Accumulation And Migration Characteristics Of Heavy Metals In Soil And Organisms Around Typical Waste Incineration Power Plant

Long-term accumulation of heavy metals in environmental media or terrestrial organisms may cause potential harm to animals,plants and human body.Studies have been carried out on the accumulation of heavy metals in the surrounding environment of characteristic polluted areas such as coal-fired power plants,e-waste dismantling sites and plastic waste recycling sites,and the results provide an important basis for local heavy metal risk management.In recent years,garbage incineration power generation has gradually become a major treatment method of living garbage.However,the accumulation of heavy metals in the ecological environment around the waste incineration power plant remains unclear.Therefore,the research on the accumulation characteristics of heavy metals in the soil and terrestrial organisms around the waste incineration power plant as well as the migration rules in the terrestrial food web can provide a scientific basis for the risk assessment and risk prevention and control of heavy metals.This study selected waste incineration power plants and their surrounding areas.According to the local geographical conditions and environmental characteristics,we collected soil samples,roots,stems,leaves,and rhizosphere soil of Setaria viridis(L.)Beauv,Artemisia caruifolia,Abutilon theophrasti Medikus,Humulus scandens(Lour.)Merr,Chenopodium ficifolium Sm and Erigeron canadensis L;At the same time,6 species of insects,including Millipede,Locusta migratoria manilensis,Gryllulus,Araneida,Rhopalocera,Cicadidae,were collected near the plant sampling site;In addition,domestic chickens and pigeons were collected.The occurrence characteristics of seven heavy metals in soil and plant were analyzed,and the heavy metal accumulation rule in soil-plant system was clarified.At the same time,based on the stable isotope technique,the vegetable-animal and animal feed-source relationships and the trophic levels of animals were determined,and the trophic level migration behavior of seven heavy metals in the terrestrial ecosystem around the incineration plant was analyzed.The main results are as follows:(1)The contents of Pb,Cd,As,Sb,Mn and Hg in 12.8%,97.4%,79.5%,64.1%,56.4%and 15.4%samples were higher than the background values in Hebei Province.The content of As in this study was 1.29-6.10 times that of agricultural soil,urban soil and some characteristic polluted soil in other regions.Principal component analysis indicated that Zn,Pb,Cd and As in soil may be derived from flue gas emissions from waste incineration power plants,Sb and Hg from agricultural production and road traffic,and Mn from natural sources.The evaluation results of single factor and comprehensive potential ecological hazard index showed that the heavy metals in the soil of this area were of minor hazard level.The non-carcinogenic risk values of soil heavy metals for adults and children were 0.026-0.203 and 0.042-0.998,respectively.Cd and Sb were the major contributors to the total risk.The median carcinogenic risk of heavy metals in soil for both adults and children is much lower than 1.0×10-6,which is acceptable.However,it is worth noting that the non-carcinogenic risk of soil heavy metals in children is close to 1,which should be paid attention to.(2)Pb content was the highest in the roots and stems of Setaria viridis(L.)Beauv.,Cd content was the highest in the roots and leaves of Artemisia caruifolia,and Mn content was the highest in the stems and leaves of Erigeron canadensis L.Compared with other studies,the content of As in the roots and leaves of plants in this study was higher,and the content of other heavy metals was at a moderate level,indicating that heavy metals in the flue gas of waste incineration power plant may have an impact on soil and plants.The bioenrichment coefficient of soil-root ranged from 0.037 to 2.89,and the soil-root enrichment coefficient of Cd was higher than 1 for all the six species.The absorption of Pb,Cd and Mn in the roots was different among species,but there was no significant difference in the absorption of the other four metals by different plants.The transport coefficients of heavy metals from stem to root ranged from 0.35 to 2.05,and the transport capacities of Cd and Hg were the strongest.The transport coefficients of Zn were different among the six species.The transport coefficients of heavy metals from stem to leaf ranged from 0.510 to 2.67,and the transport capacity of heavy metals for Mn and Hg was the strongest.There were significant differences in the transport capacity of Zn,Cd and Mn from the leaves of the six plant species.(3)Among the six insects,the content of heavy metals in insects was higher in Millipede,Locusta migratoria manilensis,Grylluus,Cicadidae,but lower in Araneida and Rhopalocera.The reason for the difference of heavy metal content in different insects needs further study.There were no significant differences in the contents of Zn,Pb and As,but significant differences in the contents of Cd,Sb,Mn and Hg(p<0.05).The content of As in insects in this study was higher than that in other studies,the content of Pb and Hg was lower than that in other studies,and the content of other heavy metals was at a medium level.The content of heavy metals in muscle and tissues of pigeon was higher than that of chicken on the whole except Cd.The levels of As in domestic chickens and pigeons were also higher than in other studies.In domestic chickens,Pb,As and Hg are mainly accumulated in the brain,Zn and Cd are mainly accumulated in the stomach and kidney,and Mn is mainly accumulated in the intestine,kidney and liver.In pigeon,Zn mainly accumulated in intestine and other heavy metals mainly accumulated in kidney.(4)In this study,Cicadidae and Rhopalocera mainly feed on C3 plants,while domestic pigeons mainly feed on C4 plants.In the chains of Setaria viridis(L.)Beauv.-gray pigeon/black golden eyed pigeon,and Erigeron canadensis L.-gray pigeon/black golden eyed pigeon,both Zn and As undergo biomagnification;BMF of Zn and As in four food chains were 1.22-1.71 and 1.34-1.40;In addition,Hg also undergoes biomagnification in the food chain of Setaria viridis(L.)Beauv.-gray pigeons;In the food chain of the herb-Rhopalocera,all heavy metals undergo biomagnification;In the Setaria viridis(L.)Beauv.-Rhopalocera food chain,the BMF of Hg was as high as 16.1,indicating that Rhopalocera have a strong ability to absorb heavy metals from Setaria viridis(L.)Beauv.-Rhopalocera.In the food web of Erigeron canadensis L.-Locusta migratoria manilensisAraneida,the logarithmic transformation concentrations of Zn,Pb,Cd,As and Sb were significantly positively correlated with the δ15N of organisms,while the logarithmic transformation concentrations of Hg were significantly negatively correlated with the δ15N of organisms;In the artemisia Artemisia caruifoliaCicadidae-Araneida food web,Pb,As,and Sb undergo trophic level amplification,and Mn undergo trophic level dilution;In the food chain of Artemisia caruifoliaCicadidae-chicken,there is no trophic level amplification of the seven heavy metals between trophic levels.However,the migration behavior of heavy metals in the food chain is very complex,and its trophic level migration rule needs to be further studied.