Methods for identification of arsenic compounds

Dust samples from two mineral processing operations, a gold extraction plant and an iron ore pelletizing operation, have been studied to determine the amount of As and its compounds which are present. Results indicate the probable presence of large amounts of AS₂0₃ in the gold roaster dust and relatively small fractions of AS₂0₃ in the pelletizing plant dust. Sample analysis was carried out by use of colormetric, volumetric, X-ray fluorescence and X-ray diffraction techniques.     

Summary of phytotoxic levels of soil arsenic

In the absence of site-specific data, generic guidelines are important to indicate whether soils contaminated with As require attention or remediation. It is important that the data used to set generic guidelines come from as broad a survey as possible. The objective of this paper is to summarize the data on the phytotoxicity of As from the literature, and to analyze the associated variance. The very narrow margin between background and toxic concentrations of As in soils is clearly shown. The source of As is important; the inorganic sources are less toxic than the organic sources. When only the inorganic sources are considered, soil type is the only other significant variable. Monocotyledonous and dicotyledonous plants did not differ significantly in response to soil As. Inorganic As is 5-fold more toxic in sands and loams (the geometric mean, GM, of the reported toxicity thresholds is 40 mg kg^?1) than in clay soils (where the GM is 200 mg kg^?1). Deviation of a single geometric standard deviation is 3.6-fold above and below these GM values. The results show that it is appropriate to set generic regulatory criteria by soil type, but that site- or soil-specific data is likely needed past a screening stage.     

Fractionation of soil cadmium from some new zealand soils

Abstract

The concentrations and forms of soil cadmium (Cd) in 12 different New Zealand topsoils were investigated using a sequential fractionation procedure. Total soil Cd concentrations were low and ranged between 0.03 μg g^‐1 to 1.34 μg g^‐1 and were highly correlated with total soil phosphorus (r²=0.85, P<0.01). Results indicated that there was a wide range in the concentrations of Cd associated with individual soil fractions and large variations between soils. On average for all soils, the smallest proportion of Cd was in exchangeable forms, i.e., 3%, with 12% in the crystalline oxide fraction, 13% in the amorphous oxide fraction and the greatest proportion of Cd associated with the organic 34% and residual 38% fractions. There was evidence to show that a soil extractant which is commonly used to predict plant uptake of Cd from soils, i.e., 0.04 M ethylene diamine terra acetic acid (EDTA), extracts Cd from both exchangeable and organic forms of soil Cd.     

土壤Se的分级与Se的植物有效性的关系

Nine soils with distinct properties and Se levels were selected to test a fractionation procedure of soil Se based on sequential extraction. Soil Se was fractionated into readily available Se (fraction Ⅰ, extracted by 0.5 M NaHCO₃), slowly available Se (fraction Ⅱ, extracted by 0.1 M NaOH-0.1 M Na₄P₂O₇), amorphous oxide-occluded Se (fraction Ⅲ, extracted by acid ammonium oxalate), free oxide-occluded Se (fraction Ⅵ, extracted by dithionite-citrate-bicarbonate buffer solution) and residual Se (fraction Ⅴ, determined by HNO₃-HClO₄ digestion of the final soil residue). The recovery of soil Se (the sum of all fractions over total soil Se determined independently) by this procedure was from 88.1% to 110.9%, mean 99.2%±6.4% for the test soils. The sum of fractions Ⅰ and Ⅱ, provided a good measure of available Se in soils and the percentage of fraction Ⅰ plus Ⅱ over the total soil Se, tentatively defined as Se availability index, could be used to indicate soil Se status and predict Se deficiency.     

酸性土壤中度和高度稳定有机磷的分组研究

The fractionation of moderately and highly organic phosphorus (P_o) in acid soil was studied by two methods. By the first method, after incubation for 40 d, the mineralization rates of eight constituents of stable P_o in the soil were determined. By the second method, five constituents of precipitates of stable P_o in the soil were separated, then the five precipitates were put back into the original soils and incubated for 40 d and 60 d. Then, mineralization rates of the five precipitates were determined. The same results were obtained by the two methods. When the pH of the alkali solution containing stable P_o was adjusted from 3.00 to 3.10, the mineralization rate of moderately stable P_o was rapidly raised. Therefore, the pH 3.00 is the critical point between moderately and highly stable P_o.     

