Contamination Status Of Heavy Metals In Urban Road Dust Of Hokkien Golden Triangle

Road dust is one of the important components of the urban environmental system,and its pollution status has important relations with ecological environmental quality,such as the quality of urban water environment,soil environment,atmospheric environment,as well as human health.Xiamen,Zhangzhou,and Quanzhou are important economic development areas in Fujian Province and are known as the "Hokkien Golden Triangle".Here,a total of 257 road dust samples collected from different roads in Xiamen,Zhangzhou and Quanzhou.The road dust in Xiamen Island is representative of the urban area of the Fujian Triangle,and the sampling areas outside Xiamen Island,Zhangzhou and Quanzhou are used as the intercity representative of the Fujian Triangle.The magnetic characteristics,and eight heavy metals,including V,Cr,Ni,Cu,Zn,As,Cd,and Pb were investigated.This study determine the pollution levels and sources in the road dust at the study region.It is also to evaluate ecological risks and human health risks of heavy metals in urban road dust in Xiamen,Zhangzhou,and Quanzhou.This paper provide a theoretical basis for the comprehensive control of heavy metal pollution to ensure the healthy and sustainable development of urban environment in Xiamen,Zhangzhou,and Quanzhou.The main conclusions of this study can be as follows:(1)The contents of V,Cr,Ni,Cu,Zn,As,Cd,and Pb in Hokkien Golden Triangle respectively were 41.06± 1.13 mg/kg,109.09±7.7 mg/kg,31.51±2.69 mg/kg,107.79±8.03 mg/kg,378.02±33.05 mg/kg,6.58±0.27 mg/kg,0.66±0.06 mg/kg and 75.46±44.33 mg/kg.The content of eight heavy metals in road dust of Xiamen Island is higher than that the outside of Xiamen Island,Zhangzhou and Quanzhou,which shows that the heavy metals content in road dust in urban area is higher than that in suburban area,indicating the degree of urban development,development mode and population density,which may increase the content of heavy metals in urban environment.Values of V,Cr,Ni,Cu,Zn,Cd and Pb was the greatest for commercial area,followed by the residential area and scenic area.Obviously,the concentration of Cr(346.15±230.23 mg/kg),Cu(309.84±205.54 mg/kg)and Ni(137.56±104.75 mg/kg)in commercial area were significantly higher than its national soil screening limit(GB 15618-2018)(2)Magnetic evidences,including magnetic susceptibility,susceptibility of anhysteretic remanent magnetization,saturation isothermal remanent magnetization,temperature-dependence of induced magnetization,and low-temperature experiments suggest the main magnetic carriers were magnetite-like phase of pseudo-single-domain+multi-domain grain.The magnetic susceptibility of the road dusts was much higher than that of lithogenic components in nature,the main iron oxides of the iron-bearing minerals in road dust were magnetite3+ and magnetite2.5+.Elevated concentrations of trace metals(e.g.,Cr,Co,V and Cd)were identified in spherical particles and irregularly-shaped.Prolonged expose to the dust metal-containing magnetic minerals could increase the occurrence of human health.(3)According to the accumulation index assessment results,the pollution of heavy metals Zn and Cd in road dust of urban(Xiamen Island)and intercity(Xiamen Island,Zhangzhou,Quanzhou)roads was relatively serious.The potential ecological risk of road dust in the Hokkien Golden Triangle urban area is significantly higher than that of intercity.The comprehensive potential ecological risk of heavy metals in road dust of Xiamen Island is 621.68,which is strong ecological risk.According to the health risk assessment results,the ingestion had the highest exposure dose followed by dermal contact and inhalation for children and adults.The total HI value for both children and adults was lower than safe level(1),and the total HI for children in road dust was 8.8 times compared with the results of adults.Meanwhile,these carcinogenic risk levels for children and adult in road dust were lower than the internationally accepted precautionary criterion range(10-6～10-4).(4)According to the ability of heavy metal enrichment in the leaves of Haicang Bridge and Wutong interchange,it was found that the contents of Cu and Zn were higher in the leaves of herbs;the contents of Zn,Pb,V,Cr,Ni,and Cd were higher in the leaves of shrubs.Herbs,shrubs,and arbor leaves of both places have strong absorption and accumulation capacity for Zn.The ability of plants to absorb and accumulate heavy metals is shrubs>arbors>herbs.Shrubs have strong heavy metal enrichment ability by virtue of location advantage and multiple adsorption.Arbors have lush canopy,large surface area of leaves and can change air flow so it has a strong ability of heavy metal enrichment.Among common plants in Xiamen,Duranta erecta has strong Cu,Zn,Cd enrichment ability,Terminalia catappa has higher Cd enrichment abilities,Ficusmicrocarpa,Trachycarpus fortunei and Alstonia scholaris have lower ability to enrich heavy metals.