共查询到19条相似文献，搜索用时 140 毫秒
1.
H+和有机酸对可变电荷土壤铝释放的动力学研究 总被引：4，自引：0，他引：4
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。 相似文献
2.
有机酸对几种土壤吸附铜的影响 总被引：10，自引：0，他引：10
在一定离子强度和pH值下,向几种不同的土壤中加入外源有机酸,研究有机酸对土壤吸附Cu2+的影响,结果表明:几种土壤对铜的吸附量随着铜浓度的增加而增加,但当铜浓度达到一定值时,吸附量不再发生变化。几种土壤对铜的最大吸附量的大小顺序为黄棕壤> 砖红壤> 红壤> 赤红壤;有机酸对土壤吸附铜既有促进作用,又有抑制作用,即吸附曲线呈峰型;不同有机酸对土壤吸附铜的影响不同,其中柠檬酸对吸附的抑制和促进作用都很强烈,草酸对吸附的促进作用较弱,抑制作用较强,而乙酸对吸附所起的作用则与草酸正好相反;同种有机酸对不同土壤吸附铜的影响不同。其中三种有机酸对黄棕壤吸附铜的促进作用都很弱,而对砖红壤吸附的促进作用则强。 相似文献
3.
几种亚热带土壤铁锰胶膜和基质的表面化学特征 总被引：1，自引：0，他引：1
以我国亚热带的黄褐土、黄棕壤和红壤为材料,研究了土壤铁锰胶膜和其基质的表面化学性质及其对重金属元素的吸附和氧化特点。结果表明,与基质土壤相比,铁锰胶膜的比表面积大,电荷零点(PZC)低,这与其富含粘粒、有机质和铁锰氧化物等有关;铁锰胶膜经脱锰处理后,比表面积明显降低。由盐滴定-电位滴定(STPT)法测得黄褐土、黄棕壤、红壤基质的PZC分别为3.13、3.65和3.90;黄棕壤和红壤铁锰胶膜的PZC分别为3.26和3.42。铁锰胶膜对Pb2 、Cu2 、Cd2 和Zn2 的吸附和对Cr3 的氧化能力比基质的强。铁锰胶膜经脱锰处理后,对Pb2 、Cu2 、Cd2 和Zn2 的最大吸附量比未处理时降低了53%～100%;其氧化Cr3 生成Cr6 的量比铁锰胶膜的降低了87%～100%。说明黄褐土、黄棕壤和红壤的铁锰胶膜中,氧化锰是吸附重金属离子和氧化Cr3 的主体。 相似文献
4.
以重庆金佛山岩溶区为例,分析不同石漠化程度下土壤的指纹电荷特征和土壤养分保持能力,结果表明:不同石漠化程度下,土壤指纹电荷特征变化明显,且呈衔接式-阶梯状发展,即:无石漠化阶段,土壤A、B层保持养分能力最强的pH范围与土壤实测pH较为吻合;轻度石漠化阶段,土壤A层养分保持能力受到明显扰动,而土壤B层养分保持能力与无石漠化的土壤A层较为一致;中、强度石漠化条件下,土壤A、B层保持养分能力的相对平衡点的pH值明显偏酸,这在A层表现尤为明显,主要为人为施肥的结果。并通过土壤有机质及其组分与土壤指纹电荷的相关分析,得出由于土壤富里酸有众多的活性功能团,它对土壤指纹电荷的作用明显大于胡敏酸。 相似文献
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6.
酸性条件下红壤中铝的活化及环境意义 总被引：8，自引：4，他引：8
利用动态反复浸提模拟实验研究了4种红壤中固相铝的活化过程。结果表明，红壤酸化程度与土壤表面变换性铝呈正相关关系。当高强度外源H^ 输入土壤后，有机铝和无机铝均可活化。浸提初期以弱键合的有机铝活化为主，当浸提到一定程度时，弱键合有机铝亏损，无机铝活化的相对重要性显示出来。20次浸提后，宁海红壤，嵊县红壤及永春红壤的铝总活化量中无机铝占主要部分。当土壤酸化到一定程度时（如屯溪红壤）有机铝和无机铝均亏损，铝的活化量很低。酸性条件下弱键合有机铝的快速活化产生高浓度的可溶性铝以及随后的快速亏损都将对生态环境产生重要影响。 相似文献
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用水浸法测定土壤中的可溶性盐类，当土壤与加入水的质量之比为1：6，水浸时间为24—42h，此时测定的可溶性盐类的量具有较好的准确性和可比性。 相似文献
9.
