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Based on field visits and literature research, the situations of several typical wastewater treatment plants (WWTPs) in the Rhine basin and the Yangtze basin were investigated, to compare the technology and concept of wastewater treatment in these two areas. Our results showed that WWTPs in the Rhine performed well in pollutant removal, and have shifted their focus to energy production and nutrient recovery; While in the Yangtze basin, most WWTPs still operate on the sole concept of pollution treatment. Though China's WWTPs attach importance to water reclamation, the related technologies are still under development. In years to come, the construction of New Concept WWTPs is expected by Chinese famous experts, to integrate sustainable wastewater treatment and energy/nutrient recovery. To better plan its future avenue in wastewater treatment, China is suggested to learn from the successful practice of energy production and nutrient recovery of WWTPs in the Rhine. [ABSTRACT FROM AUTHOR]

Monitoring water environmental quality of large rivers is the basis of river evaluation and local environmental protection worldwide. This study compared the water quality of the Rhine and the Yangtze River, two of the world's most important arteries, based on monitoring data collected from their monitor stations from 2007 to 2018. Dissolved oxygen (DO), pH, chemical oxygen demand (COD)/dissolved organic carbon (DOC) and ammonia-nitrogen (NH3-N) were used to evaluate their water quality. The changing trend, the temporal and special patterns were also analyzed. It was found that the overall water quality of the Rhine in the last decade (p = 0.95) was better than the Yangtze (p = 1.01). Notably, CODMn and NH3-N were identified as main pollution factors of the Rhine and the Yangtze, respectively. This study provided information for water quality modelling, therefore might be helpful for the water quality management of China. [ABSTRACT FROM AUTHOR]

The pollution control of the Rhine is a successful management mode for comprehensive cooperation in environmental governance, which could provide an important reference for the Yangtze River governance. This study explored river basin management and various pollution problems faced by these two rivers at different times, and also includes governance and management effects. The changes in water quality and aquatic life before and after policy implementation had also been compared. The results showed that the International Commission for the Protection of the Rhine (ICPR) made outstanding contributions to the water-quality improvement, demonstrating its management mode was efficient and effective. Cooperative communication and targeted policies are effective ways to improve the water quality of large river basins. Clear division of labor system and phased cooperation-governance objectives are also significant for the inter-provincial cooperative governance of Yangtze River pollution. [ABSTRACT FROM AUTHOR]

Photodegradation is an important pathway for monomethylmercury (MeHg) degradation in aquatic ecosystems. In this process, dissolved organic matter (DOM) plays an essential role. However, little information is available regarding the photo-transformation of MeHg in shallow aquatic environments, where a significant portion of MeHg is associated with soil suspensions. In this study, 14 soils sampled from different sites in China were used to simulate these conditions. Our results clearly demonstrated that soil organic matter (SOM) was the most important factor controlling the MeHg photodegradation in suspension. Degradation in this heterogeneous aqueous system was shown to be mediated by the 1O 2 produced by organic matter on the surface of the soil particles rather than by DOM. This was confirmed by the strong correlation between the kinetics rate constant of MeHg degradation and steady state concentrations of 1O 2 (R 2 = 0.81). Our results propose a new pathway of MeHg induced by sediment soils under sunlight irradiation. Identification of this pathway may improve the estimates of potential ecological risk of Hg in shallow field ecosystems. Image 1 • MeHg can be photo-degraded with simulated sunlight when soil particles are existed in natural shallow. • Soil organic matter rather than dissolved organic matter plays a dominant role in MeHg photodegradation. • Singlet oxygen is dominating active species for MeHg photodegradation on the surface of soil particles. [ABSTRACT FROM AUTHOR]

