Environmental Effect And Evaluation Of Coal Ash In The Water And Soil

Coal ash emissions has reached 620 million tons in 2015, few of it is applied to agriculture and industry. Most of it still stored in the open air, the coal ash contains some metal elements, it causes harm to animals, plants and human through the impact of natural environment. Therefore the heavy metals pollutions of coal ash has became a concern issue. In this paper, the college town of Dao Yi is regarded the study area, the college town of coal ash is the object, the research discuss the physical and chemical properties, leaching characteristic of and the law of migration of heavy metals in soil and plant, the environmental quality and ecological risk are used to evaluate the present emissions situation of coal ash. Following conclusions:(1)Investigating the leaching characteristics of heavy metals in coal ash.The physical and chemical properties of different particle sizes in coal ash is researched. Then, we analyze the relationship of leaching of heavy metals of coal ash andleaching agent, coal ash particle size, the amount of coal ash and leaching temperature by using the orthogonal experiment. Next using the continuous leaching method of pH-stat and BCR,the law ofleaching behavior in different pH and morphological distribution of heavy metals is researched, finally the extraction effect of heavy metals in coal ash by DTPA is analyzed. The results showed that the same composition and different particle sizes of coal ash, the specific surface area increases as the particle size reduction, the content of Cr,Hg inresidue more than 85% and leaching amount increases as the pH increases, the leaching amount of Cd, Pb and As in acidic and base were higher than neutral.(2) Investigating the migration of soil–plants of heavy metals of coal ash. The coal ash and soil samples were mixed in different proportions to grow plant, then treatmentingthe Solanum nigrum, Bidens grass and cabbage seed were used to the pot experiment, researching the effect of coal ash on three kinds of plant growth and heavy metal enrichment, finally the distribution of heavy metals in Solanum nigrum and Bidens were analyzd. The results showed that coal ash can make plant sprout, but can not grow normally, and heavy metal content is high in plants body, the size of 200 to 300 mesh of coal ash was choosed, mix it with the soil reached 50%, the content of heavy metalsin the body of Cabbage and Solanum nigrum are lowest, heavy metals are mainly distributed in leaves and stems in Solanum nigrums and Bidens, the roots are rarely.(3) Investigating the environmental assessmentof heavy metals pollution in coal ash. The coal ash samples in seven coal ash discharge points of DaoYi was collected, analyzing heavy metals content in coal ash that come from four origins with digestion, mixing coal ash with soil and determinate the heavy metals content by using DTPA, finally the pollution of heavy metal of coal ash in the soil and plants was evaluated through the single factor, comprehensive index and the potential ecological risk index methods. The results showed that the determination of As exceeded the national standard, Cr and Pb content are in line with national standards for four kinds of coal ash origin, environmental quality assessment and potential ecological risk assessment, Hg in soil and plants are the main pollutants, so Hg contamination should cause the relevant departments attention.