Application of an algal bioassay to heavy‐metal contaminated soil samples

The aim of this study was to test the effect of heavy‐metal contamination (Cu, Zn) on the growth of Chlorella kessleri. Two soils (Chernozem and Podzoluvisol) were contaminated with several amounts of copper and zinc (100–3000 ppm), and the effects of the soil eluates on the growth of the alga were examined over several days. The soil eluates inhibited algal growth in dependence on metal concentration and soil properties. It was shown that this algal assay, which was first developed for aquatic samples, in principle seems to be suitable also in monitoring soil contamination.     

Effective bioremediation of heavy metal–contaminated landfill soil through bioaugmentation using consortia of fungi

Purpose

Heavy metals’ contamination of soil is a serious concern as far as public health and environmental protection are concerned. As a result of their persistent and toxic properties, heavy metals need to be removed from contaminated environments using an efficient technology. This study is aimed to determine the heavy metals’ (Ni, Pb, and Zn) bioremoval capacity of consortia of filamentous fungi from landfill leachate-contaminated soil.

Materials and methods

Three different groups of consortia of fungi, namely all isolated fungi, Ascomycota, and Basidiomycota, were employed for the bioremediation of the contaminated soil. A total of thirteen fungal species were used to make up the three consortia. The setup was kept for 100 days during which regular watering was carried out. Soil subsamples were collected at day 20, day 60, and 100 for monitoring of heavy metal concentration, fungal growth, and other physicochemical parameters.

Results and discussion

Highest tolerance index of 1.0 was recorded towards Ni and Zn concentrations. The maximum metal bioremoval efficiency was observed for soil bioaugmented with the all isolated fungi for Ni and Pb with the removal efficiencies as 52% and 44% respectively. However, 36% was realized as the maximum removal for Zn, and was for Ascomycota consortium-treated soil. The order for the heavy metal removal for Ni and Pb is all isolated fungi > Basidiomycota?>?Ascomycota, while for Zn is Basidiomycota?>?all isolated fungi > Ascomycota. Spectra analysis revealed the presence of peaks (1485–1445 cm^?1) only in the consortia-treated soil which corresponded to the bending of the C–H bond which signifies the presence of methylene group.

Conclusions

Soil treated using bioaugmentation had the best heavy metal removal as compared to that of the control. This suggests the contribution of fungal bioaugmentation in the decontamination of heavy metal–contaminated soil.

     

Plant–soil interactions in metal contaminated soils

The legacy of industrialization has left many soils contaminated. However, soil organisms and plant communities can thrive in spite of metal contamination and, in some cases, metabolize and help in remediation. The responses of plants and soil organisms to contamination are mutually dependent and dynamic. Plant–soil feedbacks are central to the development of any terrestrial community; they are ongoing in both contaminated and healthy soils. However, the theory that governs plant–soil feedbacks in healthy soils needs to be studied in contaminated soils. In healthy soils, negative feedbacks (i.e. pathogens) play a central role in shaping plant community structure. However to our knowledge, the nature of feedback relationships has never been addressed in contaminated soils. Here we review literature that supports a plant–soil feedback approach to understanding the ecology of metal-contaminated soil. Further, we discuss the idea that within these soils, the role of positive as opposed to negative plant–soil feedbacks may be more important. Testing this idea in a rigorous way in any ecosystem is challenging, and metal contamination imposes an additional abiotic constraint. We discuss research goals and experimental approaches to study plant–soil interactions applicable to metal-contaminated soils; these insights can be extended to other contaminated environments and restoration efforts.     

