Assessment of eutrophication potential from fertiliser application in agricultural systems in Thailand

Integrated role of biochar and PGPR (Leclercia adecarboxylata HW04) in enhancing cadmium phytoremediation and stress tolerance in Glycine max L

Plant growth-promoting rhizobacteria (PGPR) and biochar (BC) are recognized as effective biological agents for enhancing stress tolerance and mitigating heavy metal toxicity in crops. Therefore, this study aims to investigate the effects of the cadmium (Cd)-resistant PGPR strain Leclercia adecarboxylata HW04 (>4 mM Cd resistance) on soybean plants exposed to 300 μM Cd. HW04 was observed to possess the innate ability to synthesize indole-3-acetic acid and exopolysaccharides, which facilitated the absorption of Cd in the medium. Scanning electron microscopy (SEM) images revealed that HW04 effectively colonized the porous structure of BC. Their combined treatment significantly enhanced photosynthesis and improved the morphological characteristics of soybean plants. Additionally, the Cd content in soybean shoots significantly increased following both the sole or combined treatments of BC and HW04. However, the combined treatments significantly reduced Cd content in the roots and soil by 31% and 47%, respectively. HW04 inoculation alone increased Cd content in the roots by 43.7% while lowering it in the soil by 7.4%. Additionally, the co-application of HW04 and BC significantly enhanced calcium (Ca) and magnesium (Mg) assimilation while promoting Cd/Fe accumulation in soybean shoots. The higher expression of signaling cascade genes, including GmCaMK1 and GmCDPK5 (Ca signaling) and GmMAPK4a and GmMAPK7 (MAP kinase signaling), in the co-applied crops further validate the findings. The increase in abscisic acid levels and the decrease in salicylic acid levels after HW04 and BC application were correlated with enhanced stress tolerance in crops. These findings suggest that the combined application of HW04 and BC could serve as an effective, eco-friendly approach for mitigating heavy metal toxicity in crops and promoting phytoremediation.

Integrated inactivation of Microcystis aeruginosa and degradation of microcystin-LR by direct current glow discharge plasma in liquid-phase: Mechanisms and cell deactivation process

The frequent occurrence of blooms of Microcystis aeruginosa (M. aeruginosa) and the subsequent release of microcystin-LR (MC-LR) in eutrophic waters pose a serious threat to aquatic ecosystems. This study investigated the optimal conditions for inactivating M. aeruginosa and the degrading MC-LR using direct current glow discharge plasma in liquid phase (DC-LGDP), analyzed the potential inactivation mechanisms and the cell deactivation process of M. aeruginosa. The results showed that DC-LGDP generated reactive species (i.e., •OH, 1O2, and H2O2), active Cl and electroporation effect collectively contributed to inactivation of M. aeruginosa and degradation of MC-LR. The 97.07 % inactivation efficiency of M. aeruginosa and 94.98 % degradation rate of MC-LR were achieved with higher energy yield and without generating nitrogen oxides. Meanwhile, DC-LGDP destroyed the cell integrity, eliminated their antioxidant capacity and reduced the content of photosynthetic pigments. The transcriptome analysis indicated that the transcripts of genes related to photosynthesis, ribosome biosynthesis, ABC transporters, and nitrogen metabolism pathway in M. aeruginosa were altered by DC-LGDP. This study provides insights into the inactivation of M. aeruginosa by DC-LGDP, while elucidating the potential inactivation mechanisms and the cell deactivation process involved. It may be important for the eco-friendly inactivation of M. aeruginosa blooms in natural water bodies.

Suppression of carbon footprint through the CO2-assisted pyrolysis of livestock waste

Concentrated animal feeding operation facility in modern livestock industry is pointed out as a point site causing environmental pollution due to massive generation of manure. While livestock manure is conventionally treated through biological processes, composting and anaerobic digestion, these practices pose difficulties in achieving efficient carbon utilization. To address this, this study suggests a pyrolytic valorization of livestock manure, with a focus on enhancing syngas production. Hen manure was particularly chosen due to its abundance of calcium carbonate (CaCO3) compared to other mammalian livestock, exhibiting distinctive thermolytic behaviours. The thermolysis of CaCO3 in hen manure releases carbon dioxide (CO2), simultaneously served as a partial oxidant for the carbon monoxide (CO) enhancement. To further evaluate the effectiveness of CO2, hen manure was pyrolyzed under the presence of CO2. The use of CO2 demonstrated a gas-phase interaction with hen manure-derived volatiles, re-allocating the pyrogenic products into CO-rich syngas. To accelerate the reaction kinetics of CO2, catalytic pyrolysis over a supported Ni catalyst was conducted, further enhancing CO-rich syngas. To assess the environmental advantages, the carbon footprints under various pyrolysis conditions were estimated by confirming the energy consumption and CO2 mitigation potential of pyrogenic products. Therefore, this study highlights that the CO2-mediated pyrolysis of hen manure globally generated offers a potential to mitigate 934.67 million tons of CO2 in annual.