酸沉降对土壤地球化学过程的影响 总被引：11，自引：0，他引：11
酸沉降通过影响土壤组分的化学行为进而影响土壤地球化学过程。本文就该领域的目前研究进展做了较详细的论述。考察了酸化条件下土壤中盐基离子和铝，硅的释放淋失及硅对铝毒的缓解作用；论述了酸沉降通过影响土壤中微量金属及稀土离子沉淀-溶解，吸附-解吸，络合-解离，氧化-还原平衡进而影响共存在形态和化学行为；同时关注了酸沉降对C，N，S，P循环转化直接和间接的影响。 相似文献
10.
广东省普宁市土壤硒的分布特征及影响因素研究 总被引：2，自引：0，他引：2
开展了广东省普宁市区域土壤硒调查研究,采集了413个表层土壤样品(0～20 cm)和103个深层土壤样品(> 150 cm),测定了土壤全硒含量,据此研究土壤硒分布特征及其影响因素。结果表明,普宁市土壤全硒含量变化于0. 16～2. 01 mg/kg,平均值为0. 63 mg/kg,总体上处于中硒及高硒水平,不存在缺硒和硒过剩土壤。砂页岩风化形成的赤红壤全硒含量较高,平均值达0. 86 mg/kg,以侏罗系页岩母质发育的土壤全硒含量最高,平均值达0. 89 mg/kg;三角洲第四系沉积物发育形成的水稻土全硒含量最低,平均值为0. 41 mg/kg。回归分析表明,土壤全硒含量与铁铝含量、有机碳含量具有极显著正相关,与p H呈极显著负相关。影响普宁市土壤硒含量的主要因素是成土母质,土壤p H、有机碳和铁铝含量及土地利用方式对土壤全硒含量分布与富集也有一定的影响。 相似文献
11.
《Applied Geochemistry》2005,20(1):169-178
A sampling-separation method and a dynamic monitoring method were used to investigate the time-dependent reactions of H+ ions with two contrasting types of soil, variable charge soils (VCS) and constant charge soils (CCS), by directly evaluating H+ ion consumption and other relevant consequences. The results for both CCS and VCS show that H+ ion consumption, increase in positive surface charge and increase in soluble Al are all characterized by a rapid step followed by a slow one. The higher the content of free Fe oxides in the soil, the larger the increase in positive surface charge and in H+ ion consumption in the initial rapid step. This is due mainly to protonation on external surfaces. The gradual increase in positive surface charge in the slow step for the 3 VCSs is a result of H+ ion diffusion to the reactive sites of Fe–OH on internal surfaces. The very low content of free Fe oxides on internal surfaces of the 2 CCSs render a negligible increase in positive surface charge in the slow step. For the 3 VCSs, the gradual consumption of H+ ions in the slow process is the result of protonation, Al dissolution and/or transformation into exchangeable acidity. For the 2 CCSs, however, the gradual consumption is mainly the result of Al dissolution and/or transformation into exchangeable acidity. The time-dependent Al dissolution from both VCS and CCS is influenced by several factors such as mineral components, solubility and dissolution rates of the soils, and H+ ion concentration in soil suspensions. 相似文献
12.
《Applied Geochemistry》2006,21(10):1750-1759
Low-molecular-weight (LMW) organic acids occur widely in soils. Results in pure mineral systems and podzols suggest that LMW organic acids can promote the dissolution of Al from kaolinite, Al oxides and soils, but limited information is available concerning the role of these organic acids on Al mobilization in variable charge soils as yet. This paper deals with the effect of LMW organic acids on Al mobilization and mobilized Al distributed between the solution phase and exchangeable sites in two acidic variable charge soils. The results indicated that LMW organic acids accelerated Al mobilization through proton- and ligand- promoted reactions. The ability of different organic acids to mobilize Al followed the order: citric acid > oxalic acid > malonic acid > malic acid > tartaric acid > salicylic acid > lactic acid > maleic acid. This order was in general agreement with the magnitude of the stability constants of Al–organic acid complexes. The ratio of soluble Al to exchangeable Al also increased as the stability constants increased. These results showed that the organic acids with strong Al-complexation capacity were most effective in Al mobilization, whereas the weak organic acids promoted the retention of mobilized Al by the soil exchangeable sites. Increase in both organic acid concentration and solution pH promoted Al mobilization and also increased the ratio of soluble Al to exchangeable Al due to the increase in the concentration of the effective organic ligands, especially in the strong organic acid systems. These findings may have their practical significance for establishing more effective amelioration procedures for variable charge soils with increased acidity and higher mobility of Al. 相似文献
13.
