Abstract
In this article, long-term data, statistical analysis, and spatial interpolation method were applied to the analyses of the spatial and temporal changes of total nitrogen (TN) and total phosphorus (TP) in Dianshan Lake. We also estimated the self-purification capability of TN and TP in Dianshan Lake. The results showed that interannual variability of the average concentration of TN in Dianshan Lake changed significantly, showing a characteristic increase before a decline, and the average concentration of TN showed an obvious downward trend, especially after 2007. Interannual variability of the average concentration of TP in Dianshan Lake fluctuated, and the average concentration of TP showed a downward trend after 2007. The seasonal variations of TN and TP in Dianshan Lake were similar. Higher TN concentration occurred in winter and spring, while higher TP concentration appeared in summer, autumn, and winter. The spatial distribution of TN and TP in Dianshan Lake were similar, showing a characteristic which decreased from north to south and west to east. The highest TN and TP values were mainly distributed in the inlet monitoring sites, while the lowest TP values were distributed in the outlet monitoring sites. The self-purification capability of TN and TP were about 2289.97 t/yr and 112.16 t/yr, which suggested a deterioration of natural water quality. Our research showed that Dianshan Lake was highly eutrophic and that water quality showed a substantial improvement from 1996 to 2015.
Highlights
As an important part of wetlands, lakes play vital roles in regulating runoff, providing water, purifying water quality, regulating regional climate, recording the change of the regional environment, maintaining the regional ecological balance system, and the reproductive function of biodiversity [1,2,3]
Annual variation of the concentrations of total nitrogen (TN) (2001–2015) and total phosphorus (TP) (1996–2015) in Dianshan Lake are presented based on the average concentration of 13 monitoring sites
In 2007, the average concentration of TN reached its peak of 4.53 mg/L, which far exceeded the Grade V water quality standards of China [29]
Summary
As an important part of wetlands, lakes play vital roles in regulating runoff, providing water, purifying water quality, regulating regional climate, recording the change of the regional environment, maintaining the regional ecological balance system, and the reproductive function of biodiversity [1,2,3]. Water pollution caused by organic matter is a major global issue which requires more attention [1,4,5,6,7,8,9]. Lake self-purification capacity is the capability by which lakes are enabled to dilute, lessen, or eliminate the undesirable effects of entered pollutants [13,14,15,16]. The self-purification of natural water systems is a complex process that often includes interactions and mutual influences among physical, chemical, and biological processes. Due to this complex process, water (rivers or lakes) can recover its original state [7]
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