Phytotoxicity of some chloroanilines and chlorophenols, in relation to bioavailability in soil

Soil adsorption and the effect of four chlorophenols and three chloroanilines on the growth of lettuce (Lactuca sativa) were determined in two soil types differing in organic matter content and pH. Adsorption increased with increasing organic matter content of the soils. Phytotoxicity, based on dosed amounts, was significantly higher in the soil with the low level of organic matter. This difference could be reduced by recalculating the EC₅₀ values for the effect of the test substances on plant growth in mg kg-1 dry soil towards concentrations in mg L-1 pore water using data from soil adsorption experiments. For pentachlorophenol only this recalculation increased rather than decreased the difference between the two soils, however, when the EC50 values for pentachlorophenol were corrected for the difference in soil pH, almost the same values resulted for both soils. Calculated EC₅₀ values on the basis of pore water concentrations appeared to be in good agreement with values determined in nutrient solution tests. These results indicate that, for plants, the toxicity and therefore the bioavailability of organic chemicals in soil mainly depend on the concentration in the soil solution, and can be predicted on the basis of sorption data. Attempts to develop QSARs relating log EC₅₀ values in μmol L^?1 pore water with lipophilicity (expressed as the octanol/water partition coefficient: log K_ow,) of the test substances resulted in a statistically significant relationship. This relationship was further improved by correcting the chlorophenol data for dissociation effects.     

土壤中氯苯类化合物的归趋过程及潜在修复策略研究进展

Chlorobenzenes (CBs) are a group of organic pollutants that pose a high environmental risk due to their toxicity,persistence and possible transfer in the food chain.Available data in literature show that CBs are detected in different environmental compartments such as soil,water,air and sediment.The widespread presence of CBs in the environment is related to their former extensive use in agriculture and industry.Some CBs are ranked in the list of priority pollutants by the Stockholm Convention,and their reduction or elimination from the environment is therefore of high importance.Environmental risk assessment of CBs requires knowledge on the role and importance of the main environmental fate processes,especially in soil.Furthermore,development of remediation strategies for reduction or elimination of CBs from the environment is related to the enhancement of fate processes that increase their dissipation in various environmental compartments.The main objectives of the current review were to present up-to-date data on fate processes of CBs in the soil environment and to explore possible remediation strategies for soils contaminated with CBs.Dechlorination of highly-chlorinated benzenes is the main degradation pathway under anaerobic conditions,leading to the formation of lower-chlorinated benzenes.Biodegradation of lower-chlorinated benzenes is well documented,especially by strains of adapted or specialized microorganisms.Development of techniques that combine dechlorination of highly-chlorinated benzenes with biodegradation or biomineralization of lower-chlorinated benzenes can result in useful tools for remediation of soils contaminated with CBs.In addition,immobilization of CBs in soil by use of different amendments is a useful method for reducing the environmental risk of CBs.     

Earthworm communities in alluvial forests: Influence of altitude,vegetation stages and soil parameters

In many terrestrial ecosystems, soil parameters usually regulate the distribution of earthworm communities. In alluvial ecosystems, few studies have investigated the impact of periodic floods and alluvium deposition on soil fauna. In this context, we assumed that earthworm communities may vary depending on altitude (alpine, subalpine, mountain and hill levels), forest successional stage (post-pioneer to mature forests) and some soil parameters. Our results demonstrated that the composition of earthworm communities differed depending on altitudinal gradients. No earthworm was found at the alpine level while maximum density and biomass were observed at the hill level mainly due to the contribution of anecic species. A total of 27 species and subspecies were found over the three sampling sites, and Lumbricus moliboeus was discovered for the first time in carbonated soils. Soil texture had a major effect on epigeics that were often associated with coarse sandy texture in contrast to anecics which preferred deep soils and mature forest stages, which in combination provided the highest carbon content and the finest soil texture. In our study, carbonated fluviosols (Fluvisols according to the World Reference Base) were recorded; fluviosols typiques with well-structured A layers were generally found in mature or intermediate forest stages while most of fluviosols juveniles with heterogeneous texture were observed principally in post-pioneer forests. We conclude that in alluvial ecosystems, earthworm communities were highly dependent first on soil parameters, then altitude and to a lesser extent forest successional stages. Changes in earthworm communities tend to reflect a gradient of alluvial dynamics thus reinforcing the potential role of earthworms as bioindicators in natural and/or semi natural alluvial ecosystems.     

