湖南省典型母质水稻土剖面砷的含量及空间分布

Arsenic Content and Spatial Distribution in Paddy Soil Profile of Typical Parent Material in Hunan Province

研究湖南省典型母质水稻土剖面中砷的含量变化及空间分布特征,为指导农田砷污染防控及完善农田重金属基础数据库提供依据。以湖南省6种母质发育水稻土,即河沙泥、灰泥田、黄泥田、红黄泥、紫泥田和麻沙泥为研究对象,采用定位并按土壤系统分类原则挖掘典型剖面59个及剖面土样332个,分析测定了土壤总砷和有效态砷含量以及土壤pH值、颗粒分级组成、有机质和游离氧化铁含量,研究水稻土砷的含量、剖面特征及空间分布,以及与土壤理化性质之间的关系。结果表明,供试水稻土总砷含量剖面全层为2.03~31.16 mg/kg,平均12.30 mg/kg,大多在2.00~18.00 mg/kg,不同母质水稻土总砷含量表现为河沙泥(16.78 mg/kg)>灰泥田(15.01 mg/kg)>黄泥田(13.86 mg/kg)>红黄泥(12.24 mg/kg)>紫泥田(8.44 mg/kg)>麻沙泥(7.40 mg/kg)。水耕表层和底土层总砷含量分别为12.09 mg/kg和12.34 mg/kg。整体上,以分布于湘东及少数湘南、湘西地区的母质样本总砷含量较高。土壤有效态砷含量方面,剖面全层、水耕表层、底土层分别为0.19、0.26、0.17 mg/kg,均以灰泥田最高,麻沙泥最低,其他水稻土相近。相关性分析表明,土壤游离氧化铁、有机质含量是影响土壤总砷含量的主要因子。总体来看,基于土壤分类的湖南省供试水稻土砷处于安全水平。

In order to guide the prevention and control of arsenic pollution in farmland and improve the basic database of heavy metals in farmland,the changes and spatial distribution characteristics of arsenic content in paddy soil profile of typical parent material in Hunan Province were studied.Based on the soil classification,59 typical sections and 332 soil samples were excavated from the paddy soils of Hunan typical parent materials,namely,alluvial sandy soil,grey clayey soil,yellow clayey soil,reddish yellow clayey soil,purple clayey soil and granitic sandy soil.The As content,pH,particle classification composition,organic matter and free iron oxide were detected and analyzed,with a focus on the section characteristics and spatial distribution of As in paddy soil and their relationship with physical and chemical properties of soil.The results showed that the content of total arsenic in the whole soil profile was 2.03—31.16 mg/kg,with an average of 12.30 mg/kg,mostly in the range of 2.00—18.00 mg/kg.The contents of total arsenic in alluvial sandy soil,grey clayey soil,yellow clayey soil,reddish yellow clayey soil,purple clayey soil and granitic sandy soil were 16.78,15.01,13.86,12.24,8.44,7.40 mg/kg.The arerage contents of total arsenic in the cultivated layer and the bottom layer were 12.09 mg/kg and 12.34 mg/kg,respectively.On the whole,the contents of total arsenic in soils distributed in Eastern Hunan and in a few soil samples in Southern Hunan and Western Hunan were higher.The average contents of available arsenic in paddy soil were 0.19 mg/kg in the whole layer,0.26 mg/kg in the surface layer and 0.17 mg/kg in the bottom layer,respectively.The content of available arsenic was the highest in grey clayey soil,lowest in granitic sandy soil,and similar in other paddy soils.The contents of organic matter and free iron oxide in paddy soil were the main soil factors to determine the total arsenic content.In summary,most of the paddy soils tested in Hunan Province based on soil classification were at safe arsenic levels.