有机酸对活化土壤中镉和小麦吸收镉的影响

向土壤中加入外源有机酸,研究有机酸对活化土壤中镉的作用和小麦吸收镉的影响。结果表明：有机酸对土壤中镉有一定的活化能力,对镉活化能力强弱顺序为ＥＤＴＡ〉缺铁小麦根分泌物〉柠檬酸〉苹果酸〉水。但ＥＤＴＡ却降低了小麦地上部镉的含量,缺铁小麦根分泌物明显增加了小麦地上部镉含量。与对照相比,柠檬酸和苹果酸对小麦地上部的镉含量有一定的促进作用,也增加了小麦地上部镉含量。     

有机酸对土壤中镉的解吸及影响因素

研究了酒石酸和柠檬酸对两种不同处理土壤 (镉质土和污染土 )中Cd的解吸行为 ,探讨了介质pH值、支持电解质等对其解吸镉质土和污染土中Cd的影响。结果表明 ,随有机酸浓度升高 ,柠檬酸和酒石酸对镉质土和污染土中Cd的解吸率呈先降低后升高变化 ,出现一波谷 ,波谷位置与有机酸和土壤类型有关。当解吸液起始pH值由 2升至 8时 ,柠檬酸对镉质土和污染土中Cd的解吸率呈降低—升高—降低的变化 ,先后出现一波谷和一波峰 ,且柠檬酸浓度高时变化趋势尤为明显 ;而酒石酸对镉质土和污染土中Cd的解吸率则一直降低。解吸液中支持电解质浓度提高 ,酒石酸对镉质土和污染土中Cd的解吸率增大 ,且以KCl为支持电解质时的解吸率要高于KNO3。     

有机酸对水稻镉吸收的影响

通过盆栽试验,在水稻开花期向土壤添加有机酸类物质,研究有机酸对水稻吸收镉的影响,特别是对水稻籽粒中镉含量的影响。结果表明,添加乙二胺四乙酸处理可明显抑制水稻对镉的吸收,即水稻籽粒中镉含量明显降低;而用柠檬酸和苹果酸处理时,对水稻籽粒中镉含量影响不大。     

存在有机酸时pH对镉毒害土壤微生物生物量的影响

采用室内培养实验方法,研究了存在有机酸时ＰＨ对镉毒害土壤微生物生物量的影响。结果表明,存在一定量有机酸的镉污染土壤中,土壤中微生物生物量碳（Ｃｍｉｃ）和氮（Ｎｍｉｃ）随着ＰＨ升高而升高,其中含胡和线条到为土壤中微生物生物量碳（Ｃｍｉｃ）和氮（Ｎｍｉｃ）明显比含低分子量有机酸（柠檬要到、酒石酸、乙酸、草酸）的土壤增加的快,土壤中微生物生物量碳氮比（Ｃｍｉｃ／Ｎｍｉｃ）随或高而降低,表明提高土壤ＰＨ可     

有机物料对土壤的外源铜和镉形态变化的不同影响

采用盆栽和连续提取法研究稻草和紫云英对土壤外源铜和镉形态分布的不同影响。研究结果表明，添加稻草和紫云英可促进潮土中外源铜逐步向生物有效性较低的紫有机质结合态铜和无定形铁结合态铜转化，降低铜的生物有效性，但添加有机物料对潮土中外源镉形态的影响完全不同，添加稻草和紫云英，在分蘖期可减少潮土交换态镉、提高紧有机质结合态和氧化锰结合态镉，但这种作用并不稳定。随着时间的推移，氧化锰和紧有机质吸附的镉将随着活性锰的还原和紧有机质的分解被释放出来，并向交换态镉转化，提高镉的生物有效性。铜和镉离子与土壤的固相不同的结合能力导致稳草和紫去英对潮土中外源铜、镉形态的再分配过程的影响不同。     

