How do polystyrene microplastics affect the adsorption of copper in soil?

Microplastics (MPs) commonly coexist with heavy metals in the soil environment. MPs can influence the activity of heavy metals, and the specific mechanisms need to be further explored. Here, different contents of polystyrene (PS) MPs were added to soil to explore their effects on the adsorption and desorption characteristics of copper (Cu2+) in soil. The adsorption process was mainly chemical adsorption and belonged to a spontaneous, endothermic reaction. The hydrophobicity of MPs slowed down the adsorption and desorption rates. The main adsorption mechanisms included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+. These findings provide new insights into the effects of MPs on the fate and risk of heavy metals in soil. ENVIRONMENTAL IMPLICATION: The existing literature concerning the effects of microplastics on the adsorption of heavy metals in soil is insufficient. Our investigation unveiled that the main adsorption mechanisms of different soil samples included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+.

Seasonal variation of nitrogen-concentration in the surface water and its relationship with land use in a catchment of northern China.

Surface waters can be contaminated by human activities in two ways: (1) by point sources, such as sewage treatment discharge and storm-water runoff; and (2) by non-point sources, such as runoff from urban and agricultural areas. With point-source pollution effectively controlled, non-point source pollution has become the most important environmental concern in the world. The formation of non-point source pollution is related to both the sources such as soil nutrient, the amount of fertilizer and pesticide applied, the amount of refuse, and the spatial complex combination of land uses within a heterogeneous landscape. Land-use change, dominated by human activities, has a significant impact on water resources and quality. In this study, fifteen surface water monitoring points in the Yuqiao Reservoir Basin, Zunhua, Hebei Province, northern China, were chosen to study the seasonal variation of nitrogen concentration in the surface water. Water samples were collected in low-flow period (June), high-flow period (July) and mean-flow period (October) from 1999 to 2000. The results indicated that the seasonal variation of nitrogen concentration in the surface water among the fifteen monitoring points in the rainfall-rich year is more complex than that in the rainfall-deficit year. It was found that the land use, the characteristics of the surface river system, rainfall, and human activities play an important role in the seasonal variation of N-concentration in surface water.

[Effects of land use and vegetation restoration on soil quality in a small catchment of the Loess Plateau].

Soil quality improvement plays an important role in sustaining global biosphere. This paper studied the changes of soil quality after 25 years' land use and vegetation restoration at the Anjiapo catchment of western Loess Plateau. The analyses of soil characteristics of wasteland, almond land, farmland, pineland, shrub land and fallow land showed that different land use and vegetation restoration had different effects on soil integrated fertility index. Soil organic matter content was increased due to planting shrubs and forests. Both vegetation restoration and fallow could improve soil quality. Cultivation practice could decrease soil nutrient levels, and cropland soil was degraded. Shrub soil formed "fertile island" in the semi-arid region. Fallow could improve soil fertility to some extent. Human activities and vegetation restoration could affect soil nutrient contents after land use pattern was changed. With the launch out into the "Grand development of Western China", "Grain for Green Project" and ecological restoration, both shrub planting and fallow (natural restoration) should be the optional choices to restore soil fertility, as they could decrease soil erosion and improve soil condition at catchment scale, especially in the hilly and gully loess area. Integrative control of small catchment may be the best way for the sustainable development of the semi-arid hilly area of Loess Plateau.