Research On The Bioavailability Of Potentially Dangerous Elements In Typical Urban Soil And Dust

Urban soils are the foundation of cities.In recent years,with the acceleration of industrialization and urbanization,urban soil and dust have become sources and sinks of urban pollution.The study of potentially toxic elements pollution on urban soil and dust has become a hotspot in the field of global environment.In this paper,the bioaccessibility of twelve potentially toxic elements As,Ca,Co,Cr,Cu,Fe,Mg,Mn,Ni,Pb,Sr,Zn in urban soils and dusts was studied using in vitro gastrointestinal simulation UBM method and lung simulation ALF and Gamble's solution.Chemical speciation distribution of twelve potentially toxic elements as Ca,Co,Cr,Cu,Fe,Mg,Mn,Ni,Pb,Sr and Zn in soil and dust were obtained by sequential extraction with Tessier method.By analyzing the correlationship between distribution of chemical folms and bioaccessibility value of potentially toxic elements,the main forms affecting the bioaccessibility of elements were revealed.The IEUBK model was used to predict the blood lead level of children aged 0-6 years old.The main conclusions are as follows:(l)There are some differences in gastrointestinal bioaccessibility of different elements in soil and dust.The gastrointestinal bioaccessibility of Cr in soil and dust in Xi'an and Yulin is relatively low,which indicates that it is difficult to be absorbed and utilized by human body.As and Cu are more accessible in intestinal phase than in gastric phase,mainly because of the high resolution of As in intestinal phase on the surface of soil and dust.Cu2+ is easily combined with bile salts and trypsinase in intestinal fluid,so its bioaccessibility of intestinal phase was improved.Co,Mn,Ni,Pb,Sr and Zn in soil and dust of Xi'an are higher than those in intestinal phase.In Yulin soil and dust,the bioaccessibility of Co,Mg,Mn,Ni,Pb,Sr and Zn are higher in gastric phase than that in intestinal phase.This is due to the lower pH value of gastric phase environment,the presence of more organic acids,and the increase of enzyme activity.Therefore,elements are easy to exist in soluble form.Because of the increase of pH value in intestinal environment,elements will precipitate or adsorb in the corresponding precipitation.(2)The pulmonary phase bioaccessibility of potentially toxic elements in Xi'an and Yulin media was comparatively consistent in the two environments.Except that As is more available in Gamble's solution than in ALF,Ca,Co,Cr,Cu,Fe,Mg,Mn,Ni,Pb,Sr and Zn all show higher bioaccessibility in ALF.The main reason for this situation is that the ALF simulated solution contains organic acids,and its pH value is low,which promotes the dissolution of elements.In Gamble's solution,the solution is neutral and the elements are easily converted to non-free state.Therefore,the bioaccessibility of many elements in Gamble's solution is small.ALF represents the lung solution in the immune response of the body,and Gamble's solution represents the normal state.The lung solution showed that elements were difficult to be absorbed and utilized by lungs under normal conditions.(3)In the correlation analysis of bioaccessibility and element morphology,the bioaccessibility of elements is not correlated or negatively correlated with their residue state,which indicates that the residue state hardly participates in various natural reactions and is difficult to be absorbed and utilized by organisms.In soil and dust of Xi'an,the elements related to bioaccessibility and exchangeable state are Co,Sr and Zn,those related to carbonate binding state are Co,Ni,Pb and Zn,those related to iron-manganese oxide binding state are As,Cr,Cu,Mn,Ni and Sr,and those related to organic binding state are Cu and Sr.In soil and dust of Yulin,the elements that are related to the availability and exchangeability are Co,Cu and Pb,the elements that are significantly related to the carbonate binding state are As,Mg,Ni and Zn,the elements that are significantly related to the iron-manganese oxide binding state are Ca,Co,Mg,Pb and Zn,and the elements that are related to the organic binding state are only Cu.The results show that the biological availability of elements is affected by various forms and other natural and human factors,and different forms contribute different to the availability of different elements.(4)The total non-carcinogenic risk index of nine potentially toxic elements in Xi'an soil for children is more than 1,which indicates that many potentially toxic elements in Xi'an soil have non-carcinogenic risk for children and need attention.Both carcinogenic and non-carcinogenic risks of the potentially toxic elements in Xi'an dust and Yulin soil and dust are harmful to human body.are acceptable.Lead in soil and dust in Xi'an contributes most to the non-carcinogenic risk of human and children,while Co in Yulin contributes more to the non-carcinogenic risk of children,while Ni in both urban soils and dust contributes more to the carcinogenic risk of children and adults.(5)According to the lead concentration and bioaccessibility of two medias in two cities,the blood lead level of children aged 0-6 years in Xi'an and Yulin was predicted by IEUBK model.The blood lead level of children aged 1-2,2-3 and 3-4 years in Xi'an and Yulin cities was higher than the US standard of 50 g/L.Among them,the predicted blood lead level of children aged 1-2 and 2-3 years in Xi'an area exceeded the international standard of 100 g/L,and the predicted blood lead level of children aged 2-3 years in two cities exceeded the international standard of 100 The predicted blood lead levels of children of other age groups did not exceed the US standard of-50 g/L,and were within acceptable levels.The government of-Xi'an and Yulin should pay attention to controlling the sources of lead pollution and strengthening the prevention and control of lead pollution.The blood lead level of children aged 1-2,2-3 and 3-4 should be surveyed.At the same time,parents should pay attention to children's healthy diet and living habits.