Studies on the Characteristics of Nitrogen and Phosphorus Pollution of Natural Outcrop Springs in Wudalianchi

Objective] The research aimed to study the characteristics of nitrogen and phosphorus pollution of 30 natural outcrop springs in Wudalianchi, which provides a theoretical basis for the sustainable development and utilization and protection of Wudalianchi natural mineral resources. [Method] Choosing the 30 natural outcrop spring representatives in different regions, samples were collected in low water period, normal water period, wet period respectively, and the content of nitrogen, phosphorus and other contaminants in the samples were determined. Besides, the pollution characteristics of nitrogen and phosphorus in Wudalianchi natural outcrop spring were analyzed. [Result] The 30 natural outcrop spring in Wudalianchi area were seriously polluted by nitrogen. Total nitrogen and nitrate nitrogen were the main forms of nitrogen pollution. The content of total phosphorus and ammonia nitrogen were low. [Conclusion] The natural outcrop spring is mainly caused by agricultural non-point source pollution.

Non-Point-Source Nitrogen and Phosphorus Loadings from a Small Watershed in the Three Gorges Reservoir Area

Non-point-source pollution has become a major threat to the water quality of the Three Gorges Reservoir(TGR);however,nutrient loadings from terrestrial sources are unclear due to a lack of in situ monitoring.A representative small watershed in the central part of the TGR area was selected to monitor the loss of nitrogen(N) and phosphorous(P) continuously along with the runoff from 2007 through 2009 to understand the exact sources and loadings.Results show that the non-point-source nitrogen and phosphorus comes mainly from the storm runoff from residential areas,citrus orchards and sloping croplands,which contributes up to 76% of the loadings in this watershed.Thus,a crucial measure for controlling non-point-source pollution is to intercept storm runoff from the three sources.Paddy fields provide a sink for non-point-source N and P by intercepting the runoff and sediment along with their different forms of nitrogen and phosphorus.The N and P removal efficiency by paddy fields from residential areas is within the range of 56% to 98%.Paddy fields are an important land-use option for reducing the non-point-source loading of N and P in the TGR area.

Effect of groundwater on the ecological water environment of typical inland lakes in the Inner Mongolian Plateau

To explore the causes of the ecological environment deterioration of lakes in the Inner Mongolia Plateau,this study took a typical inland lake Daihai as an example,and investigated the groundwater recharge in the process of lake shrinkage and eutrophication.Using the radon isotope(^(222)Rn)as the main means of investigation,the ^(222)Rn mass balance equation was established to evaluate the groundwater recharge in Daihai.The spatial variability of ^(222)Rn activity in lake water and groundwater,the contribution of groundwater recharge to lake water balance and its effect on nitrogen and phosphorus pollution in lake water were discussed.The analysis showed that,mainly controlled by the fault structure,the activity of ^(222)Rn in groundwater north and south of Daihai is higher than that in the east and west,and the difference in lithology and hydraulic gradient may also be the influencing factors of this phenomenon.The ^(222)Rn activity of the middle and southeast of the underlying lake is greater,indicating that the ^(222)Rn flux of groundwater inflow is higher,and the runoff intensity is greater,which is the main groundwater recharge area for the lake.The estimated groundwater recharge in 2021 was 3017×10^(4) m^(3),which was 57%of the total recharge to the lake,or 1.6 times and 8.1 times that of precipitation and surface runoff.The TN and TP contents in Daihai have been rising continuously,and the average TN and TP concentrations in the lake water in 2021 were 4.21 mg·L^(−1) and 0.12 mg·L^(−1),respectively.The TN and TP contents entering the lake with groundwater recharge were 6.8 times and 8.7 times above those of runoff,accounting for 87%and 90%of the total input,respectively.The calculation results showed that groundwater is not only the main source of recharge for Daihai,but also the main source of exogenous nutrients.In recent years,the pressurized exploitation of groundwater in the basin is beneficial in increasing the groundwater recharge to the lake,reducing the water balance difference of the lake,and slowing down the shrinking degree of the lake surface.However,under the action of high evaporation,nitrogen and phosphorus brought by groundwater recharge would become more concentrated in the lake,leading to a continuous increase in the content of nutrients and degree of eutrophication.Therefore,the impact of changes in regional groundwater quantity and quality on Daihai is an important issue that needs further assessment.