低分子量有机酸对红壤和黄褐土K^+吸附动力学的影响

EFFECT OF LOW-MOLECULAR-WEIGHT ORGANIC ACIDS ON K^+ ADSORPTION KINETICS OF RED SOIL AND YELLOW-CINNAMON SOIL

采用连续流动法研究了低分子量有机酸影响下供试土壤的钾素吸附动力学特征,探讨了描述土壤K+吸附动力学的最优模型。结果发现,有机酸(苹果酸、柠檬酸)作用下,红壤吸附的K+量均低于对照(不加有机酸)处理,0.1 mmol L-1草酸处理除外。黄褐土对K+的吸附因K+浓度的不同而差异明显。当K+浓度为0.1 mmol L-1时,有机酸作用下黄褐土吸附的K+量低于对照,而当K+浓度为1.0 mmol L-1时,有机酸作用下的黄褐土K+吸附量高于对照。K+吸附反应速度与时间的自然对数lnt间存在良好的线性关系(r0.05=0.754,r0.01=0.874)。1.0 mmol L-1KCl处理的初始吸附速率较高,反应速度降低的较快。对红壤、黄褐土吸附K+的数据进行拟合,双常数方程、指数方程和Elovich方程拟合效果较好,都达到了极显著水平,一级动力学方程拟合效果不好。双常数方程的相关系数(r)高于Elovich方程和指数方程,双常数方程是描述红壤和黄褐土在有机酸作用下K+吸附动力学的最优模型。结果表明,有机酸对两种土壤吸附能力的影响均表现为草酸>柠檬酸>苹果酸。有机酸作用下红壤和黄褐土的K+吸附过程主要受土壤电荷的影响。

Effects of low molecular weight organic acids （LMWOA） on K ＋ adsorption kinetic characteristics of Red Soil and Yellow-cinnamon Soil were studied with the continuous flowing method to explore an optimal model for describing K＋ adsorption kinetics. Results show that the red soils in all the LMWOA treatments, except in the treatment of 0. 1 mmol .L-1 oxalic acid, adsorbed less K ＋ than it did in CK （soil without addition of LMWOA） , and the yellow-cinna- mon soils varied in K ＋ absorption significantly with K ＋ concentration. When K ＋ concentration was 0. 1 mmol L -1 , the yellow-cinnamon soils adsorbed less K ＋ than it did in CK, but when K＋ concentration was raised up to 1.0 mmol L-1, they adsorbed more than it did in CK. The K ＋ adsorption capacities of the two soils varied with the type of organic acid, showing an order of oxalic 〉 citric 〉 malie. The reaction velocity of K ＋ adsorption in the two soils was found to be in a good linear relationship with the natural logarithm of time ＂lnt＂ （r0.05 = 0. 754, r0.01 = 0. 874）. The treatment of 1.0 mmol L-1 K ＋ was higher in initial adsorption rate, but dropped faster in reaction velocity. In fitting the data of K ＋ adsorption in the red soil and yellow-cinnamon, the two-constant, exponential and Elovich equations were all quite effective, reaching the level of extreme significance, but the first order equation was not so good. The correlation coefficient of the two-constant e- quation was higher than that of the exponential equation and the Elovich equation, which rendered two-constant equation the best-suited model to describe K ＋ adsorption kinetics in the soils treated with organic acids. Under the effect of organic acids, K ＋ adsorption in the two soils was mainly influenced by soil charge.