低分子量有机酸对土壤有效磷及重金属释放影响的研究进展

农药化肥的过量施用、重金属矿产开发冶炼、污水灌溉等导致土壤磷素养分降低和重金属污染,对生态环境、粮食安全和人类健康带来一定的风险隐患。土壤低分子量有机酸是一类重要的土壤有机活性物质,在土壤质地、养分循环和重金属毒害等方面起重要作用,但低分子量有机酸对土壤磷素和重金属释放影响的研究尚没有系统归纳。本文结合国内外研究进展,综述了土壤低分子量有机酸的来源、浓度、功能及其影响因素,举例说明了低分子量有机酸种类、浓度等对土壤磷及重金属释放的影响。系统总结了低分子量有机酸对土壤磷活化及重金属释放的机制。低分子量有机酸与其他物质协同提升土壤磷素有效性和降低重金属污染,这些结果为土壤磷素有效性的提升和重金属污染土壤修复提供科学依据和技术支撑。     

有机肥对镉锌污染土壤的改良效应

通过对苗期玉米的盆栽试验,探讨了在镉,锌污染土壤上施入不同量的有机肥并配合淋洗措施后土壤中镉,锌污染土壤上施入不同量的有机肥并配合淋洗措施后土壤中镉,锌的形态转化,迁移规律和对植物生长的影响及改良效果。结果表明：施入有机肥后土壤中有效态镉、锌的含量明显降低,通过络合淋洗后土壤中镉,锌的总量减少显著,因而能够显著减轻Ｃｄ＾２＋,Ｚｎ＾＋对植物的毒害程度。土壤Ｃｄ＾２＋的浓度为５００ｍｇ／ｋｇ时,增放     

不同镉积累类型小麦根际土壤低分子量有机酸与镉的生物积累

采用土壤培养方法研究低镉积累小麦烟 86103和高镉积累小麦莱州 953不同生育期土壤低分子量有机酸含量与组成 ,及其与镉生物积累的关系。结果表明 ,不同镉积累类型小麦在高镉土壤中其根系镉含量差异不显著 ,但地上部镉浓度烟 86103显著低于莱州 953,而在低镉土壤中根系和地上部镉浓度烟 86 10 3均显著低于莱州 95 3。根际土壤有机酸 (柠檬酸、酒石酸、乙酸和丙酸 )含量及有机酸总量均为低镉品种烟 86103显著低于高镉品种莱州953。两个品种不同生育期有机酸含量均表现为柠檬酸 酒石酸 丙酸 乙酸 ,且各有机酸含量占有机酸总量的百分数表现稳定。小麦镉的生物积累与有机酸种类没有特异性关系 ,但与有机酸的总量有关。根际不同有机酸的水平对于土壤镉的复合或螯合溶解 ,在引起两品种地上部镉生物积累的差异方面起重要作用。     

有机酸对高岭石, 针铁矿和水铝英石吸附镉的影响

Effects of organic acids （oxalic, acetic, and citric） on adsorption characteristics of Cadmium （Cd） on soil clay minerals （kaolinite, goethite, and bayerite） were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L^-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.     

外源有机酸对红蛋植物吸收和转运镉的影响

采用溶液培养试验,研究了外源草酸和柠檬酸对镉富集植物红蛋吸收及转运镉的影响。结果表明,外源草酸或柠檬酸的加入均不同程度地增加了红蛋对Cd的耐性,表现在生物量增加,根部的镉含量提高,影响大小依次为草酸>1/2(草酸+柠檬酸)>柠檬酸,其中草酸处理效果最明显,地下部镉含量比未加有机酸处理增加了67.20%。有机酸的加入也促进了植株地上部镉的累积,除了柠檬酸处理外,植株地上部Cd含量比未加有机酸处理降低了27.83%。草酸或/和柠檬酸的加入虽未提高红蛋体内镉的迁移系数,但却增加了各处理植株地上部重金属迁移总量,从而提高了修复重金属污染地的效率。可见,草酸或/和柠檬酸的添加能够促进红蛋对重金属镉的吸收和累积,且植株的重金属迁移总量相当可观,可作为一种潜力植物用以修复镉污染土壤或水体     

