酸性森林土壤中Ca-H-Al交换过程与铝的溶解机制研究

华南酸性森林土壤分别在pH值为3．46、4．24和4．84条件下用含不同浓度盐基离子（Ca^2＋）的酸性浸提液浸提，以查明降水中盐基离子对土壤水中Al和H^＋的影响。实验结果表明：随着Ca^2＋浓度的增加，土壤浸出液中H^＋和Al都有增加的趋势。随着Ca^2＋浓度的变化，H^＋和Al有不同的来源：当Ca^2＋〈0．5mmol L^-1，土壤主要通过Ca—H交换机制释放H^＋，浸出液中Al主要来源于土壤活性铝的溶解；当Ca^2＋〉0．5mmolL^-1时，由于Ca—Al交换反应，浸出液中Al随Ca^2＋浓度增加而显著增加，此时H^＋主要来源于Al的水解反应。浸出液中pH—pAl关系也随pH值（或Ca^2＋浓度）的变化有显著不同：当浸出液pH〉3．7（Ca^2＋〈0．5mmolL^-1）时，浸出液中Al^3＋活度随pH的变化幅度较小，这可能是酸性土壤中活性铝已显著流失的缘故；当pH〈3．7（Ca^2＋〉0．5mmol L^-1）时H^＋对于Al浓度具有较强的依赖性，故pH随Al^3＋活度增加而显著降低。因此，降水中盐基离子的增加能够引起土壤水乃至地表水中酸性阳离子（特别是Al）的迅速增加，可能造成对水生生物的突发性影响。     

植物铝抗性基因及抗铝毒基因工程研究进展

酸性土壤占世界可耕作土壤的30％,而铝毒是酸性土壤中植物生长和作物生产的主要限制因素.近年来,在植物中鉴定了一系列抗铝基因,如有机酸通道蛋白基因(ALMT1和MATE),ABC通道蛋白基因(STAR1和STAR2)和转录因子基因(STOP1和ART1).通过基因工程手段在植物中过表达有机酸通道蛋白基因、有机酸代谢酶基因和其他铝胁迫响应基因均获得了很大的进展.本文综述了植物抗铝基因的克隆与鉴定,以及通过遗传操作提高植物的抗铝能力.     

添加生物炭对酸性红壤中玉米生长和氮素利用率的影响

Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving crop growth are not well understood. The objectives of this study were i） to determine the crop responses to biochar addition and ii） to understand the effect of biochar addition on N use efficiency. Seven acidic red soils varying in texture, p H, and soil nutrient were taken from southern China and subjected to four treatments： zero biochar and fertilizer as a control（CK）, 10 g kg-1biochar（BC）, NPK fertilizers（NPK）, and 10 g kg-1biochar plus NPK fertilizers（BC＋NPK）.15N-labeled fertilizer was used as a tracer to assess N use efficiency. After a 46-d pot experiment,biochar addition increased soil p H and available P, and decreased soil exchangable Al3＋, but did not impact soil availabe N and cation exchange capacity（P 〉 0.05）. The N use efficiency and N retained in the soil were not significantly affected by biochar application except for the soil with the lowest available P（3.81 mg kg-1） and highest exchanageable Al3＋（4.54 cmol kg-1）. Greater maize biomass was observed in all soils amended with biochar compared to soils without biochar（BC vs. CK, BC＋NPK vs. NPK）. This agronomic effect was negatively related to the concentration of soil exchangeable Al3＋（P 〈 0.1）. The results of this study implied that the liming effect of biochar improved plant growth through alleviating Al toxicity and P deficiency, especially in poor acidic red soils.     

Maize Inbreds' Response to Riecito Phosphate Rock and Triple Superphosphate on an Acidic Soil

Abstract

Tropical acidic soils require large inputs of nitrogen (N) and phosphorus (P) fertilizers to sustain crop production. Attempts to use phosphate rock (PR) as a cheaper P source have shown limited success because of low rock solubility. The objective of this study was to evaluate growth and P nutrition of aluminum (Al)‐tolerant maize inbreds fertilized with PR. Twelve Al‐tolerant inbreds from CIMMYT were planted in 2‐kg pots filled with an acidic soil very low in available P and fertilized with 0, 40, or 100 mg kg^?1 of Riecito PR or triple superphosphate (SP). Plant shoots were harvested 35 days after planting, and biomass, root length, P uptake, and soil residual P were determined. Inbreds were able to sustain growth when fertilized with PR. There was indication that various mechanisms were involved in the responses to PR fertilization. Cultivars combining high uptake and conversion efficiencies should improve maize utilization of PR.     