Application of soil amendments to contaminated soils for heavy metal immobilization and improved soil quality—a critical review

ABSTRACT

Today, soil metal pollution has become a significant environmental issue of great public concern. This is because soil is both a major sink for heavy metal(loid)s (HMs) released into the environment, by both pedogenic and anthropogenic activities; and also a major source of food chain contamination mainly through plant uptake and animal transfer. In addition, HM contamination of soil leads to negative impacts on soil characteristics and function by disturbing both soil biological and physiochemical properties (e.g. extreme soil pH, poor soil structure and soil fertility and lack of soil microbial activity). This eventually leads to decreased crop production. Various soil remediation techniques have been successfully employed to reduce the risks associated with HMs efflux into soil. Among these, the use of low-cost and environmentally safe inorganic and organic amendments for the in-situ immobilization of HMs has become increasingly popular. Immobilization agents have successfully reduced the availability of metal ions through a variety of adsorption, complexation, precipitation, and redox reactions. Soil amendments can also be a source of nutrients and thus can also act as a soil conditioner, improving the soil’s physiochemical properties and fertility, resulting in enhanced plant establishment in metal contaminated soils. This article critically reviews the use of immobilizing agents in HM contaminated agricultural and mining soils paying particular attention to metal immobilization chemistry and the effects of soil amendments on common soil quality parameters.     

Remediation of heavy metal(loid)s contaminated sediments—in situ iron treatment and subsequent magnetic extraction

Purpose

Surface sediments contaminated with high levels of multiple heavy metal(loid) species are very common environmental problems. Especially, the labile and bioaccessible fractions of heavy metal(loid)s in the sediments are posing serious risks to the biota and the overlaying water quality. This study aimed at developing a potential method to manage the activity of the labile fractions of heavy metal(loid)s in surface sediments.

Materials and methods

This study assessed the feasibility of adding iron powder, a low-cost industrial by-product, to sediments containing high levels of Pb, As, and Cd to adsorb labile fractions of heavy metal(loid)s onto the sorbent surfaces and to retrieve the heavy metal(loid) laden powders by applying external magnetic field. In addition, the redistribution of Pb, Cd, and As in different sediment fractions, the dissolved fraction and the sorbent-adsorbed fraction, was also investigated and characterized.

Results and discussion

The results indicate that the bioactive labile fractions (exchangeable and carbonate-bound fractions) of heavy metal(loid)s are prone to concentrating onto iron powders and can be selectively removed from the sediments by magnetic retrieval. In addition, iron addition induces conversion of labile fractions of heavy metal(loid)s into more stabilized fractions.

Conclusions

Overall, the process can effectively minimize the activity of labile fractions of heavy metal(loid)s in surface sediments.

     

From soil to rice – a typical study of transfer and bioaccumulation of heavy metals in China

For the purpose of studying the contamination, bioaccumulation and transfer of heavy metals and understanding the effects of soil properties on these, the work was carried out on a regional scale. A total of 30 sets of soil and pairing rice tissues samples (root, straw and grain) were collected in Xiangzhou of Guangxi, China; soil properties and Cd, Cu, Pb and Zn of different rice tissues were analyzed. The mobility and bioaccumulation of Cd, Cu, Pb and Zn were assessed by transfer coefficients and bioaccumulation factors of them. The results indicated that the excess proportions of Cd and Pb were 50%, 3.33% and 30%, 6.67% in soil and rice grain, respectively, according to Chinese maximum permitted concentrations of heavy metals. Cd and Zn showed stronger bioaccumulation and mobility capability; the bioaccumulation and transfer of Cu were slightly lower than Cd and Zn; Pb had the weakest mobility. The bioaccumulation and mobility of heavy metals from soil to rice were restrained by soil pH, CaO, SOC, Fe oxides and Mn.     

