Effect Of Freeze-Thawing Cycles On Arsenic Adsorption Desorption And Transfermation In Soil

Freezing and thawing is common natural phenomena in north China, is applied to the abiotic stress of soil, the will of the minerals in the soil, the kind of the charge quantity, charge and organic material and organic material form. Predecessors for the adsorption desorption behavior of arsenic in soil, and the problem such as geometrical shape has carried out comparatively detailed research, about the freezing and thawing conditions on soil physical and chemical properties and the influence of modal transformation of heavy metal Cd report are not uncommon, but the freezing and thawing conditions of adsorption and desorption behavior of arsenic in soil, the research on the effects of geometrical shape has not been reported.This study with brown soil as experimental material, adopt the method of indoor simulation training test analysis under the condition of different freezing and thawing soil adsorption-desorption characteristics of arsenic and its influencing factors, the exogenous arsenic forms in soil and its response to the freeze-thaw action, explore foreign release characteristics of arsenic in the freeze-thaw conditions, for repair of arsenic pollution in soil freezing and thawing area and its ecological environment risk assessment provides data reference and theoretical basis, has important theoretical and realistic significance.The main results and conclusions are as follows:1. By applying different isothermal adsorption model to fit the data that obtained by Langmuir model was better. Under the condition of the same moisture content, freezing and thawing soil adsorption to the As below freezing and thawing soil, the desorption rate is higher than without freezing and thawing soil, and with the increase of freezing and thawing cycle, As adsorption in soils reduced, desorption rate increases, the freezing and thawing can restrain the adsorption capacity of arsenic but the increase of capability of desorption of arsenic. The biggest buffer capacity (MBC) of As in soils with the increase of freezing and thawing cycle respectively by 40.2,35.5,31.5 down to 22.1,19.8,19.6. The freezing and thawing soil MBC value and organic matter (OM), cation exchange capacity (CEC) and variable charge (CECv) are significantly positive correlation, which under the condition of freezing and thawing soil organic matter (OM), cation exchange capacity (CEC) and the change of variable charge (CECv) that change the soil arsenic adsorption desorption characteristics of the main reasons.2. The Elovich equation and double constant equation can better fitting soil dynamic adsorption and desorption behavior of the As.Adsorption and desorption process were first fast, slow after two stages,120 minutes after the adsorption and desorption equilibrium. Elovich equation of initial rate constant decreases with the increase of freeze-thaw cycle, A double constant equation of the rate constant B increases with the increase of freezing and thawing cycle, showed that freezing and thawing effect reduces the soil on the adsorption rate of arsenic.3. After freezing and thawing process, the various forms of arsenic content in the soil there is a big difference:active arsenic and iron arsenic levels decrease with the increase of freezing and thawing cycle, arsenic and calcium aluminum arsenic arsenic and closed storage state increases with the increase of freezing and thawing cycles, and mainly arsenic refractory state arsenic and regenerative closed state to give priority to.When the water content of 40%, after dealing with the freezing and thawing of various forms of arsenic content in soil size order is:Ca-As>Al-As>Fe-As>O-As>H2O-As>A-As. When water content is 70% and 100%, after dealing with the freezing and thawing of various forms of arsenic content in soil size order was:Al-As>O-As>Ca-As>Fe-As>H2O-As>A-As.4. When the content of arsenic pollution in soil in 10 to 30 mg·kg-1, after freezing and thawing process of the release quantity of arsenic in soil were higher than without freezing and thawing soil, and the release of arsenic and increased with the increase of freezing and thawing cycle were extremely significant linear positive correlation between increased (P<0.01). Under the same exogenous arsenic concentration, freezing and thawing soil As the release rate is higher than that of without freezing and thawing soil, and with the increase of freeze-thaw cycle and increases accordingly, that freezing and thawing can promote the release of the soil As role.