Agricultural Plastic Pollution in China: Generation of Plastic Debris and Emission of Phthalic Acid Esters from Agricultural Films.

Agricultural plastic films have been proven highly advantageous, but they also cause pollution of plastic debris and associated chemicals. Phthalates (phthalic acid esters, PAEs), an important additive of agricultural films, can be released and contaminate the environment. Here, we analyzed the agricultural plastic usage and assessed plastic debris in China and developed a method to estimate PAE emissions from agricultural films. Additionally, the environmental fate of PAEs was evaluated using a fugacity-based multimedia model. The agricultural plastic film usage in China in 2017 was 2,528,600 tons. After agricultural film recycling and water erosion, the plastic debris amount was estimated as 465,016 tons. The water erosion process carried 4329 tons of plastic debris into the aquatic environment. During its lifetime, the agricultural film released a total of 91.5 tons of two typical types of PAEs. PAEs from the mulching film would mostly be removed through degradation, while those from the greenhouse film accumulate in vegetables. Populated regions exhibited more serious PAE pollution in vegetables but with no immediate health risks. The model was well evaluated using comparable measured concentrations and uncertainty analysis based on the Monte Carlo method. The findings from this study demonstrate the serious agricultural plastic pollution problem and associated PAE contamination in China.

Neonicotinoid insecticides in a large-scale agricultural basin system-Use, emission, transportation, and their contributions to the ecological risks in the Pearl River Basin, China.

Neonicotinoid pollution has increased rapidly and globally in recent years, posing significant risks to agricultural areas. Quantifying use and emission, transport and fate of these contaminants, and risks is critical for proper management of neonicotinoids in river basin. This study elucidates use and emissions of neonicotinoid pesticides in a typical large-scale agriculture basin of China, the Pearl River Basin, as well as the resulting agricultural non-point source pollution and related ecological risks using market surveys, data analysis, and the Soil and Water Assessment Tool. Neonicotinoid use in the basin was estimated at 1361 t in 2019, of which 83.1 % was used in agriculture. After application, approximately 99.1 t neonicotinoids were transported to the Pearl River, accounting for 7.2 % of the total applied. Estimated aquatic concentrations of neonicotinoids showed three seasonal peaks. Several distinct groups of neonicotinoid chemicals can be observed in the Pearl River, as estimated by the model. An estimated 3.9 % of the neonicotinoids used were transported to the South China Sea. Based on the present risk assessment result, several neonicotinoids posed risks to aquatic organism. Therefore, the use of alternative products and/or reduced use is deemed necessary. This study provides novel insights into the fate and ecological risks of neonicotinoid insecticides in large-scale watersheds, and underscores the need for greater efficiency of use and extensive environmental monitoring.

Environmental emissions and pollution characteristics of mosquitocides for the control of dengue fever in a typical urban area.

Mosquitocides are frequently used to control the spread of dengue fever in tropical and sub-tropic urban regions worldwide, resulting in their discharge into the environment via rainfall runoff, causing adverse effects on ecological health. This study quantitatively evaluated mosquitocide emissions and environmental pollution in a typical urban district in China affected by the dengue fever epidemic, using a method combining market surveys, monitoring campaigns and SWMM (storm water management model) modelling tools. During the assessment period, the total mosquitocide usage in the urban district reached 6334 kg, with an estimated load of 56.55 g entering the receiving environment via rainfall runoff, 91.04 % of which occurred in the rainy season. Monitoring results indicated that the initial 0.5-1 h was the main period of mosquitocide wash off into the receiving water. Environmental mosquitocide pollution levels were found to be affected by the mosquitocide type and the time interval between mosquitocide application and precipitation events. The measured environmental concentrations of mosquitocides in this study were generally higher than those areas unaffected by the dengue fever epidemic. The modelled mosquitocide concentrations were in accordance with monitoring results. The finding of this study are important for assessing the environmental impact of dengue fever control activities, while also providing valuable baseline data for the effective environmental management of mosquitocides.

Antibiotic pollution in lakes in China: Emission estimation and fate modeling using a temperature-dependent multimedia model.

The high use of antibiotics worldwide has poses a serious threat to both human and environmental health. Lakes are served as reservoirs for antibiotics, however, there is a lack of information available on antibiotics emissions and the subsequent pollution. Here, the emission and fate of 34 frequently detected antibiotics were studied in 226 Chinese lakes, via the built emission estimation method and a temperature-dependent multimedia lake model. It has been estimated that totally 5711 tons antibiotic were discharged into the lakes of China in 2019. Antibiotics emissions are due to human activities, with 3800-fold higher emissions in the Eastern China than that in Western China. The antibiotic fate in lakes has been successfully modelled by simulating the lake stratification, freeze-melt cycles and the stable condition throughout the year. Both stratification and freeze-melt cycles can lead to increased antibiotic concentrations in lake water. Deep-water lakes were shown to serve as a highly effective natural storage medium for antibiotics. The reliability of the model was confirmed by published measured concentrations and Monte Carlo method. This is the first study to comprehensively investigate the antibiotic fate in lakes of China, providing valuable guidance for the remediation of contaminated lakes.

