set by WHO. Multivariate statistical analyses showed that the pollution sources of PTEs were mainly from mafic-ultramafic rocks, acid mine drainage, open dumping of mine wastes and mine tailings. The hazard quotient (HQ) was the highest for children relative to that for adults, but not higher than the USEPA limits. The hazard index (HI) for ingestions of all selected PTEs was lower than the threshold value (HI_ing < 1), except for Mohmand District, which showed a value of HI >1 in mining areas through ingestion. Moreover, the carcinogenic risk (CR) values exceeded the threshold limits for Ni and Cr set by the USEPA (1.0E-04-1.0E-06). In order to protect the drinking water sources of the study areas from further contamination, management techniques and policy for mining operations need to be implemented.

Tracking the origin of trace metals in a watershed by identifying fingerprints of soils, landscape and river sediments

The identification of the spatial distribution of soil trace-elements and the contribution of different sources to the sediment yield is necessary for a better watershed and river water quality management. Until now, less attention has been paid to comprehensive assessments of sediment sources and soil trace-elements with respect to the suspended sediment production. The present study aimed at modelling the spatial distribution of soil trace-elements, quantifying the sediment sources apportionment and relating the landforms to polluted soils. Different techniques and approaches such as the Nemerow pollution index, machine learning algorithms (Random Forest (RF), generalised boosting methods (GBM), generalised linear models (GLM) and sediment fingerprinting were applied to the Kan watershed. A total of 79 soil samples having different Nemerow index values were considered for spatial modelling. Using statistical methods (Range test, Kruskal-Wallis and discrimination function analysis), an optimal set of tracers was selected. An unmixing model was applied to calculate the relative contribution of landforms for eight rainfall events. The results of the soil trace-element mapping showed that RF had the best performance with an accuracy of 83%. The evaluation of polluted soil areas showed that the landforms 'steep hills' and 'valley' contributed the most with 51% and 27% in the riparian zone, respectively. In addition, these landforms give a high contribution to sediment production in late-winter-spring events (29%) with a GOF (goodness of fit) of 0.65. The landform 'plain' had the highest contribution (28%) in sediment yield with a GOF of 0.72 in early-winter events. This means that the valley and steep hill landforms accelerate the transport of trace-elements across the watershed. Interestingly, the contribution of landforms varies during the year. Overall, the new proposed approach enables to better trace the origin of suspended sediments and trace-elements discharge into the river environment.

Study on spatial distribution, potential sources and ecological risk of heavy metals in the surface water and sediments at Shanghai Port, China

Heavy metal concentrations in surface waters and sediments of Shanghai port were measured to analyze the spatial distribution characteristics, sources and pollution degrees. The southern Shanghai port was heavily polluted by Cd, Pb, Cr and Cu in water, and the concentrations of Pb, Hg and Zn in sediments exceeded Effects Range Low. Cu, Pb, Cd and Cr in water were positively correlated in group, and they probably derived from industrial and domestic sewage, fossil fuel burning and vehicular pollution and represented 82.47 % of the contribution. Zn, Hg and As contaminations represented industrial and agricultural effluent sources and accounted for the remaining 17.53 %. Heavy metal pollution of Yangshan Port water was at high pollution, and the remaining sites were at low pollution. Most of the sampling sites were at moderate ecological risk in sediments, and the pollution of Cd, Hg and Zn were serious.

Characteristics and Assessment of Soil Heavy Metals Pollution in the Xiaohe River Irrigation Area of the Loess Plateau, China

Heavy metals in soil are a potential threat to ecosystems and human well−being. Understanding the characteristics of soil heavy metal pollution and the prediction of ecological risk are crucial for regional eco−environment and agricultural development, especially for irrigation areas. In this study, the Xiaohe River Irrigation Area in the Loess Plateau was taken as the study area, and the concentration, as well as their accumulation degree and ecological risk and distribution of soil heavy metals, were explored based on the geo−accumulation index (Igeo) and Hakanson potential ecological risk index methods. The results showed that the concentrations of soil heavy metals were all lower than the second grade Environmental Quality Standard for Soils of China. However, the average concentrations of Cu, Hg, Cd, Pb, Zn, Ni and As were higher than the above−mentioned standard. Compared with the soil background values of Shanxi Province, eight heavy metals of all samples presented different accumulation degrees, with the highest accumulation degree in Hg, followed by Cd, and the values were 11.3 and 4.0 times more than the background value, respectively. Spatially, the distribution of soil heavy metals in the Xiaohe River irrigation area was quite different, generating diverse pollution patterns with significant regional differences and complex transportation routes. The content of soil heavy metals in the Xiaohe River irrigation area was highly affected by land use types. The pollution degree varied with the distance to an urban area, declining from the urban area to suburban farmland, and the outer suburban farmland. Among these heavy metals, Hg and Cd were the principal contamination elements, and transportation, service industry and agricultural activities were the main potential contamination sources. The potential ecological risk of soil heavy metal positioned as follows: Hg > Cd > Pb > Zn > Cu > As > Ni > Cr. As indicated by the Hakanson potential ecological risk index strategies, except for the Wangwu examining site, the other six sampling sites experienced extremely strong risks, and as a whole, the entire study region was in a condition of incredibly impressive perils. Consequently, these results suggest that improving soil environmental investigation and assessment, setting up soil heavy metal contamination prevention and control innovation framework and reinforcing contamination source control are effective approaches for soil heavy metal contamination anticipation and control in irrigated areas of the Loess Plateau.