Characterization of Cu-resistant bacterial communities in Cu-contaminated soils

Bacterial communities in a spoil heap in a copper mine, a forest soil with high Cu contamination, and an agricultural soil with low Cu contamination were characterized in terms of Gram-staining, plasmid frequency, pigmentation, Cu-resistance system, and predominant Cu-resistant bacterial species. Similarity existed in that the ratio of green colonies for sorbing Cu and Gram-negative bacteria increased with the increase of the Cu content of the medium regardless of the characteristics of the bacterial communities. It was found that the plasmid was not present in most of the Cu-resistant bacteria of the soils. Curesistant genera including Burkholderia, Alcaligenes, and Methylobacterium species were isolated from the Cu contaminated soils using YG agar plates treated with 2 mM Cu. Furthermore, the bacterium with the highest Cu resistance (MIC = 5.5 mm Cu) was identified as a Gram-positive bacterium Bacillus sp., though most of the Cu-resistant bacteria were Gram-negative.     

Antibiotic-resistant mutants identified from nodules of uninoculated soybeans grown in a strongly acidic soil

Two hypotheses that antibiotic-resistant nodule isolates from uninoculated soybeans grown in a strongly acidic soil were naturally occurring rhizobia which had acquired resistance to spectinomycin and streptomycin or were contaminants from adjacent, inoculated treatments, were tested in laboratory experiments. Soybean nodule isolates (166) as well as 48 cowpea and 89 Rhizobium japonicum strains were used in tests of resistance to six concentrations (0–500 μg ml^?1) of kanamycin, spectinomycin and streptomycin, tolerance of stresses of pH 4.6, with or without 50 μm Al, and serological cross-reactivity.More strains from the strongly acidic soil were resistant to the antibiotics than from slightly acidic soils, but resistance to antibiotics did not necessarily entail resistance to pH 4.6 or to 50 μm Al. Twenty-three nodule isolates which were resistant to spectinomycin or streptomycin cross-reacted with antisera of the inoculum strains, indicating that they were contaminants. None of 59 antibiotic-sensitive nodule isolates from uninoculated plants and none of 31 from inoculated plants cross-reacted with the antisera. All 53 antibiotic-resistant isolates from nodules of plants in inoculated plots cross-reacted with test antisera, indicating stability of the antibiotic markers.Cowpea rhizobia were generally more resistant to the antibiotics and more tolerant of pH 4.6 and 50 μm Al than were R. japonicum. Among strains of R. japonicum, slow growers were more resistant to antibiotics than moderately fast growers.     

Identification and Characterization of Yeasts with Tolerance to High Acidity and Resistance to Aluminum Isolated from Tea Soils

From acidic tea soils in Kagoshima Prefecture in Japan, 38 strains of acid-tolerant microorganisms were isolated and some soil properties were determined. Different Al concentrations were applied to YG media to estimate the Al resistance. Selected microbial strains were able to grow actively in liquid media in the presence of 100 mM Al and to survive even in 300 mM Al at pH 3.0. The base sequences of 28S rDNA-D1/D2 were determined and sequence data were searched using the Basic Local Alignment Search Tool (BLAST) system. The results of sequencing revealed that the isolates belonged to two different species, Cryptococcus sp. and Candida palmioleophila . Subsequently, Neighbor-Joining molecular phylogenetic trees were constructed. When the yeasts were cultured at various Al concentrations, the growth was inhibited at a concentration of 200 mM. Pre-culture of these strains with 0–30 mM Al did not promote the growth response induced by Al. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to assess the elimination of Al from YG media. The amount of Al remaining in the culture media decreased considerably after culture. Due to a capacity for resistance to significant Al concentrations as well as high Al elimination, these acid-tolerant and Al-resistant yeasts may offer potential applications for the bio- and phyto-remediation of acid soils with a high level of Al.     