Microbial and non-biological decomposition of chlorophenols and phenol in soil

The aerobic and anaerobic degradation of phenol and selected chlorophenols was examined in a clay loam soil containing no added nutrients. A simple, efficient procedure based on the high solubility of these compounds in 95% ethanol was developed for extracting phenol and chlorophenol residues from soil. Analysis of soil extracts with UV spectrophotometry showed that phenol,o-chlorophenol,p-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol were rapidly degraded, whilem-chlorophenol, 3,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol were degraded very slowly by microorganisms in aerobically-incubated soil at 23°C. Both 3,4,5-trichlorophenol and 2,3,4,5-tetra chlorophenol appeared to be more resistant to degradation by aerobic soil microorganisms at 23°C. None of the compounds examined were degraded by microorganisms in anaerobically-incubated soil at 23°C. Direct microscopic observation revealed that phenol and selected chlorophenols stimulated aerobic and to a lesser extent, anaerobic microbial growth in soil, and aerobic soil bacteria were responsible for the degradation of 2,4-dichlorophenol in aerobically-incubated soil at 23°C. Phenol,o-chlorophenol,m-chlorophenol,p-chlorophenol and 2,4-dichlorophenol underwent rapid non-biological degradation in sterile silica sand. Non-biological decomposition contributed, perhaps substantially, to the removal of some chlorophenols from sterile aerobically-incubated soil and both sterile and non-sterile anaerobically-incubated soil.     

Biological tools for the assessment of contaminated land: applied soil ecotoxicology

Abstract. Chemical analysis alone is inadequate for comprehensively assessing the impact of soil pollution on biota. The term bioavailability can only be applied in a context specific to a target biological receptor or a proven chemical surrogate. Integration of biological and chemical data can often yield significant advances in hazard assessment and act as a suitable baseline for making site-specific risk assessments. Here, the value of biological techniques is discussed and their application described. The relative merit of test selection is considered and the new direction being developed in sublethal assessments. Currently, however, one of the major limitations is the seeming lack of flexibility of many assays in that they are either applicable to agricultural systems or industrial scenarios, but rarely to both. As a consequence, few assays have internationally adopted protocols. The introduction of new methods and the continued improvement and refinement of assays make this area of soil science dynamic and responsive.     

Phosphorus solubility and sorption in frozen, air-dried and field-moist soil

The effects of freezing on soil phosphorus (P) chemistry are poorly understood, although freezing is habitual for many soils at middle and high latitudes. We studied the effects of various freezing treatments on the solubility and sorption of P in an incubation experiment on two coarse and two fine-textured cultivated surface soils in Finland. Air-drying was included in the experimental arrangement because freezing and drying have similar features. Compared with field-moist soils stored at +5°C in the dark, freezing had few effects on P extractability by water or on sorption properties of P studied with a Q/I plot technique. Air-drying, by contrast, increased almost systematically the equilibrium concentration of P estimated with Q/I plots, water-soluble organic carbon, and the extractability of P, aluminium, iron and manganese in the soils. The results imply that drying destroys organomineral complexes. The breakdown of these complexes releases P, while simultaneously exposing new surfaces on which P could sorb. Because of the considerable impact of drying on the behaviour of P, air-drying of soil samples should be avoided in studies of the chemistry of P in soil. Freezing seems to be a safe way of storing mineral soil for such studies, but it may significantly alter the P conditions of soils rich in organic matter.     

Earthworm contributions to soil nitrogen supply in corn-soybean agroecosystems in Quebec, Canada

Accurately quantifying the soil nitrogen(N) supply in crop fields is essential for enabling environmentally sustainable and economically profitable crop production. It requires using field-based methods to account for the contribution of soil biota, including earthworms, to N mineralization in temperate agroecosystems. The direct contribution of earthworms to the soil N cycle is the N they release throughout their life and after death, and it can be estimated using the secondary production method. This study was conducted in 2014 and 2015 in two adjacent fields with annual corn-soybean rotation in Ste-Anne-de-Bellevue, Quebec, Canada. The cumulative biomass of Aporrectodea spp. in two no-till corn-soybean agroecosystems was determined, and the direct N flux from these earthworms was estimated during the corn and soybean phases of the rotation. Secondary production was estimated by sampling earthworms biweekly during April–June and September–November and inferring the change in earthworm biomass between sampling dates using a size frequency calculation. The N flux was calculated as the sum of the N released through excretion, during periods when earthworms were active, and from mortality. The secondary production of the Aporrectodea population was estimated to be 8–43 g ash-free dry weight m~(-2) year~(-1), and the N flux was 22–105 kg N ha~(-1) year~(-1). The N flux was higher at the early vegetative growth stage, which is a period of high N demand for corn. These findings suggest that refining the N fertilization recommendation by accounting for soil N supplied by earthworms could potentially reduce fertilizer costs and environmental N losses.     

