云南个旧多金属矿区农田土壤-作物系统重金属污染现状——以乍甸镇为例

Heavy-metal pollution in-situ in farming soil-crop system in multi-metal mining area—a case study of Zhadian Town,Gejiu City,Yunnan

对云南个旧市乍甸镇农田土壤和农作物重金属污染现状进行了野外调查及评价。结果表明:农田土壤Pb、Zn、Cu、Cd、As质量比均超出GB 15618—1995《土壤环境质量标准》二级标准,Hg未检出,该地区农田呈现以As、Cd为主多种重金属复合污染。Pb、Zn、Cu、Cd、As土壤有效态质量比与土壤全量呈极显著正相关(p<0.01)。农作物中Cu、As质量比与土壤有效态Cu、As质量比无显著相关,Zn质量比与土壤有效态Zn呈极显著负相关(p<0.01),Cd、Pb质量比与土壤有效态Cd、Pb呈显著正相关(p<0.05)。89%的农作物As超标,油菜籽(Brassica napusL.)As质量比最高,均值达(23.04±14.33)mg/kg(鲜重,下同)。Pb超标率达72%,油菜籽Pb质量比最高,平均为(5.55±2.53)mg/kg。Zn、Cd超标率均为11.11%,超标最严重的油菜籽Zn质量比为(46.65±13.61)mg/kg,Cd质量比为(0.24±0.10)mg/kg。Cu超标率为5.55%,油菜籽Cu质量比最高,达(16.02±2.75)mg/kg。油菜籽对As、Pb、Zn、Cu、Cd的转移系数(农作物可食部分重金属质量比(鲜重)与土壤重金属质量比的比值)远高于其他作物。农作物对Pb、Zn、Cd、As的转移顺序依次为果实类、叶菜类、根茎类,对Cu的转移顺序为果实类、根茎类、叶菜类。农作物以As、Pb污染为主,总体属重度污染。聚类分析得出:油菜籽、青蒜(Allium ampeloprasumL.)和生菜(Lactuca sativaL.var.ramosaHort.)重金属污染严重,不适合在该地区继续种植和食用。

The present paper has taken Zhadian Town,Gejiu City,Yunnan,as a case study sample for investigation and assessment of the heavy-metal pollution insitu in farming crop-soil system in the multi-metal mining area.The results of our investigation show that the following heavy metals,including the soil lead （Pb）,zinc（Zn）,copper（Cu）,cadmium（Cd） and arsenic（As）,whose concentrations all exceed the Environmental Quality Standard for Soils（GB 15618—1995）（Grade II）.Among them,mercury（Hg） could not be detected and,therefore,the soil has mainly been suffering from such heavy-metals combined pollution,as As and Cd. Since the concentrations of soil bioavailable Pb,Zn,Cu,Cd and As are significantly positively correlated with their total concentrations,respectively（p0.01）,no significant correlation can be found between Cu and As concentrations in crops and those in soil＇s crop-growing availability.However,a certain meaningful correlation was found among the crop Zn（negative）,Cd（positive）,Pb（positive） and soil bioavailable Zn,Cd and Pb,respectively.In addition,concentrations of As in 89% of crops were found exceeding the maximal limit of contaminants in food-grain,at an average of（23.04±14.33） mg/kg in Brassica napus L.,whose concentrations of As（fresh weight,the same as seen below） are maximally limited.The exceeding rate of Pb was found 72%,whose concentration was observed also highest in B.napus L.,at an average of（5.55±2.53） mg/kg. The extra rate of Zn or Cd was 11.11%,whereas the maximally limited concentrations of Zn and Cd were observed in B.napus L.,at an average of（46.65±13.61） mg/kg and（0.24±0.10） mg/kg,respectively.At the same time,the total exceeding rate of Cu was 5.55%,with the maximally limited concentrations detected in B.napus L.,at an average of（16.02±2.75） mg/kg.The transfer ability of Pb,Zn, Cd and As in crops has been found following an order of fruit leaf root vegetables,whereas Cu in crops keeps an order of fruit root leaf vegetables.The crops was mainly polluted by As and Pb,and presented as severe pollution.The results of cluster analysis indicate that B.napus L.,Allium ampeloprasum L.and Lactuca sativa L.var.ramosa Hort.were not fit for planting and/or used as human-consumptive crops because of their high-level metal transferring index.