超累积植物油茶中Al的吸收和累积

Oiltea camellia (Camellia oleifera Abel.), an aluminium (Al) hyperaccumulator, grows well on acid soils in tropical or subtropical areas. In this study, the growth of oiltea camellia in response to Al application and the characteristics of Al uptake and accumulation were investigated using laboratory and field experiments. The growth of oiltea camellia seedlings in the nutrient solution tended to be stimulated by addition of Al. Results of the field experiment showed that oiltea camellia accumulated 11000 mg kg-1 Al in leaves within 10 months, and the average rate of Al accumulation in new leaves was about 1100 mg kg-1 month?1; however, the monthly rate varied and was highest in spring and autumn. The results of the laboratory experiment on Al uptake by oiltea camellia seedlings in CaCl2 solutions with various forms of Al showed that large amounts of Al supplied as Al3+ and Al complexes Al-malate (1:1) and Al-F (1:1) were influxed into oiltea camellia roots, whereas Al supplied as Al-citrate (1:1), Al-F (1:6), Al-oxalate (1:3), and Al-oxalate (1:1) complexes exhibited low affnity to oiltea camellia roots. The kinetics of Al3+ cumulative uptake in excised roots and intact plants showed a biphasic pattern, with an initial rapid phase followed by a slow phase. The Al cumulative uptake was una?ected by low temperature, which indicated that Al uptake in oiltea camellia was a passive process. The effcient influx of Al into the roots and the high transport rate in specific seasons were presumed to account for the plentiful Al accumulation in leaves of oiltea camellia.     

Alkalinity exacerbates phosphorus deficiency in subtropical red soils: Insights from phosphate-solubilizing fungi

Red soils in subtropical regions are often low in available phosphorus (P), a vital plant nutrient. Phosphate-solubilizing microorganisms (PSMs) can release P from phosphate reservoir, making it accessible to plants. However, the complex interactions between PSMs and minerals in red soils are not yet fully understood. In this study, we investigated the effects of Aspergillus niger, a typical phosphate-solubilizing fungus (PSF), on phosphate dissolution in two representative red soils – an acidic soil and an alkaline soil. In the acidic red soil, the fungal abundance reached 3.01 × 10 ⁷ cfu g⁻¹ after a 28-day incubation period, with respiration of ~2000 mg C kg⁻¹. The secretion of oxalic acid promoted P release from inorganic phosphate (from ~1 to 187 mg kg⁻¹). Additionally, the contents of amorphous Fe/Al oxides decreased, which otherwise could have contributed to P sorption in the soil. In contrast, P availability declined in the alkaline red soil after the addition of A. niger, regardless of the P source (inorganic or organic phosphate). Meanwhile, the fungal respiration decreased to ~780 mg C kg⁻¹. Therefore, alkaline red soils with abundant carbonates are susceptible to P deficiency due to both the diminished function of PSMs and strong soil buffering. These findings have important implications for sustainable agriculture on alkaline red soils, as they suggest that the use of PSMs to improve P availability may be limited.     

离子强度和三氧化物对土壤吸附Bt毒素的影响

Chemical reactions and fate of the toxins of Bacillus thuringiensis(Bt) in the soil environment are causing increasing concerns due to the large-scale cultivation of transgenic Bt plants.In this study,the effect of ionic strength(0-1 000 mmol kg 1) adjusted by NaCl or CaCl 2 on adsorption of Bt toxin by a lateritic red soil,a paddy soil and these soils after chemical removal of organic-bound or free Fe and Al oxides,as well as by pure minerals(goethite,hematite and gibbsite) which are widespread in these soils,were studied.The results indicated that when the supporting electrolyte was NaCl,the adsorption of Bt toxin by the lateritic red soil and paddy soil increased rapidly until the ionic strength reached 250 mmol kg 1 and then gradually slowed down with the increase of ionic strength;while in case the supporting electrolyte was CaCl 2,the adsorption of Bt toxin enhanced significantly at low ionic strength(< 10 mmol kg 1) and then decreased as the ionic strength increased.The adsorption of Bt toxin by the tested minerals and soils after the removal of organic-bound or free Fe and Al oxides also increased with increasing ionic strength controlled by NaCl.Removing organic-bound Fe and Al oxides obviously increased the adsorption of Bt toxin in the tested soils.Differently,removing free Fe and Al oxides increased the Bt adsorption by the paddy soil,but decreased the adsorption by the lateritic red soil.The study indicated that the varieties of ionic strength and the presence of Fe and Al oxides affected the adsorption of Bt toxin by the soils,which would contribute to the further understanding of the fate of Bt toxin in the soil environment and provide references for the ecological risk assessment of transgenic Bt plants.     

