The Availability Of Arsenic And Antimony In Soil And Their Effects On Soil Enzymes

Arsenic(As)and antimony(Sb)are naturally occurring cocomitant metals in the earth's crust.They would seriously pollute the soil after entering the soil.Soil enzyme is involved in various biochemical processes in soil and can be used as an important biological index to evaluate the soil fertility level and the quality of soil ecological environment.Meanwhile,as the heavy metals directly affect the soil enzyme activity changes,soil enzyme can also be used to characterize the degree of heavy metal pollution.At present,there are many studies on the effects of arsenic on soil enzymes.However,most of them only considered the effectof arsenic concentration andignoredthe effect of soil water content which would regulate arsenic content.As for Sb,the study focused on the existence form of antimony,the effectiveness and the impact on plants.Only few researches investigatedthe relationships between soil enzyme and antimony pollution.Therefore,it is meaningful to study the effects of antimony pollution on soil enzymes and the effects of arsenic on soil enzyme activities regulated by different soil water content.In this work,(1)Effects of different concentrations of antimony pollution on dehydrogenase activity in typical soils of 18 provinces and the variation of water soluble antimony in soil were carried out.(2)Available arsenic changes in soil after different concentrations of arsenic contamination and effects of arsenic pollution on soil alkaline phosphatase,aryl-sulfatase and dehydrogenase at three soil moistures 35%,65%and 110% maximum water holding capacity were studied.The main results are shown as follows:1.The content of water soluble antimony increases with the increase of total antimony content.The antimonyadsorption capacity on soil decreases with the increase of total antimony concentration.The adsorption of antimony on soil was described well by Langmuir and Freundich equations.The maximum adsorption capacity of antimony is 5747.13 mg kg-1.Dehydrogenase activity was significantly inhibits by antimony.Soil pH,organic matter,and CEC arethe main factors affecting the toxicity of antimony in soil.Antimony showed the less toxicity to the soil with high organic matter and high CEC content and low pH.2.Phosphatase,dehydrogenase,and aryl-sulfatase enzyme activity were all inhibited by arsenic.The higher content of organic matter the soil had,the lower inhibition arsenic showed.3.In the long-term arsenic pollution experiment,under all three different soil moisture conditions,the soil available arsenic concentration decreased with the prolongation of culture time.Soil alkaline phosphatase,aryl-sulfatase,and dehydrogenase activity were inhibited byarsenic.With the extension of time,the inhibition is reduced.The inhibitory effect of arsenic on soil dehydrogenase was low.Under the same culture time,the content of available arsenic in soil was the lowest at 110% moisture content compared with 35% and 65% water content.The activity of the three enzymes was the most inhibited under the condition of 110% water content.The ecological toxicity of arsenic in soil was higher under the conditions of flooding(110%)and drought stress(35%).Comprehensive text,the following conclusions can be drawed : Antimony can significantly inhibit the activity of dehydrogenase,The content of water-soluble antimony is affected by the concentration of antimony and the soil properties.Arsenic has an inhibitory effect on soil alkaline phosphatase,arylsulfatase and dehydrogenase,Available arsenic content is affected by total arsenic,soil moisture and soil properties...