Multi-evidences investigation into spatiotemporal variety, sources tracing, and health risk assessment of surface water nitrogen contamination in China

A comprehensive understanding of nitrogen pollution status, especially the identification of sources and fate of nitrate is essential for effective water quality management at the local scale. However, the nitrogen contamination of surface water across China was poorly understood at the national scale. A dataset related to nitrogen was established based on 111 pieces of literature from 2000 to 2020 in this study. The spatiotemporal variability, source tracing, health risk assessment, and drivers of China's surface water nitrogen pollution were analyzed by integrating multiple methods. These results revealed a significant spatiotemporal heterogeneity in the nitrogen concentration of surface water across China. Spatially, the Haihe River Basin and Yellow River Basin were the basins where surface water was seriously contaminated by nitrogen in China, while the surface water of Southwest Basin was less affected. Temporally, significant differences were observed in the nitrogen content of surface water in the Songhua and Liaohe River Basin, Pearl River Basin, Southeast Basin, and Yellow River Basin. There were 1%, 1%, 12%, and 46% probability exceeding the unacceptable risk level (HI＞1) for children in the Songhua and Liaohe River Basin, Pearl River Basin, Haihe River Basin, and Yellow River Basin, respectively. The primary sources of surface water nitrate in China were found to be domestic sewage and manure (37.7%), soil nitrogen (31.7%), and chemical fertilizer (26.9%), with a limited contribution from atmospheric precipitation (3.7%). Human activities determined the current spatiotemporal distribution of nitrogen contamination in China as well as the future development trend. This research could provide scientifically reasonable recommendations for the containment of surface water nitrogen contamination in China and even globally.

Enhanced phosphorus adsorption using modified drinking water treatment residues: A comparative analysis of powder and alginate bead forms

This study provides an analysis of the phosphorus adsorption efficacy of three modified drinking water treatment residues (MDWTRs): MDWTR-P (powdered form), MDWTR-D2, and MDWTR-D5 (alginate bead-entrapped forms with bead diameters of 2 mm and 5 mm, respectively). The preparation process involved washing and drying the drinking water treatment residue, followed by grinding and sieving to achieve particle sizes below 90 μm. The residue was then incinerated at 600 °C in oxygen-limited conditions. Subsequently, the MDWTR was formulated into alginate beads by mixing with sodium alginate and FeCl3 solutions, resulting in spherical particles of specified diameters. The evaluation of surface area, pore volume, pore size, and CHN concentration revealed that MDWTR-D5 possesses the largest surface area (284.7 m2 g-1) and highest micropore volume (0.04 cm3 g-1), indicating a greater capacity for adsorption. SEM-EDS analysis demonstrated significant compositional changes post-treatment, particularly elevated phosphorus levels, confirming effective adsorption. Metal content analysis indicated high aluminum levels in MDWTR-P and increased iron content in MDWTR-D5. Toxicity Characteristic Leaching Procedure (TCLP) and in vitro bioaccessibility (IVBA) tests confirmed the non-hazardous nature of all MDWTRs, ensuring their safety for environmental applications. Kinetic analyses using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models highlighted the superior performance of MDWTR-D5, with the highest equilibrium adsorption capacity and initial adsorption rate across all tested concentrations, suggesting both high efficiency and rapid adsorption potential. Further validation using Langmuir and Freundlich isotherms revealed MDWTR-D5's highest monolayer adsorption capacity (22.88 mg g-1) and Freundlich adsorption capacity parameter (6.97 mg g-1). Statistical analysis via one-way ANOVA confirmed significant differences in phosphorus concentrations among the MDWTRs samples (p-value <0.001), consistently underscoring MDWTR-D5's superior adsorption performance. These findings highlight MDWTR-D5's potential as an effective adsorbent for phosphorus removal in wastewater treatment, emphasizing its applicability in environmental remediation strategies.

Thailand - how far are we from achieving a healthy and sustainable diet? A longitudinal ecological study

Background

Newly industrialized countries like Thailand have been influenced by globalization, westernization, and urbanization over the last decades, leading to changes in dietary habits as well as food production. Consequences of these changes include rising non-communicable diseases (NCDs) and environmental degradation, which are defined as the leading global challenges today. The objectives of this study are to identify Thailand's dietary changes, considering health and sustainability aspects, and to determine correlations between these changes and NCD cases as well as environmental impacts (GHG emissions, land-, nitrogen-, phosphorus-use). In this way, diet-related adjustments can be identified to promote planetary and human health.