KC1‐extractable aluminium in highly weathered soils. Is it exchangeable?

Abstract

In a study involving 212 samples of surface and sub‐surface soils derived from basaltic, granitic, and metamorphic parent materials in the high rainfall region of north Queensland, Australia, the Al extracted with 1 M KC1 has been compared with ‘exchangeable aluminium’, defined as the difference between CEC and sum of basic exchangeable cations. It was concluded that for these highly weathered soils KCl‐extractable Al is exchangeable, and therefore that the sum of basic and acidic cations (ECEC) is a reliable measure of CEC at field conditions.     

Phosphorus Alleviates Aluminum Toxicity in Al-Sensitive Wheat Seedlings

The role of phosphorus (P) in the amelioration of aluminum (Al) toxicity to plants is still unclear. The aim of this study was to examine the amelioration of Al toxicity by P supply. The study involved growing Al-sensitive wheat seedlings for 13 days in an acidic soil [pH 4.5 in calcium chloride (CaCl₂)] with increasing added rates of P (0, 20, 40, and 80 mg P kg^?1 soil) and Al [0, 50, and 150 mg aluminum chloride (AlCl₃) kg^?1 soil]. The results indicated that the effects of Al toxicity in this soil could be fully alleviated by the application of P at 50 mg AlCl₃ kg^?1. The 150 mg kg^?1 AlCl₃ treatment significantly reduced root growth, but this was partially overcome by the 80 mg kg^?1 P treatment. High P significantly reduced the concentration of Al in the apoplast, root, and shoot. It is possible that an insoluble Al-P complex forms in the soil and this decreases Al bound in apoplast as well as uptake into the roots. High P decreased the translocation of Al from root to shoot. This study also concluded that detoxification of Al³⁺ by P mainly occurs in soil but not within the plant tissue.     

Stabilization of dissolved organic matter by aluminium: a toxic effect or stabilization through precipitation?

Carbon mineralization in acidic forest soils can be retarded by large concentrations of aluminium (Al). However, it is still unclear whether Al reduces C mineralization by direct toxicity to microorganisms or by decreased bioavailability of organic matter (OM) because dissolved organic matter (DOM) is precipitated by Al. We conducted an incubation experiment (6 weeks) with two DOM solutions (40 mg C litre^?1) derived from two acidic forests and possessing large differences in composition. Aluminium was added to the solutions in realistic ranges for acidic soils (1.6–24 mg Al litre^?1) at pHs of 3.8 and 4.5, to achieve differences in Al speciation. We determined different Al species, including the potentially toxic Al³⁺, by Diffusive Gradients in Thin Films (DGT) to evaluate toxic effects on microorganisms. Precipitation of OM increased with larger amounts of added Al and higher pH, and we measured a larger fraction of dissolved ‘free’ Al at pH 3.8 than at pH 4.5. Organic matter degradation decreased significantly with Al addition, and we found more organic matter degraded at pH 3.8 than at pH 4.5 for the respective Al additions. Consequently, the observed reduction in OM degradation (i.e. stabilization) cannot be explained by toxic effects of ‘free’ Al. However, C stabilization correlated significantly with C precipitation. The pH did not influence C stabilization directly, but determined the amount of C being precipitated. Phosphorus was removed along with OM by precipitation, which possibly also affected C stabilization. We conclude that C stabilization upon Al addition did not result from toxic effects, but was caused by reduced bioavailability of OM after its precipitation. The reduction in OM degradation by 65% is of great relevance for the overall C stabilization in acidic forest soils. Increasing pH and decreasing Al concentrations upon recovery from acidic deposition should therefore not result in decreased stabilization of precipitated OM.     

