Rapid Diagnosis and Assessment of Heavy Metal Pollution in Greenhouse Vegetable Production Soils Based on Portable X-ray Fluorescence Spectroscopy
[Objective]Guangdong is a major province of vegetable production and consumption in China,and is also an important vegetable production base for Hong Kong,Macao,and the'Southern Vegetables and Northern Transportation'.Therefore,rapid diagnosis and assessment of soil heavy metal pollution is the premise of soil pollution prevention and control and risk management.This study aimed to investigate the applicability of in situ and ex situ portable X-ray fluorescence spectroscopy(PXRF)for rapid detection of heavy metals in greenhouse vegetable production soils of Guangdong Province and to diagnose and evaluate heavy metal pollution in greenhouse vegetable production soils based on portable X-ray fluorescence spectroscopy.[Method]A total of 110 greenhouse vegetable production soil sampling sites and 26 open-field soil sampling sites were set up in the study area.PXRF was used in situ to rapidly detect soil heavy metal contents(Cd,Cu,Cr,Pb,Zn,As,Ni and Hg).The accuracy of the PXRF method was verified by analyzing the correlation between the values of soil heavy metals measured by the PXRF and the traditional laboratory analysis and based on this,the soil heavy metal pollution status was quickly diagnosed.The risk of soil heavy metal pollution was evaluated by the single factor pollution index and the Nemerow composite pollution index method.[Result]The results indicated that:(1)the concentrations of Cd,Cu,Cr,Pb,Zn,As and Ni detected by the ex situ PXRF method were significantly correlated with those determined by traditional laboratory methods(P<0.01),and the R2 were 0.69,0.50,0.56,0.58,0.47,0.54 and 0.62,respectively.Also,the results of in situ determination of Pb and As in soil by the PXRF method were significantly correlated with those by traditional laboratory methods(P<0.01),and the R2 were 0.73 and 0.74,respectively.(2)When the soil moisture content was 150 g·kg-1-200 g·kg-1,the results of in situ determination of Cr,Pb,Zn and As in soil by the PXRF method were significantly correlated with those by traditional laboratory methods(P<0.01),and the R2 were 0.77,0.94,0.72 and 0.93,respectively.(3)Soil Cd and Cu pollutions were prominent in greenhouse vegetable production soils of Guangdong Province.The point exceeding rates were 20.9%and 10.0%,respectively,according to the Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land(GB 15618-2018).In addition,the average content of Cd in greenhouse vegetable production soil was 0.21 mg·kg-1,which was 1.2 times greater than that in open-field soil.The contents of Cd,Cu,Cr,Pb,Zn,As and Ni in the greenhouse vegetable production soil in the Pearl River Delta were generally higher than those in other areas.(4)The single pollution index of Cd,Cu,Cr,Pb,Zn,As,Ni and Hg were all less than 1,and the order was Cd>Cu>Pb>Zn>Cr>As>Ni>Hg.The mean value of the Nemerow comprehensive pollution index was 0.69.From the overall average,the degree of soil heavy metal pollution was at a clean level.[Conclusion]In summary,PXRF is an effective method for the rapid diagnosis of heavy metal pollution in greenhouse vegetable production soils in Guangdong Province.Furthermore,Cd and Cu can be quickly identified as the primary pollution elements with high risk in greenhouse vegetable production soils of Guangdong Province.The results of this study will serve as a reference for the evaluation of soil environmental quality and sustainable development of greenhouse agriculture.
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