Environmental carrying capacity and ecological risk assessment of pesticides under different soil use types in the Central Plains Urban Agglomeration (CPUA), China

Soil environmental safety has received much attention during the past few decades due to its significance in agricultural production and human health. Special attention is required for soil pesticide residues and ecological risks. This study examined 197 soil samples from industrial, residential and agricultural areas for the presence of 12 organophosphorus pesticides (OPPs) and 8 synthetic pyrethroids (SYPs) in the 16 cities in Henan Province, and the center of CPUA, based on the Central Plains Urban Agglomeration (CPUA) concept proposed by China. The total average concentrations of ∑12OPPs in industrial, residential and agricultural soils were 194, 217, 267 ng/g dry weight, and those of ∑8SYPs were 26.8, 35.7, 25.5 ng/g dry weight, respectively. The two pollutants with the greatest concentrations in the soils were malathion and fenpropathrin, respectively, the dominant components of OPPs and SYPs. The soil environmental carrying capacity (SECC) analysis, representing the maximum residual load that can be supported, shows that acephate and cyhalothrin were overloaded, with a predicted period of over 500 years. Among the 16 cities of CPUA, a higher frequency of high ecological risk could be observed only in Shangqiu. The OPPs in children had total non-carcinogenic risk values of more than 1.0. Similarly, the non-carcinogenic risks of SYPs in adults and children in the residential areas were more than 1.0. The study provides knowledge on how to effectively manage soil safety in Henan Province, which is the center of the CPUA, with a large population and grain province to protect ecosystems and reduce the risks of soil pesticide residues in humans.

Soil contamination and carrying capacity across the Tibetan plateau using structural equation models

Soil contamination is a major environmental issue worldwide. Compared with Arctic, European Alps and Rocky Mountains, the soil contamination and soil environment carrying capacity (SECC) of the Tibetan Plateau (TP) is not systematic and multidimensional. In this study, the levels, influencing factors including climate factors [(i.e., mean annual precipitation (MAP) and mean annual temperature (MAT)], socio-economic factors [(i.e., population, population density and gross domestic product (GDP)], vegetation coverage factor, soil factors [(i.e., pH, soil organic carbon (SOC), total phosphorus and total nitrogen] and topographic factors [(i.e., longitude, latitude and digital elevation model (DEM)] and carrying capacity of multiple soil contaminants [persistent organic pollutants (POPs), heavy metals (HMs) and microplastics (MPs)] was systematically studied. Results show that the spatial distribution of POPs in the eastern was higher than that in the western region, and the structural equation model (SEM) demonstrate that SOC and MAT were the key factors influencing distribution. Regarding HMs, except As, moderate and heavy pollution of the remaining elements were found in the northern and eastern TP regions, and pH and MAP were the main influencing factors. The MPs showed that the distribution of the patches was influenced by GDP and MAP. Furthermore, a higher SECC in the eastern region that gradually decreased from east to west. pH is the primary factors affecting SECC, followed by normalized difference vegetation index (NDVI). An increase of pH and NDVI by one unit is likely to make SECC scores decrease by 0.8 and increase by 0.32, respectively. Taken together, these studies provide a system, cost-effective, and quantitative framework for soil contamination and carrying capacity in the TP.

Ecological risk assessment and environment carrying capacity of soil pesticide residues in vegetable ecosystem in the Three Gorges Reservoir Area

Soil contamination by pesticide residues has become an increasing concern of ecological protection. However, the soil environmental carrying capacity (SECC) of pesticide residues in agricultural ecosystems was limited studied. Based on the concept of ecological risk assessment, a modified system on the environment carrying capacity was proposed for estimate SECC of pesticide residues in agricultural soils. Subsequently, the assessment on ecological risk and SECC of soil pesticide residues in vegetable ecosystem were performed in the Three Gorges Reservoir Area (TGRA). In 201 topsoil samples, 62.1% of the pesticide compounds were detected over limit of quantitation, and exhibit a high proportion of multiple pesticide contamination. Pyrethroid insecticides and herbicide glyphosate showed most frequent occurrence and high levels. The SECC of the TGRA varies with the limit standard, annual cumulative amount and risk quotient of each pesticide contaminant in soils. Except that fenpropathrin has exceeded SECC, chlorfenapyr, β-cyfluthrin and glyphosate posed the greatest threat to SECC in the next 50 years. Additionally, ecological risks by pesticide residues in vegetable ecosystem can be affected by various planting activities. These results will contribute to guide the rational application of pesticides and control soil environmental risks, thereby achieving the agricultural green development in the TGRA.