Fractionation of selenium and detection of selenomethionine in a soil extract

Abstract

A procedure is described to fractionate, identify and quantify organic selenium compounds at μg/kg levels in soil extracts. The fractionation is based first on the different solubility of humates and fulvates at low pH, followed by adsorption chromatography with XAD‐8 resin. The latter uses a pH gradient to elute the acidic and basic hydrophobic fulvates as well as hydrophilic fulvates. The neutral hydrophobic fulvates were retained on the column and determined by difference from the total extractable selenium. A 0.1MNaOH/0.1 M Na₄P₂O₇solution extracted 33% of the total soil selenium. In the soil studied, organic selenium was 20% of total extractable selenium. One of the hydrophilic fulvates has been identified as selenomethionine by gas chromatography‐mass spectrometry. The quantity of organic selenium and the presence of selenomethionine suggests that organoselenium compounds could be an important source of plant available selenium     

Earthworm activity alters geogenic arsenic and soil nutrient dynamics

Environmental pollution due to arsenic (As) has been well studied and most investigations have focused on inorganic As coming from industrial areas. However, the natural rock-borne contamination of this metalloid has been underestimated and few studies focusing on annelids have addressed the question of geogenic As distribution in earthworm biogenic structures. Our study concentrated on the earthworm drilosphere and investigated the distribution of As in surface-casts and burrow-linings. In this context, we assumed that the concentration of geogenic As should differ in biogenic structures (faeces, burrow-linings) compared to non-ingested soil. To test our hypothesis, microcosms in controlled conditions were filled with soil containing 157 mg As kg^?1 from a geogenic origin. The soil was collected from a meadow in the Jura Mountains. The earthworm Aporrectodea giardi was selected because of its natural presence in the meadow and its anecic behaviour.We found that while earthworm surface-casts were enriched in carbon, nitrogen and available phosphorus compared to non-ingested soil, no enrichment was found for geogenic arsenic. The coarse sand fraction contained 3.5 times more As than silt and clay fractions but no significant difference existed between surface-casts and non-ingested soil. Iron was shown to be the main mineral bearing phase for As and predominated in the coarse sand fraction. No retention effect of organic matter on geogenic arsenic was observed. In conclusion, it appeared that geogenic As did not affect biological components and environmental aspects. These findings are particularly encouraging considering that most of the environments at an altitude of 1330 m in the Jura Mountains have exposed rocks, especially on meadows that are regularly grazed by cattle.     

Determination of water-soluble arsenic compounds in commercial edible seaweed by LC-ICPMS

This paper reports arsenic speciation in edible seaweed (from the Galician coast, northwestern Spain) produced for human consumption. Chondrus crispus , Porphyra purpurea , Ulva rigida , Laminaria ochroleuca , Laminaria saccharina , and Undaria pinnatifida were analyzed. The study focused on arsenosugars, the most frequently occurring arsenic species in algae. As(III) and As(V) were also determined in aqueous extracts. Total arsenic in the samples was determined by microwave digestion and inductively coupled plasma mass spectrometry (ICPMS). For arsenic speciation, a water extraction especially suitable for arsenosugars was used, and the arsenic species were analyzed by liquid chromatography with both anionic and cationic exchange and ICPMS detection (LC-ICPMS). The total arsenic content of the alga samples ranged from 5.8 to 56.8 mg As kg(-1). The mass budgets obtained in the extracts (column recovery × extraction efficiency) ranged from 38 to 92% except for U. pinnatifida (4%). The following compounds were detected in the extracts: arsenite (As(III)), arsenate (As(V)), methylarsonate (MA), dimethylarsinate (DMA), sulfonate sugar (SO(3)-sug), phosphate sugar (PO(4)-sug), arsenobetaine (AB), and glycerol sugar (Gly-sug). The highest concentrations corresponded to the arsenosugars.     

