Use of the Sediment Quality Triad to Assess Metal Contamination in Freshwater Superficial Sediments from the Le An River, China

By integrating data on the chemistry, toxicity and benthic community structure, the sediment quality triad was used to evaluate the current situation of superficial sediments from the Le An River. This river has been strongly polluted with large amounts of copper, lead and zinc in waste water discharging from riparian mining and smelting activities. The response of the benthic environment was illustrated by ratio-to-reference (RTR) scale in corresponding triaxial graph. From upstream to downstream, the response intensity of three components showed sectional characteristics. The upstream area was relatively clean due to less disturbance. Within the middle stream area, extreme toxicity and serious deterioration of the benthic community structure could be mainly ascribed to strong acidity in drainage and high concentrations of multiple metals in superficial sediments, especially copper. Because of the river self-purification capability, pollution gradually declined and the sediment quality began to recover downstream. The situation was closely associated to the distribution of major pollution sources, therefore, source control and dredging operation on contaminated sediments in the middle stream area are required urgently.