Effect of Plant Buffer Zone–Antifouling Curtain Wall on Reducing Non-Point Source Pollution in Paddy Fields, China

Phycospheric bacteria limits the effect of nitrogen and phosphorus imbalance on diatom bloom

Human activities have caused an imbalance in the input nitrogen and phosphorus (N/P) in the biosphere. The imbalance of N/P is one of the characteristics of water eutrophication, which is the fundamental factor responsible for the blooms. The effects of the N/P imbalance on diatom and phycospheric bacteria in blooms are poorly understood. In this study, the N/P molar ratio in real water (14:1) and the predicted N/P molar ratio in future water (65:1) were simulated to analyze the response of Cyclotella sp. and phycospheric bacteria to the N/P imbalance. The results showed that the N/P imbalance inhibited the growth of Cyclotella sp., but prolonged diatom bloom duration. The resistance of Cyclotella sp. to the N/P imbalance is related to phycospheric bacteria, and there are dynamic regulatory mechanisms within the phycospheric bacteria community to resist the N/P imbalance: (1) the increase of HNA bacterial density, the decrease of LNA bacterial density, (2) the increase of phycospheric bacterial diversity and eutrophic bacteria abundance, and the change of denitrifying bacteria abundance, (3) the activity of nitrogen and phosphorus metabolism of HNA bacteria enhanced, while that of LNA bacteria decreased. And the gene hosts of nitrogen and phosphorus metabolism were most enriched in Proteobacteria, indicating that Proteobacteria played an important role in maintaining the stability of phycospheric bacteria and was the dominant phylum resistant to the N/P imbalance. This study clarified that the algal-bacteria system was resistant to the N/P imbalance and implied that the N/P imbalance had little effect on the occurrence of diatom bloom events due to the presence of phycospheric bacteria.

Application of riparian buffer zone in agricultural non-point source pollution control—A review

Water is an important natural element of our environment, and its management and security are also serious concerns. Agricultural non-point source pollution (NPSP) is one of the major sources of contaminants causing water quality degradation. A riparian buffer zone is a vegetative cover adjacent to water channels that positively contributes to pollutant filtration and sediment trapping. It has the potential to filter nutrients, reduce nutrients and pesticide leakage, provide habitat and protection against floods, minimize erosion issues, improve biodiversity and ecological connectivity, and add aesthetics to the area. Moreover, it is inexpensive and requires little maintenance making buffer zone an attractive approach to NPSP control. In this review, we have enlightened the effects of the riparian buffer zone on water quality and agricultural NPSP and how its structures and mechanisms contribute to controlling water pollution effectively. We conclude that the riparian buffer zone is an effective technique for water safety, NPSP control, and creating a suitable environment for terrestrial and aquatic species. Moreover, it has the potential to reduce the water temperature due to the shading effect and sustain water habitat acting as a climate adaptation tools. Buffer zones should be adopted for agricultural non-point source pollution and achieve environmental sustainability. However, the long-term influence of the riparian buffer zone on trapping NPS pollutants, soil properties, and groundwater quality is s research gap.

An improved minimum cumulative resistance model for risk assessment of agricultural non-point source pollution in the coastal zone

Agricultural non-point source pollution (AGNPSP) is an important risk factor affecting the water environment. Among the areas where cropland NPSP occurs, the coastal zone should be of greater concern. Typhoons, heavy precipitation, and abundant rivers and ponds accelerate the transport process of AGNPSP to the offshore waters. It is urgent to construct a simple and accurate model to assess the risk of AGNPSP in the coastal zones. Thus, this study takes the nitrogen pollution from agricultural cultivation in the coastal zone of the Yellow River Delta as an example. A new minimum cumulative resistance (MCR) to agricultural non-point source pollution (AGNPSP-MCR) model is first proposed to simulate the transport process of cropland NPSP into the sea based on the "source-sink" theory in landscape ecology. Finally, the risk is assessed for AGNPSP transport into the sea. The results show the following. (1) The environmental factors of vegetation cover, rainfall erosivity, and soil erodibility are the three most important factors in pollution transportation, weighted 0.3433, 0.2608, and 0.2219, respectively, while the least influential factor is slope, with a weight of only 0.0053. (2) The minimum cumulative resistance of AGNPSP transportation shows a significant positive correlation with the distance to the river and sea, and is higher on the west sides away from the ocean, and smaller in the eastern coastal area near the sea. (3) Similarly, the regions facing serious AGNPSP risk are concentrated in the eastern coastal area, and the cropland area above medium risk was 252.72 km², accounting for 47.57% of the total cultivated land area. (4) Compared with the traditional MCR model, the AGNPSP-MCR model takes into account the quantitative differences of the transport process characteristics of AGNPSP, and it is constrained by the topographical parameter, so the results of AGNPSP risk are more reliable. This study provides a new reference for risk assessments of AGNPSP in the coastal zones.