| Soil , being in a centeral position within entironment, is the important part of the environmental factor , undertaking approximately ninety percents contamination which comes from each routes . Soil polution of mining area is mainly caused by heavy mentals , and be attached much importance to by pursuers , because of its more source > enshroud , durative and sequential ponderance ,etc.In this article , the investigation covers from goldfield and its influential region in Tongguan , Shaanxi . The emphases includs : carving up environmental geochemical landscape of mine types , studying environmental geochemical characteristic and distributing rule which behaving from five sorts heavy mental — Hg,Pb,Cd,Cr,As, etc, from farmland soil which caused by mining exploitation, analyzing polution actuality and tendency , and fundamentally appraising this area's soil environmental contamination.This article chooses goldfield and its influential region ,especially northern loess section which human being living environment seriously destroied , carry through field survey ,gathers soil samples ,according as analysis outcome from cyanide geochemical AF (Hg, As) and AAS (Pb,Cd,Cr) analysis measures, using plot softwares such as Grapher, MapGis,Coreldraw, SPSS , and so on , draw pictures which is reporting environmental geochemical characteristic and distributing rule which behaving from five sorts heavy mental and present situation in soil ,make use of Index methods to appraise this area's soil environmental contamination.The flowing conclusions we have been drawn :1. According to the difference of scale of nining area , position , types , surficial damage of nining environment , distance away from mining area , and climate condition, rock types, hypsography, physiognomy, surficial runoff, vegetation bestrow ratio, soil feature , and face geochemical codition , district research region as five district geochemical landscape as below : Bedrock mountainous region , Inclined primary of alluvium before southern mountain , Deficient primary of loess avine , Yellow and Wei River alluvial plain , and alluvial terrace round Shuangqiao River.Southern bedrock mountainous region is vastr , Yet the cropland cover rate is exceedingly low , Not bring into the research district range.2. The maximum ,mean square deviation and mean value of Pb,Cr,Cd,As, Hg in the soil in research region separately are 6310μg/g,69.8μg/g,4.8μg/g, 35.7μg/g,111μg/g, and 131.34, 6.38,0.446, 3.8,10.79 , and 119.7μg/g, 44.076 μg/g,0.20μg/g, 13.97μg/g, 1.47μg/g.3. except for Cr ,in five sorts of heavy metal in the research district ,the mean value of Pb, Cd , Hg and As that all being more than the Chinese soil background value , the river system deposit background value and the earth's crust mean value , also be more than backdrop average value (not polluted region); Cr's meanvalue is lower than the Chinese earth backdrop value > the water system deposit backdrop value and the earth's crust mean value , Merely a little more than backdrop average value (not polluted region).Thereby we drawn conclusion that the reserch district soil heavy metal mean value total content is taller (Not counting Cr ).4. In research district and every geochemical landscape , the frequency distribution pattern of Pb , Hg and Cd as is analogous , obey the non- normal distribution , the peak value is leaning left , and have being interrupted on peak value right side .The data flunctuate very much obviously , and the scattered extent are high ; The frequency distribution pattern of G\ As is analogous > obey the normal distribution essentially , yet on the peak value right side date also possess being interrupted , reflect that very few data dispersion is great.5. Supposing enrichment modulus (F) less than 0.5 ,we say it as dispersedness; 0.5 < F < 1.0, we say it as light dispersedness ; 1.0 < F < 2.0 is fair enrichment ; 2.0 < F < 5.0 is the exceeding enrichment ; F > 5.0 is high enrichment, we comes to distinguish every element's enrichment degree in the research district, Knowably :?Compared with Chinese soil background value : the element of Hg is fairly high in the research district; Three elements of Pb> Cd and As are exceedingly abundant; the element of Cr have a light enrichment. Compared with the mean value of earth's crust of China : Three elements of Hg -. Pb^ As have a high enrichment ; Cd are exceedingly abundant; and the Cr take on a light dispersedness.?Compared with the background mean value : Compositor of enrichment degree of five sorts of element in Inclined primary of alluvium before southern mountain ,Deficient primary of loess avine , Yellow and Wei River alluvial plain , and alluvial terrace round Shuangqiao River is on the whole unanimous > and shown that : Cr The modulus of Cr and As is 0.5 Cr> CdandAsis0.5 As, Cd, Cr being subjected to impact which come from mining exploitation -. activity of selection and smelt metal and the earth's surface runoff effect ,and theirs" position tend to showing no difference . Distribution of abnormality of As, Cd, and Cr have a tendency from "spot shape" to string shape ; and distribution of abnormality of Pb, Hg haveappeared lump.7 . Research district There are 42.3 % sample spot which have been subjected to pollution by heavy metals . The 14, 30, 111 is subjected to synthetical pollution by Pb , Hg, and Cd ?, The sign specimen of 27 is subjected to synthetical pollution byPbandCd ; 2. 21, 22, 43, 68, 79, 89, 114, 118, 119, 120, 130 is subjected to synthetical pollution by Pb and Hg ; 35 is subjected to pollution by As; The number of samples subjected to pollution by Hg is most , account for 94.5 % in the contaminated samples' sumtotal.8 . The taxis of sample synthetical pollution state toward every landscape is : Alluvial terrace round Shuangqiao River > Inclined primary of alluvium before southern mountain > Deficient primary of loess avine > Yellow and Wei River alluvial plain , and the pollution rank successively is : strong pollution , Middle pollution , gently pollution and security level ,etc .9 . The soil in every landscape of research district all is subjected to the different extent pollution . And the pollution degree in Alluvial terrace round Shuangqiao River is considerably strong. |
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