Gels based on calcium alginate/pillared bentonite: structural characterization and their use as cadmium removal agent

In this work, calcium alginate hydrogels with natural and pillared bentonites (0.5 and 5% w/w) were synthetized in two geometries (disks and beads) and their capacity to adsorb cadmium ion from aqueous media was evaluated. Pillarization effect on bentonite morphology was evidenced by SEM, XRD, LD and BET isotherms. Structure and swelling capacity of hydrogels were determined, showing that hydrogels beads with pillared clays presented the higher ability to retain water. Regarding cadmium adsorption capacity, the effect of pH media (3, 5 and 7), the contact time (0 to 320 min.) and the initial cadmium ion concentration (6 to 42 mg/L) were studied employing hydrogel beads. Regardless bentonite type and concentration, the optimal pH cadmium adsorption was 7, reaching the highest adsorption capacity (93%) for hydrogel with 0.5% natural bentonite. Besides, the equilibrium adsorption time was reached at 120 min for all studied hydrogels and experimental data fitted with a pseudo-second order kinetic model.

Sediment contamination by trace elements and the associated ecological and health risk assessment: A case study from a large reservoir (Turkey)

Although Keban Reservoir (KR) is Turkey's the second largest man-made reservoir, limited data are available on the contents of trace elements (TEs) in sediments of the KR. The concentrations of 23 less- and commonly-monitored TEs in the sediments from 49 sites in the reservoir were measured to assess health risks, contamination levels and ecological risks of TEs. Concerning median Enrichment Factor values of TEs, chromium (Cr), strontium (Sr) and nickel (Ni) showed moderate enrichment, while other TEs showed minimal enrichment. Pollution Load Index values ranged from 0.33 to 0.63, indicating no a multi-element contamination case in the study area. Low ecological risk was found at 47 sites, while moderate ecological risk was recorded at two sites. The PEC (probable effect concentration) values were exceeded for Ni and Cr. Although wastewater from leather processing factory partly contributed to Cr enrichment at site 2, all TEs mainly originated from lithogenic sources. Median hazard quotient (HQ) values of zirconium (Zr) and lanthanum (La) for children from sediment ingestion were above the risk threshold of unity (HQ = 4.81 and 1.39) and contributed 62.9% and 18.2% of the total health risk. Such high HQ values of Zr and La have never been reported in the literature. Hazard index values for children exceeded those for adults, indicating that children are more vulnerable to health risks than adults. Carcinogenic risk values of arsenic (As) were within the acceptable limits. Our findings indicated that in a multi-element sediment study, some less-monitored elements such as Zr and La may have an important role in health risk assessment even if they are found in the sediment at low concentrations. Therefore, this study can be a model for future similar studies evaluating the health risks of multi-elements in sediments.

Surface water quality analysis using multivariate statistical techniques: a case study of Fars Province rivers, Iran

This study aimed to transform the input of a large dataset into the output of interpretable information. Hence, multivariate statistical methods were carried out to analyze physicochemical parameters in 34 rivers during a 17-year period (1997-2014). Cluster analysis divided the study area into spatially different riverine water quality sub-regions described in ascending order of water quality as severely polluted (SP), highly polluted (HP), polluted (P), moderately polluted (MP), lightly polluted (LP), and not polluted (NP). By diagnosing threats and identifying fragile zones, water contamination sources responsible for impaired water quality in the study area recognized as natural pollutants in LP, municipal wastes in P, discharge of industrial effluents in MP, natural geochemical formations in SP and HP, and superficial flows of agricultural lands in SP, HP, and MP. The dominant water type in each zone was classified into Na-Cl, Na-Cl, Na-Mg-Ca-Cl-SO₄, Na-Ca-Mg-Cl-SO₄, Na-Ca-Cl, and Ca-Mg-HCO₃-SO₄ groups for SP, HP, P, MP, LP, and NP, respectively. To explore aesthetic aspects of drinking water application, hazard quotient (HQ) was applied for children and adults in terms of ingestion and dermal exposure. Overall health risk assessment revealed the order of impacts of the secondary water quality parameters as Cl^-  > Na⁺  > total dissolved solids (TDS) > Ca²⁺  > SO₄^2-  > Mg²⁺. Furthermore, hazard index (HI) ranged from 0.011 to 31.439 and 0.010 to 30.122 for children and adults, respectively, indicating a potential health risk regarding chloride throughout the whole region excluding NP. To identify significant agents in water quality, principal component analysis extracted 3 varifactors (VFs), with the eigenvalues of 4.74, 1.19, and 0.85, respectively, explained about 83% of the variance. The most important parameters in the first factor were TDS, electrical conductivity, SAR, TH, Na⁺, Cl^-, and SO₄^2- accounting for 58% of the total variance. The most influenced parameters in the second and third factors were pH and HCO₃^-, respectively, with variance coverage of 26%. These factors indicated that the hydrochemical characteristics of the water originated by natural interactions (existing salt domes, evaporation, weathering, and soil erosion) and anthropogenic activities (fertilizer-rich flows of agro-fields and domestic/industrial disposals), which must be minimized in rivers to supply the population with hygienic water.