Ecological implications of motor oil pollution: Earthworm survival and soil health

The nontarget effects of fresh and used motor oil were studied in a soil test system involving such criteria as earthworm survival, response of soil dehydrogenase and urease, and nitrification. When earthworms were exposed to motor oil-contaminated soil for 4 weeks, the observed median lethal concentrations (LC₅₀) were 40.33 and 3.88 g kg⁻¹ soil for fresh and used oil, respectively. Only fresh motor oil application increased earthworms' body weight even at the higher dose of 19 g kg⁻¹ soil. Gas chromatography/mass spectrometry revealed that used motor oil contained more of aromatic hydrocarbons and heavy metals than fresh oil. This disparity in the chemical composition might be the factor responsible for the significant toxicity of used motor oil towards earthworms. Activities of soil dehydrogenase and urease were significantly enhanced in presence of both the motor oils, while there was a significant inhibition in nitrification by the used motor oil even at a low concentration of 0.2 g kg⁻¹ soil. This study clearly demonstrated that earthworm survival and nitrification could serve as suitable indices to assess motor oil pollution in soil.     

复垦沉积池土壤中镍、铅、锌的吸附

The wastes used to amend soils sometimes have high concentrations of metals such as nickel (Ni), lead (Pb) and zinc (Zn). To determine the capacity of soils to retain these metals, the sorption capacities of different mine soils with and without reclamation treatments (tree vegetation and waste amendment) for Ni, Pb and Zn in individual and competitive situations were evaluated using the batch sorption technique. The untreated settling pond soil had low capacity for Ni, Pb and Zn retention. The site amended with wastes (sewage sludges and paper mill residues) increased the sorption capacity most, probably because of the higher concentrations of soil components with high retention capacity such as carbon and clay fraction. No significant competition was observed between metals in the competitive sorption experiment, indicating that the maximum of sorption was not achieved by adding 0.5 mmol L^-1 of metal. We can conclude that, despite the possible additions of Ni, Pb and Zn from wastes to degraded soils, sewage sludges and paper mill residues have a high sorption capacity that would prevent the metals from being in a mobile form.     

Cadmium soil sorption at low concentrations: II. Reversibility,effect of changes in solute composition,and effect of soil aging

Water, Air, & Soil Pollution - Desorption of Cd from two Danish soils (loamy sand, sandy loam) previously exposed to low concentrations of Cd was examined in terms of reversibility, effect of...     

Earthworm response to rotation and tillage in a Missouri claypan soil

 Agricultural management practices affect earthworm populations. A field experiment was conducted to determine the effect of two rotations and two tillage systems on earthworm population density and biomass in a claypan soil. The rotations were soybean/corn and wheat/corn, and the tillage systems were conventional tillage (chisel plowed and disked) and no-tillage. Earthworm and soil samples were collected in fall 1995, spring 1996, and fall 1996. Aporrectodea trapezoides and Diplocardia singularis were the species identified at the site. A. trapezoides accounted for 92–96% of the total earthworm population density and D. singularis accounted for only 4–8%. In a no-till system, soybean/corn rotation resulted in significantly greater population density of A. trapezoides compared with the wheat/corn rotation. Crop residue quality (low C:N ratio) and quantity were important factors in increasing A. trapezoides population density and biomass. Conventional tillage markedly decreased population density and biomass of both earthworm species. Our results suggest that rotation and tillage significantly affect earthworm population density and biomass. Received: 6 June 1998     

Biochar-induced soil phosphate sorption and availability depend on soil properties: a microcosm study

Journal of Soils and Sediments - The effects of soil properties on biochar-induced soil phosphate sorption and availability are not well investigated. An alkaline biochar-induced soil phosphate...     

Earthworm effects on selected physical and chemical properties of soil aggregates

Summary Some physical and chemical properties of 1-to 2-mm aggregates obtained from casts and the burrow-wall material of the earthworm species Lumbricus terrestris, Aporrectodea longa, and Aporrectodea caliginosa were determined in order to show the effects of earthworms on the stabilization of soil aggregates. The results were compared with those of the natural soil from the Ap horizon of a Parabraunerde (Luvisol, FAO). Both the tensile strength and the water stability of aggregates from casts and burrow-wall material were reduced compared with those of the natural aggregates but were increased compared with those of remoulded aggregates. These results indicate that to a great extent existing bonds are destroyed by earthworm ingestion. Nevertheless, earthworm activities are advantageous for the stabilization of reformed aggregates. The coarse sand fraction is reduced by selective ingestion by earthworms. The organic C content is increased by 4.1–21.0% for burrow-wall material and by 21.2–43.0% for casts. The carbonate content of aggregates from casts and burrow-wall material of L. terrestris was reduced by more than 50%, while that of A. longa showed no noticeable changes and that of A. caliginosa was increased by more than 60%. The total content of polysaccharides was increased by 35–87% for casts and by 33–46% for the burrow-wall material of all earthworm species. The most frequently detected monosaccharides were glucose, galactose, and glucosamine. L. terrestris appeared to have the strongest effect on the interparticle bonding of the reformed aggregates, measured both as tensile strength and water stability, followed by A. longa and A. caliginosa.     

