| Heavy metals were pollutants and could threaten agricultural productivity,biodiversity,food safety and human health for their non-biodegradability,toxicity and persistence.The concentration of heavy metals in soil largely depends on the parent material and variety of anthropogenic activities.Many factors such as rapid industrialization,urbanization,heavy traffic,non-judicial use of agrochemicals and untreated waste water for irrigation put an immense stress on local environment.The effective management of environmental and food heavy metal pollution needs to first clarify its sources of pollution and pollution pathways.In this paper,the heavy metal pollution status of soil and rice grain heavy metals was analyzed in industrial area in Hunan.Heavy metal element fingerprint analysis combined with principal component analysis method,geostatistical analysis method and positive definite matrix factorization model was used to analyze the source of heavy metal pollution in the soil.On the basis of this,the cadmium isotope fingerprint was used to accurately analyze the pollution source and contribution rate of soil cadmium.The accumulation and transport of cadmium in various organs of rice were determined by pot experiment and field scale test.The fractionation coefficient of cadmium isotopes in rice relative to soil was determined.Finally,the cadmium isotope fingerprint analysis method was used to analyze the pollution source and contribution rate of rice cadmium.It provides theoretical and technical support for the prevention and control of heavy metal pollution.The main conclusions are as follows:?1?As,Hg,Cr,Cd,Ni,Pb,Cu and Zn in the topsoil and parent soil of the study area were polluted.Cd pollution was most serious and its exceeded rate was 94.4%.The heavy metal concentration of rice grains also exceeded the standard value.Cd pollution was heaviest and its exceeded rate was 95.0%.?2?Heavy metal element fingerprint was used to analyze the main sources of heavy metal pollution in this area.The pollution sources consists of natural sources,agricultural sources,industrial sources,and transportation and industrial sources and their contribution rates are 24.9%,19.1%,30.1%and 25.9%,respectively.Cd isotope fingerprint was used to analyze the contribution rate of pollution sources.The contribution rates of automobile exhaust,cement factory dust,agricultural fertilizer and smelter dust to soil Cd pollution were 2%,8%,15%and 75%,respectively.The contribution rate of smelter dust to agricultural soil was biggest.?3?The results of pot experiments showed that when the concentration of cadmium in roots of rice reached 40 mg kg-1 and the concentration of cadmium in rice leaves reached 20 mg kg-1,the common pollution of roots and leaves would produce significant synergy.No significant synergistic effect was found below this concentration.Thus,rice cadmium was mainly derived from root absorption at low concentrations.?4?The fractionation coefficient of rice grain relative to soil?114/110Cd was 0.208‰.Cd isotope fingerprint was used to analyze the contribution rate of pollution source and the pollution contribution rate of automobile exhaust,cement factory dust,agricultural fertilizer and smelter dust were 2%,8%,16%,and 74%,respectively.The contribution rate of smelter dust to rice was biggest.?5?The general mechanism of the pollution apportionment was:firstly,heavy metal element fingerprint was used to analyze the number,nature and contribution rate of pollution sources;then heavy metal isotope fingerprint was used to directly analyze the contribution rate of detailed pollution sources;In the analysis of isotope contamination sources of rice grains,it is necessary to consider the fractionation coefficient during the growth process. |
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