Changes in organic matter and enzymatic activity of an agricultural soil amended with metal‐contaminated sewage sludge compost

Abstract

The effect of organic amendment with sewage sludge composts of varying heavy metal content on the organic matter content and enzymatic activity of an agricultural soil supporting barley (Hordeum vulgare L.) or lettuce (Lactuca sativa L.) crops was studied. The organic amendments did not improved lettuce growth, the contaminated composts having a negative effect on yield. However, all organic amendments improved barley straw yields although they did not affect grain yields. The addition of the organic materials increased the total carbohydrate content of the soil although this content decreased with cultivation. There was a clearly observed effect of crop type and the degree of heavy metal contamination of the amendment on the most labile carbon (C) fractions (water‐soluble C, carbohydrates, and polyphenolics). In general, soil enzymatic activities were stimulated by addition of sewage sludge compost with low heavy metal content. The compost containing high level of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) inhibited protease‐BAA activity with respect to the other composts. After cultivation, urease activity increased in soil amended with the high dose of composts, regardless their degree of metallic contamination. Both crop type and metallic contamination contained in the organic materials added influenced phosphatase and ß‐glucosidase activity.     

Chemical fractions of copper and zinc in organic‐rich particles from aqueous extracts of a metal‐contaminated granite soil

Abstract

Chemical fractions of copper (Cu) and zinc (Zn) in the organic‐rich particles collected from filtered aqueous extracts (<20 μm) of an acid soil were determined. A sequential extraction procedure was used to partition the particulate Cu and Zn into four operationally defined chemical fractions: adsorbed (ADS), iron (Fe) and manganese (Mn) oxides bound (FeMnOX), organic matter bound (OM) and residual (RESD). Total extractable concentrations of Cu and Zn in the fine particles were higher than their total concentrations in the original bulk soil. The concentration of particulate Cu was usually much higher than that of particulate Zn. Addition of lime stabilized sewage sludge cake and/or inorganic metal salts markedly increased the concentrations of particulate Cu and Zn in aqueous extracts, especially from limed soil. The proportional distributions of particulate Cu and Zn were quite similar. The two particulate metals were present predominantly in the ADS and FeMnOX fractions, with less (about 20%) in the OM and RESD fractions. Some of the ADS metal fraction was associated with dissolved organic substances. The concentrations of particulate Cu and Zn in the various extractable fractions were significantly affected by the application of lime, lime stabilized sewage sludge cake, or inorganic metal salts.     

The effect of concentrations and properties of phenanthrene, pyrene, and benzo(a)pyrene on desorption in contaminated soil aged for 1 year

Purpose

The choice and timing of microorganisms added to soils for bioremediation is affected by the dominant bioavailable contaminants in the soil. However, changes to the concentration of bioavailable PAHs in soil are not clear, especially when several PAHs coexist. This study investigated the effects of PAH concentration and chemical properties on desorption in meadow brown soil after a 1-year aging period, which could reflect changes of PAH bioavailability during bioremediation.

Materials and methods

Based on the percentage of different molecular weights in a field investigation, high-level contaminated soil (HCS) and low-level contaminated soil (LCS) were prepared by adding phenanthrene (PHE), pyrene (PYR) and benzo(a)pyrene (BaP) to uncontaminated meadow brown soil. The concentrations of HCS and LCS were 250 mg?kg^?1 (PHE, PYR, and BaP: 100, 100, and 50 mg?kg^?1) and 50 mg?kg^?1 (PHE, PYR, and BaP: 20, 20, and 10 mg?kg^?1) respectively. The soils were aged for 1 year, after which desorption was induced by means of a XAD-2 adsorption technique over a 96-h period.

Results and discussion

The range of the rapidly desorbing fraction (F _rap) for PHE, PYR, and BaP in HCS and LCS was from 1.9 to 27.8 %. In HCS, desorption of PYR was most difficult, and the rate constant of very slow desorption (K _vs) of PYR was 8 orders of magnitude lower than that of BaP, which had similar very slow desorbing fractions (49.8 and 50.5 %, respectively). However, in LCS, desorption of PYR was the easiest; the K_vs of PYR was 8–10 orders of magnitude higher than those of PHE and BaP. In HCS, the time scale for release of 50 % of the PAHs was ranked as BaP?>?PYR?>?PHE, while in LCS this was BaP?>?PHE?>?PYR.

