Decomposition of nitrilotriacetate (NTA) in soils

The trisodium salt of nitrilotriacetic acid (NTA) has been proposed as a substitute for phosphate in detergents. The decomposition of this chelating agent in soils was studied by performing analyses for NTA and inorganic nitrogen after incubation of NTA-treated soils for various times. The results showed that NTA is readily decomposed by soil micro-organisms under aerobic or anaerobic conditions and that NTA-nitrogen is converted to nitrate under aerobic conditions. The latter finding indicates that use of detergents containing NTA may lead to nitrate enrichment of water resources.     

Comparative evaluation of residual and total metal analyses in polluted soils

Abstract

Two digestion procedures, employing aqua regia‐HF (ARHF) and HNO₃‐HCIO4‐HF (HHH), were used to analyze residual metals (following a chemical fractionation scheme) and total metal content of two soils, one moderately polluted by municipal sludge applications and the other a grossly‐contaminated sample (20.8% Pb) from a battery recycling site. Although commonly used in sequential extraction analyses, the ARHF method solubilized only 53% (significant at p = 0.05) of the HHH‐determined residual Pb in the battery soil. For the sludge‐amended soil, residual Cd, Pb, and Zn were not statistically different by the two methods. For the battery soil, a single ARHF extraction also underestimated total Pb and Cu relative to HHH, but both methods gave statistically‐similar total Cd, Cu, Pb, and Zn for the sludge‐amended soil. As the sample metal concentration increased, the ability of ARHF to solubilize HHH‐equivalent metal quantities generally decreased. Since the degree of contamination is often unknown for environmental samples, the HHH method is more reliable for assessing residual and total metals in polluted soils     

利用磷进行铅污染土壤原位修复中需考虑的几个问题

由于土壤中磷与铅形成难溶性的磷酸铅类化合物[Pb5(PO4)3X,X=Cl-,OH-,F-等],利用不同廉价含磷物质进行铅污染土壤原位修复被认为是目前最好的铅污染土壤管理措施,受到国内外广泛关注。本文对目前国内外利用磷进行铅污染修复研究的现状进行了综述,对该研究领域中的关键问题,如磷酸铅类化合物形成的反应动力学过程控制、最佳pH、土壤中磷/铅摩尔比等进行了较深入的探讨,并展望了今后的研究方向,以期为铅污染土壤的修复及其效果评价提供参考。     

镉污染土壤的植物修复及其EDTA调控研究：Ⅰ、镉对富集植物印度芥菜的毒性

本通过温控盆栽试验研究在10－190mg/kg共10个浓度梯度的Cd处理下，印度芥菜生长对Cd的响应，Cd在根与地上部的积累以及在Cd胁迫和毒害条件下对Ca和Zn吸收的影响，结果表明，Cd对印度芥菜生长的毒害浓度在各个生育期各有不同：幼功期与营养生长前期在70－110mg/kg左右；营养生长后期在110mg/kg以上；成熟期在150mg/kg左右。植物吸收的镉随土壤镉处理浓度的增加而增加，本试验中印度茶菜根和叶积累镉最高浓度分别为300和160mg/kg，在Cd胁迫下，印度芥菜吸收的Ca和Zn增加，在Cd毒害条件下，印度芥菜吸收的Ca和Zn下降。认为高浓度的Cd对印度芥菜生产有抑制，但印度芥菜对镉也表现出很强的耐性，这种耐性可与植物体内Cd和Ca，Zn之间的平衡有关。     

Comparative evaluation of Ca chloride and Ca phosphate for extractable sulfur in soils with a wide range in pH

