| Sedimentary records of the basin and its response to the human activities is one of the hot spots in the study of modern earth surface processes. This thesis selected the Qiantang River Basin, which is located in East China and is influenced by intensive human activities, as study area and analyzed the sedimentary record (total content) of six kinds of heavy metals including Cu, Zn, Pb, Cr, CD, Ni, to investigate the spatial distribution of different heavy metals in different tributaries (mainstream) and make a preliminary explanation of this patterns. All the 93 samples were collected from the fine sediment of the edge of the beach. The Germany contrAA(?)700 Atomic Absorption Spectrometer was used to measure the total heavy metal content. Besides, the organic matter, pH (pH) and redox potential (Eh) were analyzed to reveal their effects on the formation of heavy metals. Based on the measurement results of sediments particle size and data of heavy metal source related to human activities, four preliminary conclusions are drawn as follows:(1) The results indicate that the content of six kinds of heavy metal in the sediments within the Qiantang River Basin is ascended as:Zn>Cd>Cu>Pb>Cr> Ni, and there are some differences between Hangzhou Bay and the Basin. The average content of Zn, Cr, Cu, Ni, Pb, Cd in the surface sediment of inlet reach and estuary are 546.72 mg·kg-1,105.88 mg·kg-1,64.9 mg·kg-1,40.59 mg·kg-1,38.43 mg·kg-1,1.94 mg·kg-1, respectively. While the average content of above six heavy metals in Hangzhou Bay are 345.22 mg·kg-1,76.26 mg·kg-1,31.25 mg·kg-1,42.15 mg·kg-1, 26.11 mg·kg-1,0.098 mg·kg-1, respectively. The average content of above six heavy metals in Yong River are 368.33 mg·kg-1,321.21 mg·kg-1,109.16 mg·kg-1,68.13 mg·kg-1,38.04 mg·kg-1,0.66 mg·kg-1, respectively.(2) The contents of heavy metals in the upper reaches of the river was higher than the downstream. Within the whole basin, the content of heavy metals is highest in the tributaries including Huyuan River, Luzhu River Fuchun River and Yongjiang. In Huyuan River, the highest value of Cu Cd was 124.63 mg·kg-1,104.7 mg·kg-1; Zn and Ni was the highest in Lan River and its mean 1727.85 mg·kg-1,43.87 mg·kg-1; Cr was the highest in Xin’an River and its mean was 164.16 mg·kg-1; Pb was the highest in Fuchun River and its mean value was 53.39 mg·kg-1, Ni in Puyang River was 43.05 mg·kg-1. In the Fenshui and Cao’e River, all 5 kinds of heavy metals were low except Zn. In addition, the content of Cr and Ni were 321.21 mg·kg-1,68.13 mg·kg-1 respectively in Yong River, which was higher than that in the Qian Tang River basin. Above Luci, the content of Cu, Pb, Cr, Cd varies as a pattern of rise-fall-rise again. Below Luci, they decline slowly. The content of Ni rise slowly after in Hangzhou Bay.(3) The main sources of heavy metals in the sediments of the Qian Tang River Basin are anthropogenic sources. Peak values of Cd, Pb, Zn were found in Xin’an River, Fuchun River, Hangzhou Bay and its tributaries such as Lan River, Huyuan River, Puyang River and Yong River, which is mainly caused by the waste water discharged from local industrial enterprises. Pb is influenced by the atmospheric deposition of nearby factories. Results also indicated that the content of all kinds of heavy metal elements in the whole Qiantang River and Hangzhou Bay basin is low due to an effective dilution. The content of Cu, Pb, Cd, Cr, Ni and Zn was 25.51 mg·kg-1,23.54 mg·kg-1,0.12 mg·kg-1,64.93 mg·kg-1,37.42 mg·kg-1 and 307.19 307.19, respectively. Except that Zn is a serious pollution, Cr is no moderate pollution, the other four kinds of heavy metals belongs to the clean level, which indicates that the heavy metals in sediments of Qiantang River and Hangzhou Bay are severely restricted by non-human factors.(4) The organic matter in the mainstream is lower than that in the tributaries. Differences in organic matter content at different sites are influenced by local organic pollutant emissions related to human activity, and the particle size, pH and the hydrodynamic actions. Both pollution of heavy metals and organic matters exist in the watershed. Measured pH showed that the river basin was neutral and alkaline. Both pH and Eh in the Qian Tang River Basin have a slight influence on the distribution of heavy metals. In addition, the spatial distribution of heavy metals Cr and Pb in the study area are severely affected by the distribution of fine particles. |
PDF Full Text Request