Conclusions

The combined effect of PAH concentrations and properties should be taken into account during desorption. The desorption of PAH did not always decrease with increasing molecular weight, and the desorption of four-ring PAHs might be special. These results are useful for screening biodegrading microbes and determining when they should be added to soils based on the dominant contaminants present during different periods, thus improving the efficiency of soil bioremediation.     

Microbial reduction of dinitrotoluene sulfonates in TNT red water–contaminated soil

Journal of Soils and Sediments - Large quantities of TNT red water which contained mainly dinitrotoluene sulfonates (DNTS) were produced during the production of TNT, threatening the surrounding...     

Physico‐chemical heterogeneity of superficial soil layers in conifer plantations versus original broad leaf forests in Ariege (Pyrenees,France)

Abstract

Changes in physico‐chemical properties of superficial soil layers following the substitution of broad leaf trees by conifers have been studied in four Pyrenean sites. Parameter values may change significantly from native to reforested plots, but sometimes in opposite directions. Initial conditions (historical, pedological, and climatic) were not the same in each plot and the present A soil horizon is highly dependent on these. A lessening of organic matter degradation and humification conditions can be, however, inferred from direct humus observations, but differences between physico‐chemical properties in native and reforested plots are, nevertheless, quantitatively low, particularly in the pH range usually appropriate for conifer plantations.     

Assay and properties of 1,3-β-glucanase in soil

1.3-β-Glucanase (laminarinase) activity in soil was measured using laminarin as the substrate. Activity was optimal in sodium acid-maleate buffer at pH 5.4 and followed Michaelis-Menten kinetics. Three methods of analysing kinetic data gave K_m values of 0.23, 0.21 and 0.20 mg.ml^?1. V_max values were 0.41, 0.39 and 0.39 μmole glucose, g^?1. h^?1. The activation energy of the reaction was 49 kJ. mole^?1. A proportion of the activity was highly resistant to storage at various temperatures: at 50 C 1,3-β-glucanase had a half-life of 28 days.     

Accumulation mechanism of γ-aminobutyric acid in tomatoes (Solanum lycopersicum L.) under low O2 with and without CO2

The storage of ripe tomatoes in low-O(2) conditions with and without CO(2) promotes γ-aminobutyric acid (GABA) accumulation. The activities of glutamate decarboxylase (GAD) and α-ketoglutarate-dependent GABA transaminase (GABA-TK) were higher and lower, respectively, following storage under hypoxic (2.4 or 3.5% O(2)) or adjusted aerobic (11% O(2)) conditions compared to the activities in air for 7 days at 25 °C. GAD activity was consistent with the expression level of mRNA for GAD. The GABA concentration in tomatoes stored under hypoxic conditions and adjusted aerobic conditions was 60-90% higher than that when they are stored in air on the same day. These results demonstrate that upregulation of GAD activity and downregulation of GABA-TK activity cause GABA accumulation in tomatoes stored under low-O(2) conditions. Meanwhile, the effect of CO(2) on GABA accumulation is probably minimal.     

Response surface methodology to understand the anaerobic biodegradation of organochlorine pesticides (OCPs) in contaminated soil—significance of nitrate concentration and bioaccessibility

Purpose

Problems associated with Organochlorine pesticide (OCP)-contaminated soils have received wide attention. To understand the anaerobic biodegradation process constraints, innovative mathematical analysis methods are effective.

Materials and methods

Response surface methodology (RSM) and Tenax TA extraction method combined with the first-three-compartment model were employed to systematically investigate the role of nitrate concentration and bioaccessibility enhancer (methyl-β-cyclodextrin, MCD) in the anaerobic biodegradation of OCPs in contaminated soil.