红酵母RS1的高耐铝能力与增厚的细胞壁有关而不来自体外铝离子的螯合作用

Aluminum (Al) is very toxic to many living organisms, including plants, animals and microorganisms. However, despite many studies on Al tolerance in plants, little has been reported concerning these mechanisms in microorganisms. In this study, a red yeast, which could tolerate Al 3+ concentrations as high as 200 mmol L-1 , was isolated from acidic soils, identified as Rhodotorula sp. and designated as RS1. As the medium compositions can greatly affect the responses of microorganisms to Al, two culture mediums, glucose medium (GM) and lysogeny broth medium containing soil extract (S-LBM), were used. During growth of RS1, the pH of medium decreased in GM but increased in S-LBM. These changes in the pH of the media were not induced by Al addition. No or little secretion of organic acids was observed in RS1 growth media. Importantly, the thickness of the cell walls and the ratio of cell wall to biomass of RS1 significantly increased in GM with high Al 3+ concentrations. In the presence of 100 mmol Al L-1 , 78.0% of the total Al of whole cells was present in the thickened cell walls. The Al in cell walls was mostly bound to OH, amide and CO groups of polysaccharides. These results suggest that thickening of the cell wall in response to the high Al 3+ concentrations may play an important role in the high tolerance of RS1 to Al and that pH increase of the medium and chelation of Al ions are not involved in Al tolerance of this organism.     

Identification and Characterization of High Acid Tolerant and Aluminum Resistant Yeasts Isolated from Tea Soils

From acidic tea soils of Kagoshima Prefecture in Japan, some soil properties were determined and 38 strains of acid tolerant microorganisms were isolated. Different Al³⁺ concentrations were applied to YG media to estimate Al resistance. Selected microbial strains could grow strongly in the liquid media in the presence of 100 mM Al³⁺ and survive even in 300 mM Al³⁺ at pH 3.0. Their base sequences of 28S rDNA-D1/D2 were determined and sequence data were searched using the Basic Local Alignment Search Tool (BLAST) system. The results of sequencing revealed that the isolates belong to two different species, Cryptococcus sp. and Candida palmioleophila. When cultivated with various Al³⁺ concentrations, the yeast growth was inhibited at a concentration of 200 mM. Pre-cultivation of these strains with 0–30 mM Al³⁺ did not promote the growth response caused by Al³⁺. Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS) was used to assess the elimination of Al. The amount of Al remaining in culture media was decreased considerably after cultivation. Due to a capacity for resistance to significant Al concentrations as well as high Al elimination, these acid tolerant and Al resistant yeasts may have potential applications in the bio- and phyto-remediation of Al and acid-contaminated soils.     

高耐铝红酵母RS1耐铝特性初步研究

红酵母RS1是从酸性土壤中筛选出的一株高耐铝微生物,本文对其耐铝特性进行了初步研究.结果发现,RS1可以在pH 2.5的培养基中生长,50 ～ 200 mmol/L A13+处理对RS1产生了毒害作用,其毒害并未对细胞表面形态产生影响.RS1对Al2(SO4)3的忍耐能力高于AlCl3,这种高的忍耐能力是遗传固有的,并不被诱导产生.此外,RS1可以增加体内蛋白含量来适应高的铝毒,其中蛋白型巯基可能在耐铝中表现重要作用.     

Response of Soil and Plant to Boron-Doped Aluminum Hydroxide

The aims of this work are to test whether boron (B) may alleviate soil acidification and aluminum (Al) phytotoxicity to rape (Brassica napus L.) in acidic soil. The Al hydroxide that reacted with borax was called ad-B-Al hydroxide. Point of zero charge (PZC) of Al hydroxide (pH 4.86) was greater than that of ad-B-Al hydroxide (pH 4.68). Compared with the control, ad-B-Al hydroxide raised the soil pH significantly by 0.10 pH units. Rape was planted in the control soil, the soil treated with Al hydroxide, and the soil treated with ad-B-Al hydroxide. It was found that the B content of the soil and rape seedlings grown on the soil treated with ad-B-Al hydroxide was greater than the others. Biomass production of rape seedlings grown in the soil treated with ad-B-Al hydroxide was significantly increased compared to that in the others. These demonstrated that ad-B-Al hydroxide can be an important source of B for plants and alleviate acidity of acidic soils because it can decrease exchangeable acid and Al toxicity in soil significantly.     

