Loss Characteristics And Control Strategies Of Soil Particulate Phosphorus Loss In Non-point Source Pollution Loss In Non-point Source Pollution

In recent years,phosphorus loss from farmland has been an important cause of water eutrophication and outbreaks of water blooms.particulate phosphorus is the main form of phosphorus loss in farmland.However,due to the lack of in-depth understanding of the bioavailability of particulate phosphorus loss in existing research,there is a lack of important links and basis for objectively describing the water environmental risks of phosphorus loss in farmland,leading to inadequate control measures.Therefore,this study investigated the bioavailability of particulate phosphorus in different types of soil and under different fertilization treatments through algae cultivation experiments.Continuous extraction of particulate phosphorus during the cultivation process was carried out,and the changes in different forms of phosphorus during algae cultivation were analyzed,thus revealing the biological utilization mechanism of particulate phosphorus in farmland more deeply.In addition,taking the Zhuxi River Basin as the research object,the modified universal soil loss equation（RUSLE）and sediment transport ratio distribution model（SEDD）were used to simulate the situation of particulate phosphorus loss in the basin from a spatiotemporal perspective,quantitatively evaluate the phosphorus loss in farmland in the basin,and analyze the location selection of pollution interception points based on the simulation results of particulate phosphorus loss,thus clarifying the key areas for pollution control,provide reference basis for subsequent prevention and control of non-point source pollution in farmland.The main conclusions are as follows:（1）During the process of algae cultivation,the growth of particulate phosphorus in farmland was consistently higher than that in the blank treatment,indicating that particulate phosphorus in farmland can significantly promote algae growth.Algal growth mainly utilizes Fe-P,Al-P,and Org-P.The correlation between Fe-P and Al-P contents and algal growth gradually decreases over time,while the correlation between Org-P content and algal growth gradually increases over time.This indicates that as inorganic phosphorus is consumed in the system,organic phosphorus is gradually hydrolyzed into inorganic phosphorus to supply algal growth.（2）The final concentration of chlorophyll in the algal solution with different fertilization treatments for soil particulate phosphorus is:organic fertilizer 100%>organic fertilizer 85%>green fertilizer 100%>inorganic fertilizer 100%>blank group.The organic fertilizer group is higher than the inorganic fertilizer group and the green fertilizer group,indicating that the soil treated with organic fertilizer can more stimulate the growth of algae.According to the destructive sampling experiment of algae,it can be seen that NH₄Cl-P,Fe-P,Al-P,and Org-P show an overall downward trend during the cultivation process of algae,while Org-P and Res-P have no obvious changes.This indicates that algae growth mainly utilizes NH₄Cl-P,Fe-P,Al-P,and Org-P,and the utilization of Fe-P,Al-P,and Org-P in the organic fertilizer group is higher than that in the inorganic fertilizer group.（3）The main conclusion of the loss characteristics and control strategies of soil particulate phosphorus in hilly areas is that the TP load in the Zhuxi Basin was 12863.3kg in 2000,6116.4 kg in 2010,and 2308.1 kg in 2020,showing an overall downward trend.The main reason for the decrease is that the quality and quantity of forests within the watershed are improving.Analyzing the land use changes from 2000 to 2020,it can be seen that the overall situation in the Zhuxi River Basin shows an increase in construction land,with active changes in farmland,forest land,and grassland occurring in a wide range and small areas.Analyzed the changes in phosphorus load caused by land-use changes under three urbanization scenarios.Scenario I is based on historical land use change patterns.Under this assumption,the TP load brought about by rapid urbanization in the watershed in 2040 is 2639.15 kg,which is 50.66 kg higher than the TP load brought about by urbanization under historical patterns.When the watershed experiences a slowdown in the urbanization process proposed by the ecological protection scenario（Scenario III）,the TP load decreases to 2553.32 kg.At the same time,screening and optimization work was conducted on the ED sites that can control particulate phosphorus loss,and assistance was provided to planners and local governments in managing land use change.