Results and discussion

The sole addition of either KNO₃ or MCD could facilitate the anaerobic biodegradation of OCPs. The highest biodegradation for total OCPs, hexachlorocyclohexanes, endosulfans, and chlordanes were 71.6, 82.1, 68.3, and 55.6 %, respectively, when 20 mM KNO₃ and 3.0 % (w/w) MCD were applied simultaneously. As predicted by RSM, the theoretical maximum biodegradation for total OCPs ranged from 60 to 80 % when 20 to 25 mM KNO₃ and >2.5 % (w/w) MCD were applied simultaneously. Tenax TA extraction method demonstrated the enhancement of OCP bioaccessibility caused by MCD addition. Changes in the soil microbial activities also suggested the positive effects of adding suitable amounts of KNO₃ as a cosubstrate to facilitate the anaerobic biodegradation of OCPs.

Conclusions

The amount of KNO₃ and MCD are crucial in influencing OCP biodegradation. RSM was demonstrated to be a powerful tool to estimate and predicting the optimal OCP biodegradation under KNO₃ and MCD application simultaneously.     

Control of arsenic toxicity in rice plants grown on an arsenic‐polluted paddy soil

Abstract

Paddy soils of over 500 hectares had been polluted by arsenic (As) from tailings at an abandoned lead‐zinc mine at Shaoxing, Zhejiang, China. Several field experiments were conducted to establish measures for reducing As toxicity to rice plants. The results obtained were as follows. Fresh Chinese milkvetch (Astragalus sinicus L.) was not supposed to be used as green manure in arsenic polluted paddy soils. Although liming (1,500 kg CaO hectare^‐1) could reduce water‐soluble As (H₂O‐As) in the soil, the rice plant grew badly. The treatments of FeCl₃ (25 mg Fe kg^‐1 soil) and MnO₂ (25 mg Mn kg^‐1 soil) could markedly lower the H₂O‐As and arsenite [As(III)] percentage in the soil and make the plant grow better than the control experiment (CK). Without adding any materials to the soil, wetting and drying (furrowing and draining) in the paddy soil could increase soil redox potential greatly and lower the H₂O‐As and As(III) percentage obviously leading to better rice growth. In addition, the As contents of roots, flag leaf, grain, and husked rice of 11 new cultivare of early rice were determined and correlation analysis was conducted. Uptake and accumulation of As in different parts of cultivars Zhefu‐802 and Erjiufeng at the 4 As levels of the paddy soil demonstrated that the As contents in husked rice of both cultivars exceeded the hygienic standard (0.7 mg As kg^‐1) when they grew in the paddy soil having total As content of about 70 mg kg^‐1 for Zhefu‐802 and 100 mg kg^‐1 for Erjiufeng, respectively.     

Relationship of soil properties to p‐fixing capacity of soils in northern Idaho

Abstract

Phosphorus sorption studies were conducted on volcanic ash influenced surface horizons of 29 northern Idaho soils. Results show that the amount of P sorbed was significantly correlated with citrate‐dithionite extractable aluminum (r = .64**), but not with Fe. Other significantly correlated soil properties were: percent base saturation (r = ‐.73**), percent clay (r = .42**), and exchangeable acidity (r = .39*).     

Changes in physico-chemical and biological properties of soil under conservation agriculture based pearl millet – mustard cropping system in rainfed semi-arid region

Poor soil health and low soil water content during crop growing period are major factor for low productivity of pearl millet – mustard rotation under rainfed semi-arid regions. The authors evaluated five different tillage and residue management practices for improving physico–chemical and biological properties of soil. Results showed that conservation agriculture (CA) practice (zero tillage (ZT) with 4 t ha^–1 residue retention) exhibited higher proportion of soil macro-aggregate. It also increased infiltration rate of about 15.2% over conventional tillage without residue but ZT increased soil penetration resistance in surface soil layer. In the residue applied plots, ~2–4% (w/w) higher soil water content was maintained throughout the season than the no-residue plots. CA practice had the highest soil organic carbon (4.96 g kg^–1) and microbial biomass carbon (188.3 μg g^–1 soil). Significant and positive correlation was also found between soil organic carbon with infiltration rate (r = 0.73**), mean weight diameter (r = 0.80**) and microbial biomass carbon (r = 0.86**). Thus, this study suggests that ZT with residue retention can be advocated in pearl millet – mustard rotations for improving, productivity, soil health and maintaining higher soil water content in rainfed semi-arid regions.     