Identification and Characterization of High Acid Tolerant and Aluminum Resistant Yeasts Isolated from Tea Soils

From acidic tea soils of Kagoshima Prefecture in Japan, some soil properties were determined and 38 strains of acid tolerant microorganisms were isolated. Different Al³⁺ concentrations were applied to YG media to estimate Al resistance. Selected microbial strains could grow strongly in the liquid media in the presence of 100 mM Al³⁺ and survive even in 300 mM Al³⁺ at pH 3.0. Their base sequences of 28S rDNA-D1/D2 were determined and sequence data were searched using the Basic Local Alignment Search Tool (BLAST) system. The results of sequencing revealed that the isolates belong to two different species, Cryptococcus sp. and Candida palmioleophila. When cultivated with various Al³⁺ concentrations, the yeast growth was inhibited at a concentration of 200 mM. Pre-cultivation of these strains with 0–30 mM Al³⁺ did not promote the growth response caused by Al³⁺. Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS) was used to assess the elimination of Al. The amount of Al remaining in culture media was decreased considerably after cultivation. Due to a capacity for resistance to significant Al concentrations as well as high Al elimination, these acid tolerant and Al resistant yeasts may have potential applications in the bio- and phyto-remediation of Al and acid-contaminated soils.     

Increased Concentration of Molybdenum in Sown Wheat Seed Decreases Grain Yield Responses to Applied Molybdenum Fertilizer in Naturally Acidic Sandplain Soils

Spring wheat (Triticum aestivum L.) is the major crop in southwestern Australia where 75% of the 18 million hectares comprise sandy duplex and deep sandy soils, including uniform yellow sandplain soils. Some of the sandplain soils in the lower rainfall (< 350 mm annual average) eastern region are naturally very acidic (soil pH, as measured in 1:5 soil:0.01 M calcium chloride, 3.7–4.5) in soil horizons explored by wheat roots so molybdenum (Mo) deficiency and aluminium (Al) toxicity adversely affects grain production of wheat. Liming is not an economic option to ameliorate Mo deficiency and Al toxicity in these soils because uneconomical large amounts are required. However, despite Al toxicity, applying Mo fertilizer produces profitable grain yield. The fertilizer also increases Mo concentration in grain, and if this grain was used to sow the next crop, it may reduce the amount of Mo fertilizer required by the subsequent crop. To test this hypothesis we grew wheat in an experiment on naturally acidic sandplain soil (pH 4.5) when either 0 or 160 g/ha fertilizer Mo was applied. The grain harvested at the end of the growing season had Mo concentrations of 0.07 mg/kg when no Mo was applied (low Mo seed) and 0.27 mg/kg when Mo was applied (high Mo seed). In two further field experiments on naturally acidic sandplain soil (pH 4.3 and 4.4) we sowed low and high Mo seed of the same size (36.4 ± 0.2 mg per seed) when 4 rates of Mo fertilizer (0, 35, 70, and 140 g/ha Mo) was applied to soil. Grain yield responses to the Mo fertilizer were 59% for low Mo seed and 55 g/ha fertilizer Mo was required to produce 90% of the maximum grain yield. Corresponding values for high Mo seed were 15% response and 15 g/ha fertilizer Mo. Rather than sowing wheat seed harvested from acidic soils to sow wheat crops on the acidic sandplain soils, we instead recommend seed harvested from alkaline soils with larger concentrations of Mo in the seed be used reducing the rate of fertilizer Mo required for that crop.

The concentration of Mo in the youngest emerged leaf blades (YEB) that was related to 90% of the maximum grain yield (critical prognostic tissue test value for grain production) was about 0.08–0.09 mg/kg at tillering (Gs24) and at emergence of wheat heads (Gs59).     

低分子量有机酸对可变电荷土壤铝活化动力学的影响

从动力学角度研究了几种低分子量有机酸对2种酸性土壤中铝的活化和活化铝在土壤固/液相之间分配的影响。结果表明:对于络合能力弱的醋酸和乳酸,主要通过质子作用活化铝,且活化作用明显小于盐酸。而络合能力较强的苹果酸、草酸和柠檬酸,主要通过络合作用促进铝的释放,且这种作用随有机酸根阴离子络合能力的增强而增加。在氧化铁含量较高的砖红壤中,苹果酸、草酸和柠檬酸通过专性吸附增加土壤表面负电荷,从而增加土壤交换态铝;但在氧化铁含量较低的红壤中,草酸和柠檬酸主要通过形成可溶性铝络合物降低交换态铝。活化铝在土壤固/液相间的分配主要决定于溶液中有机阴离子与土壤固相表面对铝离子的竞争。醋酸和乳酸活化的铝主要以交换态铝存在;而草酸和柠檬酸活化的铝主要以有机酸-铝络合物存在于溶液中,特别是在氧化铁低的红壤中,这将促进铝在土壤-水体中的迁移。