Hypothetical scenarios estimating and simulating the fate of antibiotics: Implications for antibiotic environmental pollution caused by manure application.

The application of animal manure containing antibiotic residues as an organic fertilizer to farmlands, poses a major threat to the health of river basin ecosystems. Waste treatment processes can help reduce antibiotic pollution levels in river basins following manure application, but the overall influence of these processes remains unclear. This study evaluates the impact of manure treatment methods on the emission and subsequent river pollution caused by 14 frequently detected antibiotics in a typical pig breeding area in China, by using hypothetical scenarios method. Three scenarios were constructed based on possible fate pathways of antibiotics, representing in 47.0, 55.3, and 81.6 ton·yr-1 antibiotic emissions into the river basin. The soil and water assessment tool (SWAT) model successfully simulated the transport of antibiotics from farmland to surface water, with calibration and verification performed using hydrological station monthly data over 8 consecutive years. Field measured concentrations also verified the reliability of the model and were used to determine the most realistic scenario. In basins applied with manure, environmental antibiotic pollution is most affected by the wastewater treatment process and manure applied patterns, followed by changes in streamflow. The antibiotic pollution in manure applied areas showed significant spatial and temporal differences, resulting from the different manure application patterns. The simulated total outflow of antibiotics in the river basin accounted for 18.1% of the inflow, with the loss of target antibiotics by degradation, volatilization and sedimentation deposition in the river basin being 0.23, 0.01 and 33.2 ton·yr-1, respectively. This study can help to clarify the environmental fate of antibiotics in the basin following manure application, provide guidance for policy makers and help to design the effective corrective interventions for reducing the environmental pollution.

How much do human and livestock actually contribute to steroids emission and surface water pollution from past to the future: A global research.

A comprehensive global inventory of past, present, and future steroid emissions was firstly developed based on the global 5' × 5' grids relevant data available. From 1970 to 2070, the growth rate of the annual global steroid emission was relatively stable around 10%. At present (in 2015), the global steroid emissions was 18,270 t, with 17% contributed by humans. Almost one-third of total animal emissions have been occurring in India and Brazil. India also had the highest value of human steroid emissions. Regions with highest steroid emissions were concentrated between 10° ~ 35° N and 70° ~ 90° E. The increase of sewage treatment rates can effectively reduce the total quantity of steroids entering the environment, especially for some developing countries. But the "technology bonus" from sewage treatment process will be exhausted until to 2030. Meanwhile, global surface water pollution was predicted based on steroid emissions into water compartment and on the digital river network with annual river discharge. The modelling results show that steroids are widely distributed across the globe, with concentrations mostly below 100 ng/L. However, if no proper treatment measures for animal excretions, in another 100 years, the range of the surface water contaminated by steroids will increase by 1.2 times. The Nile River resulted as the most polluted among the eight world's longest and famous rivers during the whole period investigated. Various measured concentrations worldwide validated our modelling result. The global steroid emission inventory and surface water pollution from past to the future will stand as an important data and knowledge base for the management of pollution from different types of steroids at global and regional level.

[Construction of Continuous Dynamic Model for River Networks and Its Application in Simulation of Spatiotemporal Migration of Typical Biocides].

Biocides are widely added to personal care products and enter the environment through sewage treatment plant (STP) discharge, which affects ecological health. This paper evaluated the pollution characteristics of triclosan and triclocarban in a river network during the COVID-19 epidemic. Moreover, a continuous dynamic river network model coupling a one-dimensional hydrodynamic model and four-level fugacity model was established to address the temporal and spatial heterogeneity of pollutants in the river network migration process; then, this model was applied to evaluate two biocides in the Shima River Basin. The model passed calibration and in-field concentration verification tests and yielded satisfactory simulation results. The results of the study showed that the concentration of biocides in the river network during the new crown epidemic was twice that of the non-epidemic period. The concentration of triclosan and triclocarban in the river channel first increased and then decreased with the increase of the river migration distance after STP discharge. The time variation characteristics of the concentrations were affected by the river flow. The biocide concentration in the river network of the low flow upstream area first increased and then decreased, gradually stabilizing in about 20 h. The pollution concentration in the high flow downstream area was increased, and the concentration did not stabilize at 24 h. These results indicate the necessity of evaluating the temporal and spatial characteristics of migration of typical biocides in the river network by stages and time on the premise of distinguishing the flow.