施用牛粪肥和复混肥对碳酸盐岩试片溶蚀作用影响的室内模拟研究

Impact of Cattle Dung and Compound Fertilizer Addition on the Dissolution of Carbonate Rock Tablets:A Column Experiment

农业施肥影响土壤的理化性质,影响土壤碳酸盐风化动力学,以至影响碳循环系统。本研究通过土柱模拟试验,结合底部埋置碳酸盐岩试片,依据淋滤液的水化学对比分析,研究了施用牛粪肥及复混肥对土下碳酸盐岩试片溶蚀作用的影响。结果表明,施用牛粪肥后,淋滤液中的HCO3-、Cl-、NH4+、耗氧量(COD)、K+、Ca2+、Mg2+、Na+、NO3-、游离CO2、SO24-、HPO42-等很快升高。但随着牛粪肥的降解与淋滤,其浓度又很快恢复到与空白土柱淋滤液相当。这表明,牛粪肥的施用对碳酸盐岩溶蚀作用的影响不大。而施用复混肥后,淋滤液中NH4+、游离CO2、HCO3-、HPO42-、COD等浓度均明显的变大,pH却明显减低。这主要是因为复混肥中NH4+经硝化作用产生了H+所致。复混肥的施用增大了白云岩和石灰岩试片的溶蚀量,空白土柱中石灰岩和白云岩试片的溶蚀量均为0.0008g,而复混肥土柱的中石灰岩和白云岩试片的溶蚀量分别为0.0034g和0.0015g。同时用水化学模拟软件Phreeqci计算了空白土柱和复混肥土柱淋滤液的方解石和白云石的饱和指数,结果显示施用复混肥降低了方解石和白云石的饱和指数,而牛粪肥的施用对方解石和白云石饱和指数的影响不大。此外,通过水化学方法估算区域尺度甚至全球尺度的风化碳汇时,氮肥的影响不可忽略。

Fertilization is exerting a significant effect on the physical and chemical characteristics of soil and chemical weathering dynamics of carbonates,and then on the carbon cycle system.In this study,three columns(control column,cattle dung column and compound fertilizer column) with carbonate rock tablets at their bottoms were established to explore the impact of cattle dung and compound fertilizer addition on the dissolution of carbonate rock tablets according to the hydro-chemical analysis on the leachates of the three columns and the comparison of the dissolution amounts of carbonate rock tablets.Here,the results showed that the transitory increases of HCO-3,Cl-,NH+4,COD,K+,Ca2+,Mg2+,Na+,NO-3,free CO2,SO2-4 and HPO2-4 in the leachate are brought by cattle dung addition,and an evident impact of cattle dung addition on the dissolution of carbonate rock tablets cannot be detected in this study.The indistinct increases of NH+4,free CO2,HCO-3,HPO2-4 and COD in the leachate can be observed after the compound fertilizer addition,whilst the pH decreases,which was mainly attributed to the release of protons from the nitrification reaction.The dissolution amounts of limestone and dolomite tablets decreased owing to the application of compound fertilizer,where the dissolution amounts of both limestone and dolomite were 0.0008 g in the control column,however,those of limestone and dolomite were 0.0034 g and 0.0015 g in the compound fertilizer column,respectively.Furthermore,the calculated results of the saturation indices of calcite and dolomite by using Phreeqci showed that the saturation indices of calcite and dolomite decreased after the compound fertilizer addition and changed slightly after the addition of cattle dung.Thus,it should be noted that the impact of compound fertilizer,especially ammonium fertilizer.on the budget of CO2 sink cannot be omitted on both regional and global scales.