Research On The Effect Of Reclaimed Water Irrigated Greenland On Soil Environment And Human Potential Risks In Zhongwei City

This paper aimed at the potential risks of soil,plants and human body in the process of reclaimed water reuse for greenland irrigation,taking Zhongwei City,a typical arid area,as the research object,carried out indoor evaporative leaching simulation experiments and field experiments.The indoor evaporative leaching simulation experiment was set as a factor Two levels(reclaimed water,original afforestation irrigation water)complete test,comparative analysis of soil EC,pH,Hg,As,Zn,Pb,Cd,Cr and other six heavy metal elements after irrigation with reclaimed water in the vertical direction of the soil migration distribution regular research;field experiments conducted sampling and analysis of irrigation water,soil and green plants in the reclaimed water irrigation area and the original green water irrigation area in the study area.The main analysis indicators were potentially toxic elements Hg,As,Zn,Pb,Cd,Cr and Endocrine pollutant BPA.Finally,the potential carcinogenic and non-carcinogenic risks of different groups of people in the greenland irrigation process by reclaimed water were evaluated.There are six main conclusions.(1)The reclaimed water irrigated the soil with a higher accumulation of salt.The area with the highest accumulation of salt under evaporation is the soil surface,and the accumulation reached 1.304g/kg.Enhanced.Under evaporation conditions,the TN content of the reclaimed water irrigated soil forms and accumulates in the 20-40 cm soil,and-showed a tendency of leaching in the remaining soil layers.Under short-term reclaimed water irrigation,AP leached in all layers of the soil,but the total AP leaching rate in each soil layer under reclaimed water treatment was lower than that of the original green water treatment.(2)After irrigation with reclaimed water,Hg,As,Zn,Pb,and Cd in the soil showed a tendency to accumulate in each layer of soil,while Cr only had a tendency to accumulate in the top soil,and the other soil layers showed a tendency to leaching.The soil layer with the largest pollutant content of Hg,As,Zn,Pb,Cd and the accumulation of pollutants under the reclaimed water treatment is the Z3 layer(20-40cm).The order of the accumulation ability of heavy metals in the vertical direction of the soil after the two water quality irrigations is the same.The accumulation ability of heavy metals in the soil is mainly related to the chemical properties of the heavy metals themselves.The irrigation water quality has a certain impact on the accumulation of heavy metals in the soil.(3)Using three soil pollution evaluation methods,firstly taking the soil background value as a reference,the results showed that the element with the highest degree of potential heavy metal pollution in the two regions is Hg.Hg pollution had reached a strong risk,followed by Cd and Cr,and heavy metals in the soil in the reclaimed water irrigation area.The potential risk level was higher than the original greening water irrigation area;based on the screening value of the first type of land use in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard"(GB36600-2018),it was found that the soil heavy metal pollution level in the two regions was generally low,Cr was the most polluted element.(4)Using ultra-high performance liquid chromatography,the highest BPA content in the reclaimed water reached 0.07μg/L,and the average BPA content in the soil and tall fescue grass in the reclaimed water irrigation area was higher than that in the original green water irrigation area.Comparing the absorption capacity of tall fescue grass to 6 kinds of heavy metals and BPA,it was found that the absorption capacity of this kind of green grass to endocrine disruptor BPA was higher than that of heavy metal pollutants.Principal component analysis results showed that BPA was one of the main pollutants in tall fescue grass.(5)The non-carcinogenic risk of Cr and Hg in occupational population under the route of reclaimed water inhalation is generally higher than that of urban residents of all ages.The exposure risk of Cr in the four types of exposed populations is higher than that of Hg,and the occupational population has a greater potential risk of non-carcinogenic Cr.For the four heavy metals As,Zn,Cd,Cr and BPA,the potential risks of the human body in the three contact media under this exposure route of skin contact are all within an acceptable and safe range.In general,the non-carcinogenic pollutant with the highest risk is Cr,which has caused a greater risk to human health,followed by Hg,As,Cd,Zn,and BPA.The occupational population has the highest carcinogenic risk of inhaling Cr,and there is a potential carcinogenic risk.In general,Cr has the highest carcinogenic and non-carcinogenic risks under the inhalation route,and attention needs to be paid to the content of Cr in the reclaimed water.(6)Judging from the evaluation results of soil,plant and human health risks after reclaimed water irrigation,the current level of heavy metals and endocrine disruptors in the soil and plants after the use of reclaimed water in this area is low,and the potential human health risk is relatively light.Reclaimed water has a certain degree of applicability.Sex.However,from the research results,it is necessary to monitor and control the heavy metal Cr content in reclaimed water,soil and plants to ensure the safety of the use of reclaimed water.