| In recent years,with the rapid development of urbanization,a large number of people have gathered in cities,and the consequent urban pollution problem has received continuous attentions.Heavy metals,kinds of toxic and harmful inorganic pollutants,are apt to accumulate in urban road dust and threaten the ecosystem and human health.In order to evaluate the pollution characteristics and environmental risk of heavy metals in road dust from Jinan City,77 road dust samples were collected.The road dust physicochemical properties including pH value,conductivity(EC),total carbon(TC),total organic carbon(TOC)and inorganic carbon(IC),and low,high,and frequency susceptibilities(LF,HF,and FD),and clay,silt and sand were analyzed by utilizing the pH meter,Conductivity meter.Susceptibility meters,and TOC Analyzer and Laser Particle Size Analyzer(LPSA).Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES)were adapted to detect the concentrations of heavy metals including Co,Cr,Cu,Cd,Mn,Ni,Pb,Zn,V and Ba.Based on the physicochemical properties,GIS spatial analysis supported the spatial distribution characteristic of heavy metals.The sources apportionment and their contributions of heavy metals were diagnosed by receptor models including Positive Matrix Factorization(PMF),UNMIX and Principal Component Analysis-Multiple Liner Regression(PCA-MLR).The BCR fractional and PBET gastrointestinal simulation experiments were carried out to explore the existing forms,mobility and bio-accessibility of heavy metals.The pollution levels of heavy metals were analyzed by Geo-accumulate pollution index(Igeo)and Pollution loading index(PLI).The potential ecological risks of heavy metals were analyzed by comprehensively adapting the potential ecological risk index(RI)and fractional risk assessment index(RAC).The health risks were analyzed by US EPA exposure health risk model,and the health risks evaluation values were corrected by the fractional and gastrointestinal bio-accessibility.Pearson correlation and Redundancy analysis(RDA)were adapted to estimate the correlation between fractional and gastrointestinal bio-accessibility,and to estimate the effects of controlling factors on the concentrations,fractional characteristics and gastrointestinal bio-accessibility of heavy metals in road dust from Jinan City.This article was intended to provide theoretical and practical basis for urban environmental management and protection.The results were as follows.(1)The mean concentrations of Co,Cr,Cu,Cd,Mn,Ni,Pb,Zn,V and Ba in road dust from Jinan City were 8.25,114.09,87.71,1.08,517.04,30.29,85.71,497.64.51.76 and 642.77 mg/kg.Heavy metals except for Co,Mn and V,exceeded the corresponding background values,with the highest mean concentration of Cd being 12.91 times that of its background.The high concentrations areas were mainly concentrated in the intensively industrial and traffic areas within the north areas of Jinan City.(2)Three similar sources(natural and coal-burning sources,industrial sources and transportation sources)were diagnosed by PMF,UNMIX and PCA-MLR,with contribution rates of 35.92%.41.33%and 22.75%from PMF,and,46.28%,18.89%and 34.89%from UNMIX,and,40.85%,41.33%and 17.82%from PCA-MLR.(3)BCR fractional analysis showed that acid-soluble form of Cd,Zn and Mn were up to 39.9%,27.8%and 24.3%of the total concentration in urban road dust respectively,indicating strong mobility and high risk to the environment.The reduction form of Zn was reached 30.0%of the total concentration,and Pb and Zn were mainly consisted of oxidation form with 59.2%and 48.4%of the total concentration that indicating potential mobility and risk.Cd,Zn,Pb,Cu and Mn were mainly consisted of extractable form,while Co,Cr,Ba,V and Ni were dominantly composed of the residual form.The acid-soluble form with strongest mobility and ecological risk of heavy metal was in order of Zn>Mn>Ni>Co>Ba>Pb>Cu>V>Cr,and the extractable form being capable of transforming and mobility in the environment was ordering for Cd>Zn>Cu>Pb>Mn>Ba>Co>Ni>V>Cr.(4)Gastrointestinal bio-accessibility of heavy metals results indicated that Cd and Cu possessed the highest bio-accessibility with 82.7%and 24.6%of the total concentrations in gastric and intestinal phases respectively.The bio-accessibility was in order of Cd>Zn>Mn>Ni>Pb>Cu>Cr>V>Co = Ba in gastric phase,and ordering for Cu>Cd>Mn>Ni>Pb>Zn>Cr>V>Co = Ba in intestinal phase.The correlations between the fractional and gastrointestinal bio-accessibility of heavy metals indicated that the bio-accessibility of most heavy metals in gastric phase were mainly related to the acid-soluble and extractable forms,while it was of insignificant bio-accessibility between fraction and intestinal phase.(5)The Igeo analyses results indicated that Cr and Pb were slightly polluted,and Cu and Zn were moderately polluted,and Cd was polluted in a moderately to heavy degree,and others were practically unpolluted,respectively.The average Igeo values of heavy metals were in order of Cd>Zn>Cu>Pb>Cr>Ba>Ni>Mn>V>Co.Pollution loading index(PLI)presented overall moderate pollution,while several extremely heavy pollution samples were mainly distributed in the north areas of Jinan City.(6)The potential ecological risk of Cd was extreme and much higher than other heavy metals.Pb,Zn and Cr showed moderate and above ecological risk in several samples,and most of the heavy metals were of insignificant ecological risks.The total ecological risk index(RI)results:indicated that the highest ecological risks samples were mainly distributed in the north areas of Jinan City,which w-ere mainly associated with the Cd distribution.(7)The results of health risks showed that the non-carcinogenic risk index(HI)of children and adults were less than 1,indicating non-significant risks.The non-carcinogenic risk of children was greater than that of adults.The exposure doses and non-carcinogenic risks of heavy metals from direct ingestion were much higher than that of respiratory inhalation and skin adhesion absorption pathways.Among the carcinogenic risks(CR),CR index of Cd ranged from10-6 to 10-4,indicating that the CR of Cd was in an acceptable range,and the CR of Cd was much higher than that of other heavy metals.The correctional health risks based on extractable form and gastrointestinal bio-accessibility indicated that there were no significant non-carcinogenic risks in both extractable form and gastrointestinal phases,while the carcinogenic risks of Cd in both extractable form and gastric phases were within an acceptable range,while the intestinal phase was risk-free.(8)The controlling factors analysis indicated that heavy metals concentrations were mainly associated with the low and high susceptibilities of dust,but were independent from other controlling factors(including pH,EC,TC,etc.).The control factors of heavy metals fraction were complicated,while the bio-accessibility of gastric and intestinal phases were predominately associated with the factors of TC and TOC. |
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