Selection And Regulatory Effect Of Amendments On Arsenic Soil

To select reasonable stabilizer for arsenic-contaminated soil, three different kinds of materials, including nano-iron, pig bone char and cow bone char (cow bone char Ⅰ (aerobic burning), modified cow bone char Ⅰ, cow bone char Ⅱ(without oxygen burning), modified cow bone char Ⅱ) were used to investigate the adsoption and adsorption mechanisms of arsenic by adsoption experiment, indoor simulation experiment and soil column leaching experiment. The arsenic distribution, vertical mobility and transformation in soils, as well as the influence of adding organic fertilizer on soil arsenic were discussed.It indicated that As (V) adsorption rateincreased with the increasing of initial As (V) concentration. When the initial As (V) concentration was1-10mg·L-1, the As (V) adsorption capacity was in the order of nano-iron> modified cow bone char Ⅱ> modified cow bone char Ⅱ> pig bone char> cow bone char Ⅱ> cow bone char Ⅰ, with the highest arsenic adorption value of396.22mg·kg-1by nano-iron, reaching equilibrium point with2hours, and94.76%of soil arsenic was removed. While it was different for pig bone char and crow bone char Ⅰ, treated by which the adsorption capacity of soil As (V) decreased with the increasing of the dosage of materials and initial pH value. The highest arsenic adsorption capacity was1913.96mg·kg-1.The indoor simulation experiment showed that the soluble arsenic and pH value deduced a lot due to the addition of nano-iron in slate red soil and limestone soil. After incubation of84days, the available arsenic contents in both soils reduced10.5%and11.43%, companied with a pH value decreasing of0.18and0.23unit, separately. The addition of pig bone char had led to an increasing of available arsenic in both soils,16.21%in slate red soil and1.36%in limestone soil, respectively. The addition of cow bone char as a stabilizer of arsenic in limestone red soil had obviously improved the quality of the alkaline soil, and promoted the soil of arsenic transform from available to residual arsenic form.The soil column leaching experiment by arsenic-content wastewater indicated that the arsentic conten in soil arsenic leachate increased with time in different soil layers, decreased with the soil depth, and deduced significantly after the addition of nano-iron with a decreasing rate from29.89%to72.96%. Arsenic mainly distributed in the0-5cm soil layer after148days’leaching. Compared with those of before leaching, both total arsenic and available arsenic in clean soil and clean soil with nano-iron adding increased34.9times,25.49times, amounting to15.56mg·kg-1,14.68mg·kg-1, respectively. The non-specifically sorbed arsenic and specifically sorbed arsenic in0-5cm soil layer decreased24.07%,23.09%, resepectively. The residual arsenic raised5.09%resulted from the adding of nano-iron.The arsenic concentration of leaching solution gradually increased. During the first90days’leaching time, the arsenic concentration of leaching solution in contaminated soil, contaminated soil adding with nano-iron, contaminated soil adding with organic fertilizer, contaminated soil adding with nano-iron and organic fertilizer raised222.29%,193.72%,12.14times,14.81times, respectively. After90days’leaching in naturally contaminated soils, the available arsenic in contaminated soil, contaminated soil adding with nano-iron, contaminated soil adding with organic fertilizer, contaminated soil adding nano-iron and organic fertilizer significantly increased,10.61%-20.49%,12.91%-14.66%,3.22%29.04%,2.81%-14.05%, respectively, which might be the arsenic imigated downward the deeper soil layers after the adding of organic fertilizer, leading to25.01%and10.97%increasing of soil avaliable arsenic in30-40cm soil layer in the soil adding with organic fertilizer and comtaminated soil adding with nano-iron and organic fertilizer...