Study Of Sources And Pollutions Of Heavy Metals And Organic Matters In Dry Deposition And PM_2.5 In Beijing

The pollution of atmospheric particulate matter is a key topic for environmental workers and human.Many atmospheric particulate inspection stations have been set up around the world to observe and monitor the air quality.Beijing,the capital of China,was faced with two major weather problems of air pollution,dust storms and haze.Therefore,it has great significance to determine the risks and sources of pollutions in dust storms and haze weather,which controls pollution at the source.In this paper,we set the northern city of Beijing,from North Second Ring Road to Miyun District and Miyun Reservoir,as the objectives.We studied particulate matter around Miyun reservoir and PM2.5 from the other objectives to determine the sources and risks of the major air pollutants of dust and haze weather.The microstructures,mineral composition and heavy metal concentrations of the atmospheric particulate mattersamples in the surrounding areas of Miyun Reservoir were analyzed by transmission electron microscopy,X-ray diffraction and inductively coupled plasma mass spectrometry,respectively.Results showed that the pollutions of heavy metals,especially Zn and Pb,existed in the Miyun reservoir areas.The main sources,including natural sources and anthropogenic sources,of heavy metal in dry deposition was the surrounding area.The anthropogenic sources were mainly transportation and iron ore mining.Compared with the summer period,the dry deposition from the northwestern region increased due to the influence of the northwest monsoon in winter,and the concentrations of the heavy metal elements increased correspondingly.The total concentration and distribution characteristics of rare earth elements in Miyun reservoir area were analyzed.Results showed thatthe rare earth element pollution was not obvious.The concentrations of rare earth elementsin winter were higher than that in summer.The main sources of rare earth elements were soil parent materials,however,the total concentrationand distribution characteristics of them were affected by human and biological activities.Based on the concentration and isotopic tracer analysis of organic pollutants in PM2.5 samples,which was collected in the line from North Second Ring Road to Miyun,we found that the main sources of organic matter of PM2.5 in haze weather in Beijing was motor vehicle exhaust,coal combustion and biomass combustion.Organic matters of PM2.5 in haze and non-haze weathers were from the same source,but with different contribution.Motor vehicle exhaust was the main source in non-haze weather,whilecoal combustion and biomass combustion became the main sources of pollution with increased contribution in haze weather.This study of haze formation provides a theoretical basis on the control and management of haze in Beijing.The effects of atmospheric pollutants for environment and human health were analyzed and assessed.The potential risk to soil was mainly posed by Zn element,with the next Cd and Pb elements;while that of other elements was not obvious.The effect of atmospheric dry deposition on water was mainly manifested by the suspended matter in the river,in which heavy metals showed a significant positive correlation with atmospheric dry deposition.Non-carcinogenic risk for human of atmospheric dry deposition was not significant,while the values of carcinogenic risk for human exceeded the maximum acceptable range.And the health risk index for children were higher than that for adults.Which should attract attention was that while the excess carcinogenic risk of PAHs in PM2.5 for humans was within the maximum acceptable range,the carcinogenic risk value of adults in haze weathers reached the critical value of the maximum acceptable range.