低分子量有机酸对土壤磷活化影响的研究

研究两种低分子量有机酸（柠檬酸和苹果酸）对土壤磷活化影响,并用修正的Hedley法测定土壤磷活化前后磷组分的变化。结果表明,低分子量有机酸能持续活化土壤磷,活化强度随低分子量有机酸浓度的增大而增强,并且柠檬酸活化土壤磷的能力强于苹果酸。低分子量有机酸能促进作物有效态无机磷组分（H2O-P和NaHCO3-Pi）的释放;同时还促进有机磷组分（NaHCO3-Po和NaOH-Po）的矿化。在低分子量有机酸浓度达到0.5 mmol/L以上时,其对土壤磷组分的活化量的顺序为:NaOH-Pi HCl-P NaHCO3-Pi H2O-P,即铁铝结合态磷 钙结合态磷 作物有效态磷。低分子量有机酸活化土壤磷的过程中伴有大量铁、铝释放,且铁或铝的释放量与磷活化量之间显著正相关（P0.05）。说明铁、铝结合态磷是低分子量有机酸活化土壤磷的主要磷源,并且其活化机制可能与铁、铝结合态磷的螯合溶解有关。     

Evaluation of Extraction Methods for Plant-Available Soil Cadmium to Wheat by Several Extraction Methods in Cadmium-Polluted Paddy Field

To develop a new method for the extraction of plant-available cadmium (Cd), the correlation between the Cd content of polluted soil extracted with several extractants and the Cd content of wheat plants (variety “A” Triticum aestivum L.) was examined. Among the HCI concentrations of soil extractants tested, the content of 0.025 mol L^?1 HCI (HCl_0.025)-extractable Cd of soil showed a significant correlation with the Cd content of wheat grain and Cd uptake by shoot. The correlation between the soil Cd content extracted with 1 mol L^?1 NH₄Cl and the Cd content of wheat grain was nearly the same as that in the case of HCI_0.025. In contrast, other reagents such as MgCl₂, diethylenetriaminepentaacetate (DTPA) and tetra-sodium pyrophosphate (Na₄P₂O₇) could not give a good correlation between the extractable Cd content of soil and the Cd content of wheat grain. Therefore, it was considered that HCl_0.025-extractable Cd is a suitable indicator of the content of plant-available Cd of soil to wheat. This extraction method can be applied to weakly acid Grey Lowland soil. Using the equation for the relation between the content of HCl_0.025-extractable Cd of soil and the Cd content of grain of the wheat variety “A”, the Cd content of grain of other 11 wheat varieties was evaluated. The wheat variety “A” showed the lowest absorption of Cd. The Cd content of variety “B” grain was located on the regression line of that of variety “A”, suggesting that both varieties exhibited the lowest ability to absorb Cd among the varieties tested. Grain yields of both “A” and “B” varieties were reasonably high. On the other hand, other varieties showed a substantially high ability to absorb soil Cd compared with the varieties “A” and “B”. The new method proposed for the determination of the content of plantavailable Cd proved to be suitable for the evaluation of plant-available Cd of soil and also for the screening of wheat varieties with a high or low Cd accumulation capacity in grain.     

施用有机物料对土壤镉形态的影响

采用室内培养试验,研究作物新鲜秸秆和腐熟猪粪对模拟镉（Cd）污染的土壤中Cd形态转化的动态影响。结果表明,各处理土壤交换态Cd含量随培养时间均逐渐降低。碳酸盐结合态和铁锰氧化物结合态Cd含量先增加后降低, 而有机质结合态和残渣态Cd含量则逐渐增加。添加秸秆可增加土壤交换态Cd含量,但随时间延长,增幅逐渐降低, 猪粪则可降低土壤交换态Cd含量。添加有机物后土壤交换态Cd含量的变化主要是由有机质结合态或残渣态Cd含量的变化而引起。秸秆和猪粪对土壤Cd形态的转化与土壤胡敏酸（HA）和富里酸（FA）的变化有关。秸秆对能活化土壤Cd的FA增加幅度大于对能钝化土壤Cd的HA增加幅度,降低HA/FA比,但降幅随时间逐渐减少; 猪粪在整个培养阶段对HA增加幅度均大于FA的增加幅度,增加HA/FA比。秸秆和猪粪均可降低潮土pH而提高红壤pH,但只有猪粪可通过提高红壤pH降低Cd向交换态转化。添加秸秆和猪粪后,Cd由低活性态向交换态转化与HA/FA呈显著负相关。     

