The Adsorption And Desorption Of Several Calcareous Soils With Different Content Calcium Carbonate On Exogenous Pollutants

Large area of calcareous soils distribution in the the northern China, and most areagricultural soils. The different number calcareous materials of calcium carbonate orhydrogen carbonate calcium carbonate in soil profile,on the one hand, can control thetransformation and existence form of plant nutrients in soils, on the other hand caneffect the chemical behaviror and bioactivity of various exogenous pollutants into thesoils. This study used calcareous soils with different content calcium carbonate asmaterials, and key research the effect of calcium carbonate in soil on adsorptioncapacity and adsorption characteristic of exogenous heavy metals and some organicpollutants which on the basis of analyzing the basic properties of selected materials. Theaim is to clear the environmental effects of calcium carbonate in soils and to furtherjudge the environmental capacity and bearing ability on exogenous pollutants ofcalcareous soils with different calcium carbonate. The study results show that:(1)The pH was7.78⁸.18, the content of calcium carbonate is30.51g.kg^-1100.23g.kg^-1, and the content of organic matter and clay is no significant difference ofnatural calcareous soils. The pH of cultivated soils is7.02⁸.42, the content of calciumcarbonate is8.61g.kg^-1227.94g.kg^-1, the content of organic matter and clay reducewith the increase of calcium carbonate content. The effect of calcium carbonate ondifferent enzyme is different. Low calcium carbonate (the test for less than3%) canpromote the activity of alkaline phosphatase, while high calcium carbonate (the test formore than3%) inhibite the acitivty of alkaline phosphatase; low calcium carbonate(the test for less than5%) can promote the activity of urease, while high calciumcarbonate can inhibite the activity of intertase.(2)Soil pH and calcium carbonate content are very significant nonlinear related.The pH increase with calcium carbonate on the low level (89.91g.kg^-1), but the pHincrease slowly by and by with the further increase of calcium carbonate, until it reachbalance.(3)Calcareous soils have high adsorption capacity on exxpgenous heavy metalPb and Cu. The biggest adsorption capacity on Pb is11234mg.kg^-117513mg.kg^-1, andthe biggest adsorption capacity on Cu is9856mg.kg^-113039mk.kg^-1. The biggestadsorption capacity of Pb and Cu increase with the increase of calcium carbonate. The adsorption strength of calcareous soil on Pb and Cu is very strong. The rate ofdesorption of Pb adsorpted on soils is only less than2%, the rate of desorption of Cu isless than10%, and the more of the calcium carbonate is soils, the smaller of desorptionrate of heavy metal. This show that calcium carbonate is great significance about fixedand retention exogenous heavy metals in soils.(4)The content and proportion of each Pb and Cu form is are change afterexogenous heavy metals entered calcareous soils. Exchangeable form and residue formsdecreased, while the carbonate-bound form,Fe-Mn oxides bound form and organicform all increase to different extend, and the exchangeable form and organic form havethe trend that turn to carbonate-bound form and Fe-Mn oxides bound form. This is theimportant reasons that the adsorption capacity of calcareous soil on heavy metalincrease with calcium carbonate content.(5)The biggest adsorption capacity of calcareous soil with different calciumcarbonate on phenol is2571mg.kg^-1-4930mg.kg^-1, and the biggest adsorption capacityon catechol is3198mg.kg^-16211mg.kg^-1, and higer than phenol biggest adsorptioncapacity. The biggest adsorption capacity decreases with the in crease of calciumcarbonate content. The desorption rate of phenol adsorpted on soils is12%¹8%, thedesorption rate of catechol adsorpted on soils is16%²0%. The desorption rate is verylow and increases with the increase of calcium carbonate.(6)The adsorption of calcareous soil with different content calcium carbonate onchlortetracycline is different. The biggest adsorption capacity on chlortetracycline is7253mg.kg^-113517mg.kg^-1, and decreases with the in crease of calcium carbonatecontent. Calcareous soil has higher adsorption capacity and adsorption strenghth onchlortetracycline. The desorption rate of chlortetracycline adsorpted on soils is4.89%⁷.52%, and there are still most chlortetracycline adsorpted on soil. The higer ofthe calcium carbonate content is soils, the more of the desorption rate.(7)Calcareous soils has higer adsorption capacity on DOM.Adsorption rare is to12.19%⁴0.54%, and decreases with the in crease of calcium carbonate content. Thedesorption rate of DOM adsorpted on soil is to22.40%³0.66%. The more of calciumcarbonate content, the smaller of the adsorption stenghth on DOM, and the bigger ofdesorption rate.(8) The adsorption capacity of calcareous soil with different calcium carbonate on heavy metal and organic matters is different. The adsorption capacity of soil onheavy metal increases with the increase of calcium carbonate while the adsorptioncapacity on organic pollutant decreases with the increase of calcium carbonate. Theadsorption capacity and stenghth of calcareous soil on different heavy metal anddifferent organic matters is different. In practice, should based on calcium carbonatecontent and the varety of pollutants to sure the environmental capacity of calcareoussoils.