Seasonal Variation and Contamination Risk Assessment of Heavy Metals in Surface Sediment of an Estuary Alluvial Island in Eastern China

The heavy metal pollution of estuary wetlands caused by industrial and agricultural production activities has aroused widespread concern. The Hakanson Pollution index, Geo-accumulation index (I_geo) and Redundancy analysis were used to explore the seasonal variation and contamination risk of heavy metals in surface sediments. Results showed that the heavy metal concentrations were ranked in descending order: Cd > Cu > Zn > Pb > Cr. The analysis result of HPI and I_geo showed that there was a low level of heavy metal contamination both in summer and winter. Redundancy analysis showed that the correlation between heavy metals and physicochemical properties of sediment was significantly different in winter and summer. Our findings provide scientific support for the prevention of heavy metal pollution in estuary wetlands.

The Adsorption of Corn Stalk Biochar for Pb and Cd: Preparation, Characterization, and Batch Adsorption Study

Biochar adsorption emerges as a convenient and cheap treatment technology to cope with the metal pollution in wastewater. In this study, a biochar made from corn stalks was prepared and its adsorption characteristics for two heavy metals, Pb and Cd, were investigated by materials characterization and batch experiments. Biochar pyrolyzed from waste corn stalks at 400–600 °C, where biochar prepared at 600 °C (BC600) was used to perform following experiments. In materials characterization, the SEM images were initially used to reveal an obvious porous structure feature of corn stalk biochar, followed by XPS and FT-IR analyses unraveling the effects of functional groups in adsorption, especially for phenol and carboxyl groups. These functional groups provided vital adsorption sites. In batch experiment, batch experiments were conducted under different factors such as pH, temperature, and background ionic strength. The increase of pH and temperature can improve the adsorption capacity, whereas the ionic strength showed negative effects. The adsorption processes of both metals can be interpreted by fitting pseudo-first order model, as indicated in kinetic experiments, and the adsorption isotherm can be well described by the Langmuir model. Overall, this study revealed the characteristics of corn stalk biochar and deciphered the potential adsorption mechanisms.

Effect of Methylmercury Exposure on Bioaccumulation and Nonspecific Immune Respsonses in Hybrid Grouper Epinephelus fuscoguttatus × Epinephelus lanceolatus

Simple Summary

The head kidney was primary organ that accumulated methylmercury in hybrid grouper. Muscle tissue had lower methylmercury content than the head kidney and liver. Nonspecific immune responses and bioaccumulation of methylmercury were linked to hybrid grouper health.

Abstract

Mercury (Hg) is a dangerous heavy metal that can accumulate in fish and is harmful when consumed by humans. This study investigated the bioaccumulation of mercury in the form of methylmercury (MeHg) and evaluated nonspecific immune responses such as phagocytic activity and superoxide anion (O₂⁻) production in hybrid grouper (Epinephelus fuscoguttatus × E. lanceolatus). The hybrid grouper leukocytes were incubated with methylmercury chloride (CH₃HgCl) at concentrations of 10–10,000 µg/L to determine cell viability, phagocytic activity, and O₂⁻ production in vitro. Subsequently, the grouper were exposed daily to CH₃HgCl mixed in the experimental diets at concentrations of 0, 1, 5, and 10 mg/kg for 28 days. The bioaccumulation of MeHg in the liver, head kidney, and muscle tissue was measured, and the phagocytic activity and O₂⁻ production were evaluated. In vitro results indicated that cell viability was significantly lower than that of the control group at concentrations > 500 µg/L. The phagocytic rate and O₂⁻ production at concentrations ˃ 500 and ˃ 200 µg/L, respectively, were significantly lower than those of the control group. The dietary exposure demonstrated that MeHg accumulated more substantially in the liver and head kidney compared with the muscle tissue in the treatment groups. Moreover, the cumulative concentration significantly increased with higher concentrations and more days of exposure. The phagocytic rate and O₂⁻ production in the treatment groups were significantly lower than those in the control group from days 2 and 1, respectively. In conclusion, hybrid grouper accumulated significant MeHg in the liver and head kidney compared with the muscle tissue, and higher concentrations and more exposure days resulted in decreased cell viability, phagocytic activity, and O₂⁻ production.

Metal pollution in the Pearl River Estuary and implications for estuary management: The influence of hydrological connectivity associated with estuarine mixing

