Forms of Nutrients in Rivers Flowing into Lake Chaohu:  A Comparison between Urban and Rural Rivers

Chengxin Fan,Lei Zhang,Cheng Liu,Shiguang Shao,Tingting Xu

doi:10.3390/w7084523

Forms of Nutrients in Rivers Flowing into Lake Chaohu: A Comparison between Urban and Rural Rivers

Chengxin Fan, Lei Zhang + Show 3 more

Open Access

https://doi.org/10.3390/w7084523

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Abstract

Nutrient inputs from rivers play an important role in lake eutrophication. To compare the forms characteristics of phosphorus (P) and nitrogen (N) in rivers flowing through rural and urban areas, water samples were collected seasonally from five urban rivers and six rural rivers flowing to Lake Chaohu, China. Higher total phosphorus (TP), particulate phosphorus (PP), soluble reactive phosphorus (SRP), and dissolved nonreactive phosphorus (DNP) concentrations and SRP/TP percentages were observed in urban rivers than in rural rivers, and PP/TP and DNP/TP ratios were lower in urban rivers than in rural rivers. The concentrations of total nitrogen (TN) and all N forms other than dissolved organic nitrogen (DON) were significantly higher in urban rivers than in rural rivers. NH4+/TN levels were higher in urban rivers, whereas PN/TN and DON/TN ratios were significantly lower in urban rivers compared with rural rivers. NO3−/TN and NO2−/TN levels were similar between the two groups of rivers. TP, BD-P, and NaOH-P levels in urban river surface sediments were significantly higher than those in rural rivers. NaOH-P/TP ratios were significantly elevated in urban rivers, whereas HCl-P/TP and Res-P/TP ratios were significantly lower compared with rural rivers. Urban rivers have transferred large quantities of NH4+ and SRP into Lake Chaohu, resulting in higher TP and TN levels and NH4+/TN and SRP/TP ratios. Decreasing the input of NH4+ and SRP into urban rivers is a high priority for mitigating eutrophication and algal blooms in Lake Chaohu.

Highlights

Eutrophication has become the primary water quality issue in most freshwater and coastal marine ecosystems worldwide [1,2]
Of the 11 rivers flowing into Lake Chaohu, Nanfei River (NF), Paihe River (PH), Hangbu River (HB), Baishitian River (BST), Zhaohe River (ZH), and Zhegao River (ZG) were the larger and had the greater water depths (≥3.5 m, Table 1)
The highest mean annual levels of total phosphorus (TP) and total nitrogen (TN) in water were detected in Shiwuli River (SWL), whereas the lowest levels were found in Qiyang River (QY) (Figure 2)

Summary

Introduction

Eutrophication has become the primary water quality issue in most freshwater and coastal marine ecosystems worldwide [1,2]. Algal blooms resulting from eutrophication affect public health, tourism, fisheries, and ecosystems because they can be toxic and adversely affect water taste and odor [3,4]. Eutrophication is caused by excessive phosphorus (P) and nitrogen (N) inputs [2,5]. Both point and non-point nutrient inputs are key drivers of lake eutrophication [6]. Effluent from rivers is a primary point source for lakes [7]. In the absence of anthropogenic activity, the presence of nutrients in river water depends on the ecological and geological characteristics of the surrounding environment

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