From mutable compounds to soil minerals

A synopsis of the development of the many aspects of soil mineralogy is given, bearing out the great importance of mineralogy in soil science. These aspects include the identification and quantitative determination of soil minerals, the clay-mineral concept, the function of mineralogy in soil classification, the disregarded non-silicate minerals and the formation and transformation of minerals. Several of the encountered, and the remaining, problems are indicated and references containing useful specific information and/or new lines of thought are given.     

Fractionation of chromium in tannery sludge-amended soil and its availability to fenugreek plants

Purpose

Fenugreek (Trigonella foenum-graecum L.) is a medicinal plant with antidiabetic effects. Chromium has been related to better glucose tolerance in humans. The objective of this study was to determine whether tannery sludge could be used for Cr biofortification of fenugreek.

Materials and methods

Soil was mixed with tannery sludge containing 6.03 g Cr kg^?1. All Cr was in the form of Cr(III). Three treatments were disposed: control without sludge, and two treatments with 10 and 20 g sludge kg^?1, respectively. Control and the 10 g sludge kg^?1 treatments received NPK fertilizer to adjust the concentrations of major mineral nutrients to similar levels in all treatments. Soils were potted and planted with fenugreek. Plants harvested at the initial flowering stage were analysed for total Cr, Fe, Zn and Pb. Sequential soil extraction was applied to obtain operationally defined soil Cr fractions.

Results and discussion

Total Cr in all treatments was below or within the allowable range for agricultural soils (100–150 mg kg^?1). In control soils, most Cr was in the residual fraction (HF/HClO₄ digest). Tannery sludge-amended soils incorporated most Cr into the moderately reducible fraction (oxalic acid/ammonium oxalate extract). In fenugreek shoots, Cr concentrations reached 3.2 mg Cr kg^?1, a higher concentration than that reported for other leafy vegetables. Lead concentrations in plant shoots from this treatment were enhanced but hardly exceeded 1 mg Pb kg^?1.

Conclusions

Tannery sludge-amended soils containing Cr within the range of permissible concentrations can increase shoot Cr in fenugreek. Only sludge with low Pb concentrations should be used for Cr biofortification of fenugreek.     

Water-soluble and lipid-soluble arsenic compounds in japanese flying squid Todarodes pacificus

Water-soluble and lipid-soluble arsenic compounds in Japanese flying squid Todarodes pacificus were analyzed. Regardless of the tissues, the major water-soluble arsenic compound was identified as arsenobetaine by LC/ESI-MS analysis, as reported for a number of marine animals. Lipid-soluble arsenic compounds were found at relatively high levels in liver and testis. LC/ESI-MS analysis of water-soluble arsenic compounds released from liver phospholipids by either chemical hydrolysis or phospholipase D hydrolysis demonstrated that the major arsenolipids are dimethylarsinic acid (DMA)-containing glycerophospholipid (phosphatidyldimethylarsinic acid) and DMA-containing sphingomyelin where the choline moiety of sphingomyelin is replaced by DMA. This is the first work to report the presence of DMA-containing phospholipids in marine invertebrates.     

含铁介质用于修复砷污染土壤研究综述

原位固化/稳定化技术被认为是当前土壤砷污染修复中相对经济、高效的技术之一,含铁介质是土壤固砷的一类上佳材料。从含铁材料修复砷污染土壤的研究现状出发,阐述其固砷机理,主要包括吸附、络合作用以及沉淀/共沉淀作用。介绍了5种常用的固砷效果评价方法,分别为化学形态连续提取法、毒性特征浸滤法、植物指示法、体外消化模拟法以及现代物理学方法。阐述了土壤环境条件,如酸碱条件、氧化还原条件以及土壤中共存离子和有机质的变化对固砷效果的影响。总结了目前含铁材料用于修复砷污染土壤的不足之处,并指出了今后的研究重点。     