Understanding the metal pollution can help governments and estuary management groups manage metal inputs. Here, we comprehensively analyzed the behaviors of seven metals Cd, Zn, Cu, As, Pb, Cr, and Hg in water and the responses of these metals to hydrological connectivity in the Pearl River Estuary. The analyses were based on the field measurements of August-2016 in the estuary and January-2016 in the upper river mouth. We also assessed the ecosystem health of these metals. Overall, this estuary had an overall moderate pollution level, with occasional severe perturbations. The mean concentration of individual metal was in the order of Zn > As > Cu > Cr > Pb > Cd > Hg. The eastern estuary was more heavily polluted by metals (notably, Zn, Cd, and Cu) than the western estuary; this condition was attributable to sewage and industrial effluent discharges from the eastern urban cities of Dongguan and Shenzhen. Longitudinally, high levels of Cd and Zn appeared in the upper estuary, while elevated levels of Cu, As, Pb, Cr, and Hg were found in the middle and lower estuaries. The riverine inputs and estuarine mixing significantly influenced the distribution and movement of trace metals in the estuary, and have contributed to phytoplankton productivity (chlorophyll-a > 10 μg/L). River inflow inhibited the vertical diffusion of metals, and tidal currents facilitated surface-to-bottom mixing. Cu and Cd posed ecological risks. We determined the source contributions and transport routes of the metals using principal component analysis combining with multiple linear regression. The results of this study suggest that the source apportionment of metals can help to manage the source input entering into the estuary. Further, identified hydrological connectivity of metals can inform water quality managers in the highly anthropogenically influenced estuary.

Prioritizing risk mitigation measures for binary heavy metal contamination emergencies at the watershed scale using bayesian decision networks

Water pollution accidents have the characteristics of high uncertainty, rapid evolution and are difficult to control, thus posing great threats to human health, ecological security, and social stability. During the last 10 years, China has faced the occurrence of six extraordinarily serious heavy metal contamination pollution events at the watershed scale. This has alerted governments and enterprises of the significance of emergency decision-making. To quantitatively prioritize risk mitigation strategies for heavy metal emergencies, a Bayesian Decision Network-based probabilistic model is proposed under the Drivers-Pressures-States-Impacts-Responses (DPSIR) framework. A Copula-based exposure risk model is embedded to simulate the fate of heavy metal ions for each risk reduction option, whose joint probability distributions can then be used as input parameters in the Bayesian Decision Network. This method was applied to the emergency response prioritization for acute Cr(VI)-Hg(II) contamination accidents in the Danshui River watershed. The results indicated that comprehensive measure (M5) was the best option for decreasing ecological and human health risks. As for a single risk mitigation strategy, risk source prevention (M1) was the best alternative compared to exposure pathway interruption (M2) and human/ecological receptor protection (M3-M4). This probabilistic method can not only address the uncertainties between certain risk sources and receptors in the BDN structure, but also realize the risk system optimization in a satisfactory/preferred mode under the DPSIR framework. Overall, it provides the probabilistic risk estimates for watershed-scale risk management and policy making for local risk managers and stakeholders.

Spatial distribution, partitioning, ecological risk and source apportionment of potential toxic elements in water and sediments of the Hoor Al-Azim wetland and their bioaccumulation in selected commercial fish species

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.

Chitosan immobilization and Fe3O4 functionalization of olive pomace: An eco-friendly and recyclable Pb2+ biosorbent

An effective and sustainable biosorbent (MagOPIC) was prepared from chitosan and olive pomace by the combined action of immobilization and magnetic modification to remediate Pb²⁺-contaminated waters. Pb²⁺ sorption yield at the end of the equilibrium (45 min) period was estimated to be 98.56 ± 0.28% at pH 5.5. Agitation speed, ionic strength, and temperature did not significantly affect the Pb²⁺ biosorption. Biosorption kinetics are successfully fitted by the pseudo-second-order equation while the equilibrium biosorption data are properly modeled using the Freundlich and D-R isotherms. MagOPIC has also exhibited a high biosorption yield in the column tests (≥99%) and showed remarkable stability up to twenty consecutive regeneration cycles. Furthermore, it was successfully used for the treatment of Pb²⁺ containing real wastewater. The findings of this work highlighted the potential use of MagOPIC as a novel, cost-effective and eco-friendly biosorbent for the Pb²⁺ removal from the contaminated aquatic phase.

WITHDRAWN: Health risk assessment on heavy metal pollutants of groundwater on human safety in rural areas

Ahead of Print article withdrawn by publisher.

Removal of Cu(II) ions from aqueous solutions using membrane system and membrane capacitive deionization (MCDI) technology

Copper ion removal with nanofiltration membranes has accelerated in recent years. In this study, Cu²⁺ ion removal was investigated with nanofiltration membrane and a membrane capacitive deionization (MCDI) system; consequently, it was observed that the highest performance was seen when these two systems worked in an integrated system (99% Cu²⁺ ion removal) MCDI system is a purification technology through ion exchange membranes based on applying an electric field between two opposed electrodes. The flow rate, direct current voltage, and the operation time at which the Cu²⁺ ion removal rate was the highest were 50 mL/min, 1.2 V, and 15 min. respectively. Here, we report the application of the life cycle assessment (LCA) method to evaluate the environmental performance of the membrane system in different operating conditions. In the sensitivity analysis component of the study, different materials used in the membrane system and MCDI ststem were compared. Results from the LCA analysis showed that the MCDI system has far worse environmental impacts in all aspects particularly in material and energy-related effects.