Microscopic observations of bacterial sorption in soil cores

 Bacterial cells may be immobilized in soil through adsorption to a variety of soil particles. These associations affect the interaction of native soil microbes with their nutrient sources and control at least in part the distribution of foreign bacteria entering the soil system. To observe the relationship between soil structure and adsorption of amended bacterial cells, a series of intact cores of Freehold fine sandy loam were inoculated with suspensions of Arthrobacter crystallopoietes cells at concentrations ranging from 10⁶ to 10⁸ cells per ml. The cells were cultivated in a glucose-based medium to induce spherical cell formation. Following inoculation, the soil cores were rinsed with sterile water (30–40 ml h^–1), flushed with thiazine red R to stain the bacterial cells, and then prepared for examination by common micromorphological techniques. The use of fluorescence, polarizing, and reflected light microscopy of soil thin sections, allowed direct, qualitative determinations of microbial distribution and associations with soil components. A. crystallopoietes cells were detected throughout the length of the soil columns. Soil pores did not appear to be clogged by the spherical A. crystallopoietes cells. Adsorption of amended bacteria was governed by the presence of both variably charged mineral oxides and organic matter within the intergrain microaggregates and occurred along coated mineral surfaces. Amendment of non-inoculated soil columns with 0.2% (w/v) solution of glucose demonstrated that the staining and sectioning procedure was sufficiently sensitive to detect growth of indigenous bacterial populations and their distributions within the soil matrix. Received; 6 April 1997     

Earthworm burrowing in laboratory microcosms as influenced by soil temperature and moisture

Earthworm burrows contribute to soil macroporosity and support diverse microbial communities. It is not well known how fluctuations in soil temperature and moisture affect the burrowing activities of earthworms. The objective of this experiment was to evaluate the maximum depth and length of burrows created by the endogeic earthworm Aporrectodea caliginosa (Savigny) and the anecic earthworm Lumbricus terrestris L. for a range of temperatures (5–20 °C) and soil water potentials (−5 and −11 kPa). The laboratory microcosm was a plexiglass chamber (45 cm high, 45 cm wide) containing 0.14 m² of pre-moistened soil and litter, designed to house a single earthworm for 7 days. Earthworm mass, surface casting and burrowing activities were affected significantly by soil temperature, moisture and the temperature×moisture interaction. Burrow length and maximum burrow depth increased with increasing temperature, but there was less burrowing in wetter soil (−5 kPa) than drier soil (−11 kPa). Weight gain and surface casting, however, were greater in soil at −5 kPa than −11 kPa. Our results suggest more intensive feeding and limited burrowing in wetter soil than drier soil. Earthworms inhabiting the non-compacted, drier soil may have pushed aside particles without ingesting them to create burrows. The result was that earthworms explored a larger volume of soil, deeper in the chamber, when the soil was drier. How these burrowing activities may affect the community structure and activity of soil microorganisms and microfauna in the drilosphere remains to be determined.     

Chemical extraction to assess the bioavailability of chlorobenzenes in soil with different aging periods

Purpose  

Bioavailability is mainly influenced by aging and desorption of contaminants in soil. The purpose of this study was to investigate the desorption kinetics of chlorobenzenes (CBs) in soil and to investigate whether chemical extractions are suitable for the bioavailability assessment of CBs in soil.     

红壤基质组分对磷吸持指数的影响

在红壤旱地肥料长期定位试验(始于1988年)中,选取了无机肥试验区的NPK、NP、NK、PK,有机无机配施试验区的CK、CK+猪厩肥(BM)及CK+花生秸秆(SR)等7个施肥处理土壤,测定了土壤磷吸持指数(Phosphate sorption index,PSI),分析了PSI与红壤最大吸磷量(Xm)的相关关系,讨论了土壤pH、有机质、黏粒、铁铝氧化物及无机磷酸盐等基质组分对PSI的影响。结果表明:长期施磷或配施有机肥均可显著降低红壤PSI值,随着土壤pH的升高、有机质及铁结合态磷酸盐(Fe-P)含量的增加,红壤PSI显著降低;土壤游离铁铝氧化物及黏粒含量越高,PSI也越大。PSI与Xm呈显著线性相关关系(Xm=0.5PSI+412.8,n=15,r=0.967**,p<0.01),因此,可以用PSI替代Xm来表征土壤固磷能力,亦可由PSI的大小来推断土壤磷的供磷能力。