摘要
利用流动搅动法研究了在模拟酸雨和低分子量有机酸条件下可变电荷土壤铝释放的动力学特征,结果表明,在pH3.5的模拟酸雨作用下,红壤和黄壤中流出液铝的浓度范围约为15～40μmol/L,铝的释放快反应来源于土壤交换性铝和有机络合态铝,铝的释放慢反应对应于含铝矿物的溶解。赤红壤和砖红壤上在0～300min内流出液铝的浓度范围约为1～5μmol/L,流出液pH值大于4.5,对H+的缓冲作用表现为阳离子交换、SO24-的专性吸附释放OH-和矿物表面的质子化;当流出液pH值小于4.5时,H+开始溶解土壤中的含铝固相,铝释放的最后浓度为20～30μmol/L。用相近pH值的有机酸溶出土壤铝的浓度比pH3.5的模拟酸雨要高,特别是在砖红壤上,开始就有大量铝的释放,其浓度为20～75μmol/L,红壤上是70～150μmol/L,随时间延长,流出液中的铝浓度分别为10～20μmol/L和20～30μmol/L。有机酸作用下铝的释放机制主要是有机酸被土壤吸附后,有机酸与位于表面晶格中的铝原子形成络合体,促进了铝的溶解;其次是有机酸的吸附掩盖了土壤表面的质子化过程,增强了酸的溶解,以及有机配体对铝的络合作用,增加了铝的释放量。不同有机酸对铝的溶出能力也有不同,其释放铝能力的大小为:柠檬酸>酒石酸>苹果酸,这取决于有机配体与铝的络合能力。
The kinetic characteristics of aluminum release in variable charge soils under H^＋ and organic acids were studied by using the flow-stirred method. The results showed that the concentration of aluminum released under pH 3.5 simulated acid rain was about 15 ～ 40 μmol/L in red and yellow soils. The initial fast reaction of aluminum release could be described to exchangeable and organic complexing Al, while the following slow reaction to dissolution of readily weatherable Al-bearing minerals. During 0 ～ 300 min, the concentration of effluent Al was about 1 ～ 5 μmol/L and effluent pH value was above 4. 5 in latosolic red soil and latosol. Buffering reaction to H^＋ could be cation exchange, specific adsorption of SO4^2- to release OH^- for neutralizing H^＋ in the solution, and surface protonation of soil minerals. While the effluent pH was lower than about 4. 5, dissolution of Al-bearing minerals in soils was dominant mechanism of Al release. The concentration of aluminum released under pH 3.5 solution of different organic acids was 20 ～ 75 μmol/L and 70 ～ 150 μmol/L in latosol and in red soil at initial stage, and then decreased to 10 ～ 20 μmol/L and 20 ～ 30 μmol/L, respectively. The mechanism of aluminum release was apparent that organic ligand could be adsorbed and promoted dissolution of Al-bearing minerals. Secondly, the surface protonation of minerals can be covered by the adsorption of organic ligands by the soil, resulting in the decrease of solution pH value and then the increase of acidic dissolution of aluminum. Thirdly, the formation of Al-ligands complexion may increase the amount of Al release. The capability of organic acids in dissolving aluminum was in the sequence of citric acid 〉 tartaric acid 〉 malic acid, which may be dependent on complexion power of Al-ligands.
出处
《地球化学》
CAS
CSCD
北大核心
2006年第6期651-659,共9页
Geochimica
基金
国家杰出青年科学基金(40325001)
中国科学院海外合作伙伴计划项目(CXTD-Z2005-4)
河南农业大学博士基金(30200165)
河南农业大学创新基金(2006-CX-017)
关键词
H^+离子
低分子量有机酸
铝释放动力学
可变电荷土壤
H^＋ion
low molecular weight organic acids
aluminum release kinetics
variable charge soils