Heavy metal contamination and health risk assessment in grains and grain-based processed food in Arequipa region of Peru

Heavy metals (HMs) in crops and processed foods are a concern and pose a potential serious health hazard. This study investigated possible presence of HMs in grains and processed products in the Region of Arequipa in Peru. Concentrations of Cd, As, Sn, Pb, and Hg were determined for commonly consumed grains in 18 districts of the region and processed products from 3 popular markets of Arequipa city, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Cold Vapor Atomic Absorption Spectroscopy (CVAAS). HM concentrations above the Codex General Standard limits were found for As (0.17 mg kg^-1) and Cd (0.11 mg kg^-1) in cereal grains. Elevated Pb concentrations of 0.55, 0.75, and 5.08 mg kg^-1 were found for quinoa, maize, and rice products, respectively; and attributed to processing conditions. The Total Hazard Index (HI) for polished rice and rice products had values between 1 and 10, showing non-carcinogenic adverse effects. Total Target Cancer Risk (TR_T) and uncertainty analysis of percentile P_90% for polished rice and quinoa products gave values above permissible limit of 10^-4, indicating an unacceptable cancer risk. The Nemerow Composite Pollution Index method (NCPI) showed that processed products had a significant pollution level due to the presence of Pb. While most crops grains had acceptable low HM levels, this is the first report of concerning HM concentrations in some consumed grains and processed products in southern Peru and indicates the necessity to find ways to decrease certain toxic metals in foods.

Preliminary assessment of trace elements in surface and deep waters of an urban river (Korotoa) in Bangladesh and associated health risk

Korotoa River is one of the most important urban rivers in Bangladesh for its utilization in various activities like agriculture, aquaculture, fishing, cooking, and other purposes. There have been some reports on the trace element (TE) levels in the surface water of Korotoa River, but its deep water has never been studied. Therefore, the author measured 10 TEs (As, Cd, Pb, Hg, Cr, Ni, Cu, Fe, Mn, and Zn) in surface and deep water samples and assessed their health risks for residential and recreational receptors. The levels of studied elements in deep water were slightly higher than those in surface water except for Cd, Cr, Cu, Mn, and Zn during the dry season and Pb, Hg, and Fe during the wet season. Total TE levels in both surface and deep waters were higher in the dry season than in the wet season. The levels of trace elements in both surface and deep waters were much higher than the guideline values for safe limits of drinking water and the protection of freshwater aquatic life, indicating that water from this river is not safe for drinking and/or cooking purposes. All hazard quotient (HQ) and hazard index (HI) values were higher than the risk threshold of unity. HI values for children were higher than those for adults, indicating that the health of children is at dramatically higher risk than that of adults. Arsenic, Pb, and Hg for the water ingestion pathway were the primary contributors to total risk (HI), while As and Cr for the dermal pathway, indicating that As, Pb, and Cr, among the TEs, are major contributors to total health risk. Total carcinogenic risk values of As and Cr in surface and deep waters were higher than the target risk of 1 × 10-4, indicating that TEs in surface and deep waters of the Korotoa River might pose health risks to the residential and recreational users. The results of this study can provide the basic data for efficient water management and human health protection in Bangladesh.

Spatio-Temporal Distribution of Environmental Health Risk of Heavy Metals in Industrial Wastewater of China during 1999-2018

In recent decades, environmental health risk caused by heavy metals in industrial wastewater (EHR-IHM) has become a serious issue globally, especially for China. Given the spatial difference of heavy metal emissions, hydrogeography, population distribution, etc., it is essential to estimate China's EHR-IHM from a high-resolution perspective. Based on the framework of USEtox, this study constructs an environmental health risk assessment method for heavy metals discharged from industrial wastewater by coupling the Pollutant Accumulation Model (PAM). This method also considers the process of heavy metal flows between upstream and downstream areas. Based on this constructed method, we investigate the spatio-temporal distribution of EHR-IHM of As, Cd, Cr(VI), Hg, and Pb in China from 1999 to 2018. Results showed that the EHR-IHM in China increased rapidly during 1999-2007 and decreased gradually during 2007-2018, with the highest Damage Level (DL) of 6.8 × 10⁴ disability-adjusted life years (DALY). As and Cr(VI) were the major heavy metal pollutants, which induced 58.9-70.6% and 23.9-36.2% of the total EHR-IHM, respectively. Intake of aquatic products was the dominant exposure route, accounting for over 84.1% of national EHR-IHM, followed by drinking water intake, accounting for 9.5-15.8%. Regarding spatial distribution, the regions with high EHR-IHM are mainly distributed in the middle-lower reaches of the Yangtze River, southeast coastal cities, Bohai Rim, etc.

Simultaneous Removal of Antibiotics and Heavy Metals with Poly(Aspartic Acid)-Based Fenton Micromotors

The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO₂ -based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO₂ catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO₂ (R-MnO₂ ) inner layer is decorated with Fe₂ O₃ nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.

