Spatiotemporal variations of Fe and affecting factors in larger reservoirs of South China:A case study on Dashahe Reservoir
The present study investigated spatiotemporal variations in Fe contents and their affecting factors between September 2016 and October 2017 in the Dashahe Reservoir in South China.The results show that Fe in surface water was dominated by particulate Fe,while the total Fe concentration(TFe)decreased along water flow from riverine to lacustrine zone.The TFe concentrations in the riverine and transition zones were obviously higher in wet season than in dry season,which should be ascribed to the input of Fe caused by seasonal rainfall in wet season.High Fe level(i.e.,TFe＞0.3mg/L)occurred in the riverine and transition zones due to the input,while the overloading of Fe was seldom found in the lake zone because of the decrease in particulate Fe.The spatiotemporal variations in dissolved Fe(DFe)were similar to those in TFe,while the DFe concentration was more dependent on environmental parameters such as water temperature,rainfall,water depth,and dissolved oxygen.The DFe concentration was averaged being＜0.05mg/L in surface water due to high pH and dissolved oxygen,while could be up to about 6mg/L in the bottom layer due to the release of Fe from the anoxic sediment during the period from May to October.This study highlights the importance of comprehensive consideration of extemal input of Fe from rainfall and intemal release from anoxic sediment in water bodies.The surface water in lacustrine zone should be used for drinking water to avoid Fe contamination.
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