The Pollution Effects And Health Risks Of Heavy Metals In Atmospheric Wet And Dry Deposition On Leaf Vegetables In Shanghai

Vegetables are rich in a wide range of human essential vitamins,carbohydrates,dietary fiber and minerals,such as nutritional composition,playing an important role in people's daily diet.In recent years,food poisoning by heavy metals occur frequently.Recently,the "Thirteen-Five" in the National Food Security Plan issued by the State Council emphasizes the heavy metal pollution in farmland and explicitly demands the strict implementation of the whole chain monitoring from farm to table,because food safety problems due to excessive levels of heavy metals increasingly aroused social concern.As an inorganic pollutant,heavy metal has the characteristics of high concentration and low migration,doing serious threats to the natural environment and human health.In the environment of vegetable growth,heavy metal pollution in the soil,water and air,directly influences the vegetable growth and the accumulation of heavy metals in vegetables are absorbed by the body through the food chain,which is a threat to human health.The vegetable production bases and scattered fields in Shanghai suburbs provide Shanghai residents with a lot of vegetables,but those vegetables are faced with a serious risk of heavy metal pollution due to atmospheric deposition,sewage irrigation,and unreasonable soil quality,there being potential security risks.This research selected Shanghai suburb as study area,chose six kinds of heavy metal,like Cu,Zn,Pb,Cd,As and Hg as the main objects of study,analyzed systematically the effects of atmospheric deposition of heavy metals in vegetables through the combination of particulate sampling and leaves of vegetable soilless culture simulation of absorbing heavy metal.And through the dry and wet deposition simulation experiment,this research systematically studied the rate of contribution the vegetable leaves added heavy metal on vegetable roots and edible parts,revealing the transport and transformation processes in the vegetables of heavy metal through the leaves intake.This research analyzed the atmospheric particulate levels in the study area,and heavy metal pollution levels of atmospheric particulate PM2.5;the evaluation applied to different concentrations of heavy metal in vegetables after roots and edible parts of pollution levels in order to study atmospheric subsidence and the combined effect of heavy metal pollution on human health.The research made use of heavy metal in soil-less cultivation technique to reduce the effect of root absorption,improving the mechanism study of atmospheric deposition of heavy metal in vegetables in natural states.It comes to the following conclusions:?1?In PM2.5 in Minhang district,the heavy metal like Cd,Cu,Pb,Zn,Hg and As has the average concentration of 0.49,5.78,17.89,188,0.0104 and 2.62 ng m^-3 respectively.Judging from a different range of heavy metals,Pb>Cu>As>Zn>Cd>Hg.The health risk model calculates excessive age risk rate of heavy metal through respiratory pathway into the body in the atmospheric PM2.5 in Minhang district,ranking from high to low as As>Cd>Pb>Zn>Cu>Hg.Different groups of people have different risk rates,adult males ranking the highest,1.15 and 1.5 times larger than adult women and children.?2?The atmospheric exposure and indoor simulation of planting vegetables dish experiments showed that the interior four edible parts of vegetables in all elements are in the standard limits,and the concentration of Zn,Cd,Cu and As in the atmospheric exposure four kinds of vegetables,are less than the national standard of limit values of heavy metal pollution in vegetables.Indoor vegetable growth simulation environment is good with low heavy metal concentration,and vegetables heavy metal contents in the outdoor atmospheric exposure have exceeded the standard partly,where the standard rates of Pb and Hg have come to 100%.In the outdoor atmospheric exposure environment,the heavy metal concentration in edible parts of vegetables grown in tissue culture are generally higher than that in the laboratory simulation environment,showing that atmospheric deposition of heavy metal has a significant influence on heavy metal concentration in vegetables.Six heavy metal concentration in water culture vegetable roots are lower,which is safe.The Cu,Zn,Pb and As contents in edible parts of vegetables showed an obvious correlation corresponding to the heavy metal in the roots.?3?Under the condition of dry and wet deposition,the transfer coefficients of four vegetables from leaves to the roots are same in the order of large and small,followed by spinach,lettuce,Chinese cabbage and cabbage.Dry deposition has greater pollution effects on Cu,Cd and As in the most edible parts and roots in the vegetables;while Zn,Pb and Hg are just the other way.In general,the ratio of heavy metal concentration to blank group was as follows:Hg>As>Cd>Pb>Cu>Zn.?4?The heavy metal pollution assessment results show that the individual pollution index of each heavy metal in the four kinds of vegetables is in the order from large to small as Hg>Pb>Zn>Cd>Cu>As.The integrated pollution levels of outdoor four vegetables can be sorted from high to low as:lettuce,Shanghai green cabbage,spinach and Chinese cabbage.Atmospheric deposition has significant pollution effects on heavy metal in vegetables.The single pollution index of heavy metals in four kinds of vegetables in dry and wet sedimentation experiments can be ranked as Hg>Pb>Cd>Zn>As>Cu.The overall pollution level of four kinds of vegetables can be ranked from high to low as:lettuce,Shanghai green cabbage,spinach and Chinese cabbage.?5?The results of vegetables intake health risk evaluation show that the comprehensive health risk index TTHQ of four kinds of vegetables in order from large to small can be ranked as Shanghai green cabbage,spinach,lettuce and Chinese cabbage.The health risk index THQ of different heavy metals in four kinds of vegetables after the dry and wet deposition can be sorted as follows:As>Hg>Cd>Pb>Zn>Cu.Judging from the different audience groups,edible vegetables can pose a certain threat to both adults and children,and the health risk of intake heavy metals in vegetables by children is generally greater than that by adults.In general,the values of TTHQ in four kinds of vegetables are in a descending order as:lettuce,Shanghai green cabbage,spinach and Chinese cabbage.?6?The risk of atmospheric particulate matter PM2.5 heavy metal simply breathe into the human body is under control?However,through the accumulation of vegetables under dry or wet deposition in the heavy metal,Due to the health threat generated by Hg and As,So that the health of vegetables intake risk assessment is higher,all have a certain threat to human health.