Spatial distribution, risk assessment, and source identification of heavy metals in water from the Xiangxi River, Three Gorges Reservoir Region, China

Heavy metals (HMs) contamination in rivers has attracted wide concern due to its persistence and potential risks to the natural environment and human health. In this study, eight HMs (As, Hg, Cu, Pb, Ca, Zn, Mn, and Ni) were measured by inductively coupled plasma mass spectrometry in 24 water samples to investigate HMs contamination levels in the Xiangxi River of the Yangtze River basin. A geographic information systems kriging interpolation method was used to reveal the spatial distribution of HMs contamination. The results indicate that most HMs occurred at acceptable levels below the Surface Water Quality Standard (GB 3838-2002), with the highest concentration (23.23 mg kg^-1) of Mn being observed at sampling site X20. The values of the potential ecological risk index (RI) suggest that high potential ecological risks were present at sampling sites X1, X3, X4, X14, X16, X17, and X24, which reached moderate risk level. The highest value of RI (279.56) was observed at site X17. HM spatial distributions show that upstream pollution is more severe than downstream. The hazard index was below 1 for all HMs except for Mn, indicating that HMs in Xiangxi River pose a low risk to human health. HM source identification was accomplished using principal component analysis and Pearson's correlation. Cu, Cd, Ni, and Hg originate primarily from agriculture, while Pb, Zn, and As originate primarily from transportation and mining. This research provides a reference on the risks posed by HMs in Xiangxi River and will support efforts to protect and improve water quality in Xiangxi River.

A comparison of trace element concentrations in surface and deep water of the Keban Dam Lake (Turkey) and associated health risk assessment

Keban Dam Lake (KDL) is the second largest dam lake in Turkey. There have been some reports on the trace element (TE) levels in surface water of the KDL, but its deep water has been never studied. We measured 17 TEs (Pb, Hg, Cd, As, Cr, Ni, Co, Mn, Cu, Fe, Al, Sr, U, V, Zn, Zr and Ba) in surface and deep water samples and assessed their health risks for residential and recreational receptors. Copper, Zn, Ba, Ni, Mn and Pb levels in deep water were higher than those in surface water. Total TE level in deep water was higher in wet season, whereas that in surface water was higher in dry season. TE levels in both surface and deep water were much lower than the guideline values for drinking water and the protection of freshwater aquatic life, indicating that TEs in the KDL originate from natural sources. All HQ (hazard quotient) and HI (hazard index) values were below the risk threshold of unity. HI values for child were higher than those for adult, indicating that the health of children is at dramatically higher risk than adults. Arsenic and U for water ingestion were the primary contributors to total risk (HI), while V and Cr for dermal pathway. The presence of U and V, among the TEs which are major contributors to total health risk, reveals the necessity of monitoring of such less-studied elements in the surface water bodies. Carcinogenic risk values of As and Cr in surface and deep water were below the target risk of 1 × 10^-4. These findings indicated that TEs in surface and deep water of the KDL do not pose health risks to residential and recreational users. Thus this study may serve as a model for similar studies assessing health risks of multi-elements in freshwater bodies in future.

Assessment of the ecological and human health risks from metals in shrimp aquaculture environments in Central Java, Indonesia

The occurrence and contamination level of seven important toxic metals (Cd, Cu, Co, Cr, Hg, Pb, and Zn) and three additional metals (Al, Fe, and Mn) in the water, sediment, and shrimp muscle in aquaculture areas located in Central Java, Indonesia, were investigated. The results suggest that the majority of metals have higher concentrations in the inlet followed by the outlet and ponds. Cd dissolved in the waters exhibited the highest level in Pekalongan (3.15 ± 0.33 μg L^-1). Although Pb was not detected in the water, it was detected in the sediment, and the concentration ranged from 7.6 to 15.40 mg kg^-1 dw. In general, the heavy metal concentrations in the sediments were found to decrease in the sequence Al > Fe > Mn > Zn > Cr > Cu > Co > Pb. Concentrations below the effects range low level based on the Canadian sediment quality guidelines were found for Cr, Cu, Pb, and Zn, whereas moderate sediment pollution (25-75 mg kg^-1 dw) was observed for Cr (all regions), Cu (except in the Pekalongan region), and Zn (Brebes and Tegal regions) according to the US EPA standard. The status of the waters was evaluated by calculating a pollution index derived mostly from Mn and Zn. The ecological risk (geoaccumulation index (I_geo), contamination factor (CF), pollution load index (PLI), and potential ecological risk index (ERI)) determined in the sediments indicated that all studied areas had low to moderate contamination. The concentrations of all metals in shrimp were generally below the maximum limits for seafood, except for Zn (in all stations), Pb, and Cr (Tegal and Pekalongan). The hazard index values for metals indicated that consuming shrimp would not have adverse effects on human health.

Metal(loid) contamination in water, sediment, epilithic periphyton and fish in three interconnected ecosystems and health risk assessment through intake of fish cooked in Indian style

Samples of water, sediment and epilithic periphyton (EP) were collected from a lake (Dimna, DL), an intermediate canal (IC), and a river (Subarnarekha River, SR) to compare the pollution status of an urban ecosystem, and the concentrations of metal(loid) s were determined. Water characteristics were analysed by the water quality index (WQI). Sediment pollution was assessed using the ecological risk index (ERI). Accumulation of metal(loid) s in EP was determined by using bioaccumulation factor (BAF) and biota-sediment accumulation factor (BSAF). The result showed that the DL was least polluted (WQI = 30.39) and SR (WQI = 90.13) was the most polluted ecosystem. Sediment analysis revealed that Ni, Cr and Cd are the significant pollutants, especially in SR. The THQ value for fish dishes cooked in Indian style was found higher than that of raw fish, suggesting calculations considering the cooking process can provide better results. Health risk assessment shows that people inhabiting DL are vulnerable to Cr and Cu exposure, whereas people inhabiting IC and SR are susceptible to As and Co exposure due to the consumption of cooked fish. Moreover, for a developing country like India, it is important to upgrade the assessment methods and include regular monitoring of interconnecting ecosystems for the safeguard of human and ecological health.

