Heavy Metal Pollution Investigation And Environment Risk Assessment In Typical Earthquake Region

With the development of human society, social economy grows up quickly, and the rapid urban disorder expansion is sweeping the globe.While human beings are enjoying benefits of industrialization, modernization and urbanization, at the same time, we also has begun to face a series of environmental pollution and serious ecological environment problems. To improve the environment quality has become the issues that human needs to solve urgently. Among these prominent environmental problems, heavy metal pollution caused by human activities, especially soil heavy metal pollution, is more and more outstanding.Heavy metal pollution occurs widely, and can last for a long time, once polluted. Since it cannot be exchanged or decomposed in biological material circulation and energy exchange, the heavy metals will eventually be accumulated in living beings, and become pathogenic with great harm. Although heavy metal in the human body can be divided into the essential elements and poisonous elements, the content over a certain limits can be poisoning pathogenic, carcinogenic, and teratogenic.Pengzhou and Shifang city are important industrial and vegetables production base in Sichuan provience, and the two cities has been damaged badly in the earthquake of 5.12. Earthquake caused a great economic damage and casualties, and also caused chemical enterprise plant and equipment damage and heavy metal tailing leakage. An earthquake is likely to cause pollution of soil, water area, to make influence to agricultural production, and to threaten the life and health of local residents. Heavy metal pollution investigation and risk evaluation in the earthquake-stricken area can provide strong basis for post-disaster reconstruction, and also guarantee residents'lives and health.This study took and analyzed the samples collected from the two cities where exist typical pollution sources, and also survey the pollution status of other areas as a control. The heavy metals, such as arsenic, copper, chromium, nickel, lead, and zinc in surface soils, crops and human hairs were determined, the spatial distribution of soil heavy metal in selected areas by the mean of geographic information system was analyzed, and the relationship between heavy metals spatial distribution and seismic was disscused. The main results were summarized as follows.1. There exists pollution of arsenic, copper, chromium, nickel, lead and zinc in different degrees due to the combined action of quake zone industry and mining and seismic action. As, Cu, Cr, Ni, Pb, Zn concerntration range 1.05-88.lmg-kg-1, 18.1-42.1mg·kg-1,62.42-147.5mg·kg-1,20.5-49.9mg·kg-1,13.7-29.1mg·kg-1, 31.7-4514mg·kg-1 respectively. The total sample point comprehensive pollution indexes all reaching heavy pollution levels. Areas near the Longmenshan copper sand tailings was polluted most seriously, and the heavy metal synthesizing pollution index of six heavy metals were the highest.2. Six metals in selected areas were spatially correlated in medium level, and the ration of nugget values and base station values of copper and chrome was small, which was 29.07% and 38.27% respectively, and was influenced greatly by natural factors. Space mutation angles of arsenic, copper, lead and zinc fit the direction of seismic belt well.3. The main crops, such as rice, corn, wheat, soybean, vegetables in earthquake damaged areas, were polluted by heavy metals. Arsenic in rice, corn, vegetables, beans, wheat respectively range 0.00-1.03mg·kg-1,0.00-0.99mg·kg-1,0.00-1.82mg·kg-1, 0.00-0.70mg·kg-1 and 0.00-1.87mg·kg-1; Copper in five crops respectively range 0-15.8mg·kg-1,0-6.35mg·kg-1, 0.01-43.2mg·kg-1,1.07-18.8mg·kg-1,2.17-14.2mg·kg-1; Chromium in five crops respectively range 0-69.6mg·kg-1,0-9.1 lmg·kg-1,0-45.8mg·kg-1, 0-32. lmg·kg-1,0-38.6mg·kg-1; Nickel in five crops respectively range 0-23.lmg·kg-1, 0-0.622mg·kg-1,0-18.9mg·kg-1, 0-15.6mg·kg-1,0-21.7mg·kg-1; Lead in five crops respectively range 0-11.3mg·kg-1,0-5.84mg·kg-1,0-27.6mg·kg-1,0-15.82mg·kg-1,0-28.8 mg·kg-1; Zinc in five crops respectively range 0-135mg·kg-1,0.15-37.5mg·kg-1,9.18-483 mg·kg-1,11.4-85.0mg·kg-1,25.0-242mg·kg-1. However, pollution was different from crops. The ratio of surpassing limits of heavy metal content in rice and wheat was higher than in other crops. Arsenic, lead and zinc have a higher level of overstandard ratio in crops. Except for corn, arsenic overstandard ratio in crops was above 50%; Lead in four kinds of crops was above 60% except for corn; Zinc overstandard retio was above 70% except for corn, and zinc in wheat and beans overstandard rations was over 90%. The results indicated that these 3 heavy metal pollution existed seriously, and had higher risk for edible.4. The heavy metals in human hairs in earthquake area existed overstandard phenomenon. As, Cu, Cr, Ni, Pb, Zn concerntration in human hairs in selected area respectively range 0.11-5.69mg·kg-1,0-66.72mg·kg-1,0.02-6-10mg·kg-1,20.0-63.8 mg·kg-1,1.14-109 mg-kg-1 and 68.3-710 mg-kg"1. The overstandard of chromium was the highest, reaching 99.04%; followed by lead, which was 55.98%.Overstandard ratio of four other metals were around 20%, and chromium and lead had the greatest health risk to residents.