| With the exploitation of the stone coal and other mineral resources in black rock series, heavy metals and scattered elements have released from it and the ecological environment has been heavily destroyed, the government and many researchers have paid close attention to it. Lower Cambrian black rock series are widely distributed in the Western Zhejiang, and the exploitation of stone coal, pyrite, phosphorite and other mineral resources has a history of hundred of years. Studying on the soil environment influence of the releasing and migration of elements in the process of the exploitation and hypergenesis of these black rocks will contribute to the utilization of these mineral resources reasonably and also improve the living standard of the local people.Based on the intensive and systematic field and indoor investigations, the characters of the environmental geochemistry of the waste coal stack, waste water of the pit, soil and crops are studied. The characters of representative weathering profiles in the area of Longyou, Zhuji, and Kaihua are also included in this work. In addition, the rules of releasing, migration, and transformation of heavy metals and selenium in waste coal stack as well as the existing form and biological activities of heavy metals in different layers of representative black series profiles are fully investigated. The distribution characteristics of heavy metals and selenium in waste coal stack, surface water, and sediment soils are studied and the environment influences of exploitation of the stone coal are analyzed and evaluated systematically. More over, the migration of selenium in stone coal and the formation of selenium-rich soils are the focus of this work. Models of releasing, migration, and transformation of heavy metals and selenium in different mediums in the study area are established.In the western weathering profiles, compared to fresh stone coal, the content of SiO2, Al2O3, K2O, Na2O and TFe2O3 don't have greatly changed, while the content of MnO in the surface layers decreased significantly. In the eastern weathering profiles, SiO2 is enriched in the surface layer, while K2O, CaO and MgO are enriched in the middle layers. CaO and MgO are obviously defective in the surface layers. In different profiles, Mn, Co, Mo and Sc have the highest degree of enrichment, and REE, Cr, Cu, Th, Pb, Ba and Ti are also enriched to a certain degree. Mo is the most enriched element in every profile. Decreasing of major elements in rock-soils interface is due to the weathering and eluviation.The geochemical characteristics of trace and rare earth elements in the black rock series of western Zhejiang province are significant in three 3 aspects. 1) The ratios of Sr/Ba and Co/Ni are 0.00427-0.041 and 0.054-0.371, respectively, all less than 1. Correlation figures of P2O5-Y, La-Ce, U-Th and Co/Zn-(CO+Ni+Cu) all show that the chemical sediments deposited in these rock series are from mixing of normal sea water and hot water. 2) In different weathering profiles,ΣREE increases gradually from the below to up. And 3) from the distribution pattern of the rare earth elements, we find that in the 3 siliceous rocks profiles mentioned in above paragraphs, LREE/HREE is more than 1. The North American shale normalized REE patterns are aslope to the left with LREE enriched, while chondrite normalized REE patterns are obviously aslope to the left with LREE enriched. This reflects a typical REE pattern of sediments deposited from hot water, the chondrite normalized REE patterns are consistent in different weathering profiles, which indicate that they deposited in the same environment with similar genesis.Based on a series of leaching experiments, we found that most of the heavy metals were leached fast at the beginning, and gradually slowed down as the time past. Especially, in acidic conditions, the leaching rates of Cd, As, Cr, Cu, Zn, and Ni reached the maximum extent quickly, and then decrease quickly. Take Cd, Zn, and Ni elements for example, the leaching rate in seven days are respectively 10.40%, 9.66% and 9.19%. Hg, and Pb leached slowly at first, and then increased gradually, but the total leaching amount is in a low level. The leaching rate of Hg in seven days is 0.11. In alkaline conditions, Se has the higher leaching rate to 0.69% in seven days. Moreover, the leaching rate increased with the time past. This showed the great potential usage for Se.In this research, we found that the pH value and geochemical constituents of soils between the eastern and western Selenium-rich Soil areas have much difference, which are caused by the differences in geological background, depositional environment, sedimentary facies in both regions. The depositional environment of the Hetang formation in the western region was ditch phase unit, so the stone coal layer is thick, and the proportion of carbonate is less. The ratio of quartz/clay of rock is 0.65, and the contents of P2O5 and CaO in the rocks are low. The content of pyrite is as high as 9.3%. However, in the eastern region, depositional environment of Hetang formation belonged to the platform phase. The stone coal layer it is thin, and the proportion of carbonate is high. The ratio of quartz/clay is 0.30, and the contents of P2O5 and CaO are high. It contains 4% pyrite.The comparative study based on the weathering profiles find that the migration of heavy metal in profiles is relation with topography, geomorphology and weathering sedimentation. In source rock area, the stone coal layers usually produce weathering profiles, such as Fuyang profile, Changshan profile, Longyou profile and Zhuji profile. In these sections, most of the heavy metals move out. The dilution rates of heavy metal are in a high level, especially Cd, Zn and Ni. It shows that these elements are all active, and have the ability of migration in the condition of supergene. They can move with the wind, the water and other media at gravity. In quaternary deposits, there are more soil profiles. In black rock series weathering deposits of river valley, such as Anji and Kaihua in the western, Longyou in the eastern, and heavy metals are accumulation in the surface layer. Take Cd and Cu for example, the enrichment coefficient of the former is from 2.07 to 9.91, and the latter is from 0.65 to 4.74. As, Hg, Ni, Pb and Cr are also accumulation in the surface layer of soil obviously.The active