How do properties and heavy metal levels change in soils fertilized with regulated doses of urban sewage sludge in the framework of a real agronomic treatment program?

Purpose

This field study was performed to assess the variation in chemical and agronomic properties and total and extractable concentrations of heavy metals in soils fertilized with regulated doses of urban sewage sludge (USS) for 6 consecutive years in the framework of an agronomic treatment program.

Materials and methods

Chemical and agronomical properties, total contents and extractable concentrations of Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in agricultural soils treated with USS for 6 consecutive years, agricultural soils cultivated using mineral fertilizers and uncultivated soils representative of the local geochemical background.

Results and discussion

USS application caused a decrease in pH and an increase in extractable concentrations of Cr, Cu, Pb and Zn. No organic carbon, total nitrogen and total phosphorus enrichment trend was observed in the treated soils due to biodegradation of the organic compounds supplied by USS. The decomposition of USS organic matter was presumably the main process responsible for the pH decrease in the USS-fertilized soils. There was no heavy metal accumulation in treated soils, and total heavy metal contents were below the corresponding maximum threshold concentrations set by European and Italian legislation. Increased availability of Cr, Cu, Pb and Zn was found in treated soils due to an increase in their extractable concentrations in the treatment period.

Conclusions

The results of this study suggest that the environmental risks related to the accumulation and availability of heavy metals in agricultural soils fertilized with USS are limited when treatment observes recommended doses in agronomic treatment programs.

     

Characterization of a landrace collection for Tomàtiga de Ramellet (Solanum lycopersicum L.) from the Balearic Islands

Tomàtiga de Ramellet (Ramellet) is a traditional long-storage tomato from the Mediterranean Islands of Mallorca, Menorca, Eivissa (Ibiza), and Formentera (Balearic Islands). To investigate the observed phenotypic and shelf life variability within local varieties, we studied 142 accessions characterized as Ramellet varieties, and 29 accessions representing other local varieties. The 171 accessions constitute a new germplasm collection at the University of Balearic Islands (UIB). The evaluation of the collection demonstrated wide variability in most agronomic, morphological and quality traits of Ramellet accessions and clearly differentiates them from other local varieties with respect to fruit shape, size, fruit composition, and fruit storage. All accessions of Ramellet evaluated have the ripening mutation alcobaça (alc), suggesting an important role for this variant in controlling shelf life. Results of evaluation also showed wide variability between the Ramellet accessions for storage time, suggesting that other traits like fruit size and composition may play a role in fruit conservation. Observed variation within the Ramellet accessions is consistent with a genetically variable population or landrace group. The establishment of this collection will help prevent genetic erosion of this local landrace group and constitute a resource for future investigation and breeding.     

Effect of nitrogen and phosphorus on ‘delicious’ apple trees grown in caliche soil in the greenhouse

Abstract

In a greenhouse study, mono‐ammonium phosphate applications to ‘Delicious’ (Oregon spur cv) apple trees, Malus domestica Borkh., improved a low‐vigor condition associated with a caliche soil. The moderate rate of mono‐ammonium phosphate (6 grams per tree) resulted in trees with greater shoot extension, leaf numbers, a higher percent leaf phosphorus, and less purple leaf margins or spots than other soil treatments or the control. By September, trees treated with the highest rate of mono‐ammonia phosphate (12 grams per tree) had the highest level of leaf phosphorus and significantly higher levels of leaf phosphorus than all forms of nitrogen‐only fertilizer (ammonium nitrate, ammonium sulfate, calcium nitrate, and urea). In most cases, applications of the nitrogen‐only fertilizers, reduced leaf phosphorus levels throughout the experiment.