Deficiency of sulfur (S) is becoming widespread in the rainfed systems of India, and there is increasing need for diagnosing the deficiency. Calcium chloride and Ca phosphate are commonly used for extracting available S in soils. Because of cost and the ease of availability locally, we prefer using Ca chloride as an extractant over Ca phosphate, for extracting available S. However, there is paucity of data on the comparative evaluation of the two extractants to extract available S, especially in soils having a wide range in natural pH (from acidic to alkaline range). It is recognized that soil pH plays a dominant role in the adsorption–desorption and extractability of sulfate‐S in soils. We compared the extraction of S by Ca chloride and Ca phosphate in 86 Indian soils having a wide range in pH (4.5 to 10.6). Sulfur in the extracts was determined by ICP‐AES. Considering all the 86 soil samples tested, there was an excellent agreement between the values of extractable S determined by using the two extractants (r = 0.96, p < 0.001). However, the correlation coefficient (r) between the values of extractable S by the two reagents, although highly significant, varied among the groups of soil samples according to the range in soil pH. The highest correlation coefficient (r = 0.99, p < 0.0001, n = 17) was found for soils with pH in the alkaline range (8.5–10.6), and the lowest correlation coefficient (r = 0.71, p < 0.0001, n = 58) was obtained with a set of soil samples with pH in the acidic range (4.5–6.5). For soil samples having pH in the near‐neutral range (6.7–7.3), an excellent agreement was observed (r = 0.93, p < 0.0001, n =11) between the extractable‐S values obtained by the two extractants. While Ca phosphate extracted higher amount of S compared to Ca chloride in soil samples with pH in the acidic range, the two extractants were equally effective for soil samples with pH in the neutral or alkaline range. Our results suggest that for most of the soils in the semiarid tropical regions, which have pH in the neutral to alkaline range, Ca chloride can replace Ca phosphate as an extractant for removing available S in such soils.     

镉污染土壤的植物修复及其EDTA调控研究：Ⅱ．EDTA对镉的形态及其生物毒性的影响

本通过温室盆栽试验研究了10－200mg/kg共20个浓度梯度的Cd处理下，EDTA加入土壤后对Cd的形态及其生物毒性的影响，在获前一周加入EDTA，收获后测定植物根和地上部的生物量，以及H2O、NH4NO3和EDTA3种提取剂提取的Cd浓度。结果表明，EDTA加入土壤一周后，土壤水溶态Cd增加了400倍以上，交换态Cd增加了40倍以上，印度芥菜根和地上部的生长都受到抑制。可能的原因是EDTA增加了土壤中镉的移动性，提高了Cd对植物的毒性。     

Biodegradation of rhamnolipid, EDTA and citric acid in cadmium and zinc contaminated soils

Rhamnolipid, a metal sequestering agent produced by Pseudomonas Sp., has been effective in the removal of metals in soil washing technologies. Rhamnolipid has a strong affinity for cadmium (Cd) compared to some other metals (e.g. cobalt (Co), nickel (Ni)) and might also be useful in chelate-assisted phytoextraction. There have been many studies investigating the formation of metal-rhamnolipid complexes and the ability of rhamnolipid to remove metals from soil. However, to date, the longevity of rhamnolipid in soil has not been measured. Therefore, this study investigated the rate of rhamnolipid degradation in soils of varying physicochemical properties and contaminated with varying concentrations of Cd and zinc (Zn). The rate of rhamnolipid degradation was compared with ethylene diamine tetraacetic acid (EDTA) and citric acid. Our results indicate that citric acid was rapidly degraded, with 20% degradation occurring between 1 and 4 d depending on the level of soil contamination and 70% degradation within 20 d. EDTA was more persistent in the soils; only 14% of the EDTA was degraded after 20 d. Rhamnolipid had cumulative degradation between those of citric acid and EDTA. In most contaminated soils, cumulative degradation of the chelates and ligands were lower than in the uncontaminated soils. These results show that rhamnolipid may remain in the soil long enough to enhance metal phytoextraction, but not remain long enough to raise concerns regarding metal transport in the long-term.     

