The Survey Of Heavy Metal Concentrations In Vegetables And Soils In Tianjin And The Potential Risks To Human Health

Tianjin suburban farmland soil in the process of urban development, because a long timeapplying pesticide wastewater irrigation and various effects, the heavy metal content in soilincreased. Because of the heavy metal element itself has a long retention time, latent, and thecharacteristics of the poor mobility, more difficult to be microbes, long-term accumulationcan harmful to farmland to grow crops. Leaf vegetables as a species are most vulnerable topollution of the vegetables, the content of heavy metals in the body can enter human bodythrough diet, threatening human health. This study with five suburban county of Tianjinfarmland as the research unit, a total of140soil samples collected, seven kinds of leafvegetables collected samples of188. Soil samples collected in the physical and chemicalanalysis, including pH, organic matter content, soil cation exchange capacity （CEC） threemeasurement, on the soil and leaf vegetables heavy metal Cr, As, Cd, Pb, Hg five contentanalysis. On the data of heavy metals using the single factor pollution index method andinside N.L.Nemerow index method to evaluate, get the following results:（1）The outskirts of Tianjin five area whole alkaline soil, organic matter content in theoverall range of18.91g·kg^-145.44g·kg^-1, the order is Jinna> Dongli> Xiqing>Jinghai>Wuqing. Soil cation exchange capacity range is14.82mol·kg^-18.40mol·kg^-1,what content byhigh order for Jinna> Dongli> Xiqing>Jinghai> Wuqing. Through correlation analysisfound that soil cation exchange capacity and organic matter has a significant positivecorrelation （r=0.474, P <0.01）, showed the same trend of distribution.（2） The survey of the five regions, five kinds of heavy metal chromium, arsenic,cadmium, lead, mercury levels were higher than soil background value in Tianjin. Mercurycontent is20times higher than the background value of cadmium, lead, four times higher thanthe background value and three times respectively. Use of correlation matrix analysis, foundthat heavy metal chromium, cadmium, lead, mercury is extremely significant relationship, thesynergistic effect of change is very significant, heavy metals, arsenic and mercury onlysignificant relationship, there may be a homologous pollution.（3） To the state soil environment quality standard secondary index as evaluation standard, evaluation with single factor pollution index method in Tianjin suburbs soilpollution condition results show that the research area of chromium, lead, all clean, Xiqingdistrict and Wuqing had mild arsenic pollution, accounting for6%of the sample point and20%. Mercury in Xiqing district, Jinna, Dongli had mild pollution, accounted for26%,16%and64%of sampling points. Cadmium pollution in the heaviest Dongli, severe pollution ratewas32%, moderate pollution rate was24%, the rate was20%, the mild pollution Xiqingdistrict severe pollution rate was6%, the rate was20%, the mild pollution Jinna lightpollution rate was6%, Wuqing and Jinghai sample point there is no pollution.（4） to the state soil environment quality standard secondary index as evaluation standard,with N.L.Nemerow comprehensive pollution index method in evaluation of Tianjin suburbsoil pollution condition results show that the Xiqing district has31%of the sample haddifferent degree of pollution,31%of the soil in the alert level,38%of the soil is safe. Jinna66%soil security level and alert level was28%, the contamination rate of6%. Donglipollution is most serious,25sample point total pollution rate was76%,8%of the samplebelong to alert level, only16%of the soil belongs to the level of security. Wuqing and Jinghaisample point failed to meet the pollution level, the alert level of40%and7%respectively, thesecurity level of soil is60%and93%.（5） For the determination of7kinds of vegetables, a total of188fresh sample resultsshow that the removal of part of the sample did not check out the mercury, the samples weredetected chromium, arsenic, cadmium, lead, mercury, five kinds of heavy metal elementsincluding5samples to detect the lead content of more than national food contaminants inlimited （GB2762-2005） standard of leaf vegetables.（6） The hazard quotient is used to conduct the risk assessment of leaf vegetables intakeof body, the cadmium content in vegetables on the high side, large damage to the body, andinfluence on children than adults, should be caused take seriously.