Effects Of Ammonium Fulvic Acid And Sodium Humate On The Speciation Of Arsenic,Mercury In Soil And Soil Enzyme Activity

At present,heavy metal pollution in Chinese soil has received widespread attention.According to the National Soil Pollution Status Survey issued in 2014,the over-standard rates of arsenic and mercury reached 2.7% and 1.6%,respectively.Once the soil is contaminated with arsenic and mercury,it poses a serious threat to the ecological environment and human health.Humic acid is a natural organic matter naturally present in soil,peat,ocean and fresh water.Due to its structure containing a large number of active groups,Humic acid can affect the behavior of arsenic and mercury in the soil by adsorption and complexation.This study explored the effects of ammonium fulvic acid and sodium humate on heavy metal speciation and soil enzyme activities in soils contaminated with heavy metals such as arsenic or mercury.The result was hope to provide a theoretical basis to repair arsenic and mercury contaminated soils.(1)Conclusions of study that effect of ammonium fulvic acid and sodium humate on arsenic speciation in soils:With ammonium fulvic acid added,the content of exchangeable fraction,organic bound fraction,and residual fraction arsenic in soil decreased,and the content of the specifically sorbed fraction and oxide bound fraction arsenic in soil increased.The passivation effect of ammonium fulvic acid on arsenic in soil was not obvious.With sodium humate added,the content of exchangeable fraction and organic bound fraction arsenic in soil decreased,and the content of the specifically sorbed fraction and oxide bound fraction arsenic in soil increased at low concentration of sodium humate and then decreased with the concentration of sodium humate rising.However,the content of residual fraction arsenic increased.The addition of sodium humate promoted the transformation of arsenic to stable residual fraction in soil.(2)Conclusions of study that effect of ammonium fulvic acid and sodium humate on mercury speciation in soils:The addition of ammonium fulvic acid reduced exchangeable fraction and oxide bound fraction mercury content in the soil,and the specifically sorbed fraction mercury content increased first and then decreased,and the organic bound fraction and residual fraction mercury content increased;The addition of sodium humate causes the exchangeable fraction,organic bound fraction and the residual fraction mercury content to increase,and specifically sorbed fraction and oxide bound fraction mercury content decrease.The addition of ammonium fulvic acid and sodium humate changed the speciationof mercury in soil and promoted the transformation of mercury to the organic bound fraction and residual fraction in soil.(3)Conclusions of study that effect of ammonium fulvic acid and sodium humate on the activities of enzymes in soils:The activities of urease,alkaline phosphatase and sucrase in arsenic or mercury contaminated soils increased by adding ammonium fulvic acid and sodium humate.The enzyme activity was higher than control group under different content of fertilizer treatments.(4)Conclusions of study that effect of ammonium fulvic acid and sodium humate on arsenic and mercury contents in pakchoi plants in soils:In the soil contaminated with arsenic and mercury,the application of ammonium fulvic acid had no significant effect on the content of arsenic and mercury in the upper part of pakchoi.However,the application of sodium humate could reduce the content of arsenic and mercury in the upper part of pakchoi.