Methods

In this longitudinal ecological study, relative differences between the average food consumption in Thailand and the reference values of a healthy and sustainable diet, the Planetary Health Diet (PHD), were calculated. Furthermore, a bivariate correlation analysis was conducted, using data, based on Food and Agriculture Organization's (FAO's) data, results from the Global Burden of Disease Study (GBD), and PHD's reference values.

Findings

The consumption quantities of meat, eggs, saturated oils, and sugar increased significantly since 1961. The food groups, that have exceeded PHD's upper reference values, include sugar (+452%), red meat (+220%), grains (+143%), saturated oils (+20%) and eggs (+19%), while vegetables (-63%), and unsaturated oils (-61%) have fallen below PHD's lower limits. Concerning the bivariate correlation analyses, all investigated variables show significant correlations. The most significant correlations were found in NCD cases (r = 0.903, 95% CI 0.804-0.953), nitrogen use (r = 0.872, 95% CI 0.794-0.922), and land use (r = 0.870, 95% CI 0.791-0.921), followed by phosphorus use (r = 0.832, 95% CI 0.733-0.897), and green-house gas (GHG) emissions (r = 0.479, 95% CI 0.15-0.712).

Interpretation

The results show, that the determined differences of unhealthy or unsustainable food groups have increased concurrently with NCD cases and environmental impacts over the last decades in Thailand. A shift towards a reduced intake of sugar, red meat, grains, saturated oils and eggs along with an increase in vegetables and unsaturated oils, might support environmental and human health.

Funding

None.

Multidirectional Fate Path Model to Connect Phosphorus Emissions with Freshwater Eutrophication Potential

Excessive anthropogenic phosphorus (P) emissions put constant pressure on aquatic ecosystems. This pressure can be quantified as the freshwater eutrophication potential (FEP) by linking P emissions, P fate in environmental compartments, and the potentially disappeared fraction of species due to increase of P concentrations in freshwater. However, previous fate modeling on global and regional scales is mainly based on the eight-direction algorithm without distinguishing pollution sources. The algorithm fails to characterize the fate paths of point-source emissions via subsurface pipelines and wastewater treatment infrastructure, and exhibits suboptimal performance in accounting for multidirectional paths caused by river bifurcations, especially in flat terrains. Here we aim to improve the fate modeling by incorporating various fate paths and addressing multidirectional scenarios. We also update the P estimates by complementing potential untreated point-source emissions (PSu). The improved method is examined in a rapidly urbanizing area in Taihu Lake Basin, China in 2017 at a spatial resolution of 100 m × 100 m. Results show that the contribution of PSu on FEP (62.6%) is greater than that on P emissions (58.5%). The FEP is more spatially widely distributed with the improved fate modeling, facilitating targeted regulatory strategies tailored to local conditions.

Life cycle assessment for evaluation of novel solvents and technologies: A case study of flavonoids extraction from Ginkgo biloba leaves

Innovative solvents such as deep eutectic solvents (DESs) and process intensification technologies assisted by ultrasound have been demonstrated to be promising pathways for enhancing solid-liquid extraction. Nevertheless, quantitative and systematic knowledge of their environmental impact is still limited. In this work, a case study of flavonoids extraction from Ginkgo biloba leaves was evaluated by using life cycle assessment (LCA) for comparison of three extraction scenarios. The first used DES as extractant (DESE), and the other two adopted ethanol, including heat reflux extraction (HRE), and ultrasound-assisted extraction (UAE). Among eight key midpoints investigated, all these from UAE were 10.0 %-80.0 % lower than from DESE and HRE except water consumption. The UAE was the eco-friendliest option due to its higher extraction yield, shorter duration and lower solvent consumption. The DESE exhibited the lowest water consumption, the highest freshwater ecotoxicity and human carcinogenic toxicity, while HRE had the highest impacts for the other 6 midpoints. Moreover, solvent production was the key contributor for all the categories. The standardized sensitivity analysis showed that the overall environmental footprint can be further decreased by 15.4 % for DESE pathways via substituting choline chloride/glycerine with choline chloride/ethylene glycol. Furthermore, all pathways using DESs had higher standardized impacts than those employing ethanol from sugarcane or wood. Replacing ethanol from maize with other feedstocks can significantly lessen the overall impacts, among which the UAE using ethanol from sugarcane demonstrated the least environmental impacts. The promotion of DESs as "green and sustainable" alternative to traditional solvents requires careful consideration.