低分子量有机酸对促进可变电荷土壤中铝溶解的影响

Low-molecular-weight （LMW） organic acids exist widely in soils and play an important role in soil processes such as mineral weathering, nutrient mobilization and A1 detoxification. In this research, a batch experiment was conducted to examine the effects of LMW organic acids on dissolution of aluminum in two variably charged soils, an Ultisol and an Oxisol. The results showed that the LMW organic acids enhanced the dissolution of A1 in the two investigated soils in the following order： citric 〉 oxalic 〉 malonic 〉 malic 〉 tartaric 〉 salicylic 〉 lactic 〉 maleic. This was generally in agreement with the magnitude of the stability constants for the Al-organic complexes. The effects of LMW organic acids on Al dissolution were greater in the Ultisol than in the Oxisol as compared to their controls. Also, the accelerating effects of citric and oxalic acids on dissolution of A1 increased with an increase in pH, while the effects of lactic and salicylic acids decreased. Additionally, when the organic acid concentration was less than 0.2 mmol L-I, the dissolution of A1 changed Iittle with increase in acid concentration. However, when the organic acid concentration was greater than 0.2 mmol L^-1,the dissolution of A1 increased with increase in acid concentration. In addition to the acid first dissociation constant and stability constant of Al-organic complexes, the promoting effects of LMW organic acids on dissolution of A1 were also related to their sorption-desorption equilibrium in the soils.     

工业废弃地多金属污染土壤组合淋洗修复技术研究

采用批量淋洗实验方法,对比了采用人工螯合剂乙二胺四乙酸二钠盐(EDTA-Na2)和天然有机酸草酸(oxalic acid,OX)对工业废弃地污染土壤中重金属的去除效果,并采用不同浓度草酸和EDTA组合的两步淋洗法研究多金属污染土壤的最佳淋洗方式。结果表明,EDTA淋洗剂对土壤中Zn、Pb、Cu、Ni去除效果较好,而对Cr去除效果较差,实验条件下,EDTA对金属的去除率并未随着浓度增加而增加;相反,草酸对Cr去除效果较好,且去除率随着淋洗剂浓度的增加而增加,而对Zn、Cu、Ni的去除效果随着淋洗剂浓度增加而降低,对Pb的去除率非常低;采用先以0.20 mol L-1草酸提取2 h,再以0.01 mol L-1EDTA提取2 h的两步淋洗法可以达到对多金属同时去除,且对Zn、Cu、Cr、Ni的去除率明显高于单用草酸和EDTA,总去除率分别为Zn 75.21%、Pb 21.30%、Cu 59.81%、Cr 60.72%和Ni 62.10%,更为有意义的是两步淋洗法对非残渣态金属去除效果分别高达Zn 91.93%、Pb 57.75%、Cu 75.33%、Cr 73.94%、Ni 77.99%。利用不同化学淋洗剂对金属去除能力的差异进行组合的多步淋洗法是一种较为高效的去除工业废弃地污染土壤中重金属的化学淋洗修复方法。     

