安徽沿淮粮产区小麦与根系土重金属含量特征及影响因素

Characteristics and Ecological Security Assessment of Heavy Metal on Wheat and Root Soils Along Huaihe River Commercial Grain Base in Anhui Province

【目的】为地方耕地质量保护、小麦安全生产及农业种植结构调整提供依据。【方法】通过系统采集小麦籽实与根系土样品,分析根系土中重金属含量特征、赋存形态与小麦籽实重金属富集特征。【结果】小麦籽实与根系土中重金属含量低于食品与土壤中污染物含量的安全限值。根系土中As、Pb以残渣态为主,Hg以腐殖酸态、残渣态及强有机结合态为主。土壤中铁锰氧化态与残渣态Pb、腐殖酸态与残渣态Hg、残渣态As及铁锰氧化态Cd均与其全量呈正相关。离子交换态Pb、强有机结合态Hg及腐殖酸态As均与土壤pH值呈负相关。离子交换态As、碳酸盐结合态Cd均与土壤pH值呈正相关。全量Pb、Cd及Hg、腐殖酸态As与Hg均与土壤有机质呈正相关。小麦籽实对不同重金属的富集能力差异显著,其中以富集Zn的能力最强。小麦籽实中Zn含量受土壤Zn全量制约明显,Cd含量明显受土壤pH值与有效态Cd控制,Hg、Cr受土壤有机质是影响显著。【结论】研究区土壤和小麦籽实中重金属含量低于土壤与食品中污染物含量的安全限值。土壤中As、Pb以残渣态为主,Hg以腐殖酸态、残渣态及强有机态为主。土壤中各形态重金属含量明显受土壤pH值、有机质及其全量制约。小麦籽实从土壤中吸收富集不同重金属的能力差异显著,其中以富集Zn的能力最强,Zn的吸收富集强度明显受土壤Zn全量控制。

【Objective】The aim of this paper is to provide reference for local cultivated land quality protection,wheat safety production and agricultural planting structure adjustment.【Method】Wheat seeds and root soil samples were collected to investigate contents and occurrence forms of heavy metals in root soil and enrichment characteristics in wheat.【Result】The content of heavy metals in wheat seeds and root soil were lower than the safety values of food and soil referred in relative national standards.In root soil,most of As and Pb fractionated in residual fraction,while Hg concentrated in humic acid bounded fraction,residual fraction and strong organic matter bounded fraction.Moreover,In soil the content of Pb in Fe-Mn oxides bounded fraction and residual fraction,Hg in humic acid bounded fraction and residual fraction,As in residual fraction and Cd in Fe-Mn oxides bounded fraction were posetive with the total content of these corresponding elements.The content of Pb in exchangeable fration,Hg in strong organic matter bounded fraction and As in humic acid bounded fraction were passive with the pH value of soil,whereas the content of As in exchangeable fraction and Cd in carbonate bounded fraction were posetive with the pH value of soil.Additionally,the accumulation factors essential distinguished among each other in wheat seeds,where Zn was the most strong one.The content of Zn in wheat seeds was significantly restricted by the total content of Zn in soil,whilst Cd was obviously controled by both of the pH value of soil and the available content of Cd in soil,Hg and Cr were strongly limited by the content of organic matter in soil.【Conclusion】The content of heavy metals in wheat seeds and root soil in the studied area were lower than the safety values of food and soil.As and Pb were predominately appeared in residual fraction,while Hg fractionated in humic acid bounded fraction,residual fraction and strong organic bouded fraction in soil.However,the bioavailability and potential ecological hazards were greatest for Cd.Therefore,the pH value of soil,organic matter and the total content were regarded as the main factors controled the content of heavy metals in different fraction.The ability of wheat seeds accumulated heavy metals from soil were significant different.The biggest accumulation factor was observed for Zn which was intensely influenced by the total content in soil.