Is It or Isn't It: The Importance of Visual Classification in Microplastic Characterization

Microplastics are a diverse category of pollutants, comprising a range of constituent polymers modified by varying quantities of additives and sorbed pollutants, and exhibiting a range of morphologies, sizes, and visual properties. This diversity, as well as their microscopic size range, presents numerous barriers to identification and enumeration. These issues are addressed with the application of physical and chemical analytical procedures; however, these present new problems associated with researcher training, facility availability and cost, especially for large-scale monitoring programs. Perhaps more importantly, the classifications and nomenclature used by individual researchers to describe microplastics remains inconsistent. In addition to reducing comparability between studies, this limits the conclusions that may be drawn regarding plastic sources and potential environmental impacts. Additionally, where particle morphology data is presented, it is often separate from information on polymer distribution. In establishing a more rigorous and standardized visual identification procedure, it is possible to improve the targeting of complex analytical techniques and improve the standards by which we monitor and record microplastic contamination. Here we present a simple and effective protocol to enable consistent visual processing of samples with an aim to contribute to a higher degree of standardization within the microplastic scientific community. This protocol will not eliminate the need for non-subjective methods to verify plastic objects, but it will standardize the criteria by which suspected plastic items are identified and reduce the costs associated with further analysis.

Genetic Engineering-Facilitated Coassembly of Synthetic Bacterial Cells and Magnetic Nanoparticles for Efficient Heavy Metal Removal

Heavy-metal pollution is becoming a worldwide problem severely threatening our health and ecosystem. In this study, we constructed a genetic-engineering-driven coassembly of synthetic bacterial cells and magnetic nanoparticles (MNPs) for capturing heavy metals. The Escherichia coli cells were genetically engineered by introducing a de novo synthetic heavy-metal-capturing gene (encoding a protein SynHMB containing a six-histidine tag, two cystine-rich peptides, and a metallothionein sequence) and a synthetic type VI secretory system (T6SS) cluster of Pseudomonas putida, endowing the synthetic cells (SynEc2) with high ability of displaying the heavy-metal-capturing SynHMB on cell surface. MNPs were synthesized by a coprecipitation method and further modified by polyethylenimine (PEI) and diethylenetriaminepentaacetic acid (DTPA). Owing to the surface exposure of six-histidine tag on the synthetic bacteria and carboxyl groups on the modified MNPs (MNP@SiO₂-PEI-DTPA), the synthetic bacterial cells and MNPs coassembled to form biotic/abiotic complex exhibiting a self-developing characteristic. In the culture medium containing both Cd²⁺ and Pb²⁺, the coassemblies captured these heavy metals with high removal efficiency (>90% even at 50 mg/L of Cd²⁺ and 50 mg/L of Pb²⁺) and were conveniently recycled by artificial magnetic fields. Moreover, the coassemblies realized coremoval of organic carbon pollutants with the removal efficiency of >80%. This study builds a novel biotic/abiotic coassembling platform facilitated by genetic engineering and sheds light on development of artificial magnetic biological systems for efficient treatment of environmental pollution.

Toxic element (As and Hg) content and health risk assessment of commercially available rice for residents in Beijing based on their dietary consumption

Arsenic (As) and mercury (Hg) are toxic elements that are often classified as heavy metals, much like cadmium (Cd) and lead (Pb) and others. In this study, we determined the As and Hg contents in rice samples obtained from commercially available rice in Beijing and the health risks associated with daily dietary exposure to As and Hg by the consumption of this rice. Furthermore, the pollution levels of the rice were evaluated based on the Nemerow index. For this purpose, we collected 353 rice samples from 16 municipal districts in Beijing and determined the As and Hg contents in these samples by microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS). The results were as follows: (i) the average content of As in the collected rice samples was 154.91 μg/kg (95% confidence interval (CI) of 139.90-169.92 μg/kg), and the average content of Hg was 2.02 μg/kg (95% CI of 1.25-2.79 μg/kg), which did not exceed the limits established by China's National Standard; (ii) the Nemerow index indicated that the As and Hg contents in these rice samples were safe; (iii) the dietary exposure to As and Hg by rice consumption was, respectively, 15.35 μg/day and 0.20 μg/day, which accounted for 12.91% and 3.35% of the total dietary exposure, respectively; (iv) the hazard quotients (HQs) of As and Hg by the dietary consumption of rice were, respectively, 0.77 and 0.03, and both the HQ and hazard index (HI is 0.8) were less than one. These results indicate that dietary exposure to As and Hg would have no detrimental effect on the health of the residents in the study area; however, the possible carcinogenesis by As in these residents warrants serious attention.

