Distribution characteristics and sources identification of heavy metals in selenium-enriched soils in Bobai county,Yulin city,Guangxi Zhuang Autonomous Region
In order to promote the development of local green Se-enriched industry and consolidate the achievements of poverty alleviation,172 topsoil samples and main agricultural products samples(100 samples of rice,30 samples of corn and 42 samples of lychee)were collected from the contiguous farming area in the central and northern Bobai county,Yulin city,Guangxi Zhuang Autonomous Region.The contents,spatial distribution characteristics and sources of Se and heavy metals in soil were analyzed by statistics and positive matrix factor(PMF)model.The results showed that the Se-enriched rate of topsoil in Bobai county was 42.08%.Compared with the screening values of GB 15618-2018,the over-standard rates of As,Cd,Cu,Hg,Pb and Zn were low,and Cr and Ni were not exceeding the standard,and the soil quality could meet the local development of Se-enriched agriculture.The spatial distribution characteristics showed that the Se-enriched soils were mainly distributed in Jingkou town,Bobai town,Yashan town,Dungu Town and Wangmao Town.The high values of Se,As,Cr,Ni,Pb and Zn in the soils were consistent with the strata of the Devonian Donggangling Formation and the Silurian Liantan Formation.Cd,Cu,Ni,Pb and Zn were obviously enriched in Santan Town.The PMF analysis indicated that nature sources(Se,Cr and Ni),mining sources(Cd,Cu,Pb and Zn),atmospheric deposition sources(Hg)and agricultural sources(As)were the four major sources of Se and heavy metals in the study area,with contributions of 29.52%,34.87%,23.15 and 12.45%,respectively.The Se-enriched rates of rice,corn and litchi were 90.0%,76.67%and 2.38%,respectively,while the Cd over-standard rate of rice was 24%.Mining activities were the main source of soil Cd in the study area,and the soil as a whole was strong acidic to acidic,and the bioavailability of Cd increased,leading to high Cd content in rice.It is necessary to strengthen the supervision of waste residue,waste water and waste gas discharge of industrial and mining enterprises,carry out soil acidification treatment or spray Se rich leaf barrier to promote the development of green Se-enriched rice industry in Bobai county.
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