《Applied Geochemistry》2002,17(8):987-1001
Surface (0–10 cm) samples of 7 soils from tropical coastal Queensland were incubated at room temperature and at field capacity with finely ground (<150 μ) basalt rock for 3 months. The amendment was applied at 0, 1, 5, 25 and 50 t/ha to cover situations of moderate application rates to that where the amendment might be banded to produce high local concentrations. Having an abrasion pH of about 9, the amendment was able to reduce both active acidity (as estimated by an increase in soil pH) and reserve acidity (reduction in % Al saturation of the CEC). Increases in soil pH resulted in increased CEC, depending on the variable charge nature of each soil, accompanied by increases in exchangeable Ca, Mg, and K supplied by the basalt. The amounts of basic cations converted to exchangeable form constituted only a fraction of the amounts applied. Thus the cations held in reserve ensure that the effect of cation enrichment will be prolonged. In some soils phosphate sorption was significantly reduced by crushed basalt application. Furthermore, ‘available’ P as measured by extraction with 0.005 M H2SO4 was increased. These effects appear to be due to the release of silicate from the basalt as well as modest amounts of phosphate in the rock. Three extractants commonly used for estimating Si availability in sugarcane production indicated that all 7 soils contained sub-optimal levels of the element. Application of crushed basalt rock increased extractable Si levels above what is considered sufficient for this crop. The incubated soils were placed in columns and leached with the equivalent of 2750-mm (average wet season) rainfall. Re-analysis showed that the favourable chemical soil properties imparted by the amendment were retained. These results add further support to the contention that the effects of amelioration will continue for some time. 相似文献
14.
Exchange reactions between Ca2+, H+ and Al species and their effects on the aluminium mobility in two Chinese acidic forest soils were studied. The study was based on a batch experiment using extractant solutions with different base cation (calcium) concentrations and pH. The experimental data showed that increased Ca2+ concentrations increased the release of soil hydrogen—and aluminium ions, especially from the more acid soil. In agreement with a cation exchange process, the treatment with Ca2+ extracts gave significantly decreased soil aluminium saturation (AlS) and increased calcium saturation (CaS) on the ion exchanger. Geochemical calculation using AlCHEMI program showed that activities of Al3+ in the extracts were all strongly under-saturated with respect to any gibbsite mineral in the studied pH region (i.e. below 4.1). There were instead apparently two different mechanisms controlling the activities of Al3+ in extracts. At pH between about 4.1 and 3.7, the Al3+ activity did not change significantly with pH. This is especially the case in the more acid soil. Apparently there are no sizeable pools available to release Al in this pH region. At pH below 3.7 (induced by higher Ca2+concentration) the activity of Al3+ increased with H+ though not in a pattern that complies with a gibbsite solubility control. An increase of base cation deposition would therefore mainly enhance the release of hydrogen ions between pH 4.1 and 3.7 and aluminium ions below pH 3.7 from Chinese mature acidic soils. This will cause an increased acidity of soil water in the short term and a decrease in the soil acidity in the long term. More attention should be paid to this fact in Chinese acid rain studies and control options. 相似文献
15.
Mechanism of aluminum release from variable charge soils induced by low-molecular-weight organic acids: Kinetic study 总被引：3，自引：0，他引：3
The kinetic curves of aluminum release from two variable charge soils and a kaolinite within 48 h can be divided into three stages: the first stage located within the initial 30 min, at which the release rate of Al was the fastest one and the released Al dominantly originated from exchangeable Al and amorphous Al pools. The Elovich equation fit the kinetics data at this stage fairly well. The moderate and the slow stages occurred within 0.5-2 and 2-48 h, respectively. During these two stages, the released Al was mainly attributed to Al oxides, poorly crystalline kaolinite and easily weathered hydrous mica. The different linear equations also fit the kinetics data at these two stages well. The rate of Al release decreased sharply with time during the fast stage, but the rate remained constant during the moderate and slow stages. In Ultisol, Al oxides were the more important pool for Al release than poorly crystalline kaolinite and easily weathered hydrous mica during the latter two stages. In Oxisol, poorly crystalline kaolinite was the more important Al pool. Compared to the control system, the presence of organic acids increased the rate and quantity of Al release from variable charge soils. The ability of organic acids to accelerate Al release followed the order: oxalic acid > citric acid > malic acid > lactic acid. This is generally in consistent with the magnitude of the stability constants of the Al-organic complexes. The release rate of Al also increased with the rise in concentration of organic acids. 相似文献
16.