Mercury, arsenic, lead and cadmium in waters of the Singrauli coal mining and power plants industrial zone, Central East India

The present investigation is an attempt to assess the contamination of heavy metals in the ground and surface water of the Singrauli industrial belt area. Pollution indices like heavy metal index (HPI), contamination index (CD) and heavy metal evaluation index (HEI) are used for the evaluation of heavy metal pollution (arsenic As, mercury Hg, cadmium Cd, and lead Pb). Contour maps are constructed to interpret metal spatial distribution. Further, the land-use/land-cover (LULC) maps for the year 2000, 2010 and 2016 are prepared using Landsat satellite data. A total of 48 water samples (Groundwater (27), Surface water (21)) are analysed for heavy metal concentration. Eighty-eight percent of groundwater and 90% of surface water samples are contaminated with Hg. Similarly, high concentrations of Pb and Cd were found in the samples. Surprisingly, all the water samples have As concentration above the WHO permissible limit of 10 ppb. Further, 95% of the samples have an HPI value greater than 100 indicating high heavy metal contamination. CD value denotes contamination of 89% of the samples with heavy metals (As, Hg, Cd, Pb). Through spatial distribution, it can be interpreted that most of the contaminated samples lie near thermal power plants, ash ponds, and coal mines. LULC (land use/land cover) study shows a significant decrease in water bodies by (108 km²), agricultural land by (54 km²) and bare/fallow land by (51 km²) from 2000 to 2016. During these 16 years, there has been a fourfold increase in the overburden, a threefold increase in dumping yards, a 2.5 times increase in urban areas, and a twofold increase in mining areas. Both the environment and the water quality are deteriorating at an alarming rate. Such scientific investigations are relevant for risk management studies of potable water. The knowledge acquired from such assessment shall be considered with utmost priority by concerned authority considering degrading water quality in the study area. Hence, this study is applicable for designing action plans and control measures to reduce water resource pollution.

Systematic Assessment of Health Risk from Metals in Surface Sediment of the Xiangjiang River, China

The common empirical screening method is limited to a preliminary screen target from vast elements for human health risk assessments. Here, an element screening procedure was developed for assessing the human health risk of the elements in the sediment of the Xiangjiang River. Ninety-six surface sediment samples from eight sampling stations were collected and 27 elements of each sample were investigated. Thirteen of the 27 elements were screened for human health risk assessments through the three-run selections by calculating anthropogenic factors, building element maps, and the removal of unnecessary elements. Pb posed the greatest health risk and exhibited a potential noncarcinogenic risk for adults at the stations S4 and S5, although no visible noncarcinogenic and carcinogenic risk for adults and children in the Xiangjiang River. Our study also suggested that the chalcophile elements were associated with greater health risk, compared to the lithophile and siderophile ones.

Potential of green/brown algae for monitoring of metal(loid)s pollution in the coastal seawater and sediments of the Persian Gulf: ecological and health risk assessment

The current investigation evaluates metal (loid)s biomonitoring using algae as well as the metal(loid) pollution of seawaters and sediments in the northern part along the Persian Gulf. Algae, seawater, and sediment samples were collected from four coastal areas with different land applications. The concentration of Ni, V, As, and Cd in abiotic samples (seawater and sediment) and four species of algae (Enteromorpha intestinalis, Rhizoclonium riparium, Cystoseira myrica, and Sargassum boveanum) was measured using an ICP-AES device. Concentrations of potentially toxic elements in seawater, sediments, and algae species followed the trend of "Ni˃V˃As˃Cd." The area of Asaloyeh (with the highest industrial activity) and the Dayyer area (with the lowest industrial activity) provided the highest and lowest amounts of metal(loid)s pollution, respectively. The average concentrations of V and As in four algae species significantly differed for all sampled areas. Obtaining the bio-concentration factor (BCF) > 1 for seawater and < 1 for sediment indicated that the studied algae have the ability to efficiently concentrate metal(loid)s from seawater and the limited accumulation of metals in sediments. According to the Nemerow pollution index, the order of metal(loid)s pollution for the studied areas estimated as Asaloyeh>Ganaveh>Bushehr>Dayyer. Algae species of C. myrica and E. intestinalis can often serve as suitable biological tools for monitoring seawater and sediment quality.

Assessment of human health risk based on characteristics of potential toxic elements (PTEs) contents in foods sold in Beijing, China

Metals are generally classified into essential metals groups. Essential metals include copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), and nonessential metals include cadmium (Cd) and lead (Pb) etc. However, excessive intake of metals even essential metals would have detrimental effect on the body. In this study, seven potential toxic elements (PTEs) (i.e., Cd, Cr, Cu, Fe, Mn, Pb and Zn) and their distribution characteristics in the foods were analyzed as well as the combination of correlation analysis, factor analysis and cluster analysis were constructed. Meanwhile, combined with the dietary consumption data from the Fifth China Total Diet Study (FCTDS), the dietary exposure of PTEs were analyzed and a consequent safety risk assessment was conducted. The main results are as follows: (1) PTE contents in simply-processed samples were found to be lower than those in the highly-processed samples. (2) The average daily intake of the PTEs were about 12.26 (Cd), 153.17 (Cr), 25.16 (Pb) μg/d, 1.90 (Cu), 20.19 (Fe), 7.12 (Mn) and 12.69 (Zn) mg/d, respectively. (3) The total target hazard quotient (TTHQ) was 2.88, which was lower than 10. Therefore, the long-term consumption of these foods combined with the current dietary structure would not have a detrimental effect on the health of residents in Beijing.