Dissertation > Excellent graduate degree dissertation topics show

District of mercury and mercury atmospheric heavy metal pollution assessment

Author: ZhangZuo
Tutor: ZhangChengXiao；Julia Lu
School: Shaanxi Normal University
Course: Analytical Chemistry
Keywords: Mercury Mercury mine Heavy metal Surface water Soil Sediment Plant Atmosphere
CLC: X53
Type: Master's thesis
Year: 2008
Downloads: 611
Quote: 1
Read: Download Dissertation

Abstract

This thesis includes two parts:a review and a research report.In the first part,the characteristics and applications of mercury and the sources of mercury pollution were introduced.The status and prevention of mercury pollution and the effects of mercury on human health were reviewed.The development in analytical methods of total mercury was extensively presented.In the second part,a mercury mine in Xunyang County in Shaanxi Province,the largest mercury mine currently in operation in China,was selected as a case for the study.The concentrations and distributions of mercury species were studied in surface water,soil,sediment and plants（cabbage and wheat seedling） in the region affected by mercury mining activities.The environmental geochemistry behaviors and modes of transport,transformation,and enrichment of mercury in mercury mining environments were thoroughly discussed.The behaviors and modes of transport and enrichment of mercury in plants are also discussed.The data obtained indicate that the plants which grow in the region are contaminated by mercury mining.In addition,the relationship between mercury and other metals was studied.The results indicate that the contamination of mercury is accompanied by the contamination of other metals.The concentration of heavy metals and methyl mercury in wet deposition（rain and snow） was determined.Compare the percentage of methyl mercury in rain and snow samples between city of Toronto and Yellowknife.The main conclusions are as follows:1.In Xunyang mercury mining area,the total mercury concentration in surface water ranged from 0.12 to 25.57μg L^-1,with the average value of 2.08μg L^-1 and the particulate mercury typically exceeded 50%（with the average of 64%） of total mercury in the stream water.This indicates that the main transportation of mercury was performed by particulate mercury in surface water.The result showed that the concentration of total mercury dropped sharply in several kilometres from the Gongguan furnace,climbed when approaching the Qingtonggou furnace;decreased rapidly with increasing distance from the Qingtonggou mining and smelting location.2.The total mercury contents in soil samples collected from Xunyang mercury mining area ranged from 1.3 to 752.1 mg kg^-1,with the average value of 106.6 mg kg^-1.The most contaminated sites appeared at sites No.5 and No.12 with the values of 518 mg kg^-1 and 752.1 mg kg^-1, respectively.It was attrubited the fact that site No.5 was closed to Gongguan melting furnace and site No.12 was closed to Qinggonggou melting furnace.The total mercury content in soil samples was attrubited to two factors.The first one was the high mercury contents in local soil.The second one was that the mercury released from mercury smelting furnace could get into atmosphere and then a part of mercury could deposit to the soil in the area.Similar as in surface water,the total mercury contents in soil dropped first and then climbed in Gongguan area and decreased with an increase of the distance from the Qingtonggou mercury smelting furnace in Qingtonggou area.It was clearly seen that the mercury contents decreased with an increase of vertical depth at sites No.1 and No.22.3.In the Xunyang mercury mining area,the total mercury contents in sediment ranged from 59.7 to 2100 mg kg^-1,with the average value of 580 mg kg^-1,which was much higher than the mercury value from background area.It was attrubited the fact that the mercury easily deposited into sediment.The distribution of mercury content in sediment showed the similar tendency as in surface water and soil.4.The total mercury contents in plants（cabbage and wheat seedling） samples collected from Xunyang mining area ranged from 58-5370 ng g^-1（wet weight） with an average value of 1163 ng g^-1.The total mercury contents in the roots and leaves samples ranged from 62 to 4210 ng g^-1 and 58 to 3420 ng g^-1,respectively.The mercury levels in root were generally higher than those in leaf. These values were much higher than the maximum value of 20 ng g^-1 recommended by the Chinese National Agency for food sources.It indicated that the plants（cabbage and wheat seedling） were significantly contaminated by mercury mining activities.The Fit values suggested that mercury translocation into the plants from roots to aerial part occurred and the mercury source was mainly derived from soil rather than atmosphere.5.The contents of other metals（Se,Pb,Sb） in surface water,soil and sediment samples showed a common lithological correlation with mercury.There are positive correlations between mercury and other metals in surface water,rather than in sediments.It was found there was only a strong tight correlation between the contents of mercury and Sb.It indicated that the activities of mining affected the contents of other metals in this study area.Actions should be taken to clean the contaminated riverbed,manage waste discharges,and reduce the exposure of mercury to the local residents by issuing advisory for consuming the agricultural products grown in the area.6.The contents of heavy metals including Cd,Fe,Mn,Ni,Pb,T1,Zn,Co,Cu,Hg and Al in wet deposition（rain and snow） in Toronto and Yellowknife,Cannada,showed that the contents of heavy metals in rain samples were much higher than that in snow samples.The contents of Al,Fe, Pb,Cu,Zn were much higher than that of others such as Cd,Mn,Ni,T1,Co,Hg in both rain and snow samples.The percentage of methyl mercury in rain samples was higher than that in snow samples in Toronto and Yellowknife.The contamination of heavy metals in atomosphere in both Toronto and Yellowknife cities was not serious compared with other cities.

Related Dissertations

CLC: > Environmental science, safety science > Environmental pollution and its prevention > Soil Contamination and Control
© 2012 www.DissertationTopic.Net Mobile