马山县东部东岗岭组土壤砷的形态分析及其生态意义

The Analysis on the Forms of Arsenic in the Soils Formed from the Middle Devonian Donggangling Formation in Eastern Mashan County,Guangxi Zhuang Autonomous Region,and Its Ecological Effect

石灰土中高砷会影响岩溶生态系统吗?以广西马山县东部东岗岭组为例,根据岩性差异分层采取表土,测定水溶态、离子交换态、碳酸盐岩态、有机态、铁锰氧化物态、硫化物态砷和全量砷以及植物红腺忍冬中的砷。结果表明,东岗岭组土壤砷平均34.0μg/g,以下部最低,约23.3μg/g。硫化物砷是土壤砷的主要形态,占85%以上。有效态砷不足0.1%,与全量砷无相关关系。红腺忍冬花、叶、枝、茎砷分别为0.30、0.21、0.01、0.07μg/g,没有超标。东岗岭组土壤砷可能以5价无机硫化物砷为主,对中药材山银花危害轻,其原因为土壤高pH、富氧化铁、低磷,从而对砷强烈吸附。

Will high content of arsenic in calcareous soils impact karst ecosystem？ On the section of the Donggangling Formation of the Middle Devonian（D2d） in eastern Mashan county, Guangxi Zhuang Autonoumous Region, soil were sampled on the basis of petrographic differences to test water-soluble, ion-exchangeable, carbonatebound, organic matter-bound, oxide-bound, sulfate-bound and total arsenic. The flower, leaves, branches and stem of Lonicera hypoglauca Mig. growing in the soil of the Lower part of the Donggangling Formation were tested for arsenic, too. The results show that total arsenic in the D2d is averagely 34.0μg/g with the lowest of 23.3μg/g in the lower part of the Donggangling Formation. The sulfate-bound fraction predominates more than 85%. Available arsenic composed of water-soluble and ion-exchangeable fractions is less than 0. 1% seemingly correlating little with total arsenic. The flower, leaf, branch and stem of Lonicera hypoglauca Mig. has 0.30, 0.21, 0.01 and 0.07μg/g arsenic, less than the limited value of Green Professional Standard for the Import and Export of Medical Plants and Their Preparation, P. R. China. So, soil arsenic from the Donggangling Formation may mainly exist in the form of inorganic sulfate-bound fraction of five valence and be less harmful to medical plants because the soil has high pH, iron oxides and low P, adsorbs the arsenic strongly. Mig.