以四川省成都平原区农田生态系统水稻土剖面为例,探讨了Cd分配系数及其影响因素。结果表明:Cd分配系数(Kd)在污染土壤环境和本底土壤环境中是不同的,在剖面PM-3、PM-6和PM-8剖面中污染环境中分配系数(Kd)大于本底环境中的分配系数,而在剖面PM-7中,本底环境中的分配系数(Kd)大于污染环境中的值。在污染环境Cd分配系数受土壤pH值、交换性Mg和铁硅氧化物的影响比较大,而在非污染环境中分配系数受到土壤可溶性Al、Cd全量和铁锰铝氧化物的影响较大。这些土壤的物化性质对分配系数造成影响,使得土壤滤渣和土壤原土中Cd形态含量存在差异。 相似文献
17.
茶园土壤不同形态镍的含量及其影响因素 总被引：3，自引：2，他引：1
通过自然茶园土壤采样和室内实验分析,探讨浙江、江苏和安徽13个茶园土壤镍的污染状况、形态分布规律以及不同形态镍的含量与土壤镍总量和土壤理化性质的关系。结果表明：部分茶园土壤受到不同程度的镍污染;茶园土壤镍的形态分布有一定差异,按镍的含量多少排序,一般为残渣态＞交换态＞铁锰氧化物结合态＞有机结合态＞碳酸盐结合态;除了交换态以外的所有其他形态的镍含量均随土壤镍含量的增加而显著增加;碳酸盐结合态、铁锰氧化物结合态和残渣态镍含量随土壤pH的升高呈显著增加趋势,而交换态镍则呈减少趋势,但不显著;随土壤有机质含量的增加,铁锰氧化物结合态镍显著减少,而其他形态增加或减少的趋势均不显著;碳酸盐结合态、有机结合态和残渣态的镍含量均随阳离子交换量的增加显著增加;随粘粒含量的增加所有形态中的镍呈增加趋势,但除了残渣态外增加趋势均不显著。 相似文献
18.
Muhammad Aqeel Kamran Jun Jiang Jiu-yu Li Ren-yong Shi Khalid Mehmood M. Abdulaha-Al Baquy Ren-kou Xu 《Arabian Journal of Geosciences》2018,11(11):272
To increase soil productivity, ameliorate nutrient scarcity, and reduce metal toxicity in highly weathered acidic soils usually requires fertilizer and lime application. Effects of three biochars on soil acidity, Olsen-phosphorus (P), phosphatase activities, and heavy metal availability were investigated to test potential of these biochars as soil amendments in highly weathered acidic soils. Incubation experiments were conducted for 6 weeks with three acidic soils: Alfisol, Ultisol, and Oxisol. Three biochars were derived from chicken manure (CMB), pig manure (PMB), and peat moss (PB) at 400 °C and applied at 1 or 2% (wt/wt). The addition of the three biochars increased Olsen-P in the three acidic soils in the following order: CMB?>?PMB?>?PB. Application of 2% CMB increased Olsen-P contents by 2.41-, 7.4-, and 1.78-fold in the Ultisol, Oxisol, and Alfisol compared with controls, respectively. Moreover, CMB increased the soil pH, electrical conductivity (EC), cation exchange capacity (CEC), and alkaline phosphatase activity, but reduced exchangeable acidity, acid phosphatase activity, and the availability of heavy metals—more effectively than PMB and PB. Addition of CMB increased soil pH by 0.90, 0.90, and 0.92 units for the Alfisol, Ultisol, and Oxisol, respectively, correspondingly followed by 0.80, 0.84, and 0.87 units for PMB and 0.15, 0.28, and 0.25 for PM. Changes in EC, CEC, and exchangeable acidity followed the same order for the three soils: CMB?>?PMB?>?PB. The results suggested that the magnitude of changes in soil properties and Olsen-P contents depended on biochar type and application rate. Application of CMB increased nutrient availability and reduced the availability of heavy metals more than other amendments. Due to higher pH, EC, and CEC, and greater concentrations of carbon, nitrogen, and exchangeable calcium and potassium, incorporation of CMB should be a better cost-effective method to correct soil acidity and improve fertility and Olsen-P contents in Ultisols and Oxisols from tropical and subtropical regions of the world. 相似文献
19.
Influence of acidic atmospheric deposition on soil solution composition in the Daniel Boone National Forest,Kentucky, USA 总被引：1，自引：0，他引：1