Atmospheric phosphine (PH3) fluxes from typical types of wetlands and PH3 concentrations in adjacent atmospheric air were measured. The seasonal distribution of PH3 in marsh and paddy fields were observed. Positive PH3 fluxes are significantly related to high air temperature (summer season) and increased vegetation. It is concluded that vegetation speeds up the liberation of PH3 from soils, while water coverage might function as a diffusion barrier from soils or sediments to the atmosphere. The concentrations of atmospheric PH3 (ngm−3) above different wetlands decrease in the order of paddy fields (51.8±3.1)>marsh (46.5±20.5)>lake (37.0±22.7)>coastal wetland (1.71±0.73). Highest atmospheric PH3 levels in marsh are found in summer. In paddy fields, atmospheric PH3 concentrations in flourishing stages are higher than those in slowly growing stages. [Copyright &y& Elsevier]

[Display omitted] [ABSTRACT FROM AUTHOR]

Rapid and accurate prediction of metal bioaccumulation in crops are important for assessing metal environmental risks. We aimed to incorporate machine learning modeling methods to predict heavy metal contents in rice crops and identify influencing factors. We conducted a field study in Jiangsu province, China, collecting 2123 pairs of soil-rice samples in a uniform measurement and using 10 machine learning algorithms to predict the uptake of Cd, Hg, As, and Pb in rice grain. The Extremely Randomized Tree model exhibited the best performance for rice-Cd and rice-Hg (Cd: R 2 = 0.824; Hg: R 2 = 0.626), while the Random Forest model performed best for As and Pb (As: R 2 = 0.389; Pb: R 2 = 0.325). The feature importance analysis showed that soil-Cd and pH had the highest impact on rice-Cd risk, which is in line with previous studies; while temperature and soil organic carbon were more important to rice-Hg than soil-Hg. Then, based on another set of 1867 uniformly distributed paddy soil samples in Jiangsu province, the Cd and Hg risks of soil and rice were visualized using the established models. Mapping result revealed an inconsistent pattern of hotspot distribution between soil-Hg and rice-Hg, i.e., a higher rice-Hg risk in the northern area, while higher soil-Hg in south. Our findings highlight the importance of temperature on Hg bioaccumulation risk to crops, which has often been overlooked in previous risk assessment processes. [Display omitted] • Soil metal contents and properties were most important factors to rice uptake. • Temperature and precipitation negatively affected rice-Hg and rice-Pb, respectively. • Root uptake might be main pathway for Cd, while foliar uptake for Hg and Pb. • Broader features should be considered in predicting metal bioaccumulation. [ABSTRACT FROM AUTHOR]

The application of terrestrial toxicity models to real soil environments is a challenge due to the heterogeneity of soil. We presented here a novel bioassay-geochem-model coupling approach to predict the bioaccumulation and toxicity of a metal mixture in different soils. Equations describing dose-accumulation and dose-toxicity relationships of Cd-Ni mixtures to wheat root elongation were generated using a standard sand culture bioassay. A geochemical multi-surface speciation model (MSM) with default parameters was employed to predicted the dissolved metal contents C dis of three soils collected in China with different properties. Several toxicity models (TU/CAM + FIAM/BLM/GCSM) were screened to identify the one yielding the most accurate predictions. The results showed that metal bioaccumulation was better predicted by the MSM- C dis integrated with the dose-accumulation equation (RMSE < 0.58) than by the detection of metal contents in soil porewater (RMSE < 0.74). The MSM predicted metal ion activities combined with the BLM+CAM model successfully predicted Cd-Ni toxicity in all three soils (RMSE = 20.7%), but the deviation was slightly larger than that obtained in measurements of metals in soil porewater (RMSE =17.2%). Our study demonstrates that the MSM coupled with the dose-accumulation and dose-toxicity equations derived from sand bioassays offers a promising approach in risk assessments of mixed metals in actual soils while avoiding tedious soil bioassays, which will greatly improve the practical application value of terrestrial toxic models. [Display omitted] • A novel bioassay-MSMs coupling approach was proposed for soil-plant systems. • The model's toxicity parameters are derived from sand culture bioassays. • Amounts of dissolved metal in soils are predicted using a geochemical MSM. • The combination of sand bioassays and MSM enables toxicity predictions in soils. • This approach was successfully verified by predicting Cd-Ni toxicity in three soils. [ABSTRACT FROM AUTHOR]

