| The contradiction between water supply and demand has become one of the prominent problems that the arid region of northern city need to face nowadays,thus,utilization of reclaimed water reasonable has become an important way to ease or even to realize the sustainable development.This study sets the Zhang Gaiying sewage treatment plant as an example,to carry out the effect of reclaimed water reuse on plant quality and water soil environment in Hohhot Therefore,respectively research the impact of irrigation with reclaimed water on grass growth and soil properties through the indoor experiment,research the impact of natural wave’s water quality with the supplement of reclaimed water through the long term fixed point sampling of Xiao Heihe,by field investigation and sampling analysis the impact of short-term,medium-term and long-term sewage irrigation to the quality of Corn and soil properties in Tu Mote plain irrigation area,on this basis,combined with scientific evaluation methods,the potential ecological risk of using reclaimed water was evaluated.The main conclusions of this study are as follows:1.Reclaimed water for irrigation of turfgrass:The use of reclaimed water irrigation under backfill condition has a significant effect on the growth rate of lawn.Reclaimed water irrigation increased soil salinity,but did not constitute a threat to lawn growth.The concentrations of heavy metals such as As、Hg、Pb、Cd and Cr in the soil under reclaimed water irrigation are far less than those of the "soil environmental quality standard"(GB15618-1995)standard limit of two.The enrichment coefficients of different heavy metals in Lolium perenne were from high to low:Cd、Cr、Hg、Pb、As.Through the Nemero comprehensive pollution index and potential ecological risk index method of 4 kinds of evaluation methods,the evaluation results show that Pb and Hg are the main factors that constitute a threat to the ecological environment of soil.2.Reclaimed water recharge Xiao Heihe:On The time scale,TN and TP average concentration are higher than that specified in the class V water minimum allowed value,has caused water pollution,and are mainly concentrated in the winter and spring,the average concentration of chlorophyll a also in the eutrophic level,mainly concentrated in summer and Autumn.The water pollution in 2016 was lower than in 2015.On the spatial scale,using a logarithmic power function universal index formula evaluates the Xiao Heihe’s eutrophication.The results show that the EI value in the study area of Xiao Heihe is higher than the upper limit of the classification standard in the time scale and the spatial scale,and the eutrophication status of the water is not optimistic The single factor water quality identification index(Pi)and the comprehensive water quality identification index(WQ Ⅱ)results show that the Xiao Heihe both in time scale and spatial scale in the"five black and smelly" level,TN and TP are the main contribution factor.3.Reclaimed water for irrigation of maize:With the increase of irrigation years,the total salt content in soil also have different degrees of increase,with more than 20 years history of sewage irrigation,the soil salt accumulation has been mild salinization and pollution,mainly accumulated in the soil layer.The contents of heavy metals Cd,Cr,Cu,Pb,Zn and Hg in sewage irrigated soil increased with the increase of sewage irrigation years.The content of Cr and Pb in corn kernels with 10 years and 20 years of irrigation history has been 100%and 26%higher than the national food safety limits,.The contents of crude protein,crude starch and crude fiber are increased in different sewage irrigation years,but the formation of crude fat is inhibited.Through the Nemero comprehensive pollution index and potential ecological risk index method of 4 kinds of evaluation methods,the evaluation results show that Cd is one of the most important factors that cause the ecological risk of the local farmland environment. |
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