Title: western Zhejiang region Cambrian black shales in the Selenium and Heavy metal geochemistry and environmental effectsAuthor: Song MingyiDegree-granting unit: Hefei University ofKeywords: Lower Cambrian;; black shales;; selenium;; heavy metals;; table geochemistry;; enriched soil;; ZhejiangSummary:
With the black shales in the stone coal and other mineral resources are extensive exploitation, which the occurrence of heavy metals and scattered neodymium magnets elements in supergene conditions to release them, causing serious ecological damage to the environment and potential threats, the government and has caused many researchers wide attention. Widely distributed in western Zhejiang region of Lower Cambrian black shales, rich stone coal, pyrite, phosphate rock mining and other mineral resources are used, for several hundred years of history. Therefore, the study of mineralized black shales in the mining process and the role of elements in the supergene migration of the release, into the soil caused a profound impact on the environment, for land use and improve the scientific health of local residents, is of great significance.
In this paper, a large number and detailed field work and laboratory analysis of research on West Stone Mountain coal mine waste coal pile, mine waste water, soil, crops and other environmental geochemistry and the East with Longyou, Zhuji region and the West with Angelina, and other civilized region representation of mountain stone mine to study the characteristics of the profile, revealing the Hg, Cd, Cr, Pb, Ni, As, Cu, Zn and other heavy metals and selenium in the beneficial elements of the release of mine waste coal pile, migration and transformation rules, heavy metals in levels of occurrence of each soil profile morphology and biological activity of the heavy metals and selenium in waste http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php coal pile, surface water, sediment and soil characteristics of the spatial distribution, system analysis and evaluation of the Stone Mountain Coal mining areas to the west of Zhejiang with to the environmental impact of coal and stone migration of selenium and selenium-rich soil formation mechanism of in-depth discussion, the establishment of heavy metals and selenium in different media release, migration and transformation mode.
The weathering profile, compared with fresh elements of stone coal, West with SiO_2, Al_2O_3, K_2O, Na_2O, TFe_2O_3 little change, MnO significantly reduced in the surface; East SiO_2 with weathering profiles show enrichment in the surface occur, K_2O in the middle enriched layer occurs, CaO, MgO enrichment in the middle layer and the surface loss is very obvious. On a different profile, Mn, Co, Mo enrichment highest, some elements REE, Cr, Cu, Th, Pb, Ba and Ti also have some enrichment. Among the most typical of Mo, the concentration in each section are very high. Research shows that constant elements in the rock - the interface between the soil changed significantly, indicating that the role of weathering and leaching of major elements of the decrease occurred mainly in the rock - soil near the interface.
Western Zhejiang region black shales trace and REE geochemical characteristics significantly, mainly in: ① Sr/Ba0.00427-0.041, Co / Ni in the 0.054-0.371, were <1, P_2O_5 with Y, La-Ce, U- Th and Co/Zn- (CO + Ni + Cu) and other diagrams show the normal sea water and hot water mixed sedimentary features; ② weathering profiles in different parts of the bottom-up, from weak to strong or weak weathered regolith layer until the surface soil , ΣREE gradually increased, upward migration significantly, showing a strong surface enrichment capability. ③ REE patterns can be seen from the above three carbonaceous chert section LREE / HREE> 1, the North American shale REE distribution patterns in the performance of standard left-leaning, moderate enrichment of light rare earth elements show; and spherules Standardized distribution patterns in meteorites is apparent right-wing, light REE relative to heavy rare earth enrichment of performance, reflecting the typical hydrothermal sedimentary REE patterns. Different sections of rare earth in the chondrite-normalized data and the distribution of North American shale-normalized patterns, have shown good agreement, indicating that the same depositional environment and close genetic relationship.
Leaching study found that most of the initial stages of leaching of heavy metals are fast, after gradually slowed down over time. Which under acidic conditions Cd, As, Cr, Cu, Zn, Ni filter out the highest rate quickly, soon after the reduction, especially Cd, Zn, Ni high speed start-up phase, the speed will come down soon , 7-day leaching out of the amount of the corresponding elements of column leaching accounted for 10.40% of the total, 9.66%, 9.19%; and Hg, Pb filter out slow, then gradually increased, but the total is not high, such as Hg in 7 days of leaching out of the total volume of only 0.11%. Se under alkaline conditions to filter out the seven-day 0.69% of total accounts, and continued to increase over time, with great potential value in use.
Through the work zone facies Palaeogeography, two things that cause soil pH and soil enriched with the geochemical composition of the main reasons is due to large differences in the east and west with the geological background, different depositional environments and sedimentary facies. The West Hawthorn period with a ditch with depositional environments are sets, stone coal seam thickness, the proportion of low carbonate layer, quartz / clay ratio of 0.65, P_2O_5, CaO content is low, high pyrite content of 9.3%; and East period with Hawthorn platform facies sedimentary environments are stone coal seam thickness is small, more carbonate layer laminated, quartz / clay ratio of 0.30, P_2O_5, CaO content, pyrite content of 4%.
Weathering surfacing comparative study found that heavy metal migration in the section on forms, and topography, weathering, sedimentation, etc. are closely linked. In the source rock area, rock weathering profiles developed mainly coal, Fuyang, Changshan, and Zhuji Longyou mountain of coal and other places stone profile, heavy metals to move out of the main elements appear in most topsoil depletion, in which Cd, Zn, dilution rate of Ni is most evident, indicating that these elements are chemically active in the migration of supergene conditions highly, most with water, wind and other media in the migration of gravity. Mainly developed in the sedimentary soil profiles, such as the West with Angie, civilized, and other East Valley plains with the Longyou black shale weathering landfill, heavy metals to accumulate mainly in the form, compared with the C-layer profile, Cd, surface enrichment of Cu was highest in the former enrichment factor 2.07 ~ 9.91, 0.65 ~ 4.74 which; followed by As, Hg, Ni, Pb, Cr, apparent surface enrichment occurs.