An accurate model to predict Cd accumulation in crops based on soil properties would facilitate evaluations of soil quality and the potential risk posed by metals. However, given the heterogeneity of soil, such models are difficult to establish on large regional scales. This study for the first time examined the applicability of a multi-surface speciation model (MSM) in predicting Cd accumulation in wheat at a regional field scale, based on 140 soil-wheat paired samples collected from a 205-km 2 field. The MSM resulted in a better correlation between Cd accumulation in wheat grain (R 2 = 0.75) and roots (R 2 = 0.74) than obtained with chemical extraction methods (total Cd in soil, 0.01 M CaCl 2 , and 0.43 M HNO 3 ). In addition, while the performance of the MSM was comparable to that of a traditional multiple regression model, a parameter-fitting process was not required. The predictive ability of the MSM was further used to assess and predict the soil Cd risk and to develop a soil Cd sensitivity map to better localize areas of greatest sensitivity to Cd contamination. The results showed that the MSM can serve as a useful tool for regional soil risk assessments and thus in the development of soil protection measures., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In metal toxicity model studies of soil-plant systems, hydroponic culture is often employed to simulate soil conditions, but the validity of this approach has not been examined. The present study evaluated Ni toxicity to wheat root elongation using models developed in hydroponic and sand cultures and then compared the results with those obtained from real soils. Three mechanism toxicity models were examined: the free ion activity model, the biotic ligand model (BLM), and the Gouy-Chapman-Stern model. After being developed in hydroponic and sand culture bioassays, the models were validated with 18 soils from across China. The results showed that more accurate predictions were obtained with sand rather than hydroponic bioassays. Dissolved organic matter exerted only a limited effect on Ni toxicity, whereas an important role was found for osmotic effects. Of the 3 models, the sand-based BLM best predicted Ni toxicity to wheat root elongation (root-mean-square error = 16.2% and R 2  = 0.79) and was as good as the BLM estimated directly from soils. The present study shows that sand is a better matrix than solution for root elongation bioassays of Ni toxicity and that osmotic effects must be taken into account in evaluating soil conditions. Environ Toxicol Chem 2018;37:1349-1358. © 2018 SETAC., (© 2018 SETAC.)

Microcystins (MCs) are produced by cyanobacteria in aquatic environments and are a potential risk to aquatic organisms. Increasing evidence suggests that oxidative stress may play an important role in the toxicity mechanism of MCs on fish, but most studies were based on relatively high concentrations. In this study, the effect of time-dependent oxidative stress in livers of Cyprinus carpio L. (C. carpio) exposed to 10 μg l(-1) of microcystin-LR (MC-LR) for 0-14 days was investigated. MC-LR induced histopathological changes in liver and gills were also assessed after 14 days exposure. Electron paramagnetic resonance (EPR) spectrum was used to directly investigate the reactive oxygen species (ROS) in fish liver and results showed that hydroxyl radical ((∙)OH) was significantly induced at 0.5 day and then tended to decline with an increase of exposure period. As a response of antioxidant, catalase (CAT) activity increased slightly at first and then decreased with exposure period. A pronounced promotion of glutathione-S-transferase (GST) indicated that the conjugation reaction of MC-LR and GSH occurred. A time-dependent decrease of reduced glutathione (GSH) with an increase of oxidized glutathione (GSSG) level suggested GSH was involved in detoxification of MC-LR in the liver. Oxidative damage was evidenced by the significant increase of malondialdehyde (MDA) level at 2-6 days. After 14 days exposure, a series of pathological changes, like partially dissolved parenchymal architecture, vacuolar degeneration, necrosis, hemorrhage and slight inflammatory cells infiltration in fish liver tissues could be observed. Scanning electron microscopic (SEM) studies showed that dissolved MC-LR could also result in pathological changes like partial broken epithelial cells, deformed taste buds and loose gill filament and lamella in gill tissues. These results suggest that although a restoring response occurred, C. carpio could still be adversely affected by MC-LR at 10 μg l(-1).