A method of capability evaluation for upland soils

Utilizing the data and materials accumulated in the project “Observations on Soil Fertility Changes” organized by Ministry of Agriculture and Forestry and executed by 16 Prefectural Agricultural Experiment Stations throughout Japan, an attempt was made to derive a prediction equation for soil loss due to erosion.

Five Prefectural Agricultural Experiment Stations provided us with rainfall records from which monthly rainfalls by three intensity grades, under 2 mm/10 min (LE2R), 2-4 mm 10 min (MEDRi) and over 4 mm/10 min (GT4R), were read. Multiple regression of log-transformed soil loss upon these rainfall data gave the following regression equation

Log soil loss = -0.783 0.0185**GT4R+0.00597**LE2R -0.00763**MEDR for which multiple correlation coefficient (R) was 0.74. The units of measurement were kg are for soil loss mm/month for LE2R, MEDR, and GT4R.

In order to account for the contribution of slope and soil factors to soil loss, Hayashi's theory of quantification No. I was applied after coding the relevant data. R of log-transformed soil loss on GT4R, MEDR, LE2R, slope, bulk density (BD), and texture (TEXT), reached 0.80. GT4R had the highest partial correlation coefficient, followed successively by MEDR, slope, and LE2R. Bulk density (BD) and texture (TEXT) were taken from among the data available to represent characters relevant to erosion, but they had onlv low partial correlations with soil loss in this Particular study.

The method developed in this study appears to be promising only if properly collected data are available. Conditions that should be satisfied in the planning of experiments for the purpose derivation of a prediction equation have been put forward.     

A method of capability evaluation for upland soils

As one of the important capability determinants of upland soils, fertility was taken up as the object of evaluation in this study.

On the basis of correlation analysis, factor analysis (FA) was applied to a set of 12 variates (humus, total nitrogen, available nitrogen, clay. sand, total phosphorus, Bray-P. HC1-P, CEC, percentage base saturation. exchangeable calcium, and pH).

Four mutually independent and clearly definable fertility component factors were consistently extracted from the 12 variates for the entire set of 94 surface soil samples and for different strata of the samples. The fertility status of each sample soil could be objectively designated by the scores of the four factors.

As a means of summarizing the information obtained, taxonomic distances between all pairs of the samples were computed from these 4 factor scores and subjected to numerical taxonomy. Six fertility groups were formulated, each of which was characterized by one or more of the fertility components. This fertility classification based on the present state of soil properties could be of use in pointing to the proper direction of fertility amelioration and improvement for each group of Boils.     

EDTA extractable phosphorus in soils as related to available and inorganic phosphorus forms

Abstract

Twenty surface soil samples, representing two major soil orders alfisols and vertisols were extracted with 0.01N Na₂ EDTA solution (pH 4.8) at a soil/solution ratio of 1:25. Phosphorus in the extract was determined following ammonium molybdate‐stannous chloride colorimetric method. The EDTA extractable P showed significant positive correlations with extractable P according to the Olsen, Morgan, Bray 1 and 2 and also with inorganic phosphorus fractions associated with Al, Ca and Fe.     

Comparison of EDTA and ammonium Bicarbonate-DTPA for the extraction of phosphorus in calcareous soils from Kerman,Iran

Developing a fast and reliable soil testing method is critical for improving soil testing efficiency and ensuring reliable fertilizer recommendation. The objectives of this study were to evaluate sodium ethylene diamine tetra acetic acid (Na₂-EDTA) as a replacement for ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) to extract phosphorus (P) to determinate the relationships between extractable P and its uptake by crop in calcareous soils. Na₂-EDTA and AB-DTPA was compared by the amounts of extracted P by analyzing soil samples collected from agricultural production areas. There were significant correlations between Na₂-EDTA and AB-DTPA for soil test P based on soils collected from the agricultural field. Soil test P by both extractants was significantly correlated with plant P concentration. Na₂-EDTA was identified as an alternate improved extraction method instead of AB-DTPA in calcareous soils based on this study. However, more work will be needed to identify the correlation of the two extractants and crop responses under a field condition.     

