Temporal And Spatial Distribution Characteristics Of Toxic Pollutants And Microbial Response In Constructed Wetlands In Xiaoqing River Basin

Constructed Wetland as a wastewater ecological treatment technology has been widely used in municipal sewage treatment plants advanced treatment process. Verify the feasibility of mixed wastewater treatment by wetlands, purification efficiency and the impact on wetland ecosystem before and after the contaminated has become a hot topic for environmentalists. In this article, study on the Xiaoqinghe river basin reed wetland and upper reaches of the wetland’s wastewater treatment plant, monitoring of COD, TN, TP, ammonia, organic phenols and other conventional pollutants, Using inductively coupled plasma spectrometry and gas chromatography mass spectrometry to monitor heavy metals (such as Pb、Mn、As、 Hg、Zn、Cr、Cd),PAHs and OCPs toxic pollutants. Constructions of soil genomic library by molecular biological methods investigated the characteristics of distribution and source apportionment of pollutants in the water environment and soil environment in the wastewater plant and wetland areas, and soil microbial community structure. Focus on the effect of sewage irrigation on distribution of toxic pollutants and changes of soil microbial community structure. And identify the corresponding relationship of the toxic pollutant PAHs and OCPs with the soil microbial community structure.Using Nemerow index to evaluate on wetlands water pollution and the results shows that Wetland volatile phenol, TN, TP, COD and Chl-a pollution grade is GradeV, Comprehensive nutritional index to evaluate the status of wetlands water eutrophication, water body under severe eutrophication. The efficient of reed wetland on the remove of ammonia nitrogen and COD is not ideal, ammonia nitrogen removal rate is3.2%-73.3%, the average removal rate is34.4%, the removal rate of COD is%-39%, and average removal rate is12%. Reed wetland removal effect for mixed wastewater is not available.The concentration of OCPs and PAHs and pollution characteristics from the water plant and the wetland water environment showed the content of OCPs and PAHs were lower than national surface water environment water environment quality standard (GB3838-2002). The concentration ofCHs was range from0to0.24ng/L. It was possible that it be caused by the migration of the surrounding environment pollution. The concentration of hexachlorobenzene (HCB) was from0.03to0.13ng/L, which was caused by the discharge of the upstream paper-making and steel-making waste water. The concentration of endosulfan was range from0.06to2.32ng/L, and the concentration of endosulfan sulfate was between nd and0.18ng/L, which were generated by the pollution of sewage treatment plant.The concentration of Naphthaline, Acenaphthylene, Acenaphthylene, Fluorine, Phenanthrene, Fluoranthene and Pyrene is lower than the limit by The United States Environmental Protection Agency. The concentration range was from99.98to386.65ng/L accounted88.5-98.4%of EPAHs.Contents of the Pb, Zn, Mn and Cr close to the national background value, didn’t detect Cd and Hg. Heavy metals adsorption ability in wetlands is Pb> Zn> Mn> Cr. Cr is enriched in the soil surface, it is difficult to migrate to deeper soil. Sewage irrigation had no significant effect on the concentration of Zn, Pb is easy to migrate with the sewage irrigation along thesoil vertical section, and Mn is easy to migrate with the water to reach relative equilibrium. Inspection the correlation between wastewater irrigated wetlands’heavy metal contents and soil organic matter, the correlation of10-years sewage irrigated wetlands organic matters content and Cr, Mn content is not significant,but significantly associated with the Zn content in the p<0.05level and with the Pb content in the p<0.01level, correlation of3-years wastewater irrigated wetlands’soil organic matter and the As content was not significant, Organic matter and Zn, Cr, Mn and Pb are significant related at p<0.01level. Non-sewage irrigated wetlands soil organic matter were significant related with As, Zn, Cr, Mn and Pb at p<0.05level.10-year wastewater irrigation reduced the heavy metal pollution levels,repaired some of heavy metals soils pollution,but due to local industrial sewage the heavy metal pollution in3-years sewage irrigated wetlands has been strengthened, effluents deepen the heavy metals pollution in wetlands.Wetland top soil HCHs and DDT in the lower residue levels below the National Soil Environmental Quality Standard (GB15618-1995). pollution of DDT to DDE form of existence, the historical residue caused; wastewater irrigation on soil DDTand HCH residues The lower ratio of67.16%and78%higher than HCH residues of DDT residues in soil. soil surface PAHs are easily gathered at the soil surface0-6cm at6-8cm layer of polycyclic aromatic hydrocarbons down the total content was significantly reduced and the change trend leveled off, mainly because the0-6cm layer is the most abundant micro-organisms and plants, the most active parts of the soil organic matter content and a high degree of humification, so the combination of adsorption capacity of polycyclic aromatic hydrocarbons, polycyclic The arene difficult to downward migration. Sewage irrigation region PAHs contaminated by air pollution and oil pollution, the high temperature combustion common contribution of various sources of PAHs and soil organic carbon (TOC) did not show significant correlation.10-year sewage irrigation E16PAHs content9.84-357.85ng/g,12.83-116.26ng/g, three-year sewage irrigation E16PAHs content in the10.32-102.52ng/g sewage irrigation Σ16PAHs content. Description of the long-term wastewater irrigation to deepen the pollution of PAHs in the soil, but no sewage irrigation area location and10-year sewage irrigation, by the10-year wastewater irrigation, leading to pollution than three years of sewage irrigation serious.The main microbes in non sewage irrigated wetland are Gemmatimonadetes, Actinobacteria, Proteobacteria, Firmicutes and part of uncultured bacterium.Ten years of sewage irrigated wetland soil samples of main microbes in class into2types:Acidobacteria, Proteobacteria and part of uncultured bacterium.A total of two areas of microbial species accounted for44.72%and58%districts of microbial aggregates.The long-term wastewater irrigation cause the bottom microbial content decreased14percentage points. The degradative bacteria for organic chlorinated hydrocarbons, phenolic substances begin to accumulate in ten years irrigation wetland.lt can be seen from species of microorganisms, reed wetland sewage ingredients are mainly organic chlorinated hydrocarbons, pesticides, coking wastewater. Ten years of sewage irrigation area soil samples in the nitrification and denitrification reaction to the presence of a large number of microorganisms, reflect the pollution exceed the standard severe ammonia nitrogen in water.