Correlation between Nitrogen Pollution and WWTPs Discharge in Lake Taihu

Too much nitrogen (N) and phosphorus (P) in the water can cause severe eutrophication, which can make the water undrinkable. In order to find the trends and causes of N pollution in Lake Taihu over the past two decades, we collected and analyzed water quality data of Lake Taihu and surrounding wastewater treatment plants (WWTPs) discharge data. We found that the average total nitrogen (TN) concentration in the northern part of Lake Taihu reached its peak in 2006 and began to decline after that. Spatially, the concentration of TN is getting higher from the center of the lake to the north bank. Moreover, we found that the decrease in TN concentration in Lake Taihu has a moderately strong correlation with the discharge of ammonia nitrogen (NH4-N) in WWTPs. Finally, we used two machine learning models to predict the monthly average TN in Lake Taihu and discussed features of significant importance.