Effects Of Agronomic Regulation On Inhibition Of Rice Absorption And Accumulation Of Cd And As

Heavy metal pollution has threatened human health.The prevention of heavy metal pollution become more and more important in the safe production of agricultural products.Pollutants generated during the mining process enter the surrounding soil through various means,and produce heavy metal pollution to the surrounding farmland.We adopted different agronomic measures to prevent the polluted farmland,reduce the absorption of cropson heavy metals in the soil,make the heavy metal content in crops meet national standards.In this paper,the farmland near a lead-zinc mine in Anhui Province was selected as the research object.Thecontent of heavy metals in soil and crops in the area was collected and determined.We have added passivating agent to the soil for two consecutive years,to study the accumulation characteristics of heavy metal cadmium and arsenic in rice after applying charcoal and ferrous sulfate in the field.We also carried out the corresponding indoor pot experiment using the soil which collected from study area.Different water management was studied through water and fertilizer combination treatment.The effects of phosphorus fertilizer and charcoal on the absorption of cadmium and arsenic in rice under management.The main findings are as follows:(1)The results showed that the Cd content of farmland in the study area is 0.35-1.58 mg/kg,the coefficient of variation is 45.56%.The average Cd content in soil was 0.76 mg/kg in 2017 and 0.90 mg/kg in 2018.The content of As ranged from 57.36 to 117.89 mg/kg with a coefficient of variation of 31.98%.The average value of As in soil was 66.86 mg/kg in 2016 and 75.29 mg/kg in 2018,showing a slight increase trend.The content of Zn ranges from 162.49 to 448.03 mg/kg,and the coefficient of variation is 17.03%.The Zn content in soil was 323.93 mg/kg in 2017 and the highest was 343.11 mg/kg in 2018.The highest content of Zn,As and Cd exceeds the national secondary standard for soil environmental quality.(2)The proportion of residual state of As in the soil reached 98.13%among the five heavy metals,and the lowest proportion of Cd in the soil was 24.75%.In addition to the residual state,the proportion of Pb reducible state in soil is up to 51.52%,followed by Cd26.75%,and the proportion of weak acid extraction state of Cd in soil is up to 46.5%.(3)Adding charcoal and foliar application of ferrous sulfate in pot experiment can increase rice panicle length,plant height and single ear grain number.Compared with CK,the addition of charcoal increased the yield per pot by up to 28.15%;the foliar application of sulfuric acid increased the yield per pot by up to 45.10%.(4)The addition of charcoal to farmland soil for two consecutive years has a significant effect on the absorption of Cd by rice grains.The maximum decrease in Cd uptake by grain is 55.6%in 2016 and 48.2%in 2017.Ferrous iron has a significant effect on the absorption of cadmium and arsenic in rice grains.The maximum reduction of Cd uptake by grain reached 68.1%and 42.2%in 2016 and 2017,respectively.The maximum reduction of As in grain absorption was in 2016 and 2017.It reached 65.2%and 34.5%respectively.Correlation analysis showed that the cadmium uptake in rice roots was positively correlated with soil available cadmium,and the absorption of arsenic was positively correlated with soil available arsenic.The accumulation of cadmium in rice grains had a certain correlation with soil available cadmium and soil available arsenic.The absorption of arsenic by rice roots,stems and leaves and grain has a high correlation with soil pH.(5)The application of diammonium phosphate in the soil reduced the content of cadmium in rice grains by 50%.The content of cadmium in rice grains decreased by 18.1%under the condition of flooding irrigation in the whole growth period.The content of cadmium in rice grains decreased by 54.7%under the combination of soil application of phosphorus fertilizer and flooding irrigation method in whole growth period;charcoal applied in soil,cadmium in rice grains The content of cadmium in rice grains decreased by 56.1%under the combination of soil charcoal and flooding irrigation in the whole growth period.