The Bioavailability Of Artificially Synthesized And Lead-related Soil Micro-nanoparticle Lead And Its Population Health Risk

Engineering nanoparticles?ENPs?have been widely used in various fields because of its special properties.These nanomaterials will enter the environment through various ways during usage.The micronanoparticles in soil have strong adsorption for potentially toxic metals.These small-sized particles can easily enter the human body through respiratory and hand-mouth intake pathways,which poses a threat to human health.Bioaccesibility is to evaluate the bioavailability of potentially toxic metals in humans by simulating the physiological environment of different digestive organs in vivo to react and extract the solubility of potentially toxic metals.The research on bioaccesibility will provide scientific theory and technical support for the establishment of the bioavailability and environmental benchmarks;assessment and regulation of human health risk.In this study,artificially synthesized lead nano compounds and micronanoparticles of lead-contaminated soil were used as research objects.Different particle sizes fractions of lead-contaminated soil?<1 ?m?1-5 ?m?5-50 ?m and 50-250 ?m?were extracted by wet method,and nano-PbO₂ and nano-PbS were synthesized by solution method.Lung in vitro simulation?ALF and Gamble?and gastrointestinal simulation methods?UBM?PBET?SBET?SBRC and IVG?were used to simulate the bioaccesibility of different particle sizes fraction of lead-contaminated soil and synthetic lead nanoparticles in lung and gastrointestine.The effects of particle sizes on bioaccesibility and health risk assessment were explored.The important results were as followed:?1?Wet separation,ultrasonic,sieve,siphon and centrifugation were used to extract the four different particle size fractions of lead-contaminated soil:50-250 ?m?5-50 ?m?1-5?m and<1?m.The specific surface area,pH,organic matter and the contents of potentially toxic metals as,Ba,Co,Cr,Cu,Mn,Ni,Pb and Zn increased with the decrease of soil particle size.Primary minerals such as quartz,feldspar and mica mostly exist in bulk soil,50-250 ?m and 5-50 ?m fractions,while secondary minerals such as zeolite,illite,chlorite and calcite mostly exist in smaller particle size fractions 1-5 ?m and<1?m.The results of lead phase analysis showed that there were PbO₂ and PbS exist in lead-contaminated soil.?2?In vitro lung and gastrointestinal simulation methods were used to study the bioaccesibility of lead-contaminated soil and four different particle size fractions.The results showed that the bioaccesibility of potentially toxic metals in natural soil particles increased with the decrease of particle size.The bioaccesibility of Cu and Mn in ALF solution was the highest,followed by Zn,Co,Ba and Pb,and as was the lowest.The bioaccesibility of Ba,Co,Cu and Mn in Gamble solution was the highest and that of Zn was the lowest.The bioaccesibility of As,Ba,Cr and Cu in SBRC gastric phase method is higher than that in other methods,and that of Co,Mn,Ni and Pb in IVG gastric phase method is higher than that in other methods.When simulating the bioaccesibility of intestinal environment,SBRC and IVG methods were used.With the increase of reaction time,the bioaccesibility of each element increased slightly.The non-carcinogenic risk of these elements through respiratory pathway in children is higher than that in adults,and the carcinogenic risk in adults is higher than that in children.As,Co,Cr,Ni,and Pb from oral intake routes simulated by UBM,PBET,SBRC and IVG have significant total carcinogenic risk for children,and the carcinogenic risk for adults is less than that for children.With the decrease of particle size,the health risk of children and adults increases.?3?The bioaccesibility of synthetic lead nano-compounds PbO₂ and PbS was studied by lung and gastrointestinal simulation in vitro.The results showed that the bioaccesibility of nano-PbO₂ in lung and gastrointestinal simulation solutions was higher than that of nano-PbS,and the bioaccesibility of nano-PbS with smaller particle size was higher than that with larger particle size,which indicated that chemical morphology and particle size were two important factors of bioaccesibility.The bioaccesibility of micronanoparticles in natural lead-related soils is higher than that of synthetic lead compound nanoparticles,which may be related to the morphology of lead in natural soils.Exchangeable,reducible and oxidizable lead in natural soils can increase its solubility in simulated solutions,while most of the inorganic compounds of lead are insoluble,so its bioaccesibility is relatively lower.For both children and adults,the health risk of lead nanoparticles increases with the decrease of particle size,and the carcinogenic risk of children is higher than that of adults.