Research On Mercury Pollution In Green Areas Of Typical Urban Industrial Areas

Mercury,as one of the most toxic heavy metal pollutants,can travel through the atmosphere over a long distance.As the typical urban industrial areasemitting large amounts of mercury,the greenland ofBaogang Group,Jiading industries adding mercury raw meterials and Wujing industrial areas(Binjiang Park and East China Nomal University as comparision)were selected to study:(1)the mercury pollution characteristics in soils and plants;(2)the influences of soil marcofauna on mercury transformation in soils,trying to provide scientific basis for the remediation of Hg contaminated soils.The main results are as follows:(1)The total Hg content of soils in three typical industrial areas from large to small is Jiading,Wujing,Baogang.The total content of Hg in Jiading is significantly higher than that in Wujing and baogang.The total content of Hg in all investigated areas was higher than that in the control points of Binjiang Park and East China Normal University.Thegeoaccumulation Index indicates that the contaminated spots are located in the middle areas and the greenbelt along the river of Baogang,as well as the Yang Tai,Ya Ming and PHILPS in Jiading.(2)The speciation of Hg in soils were analyzed by using BCR sequential extraction procedure(acid soluble form,reducible form,oxidizable form and residual form).The results show that the content of acid soluble Hg as follows:Baogang>Wujing>Jiading.The contents of reducible and oxidizable Hg from high to low are as follows:Wujing>Baogang>Jiading.The contents of Hg in residual form are as follows:Jiading>Baogang>Wujing.It shows that the bioavailability of Hg in the soil of Baogang and Wujing is higher,the potential utilization of Hg in Wujing soil is very high,and it may cause a certain risk to the growth of animals and plants.The correlation analysis shows that pH can influence the speciation of Hg in soils.Educible and oxidizable Hg were positively correlated with pH;Hg was positively correlated with TP;oxidizable Hg was positively correlated with,soil.organic matter.and the reducible Hg;there was a significant positive correlation between residual Hg and soil TP and total Hg.(3)The Hg content in study areas of plants ranges between 13.79-257.5 g/kg,the average content is 90.14 g/kg.Hg content of plants in control points is in the range of 6.848-75.31 g/kg,with an average of 29.93 g/kg.Most plants Hg content are more than twice higher than the plants in control points.Eriobotrya japonica(201.9 g/kg)has a strong ability to accumulate mercury in arbor,whichNerium indicum Mill.(199.0?g/kg),Ligustrumlucidum(15.7?g/kg)and Pittosporumtobira(121.5?g/kg)in shrub,which the roots of Solanum nigrum L.(214.6 g/kg)in herbaceous plant.The results showed that plant Hg was significantly positively correlated with soil TN plant TC,plant TP,soil pH and soil acid soluble Hg,and positively correlated with soil TP.The results show that Hg in barks is higher that Hg in rings of Wujing industrial areas and the control points,it is speculated that Hg in barks is mainly from atmosphere.(4)There are 6 species of soil macrofauna in Wujing industrial areas,with the desity of 7.69ind/m2.The content of Hg in Pheretima guillemi was the highest(831.6?g/kg).The average content of Hg in soil macrofauna is 1176 ?g/kg,which is the highest in all samples.Earthworm activities can affect the physical and chemical properties of soil.In addition,earthworm manure can also reduce soil pH.By comparing earthworm manure and raw soil,the concentration ratio of reducible and oxidizable Hg was reduced by 137%and 42%respectively,and the content of residual Hg increased by 22%.It shows that earthworms can change the potentially biologically active Hg into an impossible reducible Hg by digestion,thus reducing the ecological risk of Hg in soil.