Profile analysis and elemental speciation analysis found that East and West with the heavy metal content of the active component of the large differences, in particular in: (1) West with a high content of active components, including Cd, water soluble, ion exchangeable accounting for 46.13%, Ni ion exchange water soluble and 4.48% of the total state. Heavy metal content so serious, Cd, Ni on the ecological environment should have a greater harm. (2) The active component of the low East with heavy metals, Cd-state ion exchange (with water soluble) of the total 17.9%, Ni ion exchange state (including water soluble) accounted for only 1.79%, the absolute content of effective state is not high, the minimal harm to the environment.
Through the soil geochemical survey and the use of high-precision testing means, for the first time in western Zhejiang region of Se-rich soil found in a large-scale, distributed in Longyou, Anji, Zhuji and other regions. Deep soil of the region, moderate texture, soil fertility, the total area of 506.8km ~ 2. According to modern theory analysis of deposition, to confirm western Zhejiang region comes mainly from the Se-Se district Lower Cambrian black rock series Hawthorn Group. Middle East with enriched soil formation characteristics: Quaternary sedimentary source rock weathering zone distance, sedimentary basin is a long strip, sterile soil type for the retention-type rice soil is slightly alkaline - alkaline soil thickness, soil texture is heavy soil, Cd, Hg content in the soil for the state environmental quality standards for two to three, Ca, Mg, Se is characterized by higher levels. High selenium area of agricultural products, heavy metals content is low. West with the formation of Se-rich soil characteristics: Quaternary sedimentary source rock weathering zone with the short distance, the terrain steep, the deposition area is an open valley, the soil type infiltration-type rice soil fertility, soil is thin, was Acid - acidic, relatively coarse particles, geochemistry to the rich Cd, Ni, Se, Zn, As, S, Fe, low Ca, Mg is characterized.
Contrast through the system, first discovered, western Zhejiang enriched soil S, Org.C, CaO, MgO, Cd, Zn, Ni, Hg, As, Se, compared with the source Stone coal has a higher inheritance. One, S, Org.C, CaO, MgO, and on soil physical and chemical properties such as pH have a profound impact. Angelina enriched soil S, Org.C content is still higher than Longyou, and Longyou CaO content in soil is still higher than Angelina, showing Longyou soil is alkaline, acidic soil Anji difference, indicating that the soil in two oxides and trace elements and their source rocks in the geological background of still more closely linked.
Correlation analysis, in the western Zhejiang Se district in different parent materials and different types of soil, the effective selenium is closely related with soil pH; in the same parent material and the same type of soil, the effective total selenium and selenium in the soil significantly correlated. According to the principle factor analysis, orthogonal rotation obtained using the maximum area of soil in the final factor loadings of indicators, F_1, F_3 respectively, reflecting the deposition area of Se and Se-rich soil Cd, Cu, Zn, and symbiosis with MgO native assemblages.
The study found that selenium-rich soil Longyou alkaline, P, Ca, Zn, Mn-rich, as phosphate, alkaline environment to promote the role of activation of Se, Ca, Zn, Mn antagonism of Cd and alkaline environment, the curing effect of Cd, the root crops to increase the absorption of Se, the absorption of Cd and other heavy metals greatly reduced, making the area of agricultural products into high-low cadmium selenium enriched natural produce. The selenium-rich areas as Angelina S, Org.C high geological background, acidic soils, Se is much lower soil clay adsorption activity, coupled with Ca, Mn content is low for Cd, Ni antagonism is not obvious, therefore, leading agricultural products in Cd, Ni and Se content exceeded the phenomenon is relatively high.
Through biogeochemical study found that the two sides of the active component with the content of the soil elements, selenium and heavy metals in agricultural and ecological effects of the correspondence between the three has a good relationship. Among them, the Western District of rice enriched with selenium in selenium threshold is only reached with the Ministry of Agriculture standards of food hygiene limited value compared to agricultural Cd, Ni content than the standard (Cd 0.26 ~ 0.63mg/kg, Ni 0.5 ~ 1.0 mg / kg), but also of zinc, selenium levels. Field survey found that local residents in good health, not a "Itai-itai disease" and other endemic diseases. Inference is the body's internal Se, Zn for Cd, Ni antagonistic shielding effect, affecting the body's Cd, Ni absorption. In contrast, the East with rice, lotus seeds and other agricultural products of high levels of Se, Cd, Ni low, showing the characteristics of high-selenium heavy metals.
First discovered in the East with enriched rice and high-quality natural Longyou Se seeds. These produce high levels of selenium, heavy metals in the Ministry of Agriculture, Food Hygiene limited range, reflecting the selenium-rich agricultural health and safety of unity. Se-rich soil research, After years of development and utilization of selenium-rich agricultural scale, has made great economic benefits. Long-term consumption of these agricultural products to local residents, expressed as energy, health and longevity, is the normal hair hair selenium content of selenium 0.28mg/kg 1.79 ~ 3.75 times.
The above study of black shale weathering profiles, leaching studies, the soil profile studies and morphological analysis of such elements, that western Zhejiang group of the Lower Cambrian black rock series Hawthorn area Cd, Zn, Ni in acidic conditions with a strong migration, but in an alkaline environment is relatively fixed; and Se in alkaline conditions, the migration ability, in the acidic environment is more stable. According to this feature, select the region to develop enriched relative to alkaline soil, barren mountain for the production of enriched natural quality of agricultural products to provide a scientific basis.Degree Year: 2009
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