Influence of landscape patterns on nitrate and particulate organic nitrogen inputs to urban stormwater runoff

This study investigated the effect of the landscape pattern of permeable/impermeable patches on NO3--N and particulate organic nitrogen (PON) concentrations during stormwater runoff transport and their source contributions. Six landscape pattern indices, namely, mean proximity index (MPI), largest patch index (LPI), mean shape index (MSI), landscape shape index (LSI), connect index (CONNECT), and splitting index (SPLIT), were selected to reflect the fragmentation, complexity, and connectivity of permeable patches in urban catchments. The results show that lower fragmentation, higher complexity, and greater connectivity can reduce NO3--N concentrations in road runoff and drainage flow (i.e., the flow in the stormwater drainage network), as well as PON concentrations in road runoff. Further, the above landscape pattern is effective for mitigating the contributions of NO3--N and PON from road runoff. Low impact development (LID) can be incorporated with the landscape pattern of permeable/impermeable patches to mitigate nitrogen pollution in urban stormwater at the catchment scale by optimizing the spatial arrangement.

Effect of capping mode on control of phosphorus release from sediment by lanthanum hydroxide

The use of in situ active capping to control phosphorus release from sediment has attracted more and more attentions in recent years. It is important to identify the effect of capping mode on the control of phosphorus release from sediment by the in situ active capping method. In this study, the impact of capping mode on the restraint of phosphorus migration from sediment into overlying water (OW) by lanthanum hydroxide (LH) was studied. Under no suspended particulate matter (SPM) deposition condition, LH capping effectively restrained the liberation of endogenous phosphorus into OW during anoxia, and the inactivation of diffusive gradient in thin film-unstable phosphorus (UP_DGT) and mobile phosphorus (P_Mobile) in the topmost sediment served as a significant role in the restraint of endogenous phosphorus migration into OW by LH capping. Under no SPM deposition, although the transformation of capping mode from the single high dose capping to the multiple smaller doses capping had a certain negative impact on the restraint efficiency of endogenous phosphorus liberation to OW by LH in the early period of application, it increased the stability of phosphorus in the static layer in the later period of application. Under SPM deposition condition, LH capping had the capability to mitigate the risk of endogenous phosphorus liberation into OW under anoxia conditions, and the inactivation of UP_DGT and P_Mobile in the topmost sediment was a significant mechanism for the control of sediment phosphorus liberation into OW by LH capping. Under SPM deposition condition, the change in the covering mode from the one-time high dose covering to the multiple smaller doses covering decreased the efficiency of LH to limit the endogenous phosphorus transport into OW in the early period of application, but it increased the performance of LH to restrain the sedimentary P liberation during the later period of application. The results of this work suggest that the multiple LH capping is a promising approach for controlling the internal phosphorus loading in freshwater bodies where SPM deposition often occurs in the long run.

Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment

Spent caustic wastewater produced in a soda plant has a high concentration of ammonia nitrogen (NH4+-N). As excessive NH4+-N discharging into water bodies would cause eutrophication as well as destruction to the ecology balance, developing an efficient technology for NH4+-N removal from the spent caustic wastewater is imperative in the current society. In this study, an electrochemical process with graphene electrodes was designed for the NH4+-N removal in the spent caustic wastewater. The removal efficiency of the NH4+-N during the electrochemical process could reach 98.7% at 4 A in a short treatment time (within 120 s) with an acceptable energy consumption (6.1 kWh/m3-order). NO3− and NO2− were not detected during the electrochemical process. An insignificant amount of NH2Cl, NHCl2, and NCl3 produced in the treatment suggested that little of the NH4+-N reacted with chlorine, that is, chlorination played a negligible role in the NH4+-N removal. By electron equilibrium and nitrogen conversion analysis, we think that NH4+-N was primarily converted to NH2(ads) on the surface of a graphene electrode by one-electron transfer during the direct oxidation of the electrochemical process. Due to the high calcium ion (Ca2+) in the spent caustic wastewater, the electrode scale significantly increased to 1.4 g after treatment of 240 s at 4 A. By X-ray diffraction (XRD) analysis, the composition of the electrode scale is portlandite Ca(OH)2. Although the electrode scale was obvious during the electrochemical treatment, it could be alleviated by alternating the electrode polarity. As a result, the life and efficiency of the graphene electrode for NH4+-N removal could remain stable for a long time. These results suggest that the electrochemical process with a graphene electrode may provide a competitive technology for NH4+-N removal in spent caustic wastewater treatment.

Recovery of phosphorus from wastewater: A review based on current phosphorous removal technologies

Phosphorus (P) as an essential nutrient for life sustains the productivity of food systems; yet misdirected P often accumulates in wastewater and triggers water eutrophication if not properly treated. Although technologies have been developed to remove P, little attention has been paid to the recovery of P from wastewater. This work provides a comprehensive review of the state-of-the-art P removal technologies in the science of wastewater treatment. Our analyses focus on the mechanisms, removal efficiencies, and recovery potential of four typical water and wastewater treatment processes including precipitation, biological treatment, membrane separation, and adsorption. The design principles, feasibility, operation parameters, and pros & cons of these technologies are analyzed and compared. Perspectives and future research of P removal and recovery are also proposed in the context of paradigm shift to sustainable water treatment technology.