不同调控措施对个旧矿区水稻土 As修复及水稻 As累积的影响

在大田试验条件下,研究了复合钝化剂A1(蛭石+硫酸亚铁),A2(纳米活性炭+硅钾钙镁肥)、A3(火山石+钙镁磷肥+有机肥)和B1(叶面硅肥)单一和联合7种不同的调控处理(A1、A2、A3、B1、A1B1、A2B1、A3B1)对云南省个旧矿区稻田As污染土壤的修复效应及对稻米As累积的影响。结果表明:添加土壤钝化剂后土壤pH值均有不同程度的升高;非专性吸附态和专性吸附态As含量均有不同程度的降低,联合调控处理效果优于单一处理;不同处理对水稻均有不同程度的增产效果,A1B1、A2B1、A3B1 3种联合调控处理后水稻产量分别增加28.0%、27.2%和29.7%,联合调控增产效果较单一好;不同处理水稻根系、茎叶、糙米中As含量和无机As含量都有不同的程度的降低,A2B1联合调控处理糙米中As含量和无机As含量分别降低60.3%和77.1%,效果较其它处理好;不同钝化剂处理下,根系到茎叶、茎叶到糙米、根系到糙米的转运系数都明显降低,A2B1联合调控处理效果较其它处理优。综上,采用土壤钝化-农艺联合调控措施,即基施蛭石和硫酸亚铁联合钝化剂,同时在水稻灌浆期和抽穗期喷施叶面硅肥(A2B1),能有效修复个旧矿区As污染土壤,有效降低糙米中As的含量和无机As含量,有效提高矿区稻米安全质量,该项技术可在As污染的农田推广应用。     

芳香族化合物对土壤硝化作用的抑制研究

Aromatic compounds (ACs) in soil can induce competitive inhibition for soil NH₃ oxidation, and nitrification inhibitors can be used to this end. A laboratory incubation experiment was performed with 12 nitroaromatic compounds (NACs), 15 amidoaromatic compounds (AACs) and 20 hydroxyaromatic compounds (HACs) to assess the inhibitory effects of ACs on soil nitrification. Based on these results, the critical and optimal concentrations of ACs were determined for better inhibitory effects. Most of the test ACs were able to inhibit soil nitrification; the effectiveness differed with soil type. Among the ACs, the NACs with m-nitryl, amino or hydroxyl and the AACs with a nitro group or a chlorine atom on aromatic ring or with a p-hydroxyl were more effective. 3-nitroaniline, 4-aminophenol and 3-nitrophenol showed the greatest potential as nitrification inhibitors. The critical concentration of these compounds in brown soil and cinnamon soil was found to be 0.5 mg kg^-1 soil. Due to the toxicity, carcinogenicity and mutagenicity of ACs, further toxicological and ecotoxicological research is necessary before ACs are used as nitrification inhibitors in agricultural and horticultural practices.     

不同类型土壤中241Am形态分析及其在土壤-植物系统中的迁移

Monitoring the behavior of radioactive contaminants associated with military applications,nuclear power facilities,and interim storage of radioactive waste materials is of significant concern in radiological analysis.Four sequential extraction schemes（SES） for fractionation of ²⁴¹Am were compared using five different types of soils,Vertisol,Cambisol,Chromic Luvisol,Eutric Fluvisol,and mixed urban soil,collected from different parts of Bulgaria.The results for the exchangeable ²⁴¹ Am were in a wide range and depended on the SES used.Soil ²⁴¹Am varied from 0.5%to 6%in the exchangeable phase,from 0.5%to 35%in the carbonate phase,from0.4%to 36%in the reducible phase（easily reducible and moderately reducible）,from 3%to 17%in the oxidizable phase,and from10%to 50%in the residual phase.After 100 d of contamination,around 50%of soil ²⁴¹Am was permanently fixed in the residual phase.There was strong evidence that the preferable soil phase for ²⁴¹ Am was the carbonate phase.The transfer factor of ²⁴¹ Am in the soil-plant system depended on ²⁴¹Am in the easily oxidizable phase（fulvic acid（FA）+humic acid（HA） phase）.These confirmed the applicability of the National Institute of Standards and Technology（NIST） sequential extraction scheme for fractionation of soil²⁴¹ Am since it includes extraction of FA+HA phase and then the carbonate phase.     