Comparative use of factor-ecological and profile-genetic classifications for studying alluvial soils

We show the feasibility of applying the 2008 profile-genetic classification for studying alluvial soils and necessity of its improvement at the genus and species levels.     

Improvement of laboratory phytotest for the ecological evaluation of soils

Analysis of methodological documents, Russian and foreign standards, and scientific publications has been performed to reveal best global practices and current trends in the improvement of laboratory phytotesting. It is proposed to increase the number of simultaneously used test cultures and the range of simultaneously controlled test functions at the first (screening) stage of phytotest to increase the information value of laboratory phytotests. Attention is focused on the assurance of the statistical reliability of test results. The advisability of creating universal regulations of Russian Federation for phytotesting methods to unify approaches to the ecological evaluation of soils.     

An assessment of EDTA as an extractant of organic-complexed and amorphous forms of Fe and Al in soils

EDTA solutions proposed as selective extractants of amorphous and organic forms of Fe and Al in soils and synthetic materials were tested. Extraction of Fe and Al from some soil samples continued at a decreasing rate beyond 120 days. For some soil samples and synthetic materials the amounts of Fe and Al extractable by EDTA (90 days) were markedly lower than those extractable by acid ammonium oxalate (2 h). Extraction of samples for 1 h with EDTA was shown to release amounts of Fe and Al far below those considered to be complexed with organic matter. The EDTA extraction procedures tested should not replace either acid ammonium oxalate for estimating amorphous forms of Fe and Al or pyrophosphate for estimating organic forms of Fe and Al in soils.     

Comparative study of selected lime requirement methods for some acid Ghanaian soils

Abstract

The acid soils of the western region of Ghana which hitherto have been relegated to forest and tree crops production are becoming increasingly important for agricultural food crop production in the country. However, on account of their strongly acidic properties, there is the need to apply agricultural lime to the soils to improve upon their productivity. At present, however, information on the lime requirement and appropriate liming practice for these soils is lacking. The objective of this study was to compare the suitability of selected chemical methods for the determination of the lime requirement to predict lime needs of these naturally occurring acid soils. The lime requirement of six acid soils were determined by calcium hydroxide [Ca(OH)₂] titration, exchangeable aluminum (Al), and Shoemaker, McLean, and Pratt (SMP) buffer methods. Correlation analysis showed that all the methods were highly correlated with one another. The SMP method was found to be somewhat better than either exchangeable Al or Ca(OH)₂ titration method for estimating the lime requirement of the soils. Hence, the SMP method is recommended for use as the diagnostic index of lime requirement of these soils because of its speed and simplicity. Regression studies on the lime requirement values by the three methods and selected soil properties showed that exchangeable Al and organic carbon were the most important soil factors contributing to the lime requirement of these soils. Clay content was significantly correlated only with the Ca(OH)₂‐based lime requirement values (r = 0.81*).     

An evaluation of chemical methods for extracting copper from rice soils

Abstract

Rice (Oryza sativaL. CV. Lemont) was grown on 19 soils, and eight extractants were evaluated for determining the availability of Cu to rice plants. Correlation analyses were employed as criteria for evaluating methods that would provide the best index of Cu availability. The order of removal of Cu from soils was: 0.5NHC1 + 0.05NA1C1₃> 0.5NHNO₃> 0.5 N HC1 > EDTA + NH₄OAc > 0.1NHC1 > EDTA + (NH₄)₂CO₃? DTPA‐TEA, pH 7.3 >>> 1 N NH₄0Ac, pH 4.8.

Uptake of Cu by rice plants was significantly correlated with soil Cu. Among the eight extractants evaluated, Cu extracted with DTPA‐TEA, pH 7.3 was better related to the concentration (r = 0.563 ) and uptake (r = 0.673 ) of Cu by rice plants grown on the soils with different chemical and physical properties.

