Assessment On Heavy Metal Pollution In The Sediments At The Hunhe River And Dahuofang Reservior

Hunhe River is a typical seasonal river in north China and Dahuofang Reservior is a typical drinking water source in Liao River basin. Due to waste water discharges from industrial enterprises, heavy metal pollution has been a prominent problem. In this paper, the content and speciation of elements Cu, Zn, Pb, and Cd in surface sediment were analyzed. Combined with physicochemical characteristics of the sediment, the content level, distribution, form and environmental impact of the heavy metals were studied. Meanwhile, assessment methods, such as geoaccumulation index, potential ecological risk index and RSP were used to evaluate their pollution extent. On the other hand, distribution of Cu, Zn, Pb, and Cd in the core sediment of Dahuofang Reservior was analyzed, combined with the result of 210Pb and 137Cs dating, the history of pollution was studied. The main results are as follows:(1)The content of heavy metals in surface sediment from Hunhe River and Dahuofang ReservoirThe content of Cu, Zn, Pb and Cd in surface sediment from Hunhe River and Dahuofang Reservoir was higher than that of soil background in Liaoning Province, exhibited obvious enrichment. The content of heavy metals in surface sediment of Dahuofang Reservoir was signally higher than that of Hunhe River, moreover, higher than the average values of Liao River basin.(2) The distribution characteristic of 4 elements in surface sediment from Hunhe River and Dahuofang ReservoirAffected by the discharge of waste water from Fushun and Shenyang city, the content of Cu, Zn, Pb, and Cd upstream Hunhe River was much higher than that downstream. But, there was still one station downstream Hunhe River where the element content was extremely high, at the lacation of Hongtoushan copper mine. Because Cu, Zn, Pb and Cd content in Dahuofang Reservoir were affected by the discharge of waster water from KQ-12 station, the contamination was roughly in a downward trend from the head to the tail of the reservoir.(3) Forms of heavy metals in surface sediment from Hunhe River and Dahuofang ReservoirThe distribution of forms of the four elements is well consistent with each other. Extractable fraction was dominant in both Hunhe River and Dahuofang Reservoir, of which Zn, Pb and Cd mostly existed in reducible, reducible and the acid -soluble fraction. However, extractable Cu mainly existed in reducible and oxidizable fraction, respectively.(4) Assessment on Heavy Metal Pollution in the Sediment in the Hunhe River and Dahuofang ReserviorGeoaccumulation index, potential ecological risk index and RSP, aiming at the enrichment, potencial ecological risk and potential release, were used to assess metal pollution. The result shared a coherence that Cd was the cardinal pollutant because of its high enrichment, strong potential ecological risk and release capacity.(5) History recorder of heavy metals in sediments of Dahuofang ReservoirSince the reservoir was constructed, four stages of the heavy metal concentration were recognized. Before 1963, natural deposition was dominant, and concentrations of all heavy metals kept stable. From 1963 to 1993, human activities aggravated gradually, and concentrations of Cu, Zn, Pb and Cd increased. From 1993 to 1997, the content of heavy metals decreased quickly mainly due to extraordinary flood in 1995, which diluted the high content of heavy metals. From 1997-2010, the concentrations of Cu, Zn, Pb and Cd increased again with the increase of human activities.