Study On Temporal And Spatial Distribution Of Persistent Organic Pollutants In Coal Mining Subsidence Area

Persistent organic pollutants(POPs)have persistence,semivolatility,bioaccumula-tion and high toxicity,which have serious harm to human health and environment.POPs can cause great harm to human health and environment.With the frequent occurrence of POPs pollution accidents,people gradually realize the harm of POPs.Polycyclic aromatic hydrocarbons(PAHs)is a kind of POPs.There are more than one hundred kinds of PAHs in the environment.16 of them were defined as priority control pollutants by EPA.This paper takes Huainan Panyi Mine Yangzhuang coal mining subsidence area as the research object.This paper takes PAHs as an example,collecting water,soil and sediment samples were collected in 2014,2015 and 2016.The temporal and spatial distribution of PAHs is analyzed in the whole subsidence area.In order to study the influence of organic matter on PAHs distribution,the correlation between TOC and PAHs in water,soil and sediment was also discussed.Results are listed as follows:The analysis of the time distribution of Yangzhuang samples from 2014 to 2016 found that:The concentration of PAHs in 2015 is the lowest because of long term rainfall.The content of PAHs between 2014 and 2016 was not significant.PAHs content is stable and there were not new pollution source.The water samples were mainly composed of 3?4 rings PAHs.Because of the insolubility of 6-ring PAHs in water and less release of high rings PAHs,6 ring material was not detected in 2015 and 2016.The water mobility is large because of fish breeding.Therefore,the distribution of PAHs in water is different in different years.In 2014,the eastern area of subsidence area was higher.In 2015,the middle area of subsidence area was higher.In 2016,the subsidence area which content is higher is close to the northwest boundary(near the coal gangue area).The content of ?16PAHs in suspended solid samples showed the characteristics of 2014>2015>2016.Suspended sediments are deposited in the bottom of the water in recent years and there were no new pollution sources.Sediment data showed that the content in 2016 was significantly higher than the previous two years.Suspended solids have been collected in the sediment.Because of the high content of organic matter in the sediment,the content of the 5 ring and the 6 ring is increased compared with water and suspended matter.Due to the east side of the water not only accept the river runoff pollutants but also collecting estuarine and coastal pollutants,suspended solid and sediment PAHs are heavily polluted in the eastern part of the coal mining subsidence area.The analysis of the spatial distribution of Yangzhuang samples in 2016 found that:In 2016,the ?16 PAHs concentrations in Yangzhuang water ranged from 79.05 to 239.14 ng/L,mainly in the three-five rings.The degree of water pollution is light.The distribution of PAHs in water is uniform.There is no obvious regularity between layers.The PAHs of 2-4 rings have little change at different depths of water.The PAHs of water in coal mining subsidence area mainly come from the burning of vegetation,coal and other materials.The concentration of samples near coal gangue is higher.The ?16 PAHs concentrations in Yangzhuang suspended solids ranged from 137.5 to 586.31 ng/L,mainly in naphthalene,phenanthrene.It was affected by lower coal and biomass combustion.The distribution of PAHs in bottom layer is obvious.The vertical distri-bution characteristics of 3?5 ring PAHs are not obvious.Because of large mobility of suspended solids,there is no obvious regularity of spatial distribution.In surface layer,the PAHs concentration in central area is high.In middle layer,the PAHs concentration in east area is high.In bottom layer,the PAHs concentration in west area is high.The ?16 PAHs concentrations in Yangzhuang soils ranged from 42.11 to 4152.379 ng/g,mainly in naphthalene,phenanthrene and pyrene,fluoranthene.The PAHs concentration in 5?10 cm depth is highest in four layers,and then decreased with the increase of depth.In 0-5 cm,the PAHs concentration in north area is high.In 5?10 cm and 10?15 cm,the PAHs concentration in southwest area is high.As the final sink of pollutants,the pollution of PAHs in sediments is the most serious.The ?16 PAHs concentrations in Yangzhuang sediments ranged from 43.968 to 7644.210 ng/g,mainly in phenanthrene.The concentration of high ring material was increased because of the organic matter.The vertical distribution characteristics are obvious.The change of two-ring and five-ring PAHs concentration with the depth is small.The three to five rings PAHs concentration were decreased with depth increasing.The spatial distribution is regular.The concentration of PAHs in west region where near coal gangues is high and there are a large area of farmland.The coal gangue pile and soil on PAHs contribute to surrounding environment in PAHs significantly.In water samples,there are no significant correlations between ?16 PAHs and dissolved organic carbon.In soil samples,the concentration of PAHs is wealy negative correlated to the concentration of the TOC.There is a strong positive correlation between the concentration of high rings PAHs(5,6 rings)and TOC.There is also a strong positive correlation between the PAHs concentration in 0?5 cm and 10?15 cm soil and TOC.In sediment samples,there is a strong positive correlation between the PAHs concentration TOC.Moreover,the PAHs content in different depths of sediment samples and in different rings are significantly correlated with TOC.It can be seen that the distribution of PAHs in soil and sediment is related to organic matter.