Fractionation of dissolved organic carbon from soil solution with immobilized metal ion affinity chromatography

The presence and identity of Cu‐complexing ligands in soil solution strongly affects biogeochemistry, bioavailability and the fate of Cu in soils. In this study, we compared the influence of heavy metal pollution, vegetation and soil type on the amount and characterization of ligands able to form ternary complexes with Cu in soil solution. For separation and characterization, we applied immobilized metal ion affinity chromatography (IMAC) combined with fluorescence spectroscopy. All separated IMAC‐fractions exhibited excitation‐emission wavelengths of humic‐like fluorescence (240–285/365–434 nm). Protein‐type fluorescence (270–280/295–365 nm) and fluorescence at 330–340/375–385 nm were detected only in the retained fraction whereas carboxylate‐type fluorescence (300–310/420–430 nm) was observed only in the non‐retained fraction. These findings are in agreement with the behaviour of model ligands. The IMAC‐retained ligands represented between 5 and 30% of dissolved organic carbon. The soil type and the vegetation had the largest influence on the quality and quantity of Cu ligands able to form ternary complexes. In the topsoil, the IMAC retained fraction was greater in soil without vegetation (16%) compared with soil with vegetation (12%). A larger amount (75%) of the protein‐type ligands able to form ternary complexes with Cu was found in soil with vegetation compared with plant‐free soil (69%). Metal pollution also affected the composition of the extracted ligands; the fraction with protein‐type ligands decreased from 75% in unpolluted to 65% in the polluted topsoil. The results show that IMAC‐retained ligands are related to the biological activity in soils.     

土壤中氯代有机化合物的环境行为

氯代有机化合物是一类重要的环境污染物质，由于其大多数具有较高的沉积物－水分配系数，胡一旦进入环境系统，可迅速被土壤、水体和沉积物吸附，并且易通过食物链在动物和人体中富集，对生态系统造成巨大的危害。因此，土壤中氯代有机化合物的环境行为是当今世界环境科学界的研究热点，本系统总结了有关这方面的研究成果和进展。     

几种吡唑类化合物的硝化抑制作用比较

采用室内土壤培养实验,考察了3,5-二甲基吡唑(3,5-DMP)、3,4-二甲基吡唑磷酸盐(3,4-DMPP)、双氰胺(DCD)、3,5-二甲基吡唑磷酸盐(3,5-DMPP)的硝化抑制作用,结果表明,在相同质量用量下,其硝化抑制作用由强到弱的顺序为3,4-DMPP>3,5-DMP>DCD>3,5-DMPP,其中3,5-DMPP的硝化抑制作用与其它抑制剂相比差异较大,可认为其硝化抑制作用较弱;因此吡唑类化合物的硝化抑制作用与其分子中含有的吡唑基团及基团数量的多少没有直接定量关系,而是与其化合物分子的物化性质有关。     

Nitrogen compounds in soil solutions of agricultural land

Plants are capable of taking up nitrogen (N) in both organic and inorganic forms, so the concentrations and relative proportions of different N forms in soils are likely to be important determinants of their N nutrition. Therefore, there is a need for greater knowledge of the N profiles of soils. In the study presented here we examined the potential plant-available N in soils from four sites with various agricultural histories (one recently fertilized), using small tension lysimeters to collect free and bound amino acids and inorganic N forms in solution, with minimal soil disturbance and with intact plants present. Subsequent analysis showed that concentrations of free amino acids ranged from 0.1 to 12.7 μM, whereas concentrations of bound amino acids were on average 50 times higher, and higher than ammonium and nitrate concentrations in all three unfertilized soils. In contrast, nitrate strongly dominated in the fertilized soil. Bound amino acids are likely to represent a potential replenishment pool for free amino acids, so the abundance and rate at which amino acid-containing substances are depolymerized might be important determinants of the availability of free amino acids. Our results highlight the need for further research on the liberation of free amino acids from polymers in agricultural soil, and the importance of bound amino acids as N sources for plants.