小麦分泌的有机酸影响钙质土中锌的释放

Rhizosphere drives plant uptake of sparingly soluble soil zinc(Zn).An investigation with three experiments was conducted to study organic acid exudation by two contrasting wheat genotypes(Sehar-06 and Vatan),Zn fractions in 10 different calcareous soils from Punjab,Pakistan,and release of different soil Zn fractions by organic acids.The two genotypes differed significantly in biomass production and Zn accumulation under deficient and optimum Zn levels in nutrient solution.At a deficient Zn level,Sehar-06 released more maleic acid in the rhizosphere than Vatan.Ten soils used in the present study had very different physicochemical properties;their total Zn and Zn distribution among different fractions varied significantly.Zinc release behaviour was determined by extracting the soils with 0.005 mol L-1 citric acid or maleic acid.The parabolic diffusion model best described Zn release as a function of time.Parabolic diffusion model fitting indicated more maleic acid-driven than citric acid-driven soil Zn mobility from different fractions.Cumulative Zn release in six consecutive extractions during 24 h ranged from 1.85 to 13.58 mg kg-1 using maleic acid and from 0.37 to 11.84 mg kg-1 using citric acid.In the selected calcareous soils,the results of stepwise linear regression indicated significant release of Fe-Mn oxide-bounded soil Zn by maleic acid and its availability to the Zn-effcient genotype.Hence,release of maleic acid by plants roots played an important role in phytoavailability of Zn from calcareous soils.     

Immobilization of cadmium in simulated contaminated soils using thermal-activated serpentine

ABSTRACT

The thermal-activated serpentine prepared by heating natural serpentine at different temperatures was used to immobilize cadmium (Cd) in simulated contaminated soils. The results showed that the increasing soil pH induced by adding serpentine was primarily responsible for reducing the content of TCLP-Cd (toxicity characteristic leaching procedure-Cd) in soil. Furthermore, adding thermal-activated serpentine could promote the transformation from exchangeable form of Cd in soil to low bioavailable Cd (Fe-Mn oxides, carbonate, and residual form) by surface adsorption and surface precipitation, and then reduced the bioavailability of Cd in soil. Under the same treatment condition, adding S700 (serpentine activated at 700°C) exhibited better performance to immobilization of Cd, and it could reduce exchangeable Cd by 23.76~36.49%, and increase carbonate, Fe-Mn oxide, and residual form of Cd by 6.03~8.03%, 6.05~8.35%, and 11.17~19.58%, respectively. These results indicated that thermal-activated serpentine would be the great potential for immobilization of Cd in soil.     

Quantification of long‐chain fatty acids in dissolved organic matter and soils

The objective was to develop and adapt a versatile analytical method for the quantification of solvent extractable, saturated long‐chain fatty acids in aquatic and terrestrial environments. Fulvic (FA) and humic (HA) acids, dissolved organic matter (DOM) in water, as well as organic matter in whole soils (SOM) of different horizons were investigated. The proposed methodology comprised extraction by dichloromethane/acetone and derivatization with tetramethylammonium hydroxide (TMAH) followed by gas chromatography/mass spectrometry (GC/MS) and library searches. The C_10:0 to C_34:0 methyl esters of n‐alkyl fatty acids were used as external standards for calibration. The total concentrations of C_14:0 to C_28:0 n‐alkyl fatty acids were determined in DOM obtained by reverse‐osmosis of Suwannee river water (309.3 μg g^—1), in freeze‐dried brown lake water (180.6 μg g^—1), its DOM concentrate (93.0 μg g^—1), humic acid (43.1 μg g^—1), and fulvic acid (42.5 μg g^—1). The concentrations of the methylated fatty acids (n‐C_16:0 to n‐C_28:0) were significantly (r² = 0.9999) correlated with the proportions of marker signals (% total ion intensity (TII), m/z 256 to m/z 508) in the corresponding pyrolysis‐field ionization (FI) mass spectra. The concentrations of terrestrial C_10:0 to C_34:0 n‐alkyl fatty acids from four soil samples ranged from 0.02 μg g^—1 to 11 μg g^—1. The total concentrations of the extractable fatty acids were quantified from a Podzol Bh horizon (26.2 μg g^—1), Phaeozem Ap unfertilized (48.1 μg g^—1), Phaeozem Ap fertilized (57.7 μg g^—1), and Gleysol Ap (66.7 μg g^—1). Our results demonstrate that the method is well suited to investigate the role of long‐chain fatty acids in humic fractions, whole soils and their particle‐size fractions and can be serve for the differentiation of plant growth and soil management.