A significant negative correlation was found between the concentration of Cu in rice plants and the organic matter content of the soils. Each one percent increase in the organic matter of the soils resulted in a corresponding decrease of approximately one mg/kg in the concentration of Cu in the rice‐plant tissue. Multiple regressions of extractable Cu by eight methods with soil organic matter content accounted for from 53.4 to 70.0% of the variations in the prediction of the concentration of Cu in the rice plants. Combinations of other soil chemical properties measured with extractable Cu did not significantly improve the predictability     

EDTA与EDDS螯合诱导印度芥菜吸取修复重金属复合污染土壤研究

盆栽试验比较研究了EDTA和易降解的EDDS对复合污染土壤中Cu、Zn、Pb、Cd的活化能力及印度芥菜对4种重金属的吸收与转运特征。结果表明:施用量相同的条件下,EDDS活化土壤Cu的能力与EDTA相当;而EDDS活化土壤Zn、Pb、Cd,尤其是活化土壤Pb、Cd的能力小于EDTA,这与两种螯合剂与不同重金属形成螯合物的稳定常数相一致。向复合污染土壤中施入3mmol/kg和6mmol/kgEDDS均可诱导印度芥菜叶中超量积累Cu。本研究中3mmol/kgEDDS的不同施用方式(单次施,分2次和4次施)对印度芥菜叶片Cu含量的影响差异不显著。各处理印度芥菜叶中的重金属浓度要远高于茎中的浓度,茎中的Cu浓度随土壤溶液Cu浓度线性增加,而叶中Cu的浓度随土壤溶液Cu浓度先增加后下降。     

An evaluation of methods for characterizing phosphate sorption in rice soils

Abstract

Two single value methods of indexing P sorption were compared to parameters derived from P adsorption isotherms in a range of waterlogged and dry rice soils. These measures of P sorption capacity correlated closely with one another. However, they did not correlate equally with several other soil properties (pH, extractable Fe and Al). Because relationships between P sorption and soil properties proved to be method dependent, results from different methods must be compared with caution.

It is suggested that the single value method of Bache and Williams² be adopted when the rapid analyses of many samples is required. It is suited to routine analysis of soils with markedly different P sorption capacities, from both waterlogged and dry conditions.

Close correlations between the single value methods and P sorbed at a standard supernatant concentration suggest they may be useful in testing soils for P fertilizer requirements.     

Complementarity of bioassays and microbial activity measurements for the evaluation of hydrocarbon-contaminated soils quality

In order to describe a soil polluted with hydrocarbons, the complementarity of bioassays and microbial activities measurements was studied. The samples of soil were taken from a site which had received oil tank residues over 50 years. Five zones were sampled. Each sample was characterized by chemical analyses, the measurement of dehydrogenase, phosphatase, hydrolysis of FDA and urease activities, soil respiration, and Microtox and Metplate bioassays. The chemical analyses revealed different levels of total hydrocarbon concentrations (from 1.5 to 78.8 mg/kg of dry soil) but also relatively high quantities of nickel (from 14.5 to 841.6 mg/kg of dry soil) and lead (30.9–355.4 mg/kg of dry soil) or cadmium (0–1.2 mg/kg of dry soil) in the different zones. Urease and dehydrogenase were sensitive to the presence of metals (31% inhibition of urease and 50% inhibition of dehydrogenase in the most contaminated soil). Measurements of Substrate Induced Respiration showed that the soil microflora were stressed in the presence of the pollutants. In the zone containing the highest concentration of metals, the microbial activities were low and the bioassays revealed a high potential toxicity (e.g. IC50 for Microtox obtained with a 15% dilution of soil, 90% inhibition of β-galactosidase activity). In the other zones, the soil microbial activities were not depressed in comparison to the reference zone whereas the bioassays revealed the presence of toxic compounds extracted with the solvent used.