component of heavy metals in the soil are also obviously different between the eastern and the western region: The contents of active component of heavy metals are higher in western region, for example, the contents of water soluble and ion-exchange state of Cd take up 46.13% of the total, and Ni takes up 4.48%. Cd and Ni are greatly hazard on the ecological environment in this region. The contents of active component are lower in the eastern region. The contents of water soluble and ion-exchange state of Cd take up only 46.13% of the total, and Ni takes up only 4.48%. The concentration of the element effective form is not high, which indicate the heavy metals in the rocks are not much harmful to the ecological environment at the present. Based on geochemistry survey also with precise analysis, a large-scale selenium-rich soil distributed area 506.8km2 first found in the western Zhejiang, Longyou, Anji, and Zhuji contained. In this area, the soil is thick and fecundity. These selenium-rich soils in the western Zhejiang were from the decay of the Lower Cambrian black rock series. The characters of eastern belt are summarized as follow: There is long distance between quaternary deposits and weathering zone of source rock. The deposit area is a rectangular basin, and the soil belongs to paddy soil, and the layer is thick. The pH changes from weak alkaline to alkaline, and the texture is weight loam. T Cd, Hg content in the soil exceed the national environmental quality standards for 2-3 level, and the content of Ca, Mg, Se are also high. The content of Se in agricultural products is high in this area, but the heavy metals content is low. Western belt has the following characteristics: The quaternary deposit is near to the weathering zone of source rock, and slope is steep. The sedimentation area is an opened river valley. The type of soil is paddy soil, and the layer is thin. The pH changes from weak acid to acid and the particles are coarse relatively. The contents of Cd, Ni, Se, Zn, As, S and Fe are high, but the contents of Ca and Mg are low.Based on the result of comparison, it is first found that, to a great extent, S, Org.C, CaO, MgO, Cd, Zn, Ni, Hg, As, and Se in selenium-rich soil in the western Zhejiang are inherited from the source stone coal, and alkalinity acidity and physicochemical properties in the soil are deeply influenced by S, Org.C, CaO and MgO. The content of S and Org.C in selenium-rich soil is higher in Anji than in Longyou, while the content of CaO is higher in Longyou than in Anji. Moreover, soil in Longyou presents alkaline to weak alkaline, while soil in Anji presents acid. The result shows that oxides and trace elements in the soil of studied area have a close relationship with source rock.According to correlation analysis, in the soil of different parent materials and different types in selenium-rich area of western Zhejiang, we find that the content of effective selenium and pH has a great relationship. In the soil of same parent material and same type, the content of effective selenium and selenium(total) has a great relationship. Based on the theory of factor analysis, we obtain the factor loading of elements in studied soils after varimax rotation. The reslut shows that F1 and F3 reflect the characteristics of paragenetic association of Se and Cd, Cu, Zn and MgO respectively in selenium-rich soil of sedimentary area.The research shows that, the soil presents alkaline, and the content of P, Ca, Zn, and Mn is rich in selenium-rich area in Longyou. Because phosphate and alkaline condition can promote Se activation, and Ca, Zn and Mn can antagonize Cd, the Se absorption of the root of crops increase, while absorption of the heavy metal such as Cd decrease. Therefore, agricultural products in selenium-rich area are higher in selenium and lower in cadmium. However, the content of S and Org.C is high in selenium-rich area in Anji and the soil presents acid. Because of absorption of soil clay, the activation of Se is low. What is more, the antagonism to Cd and Ni is not obvious, because the content of Ca and Mn is low. Therefore, agricultural products are higher in cadmium and nickel and lower in selenium.According to the investigation on crop, the content of elements active component in the . eastern and western region, the content of selenium and heavy metal, and ecological effect has a great relationship. In western area, compared to limited value of food security standards of the Ministry of Agriculture, the content of Cd and Ni exceed seriously(Cd 0.26-0.63mg/kg, Ni 0.5-1.0mg/kg). However, the crops are also zinc-enriched and selenium-enriched. Based on the field survey, local residents are in good health, and there isn't any endemic disease such as "itai-itai disease". It is inferred that there are antagonism effects between Se, Zn and Cd, Ni in Human, and absorption of Cd and Ni is less. On the contrary, in the eastern area, the content of Se is high in crops such as rice and lotus seed, while Cd and Ni are low. It is showed that the content of Se is high and heavy metal is low.In this study, natural selenium-rich rice, lotus seed and other selenium-rich crop are found for the first time in the eastern area. The content of Se is high in these crops. Moreover, the content of heavy metal is low and isn't over standard. This reflects the unity of health and safety in selenium-rich crops. Enormous economic benefits are made by scale development of selenium-rich soil. Local residents who live on these crops for long term are energetic, health and longevity. According to statistics, content of selenium in their hair is 1.79-3.75 times of others.In this thesis, we study on the characters of representative weathering profiles of black rock series in western Zhejiang. We also do some leaching experiments, and study on elemental speciation of profiles. The results showed that in the condition of acid, Cd, Zn, and Ni have strong ability of migration in black rock series of Lower Cambrian Hetang Group in western Zhejiang. However, Se has strong ability of migration in the alkaline condition. According to the research, the development of selenium-rich soil can be chosen in the area where is relative alkaline. And we hope to provide a scientific basis of producing selenium-rich natural and quality of agricultural products in barren mountain.
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