Remediated Soil Research Articles

Enhanced oxidative activation of chlorine dioxide by divalent manganese ion for efficient removal of PAHs in industrial soil

Chlorine dioxide (ClO2) takes effect as a promising chemical oxidant to remove polycyclic aromatic hydrocarbons (PAHs) from contaminated soil in situ. However, the conventional ClO2 degradation procedure is limited by its reaction selectivity to organic pollutants, as well as its low economic efficiency with huge dosage. Systematical study of activated ClO2 oxidation which is more efficient to remove PAHs in soil is still scarce. Herein, the impact of divalent manganese ion [Mn(Ⅱ)] on activating ClO2 to oxidize PAHs in real contaminated soil was currently studied, including the kinetics, degradation products, mechanisms, and biological toxicity. The results revealed that the PAHs removal rate constants (k1) had a quadratic relationship with Mn(II) concentrations (k1 = -0.005 × [Mn(Ⅱ)]2 + 0.0033 × [Mn(Ⅱ)] + 0.0222, R2 = 0.9084, [Mn(Ⅱ)] = 0 ∼ 5 mM), the best degradation performance was obtained when the molar ratio of Mn(II)/ClO2 was 1/20. Furthermore, the optimal initial ClO2 concentration of 2500 mg/L could satisfy the comprehensive considerations of efficiency and economy. At the pH range of 3 ∼ 11, the removal efficiency decreased with increasing pH. Four representative PAH congeners (anthracene, phenanthrene, pyrene, and fluoranthene) had been chlorine substituted and oxygenated, but benzene ring rupture was observed only in fluoranthene simultaneously. XPS spectra, EPR analysis, and quenching experiments indicated the mechanisms that HOCl and •OH were the principal active species in the oxidation reaction. The toxicity evaluation by earthworms Eisenia fetida resulted out that high toxic effect to organism still remained in remediated soil which should be paid attention to.

Application of Pteris vittata L. for phytoremediation of arsenic and biomonitoring of the process through cyto-genetic biomarkers of Trigonella foenum-graecum L.

The arsenic (As) contamination demands its remediation from the environment which is naturally possible by the application of Pteris vittata L. However, biomonitoring of phytoremediation potential of P. vittata at chromosomal and DNA level is still meager. The present study was designed to biomonitor the phytoremediation efficiency of P. vittata through phytotoxic and cyto-genotoxic biomarkers assessment using Trigonella foenum-graecum L. (Fenugreek; Methi) as test system. Study revealed hyperaccumulation potential of P. vittata which extracted arsenic in its tissues. Biomonitoring evaluation depicted that phytotoxic damage was reduced in Trigonella exposed to remediated soil, which was revealed through reduced electrolyte leakage, hydrogen peroxide and MDA content. Moreover, cyto-genetic endpoints like mitotic depression (44.03%), relative abnormality rate (16.6%) and chromosomal abnormality frequency (1.06%) were also lesser in test plants grown in remediated soil compared to those grown in non-remediated soil. Along with this various chromosomal aberrations like stickiness, breaks, laggards, bridges, fragmentations and micronuclei were also augmented in test plants exposed to non-remediated arsenic enriched soil. It was evident that arsenic enriched soil caused toxicity to plants in dose-dependent manner that was assessable through the analysis of biochemical parameters and cyto-genetic biomarkers. The cyto-genetic biomarkers are very efficient, simple and non-expensive tools to biomonitor arsenic toxicity at chromosomal as well as DNA level to assess the remediation potential of P. vittata in field conditions.

Changes in organic matter composition caused by EDTA washing of two soils contaminated with toxic metals

Two soils contaminated with potentially toxic metals (PTMs) contrasting in pH and mineralogy were remediated with CaEDTA, and changes in soil organic matter (SOM) composition were investigated. Previous studies showed no significant loss of SOM from CaEDTA-treated soils, but the results of our study reflected significant decreases (from 46 to 49%) in the free fraction of humic acids (HAs). Remediation affected the composition of the free HA fraction via disturbance of intermolecular bonds — an increase in phenolic and aromatic groups with a simultaneous decrease in carbohydrates — which was confirmed by FTIR spectroscopy in both soils. Because non-radical molecules such as carbohydrates were selectively removed, the concentration of free radicals in the free HA fraction increased in acidic soil. The bound fraction of HAs and fulvic acids (FAs) in SOM, which are important due to their stability and the permanent effects they have on the soil’s physical properties, remained unchanged in both remediated soils. The effect of soil recultivation was observed only in the excitation emission matrix (EEM) fluorescence spectra of HAs. In terms of SOM, CaEDTA soil washing can be considered moderately conservative; however, the restoration of free humic fractions is likely to be a long-term process.

Evaluation of Phytoremediation Potential of Pteris vittata L. on Arsenic Contaminated Soil Using Allium cepaBioassay.

The present study assessed the utility of Allium cepa based cyto-genotoxicity bioassays in evaluating the arsenic toxicity and remediation potential of Pteris vittata on contaminated soil of Lakhimpur-Kheri district. Untreated and P. vittata treated soil extracts were used for cyto-genotoxicity tests in A. cepa. Results showed that P. vittata extracted high concentration of arsenic, which ranged from 220 to 1420 mgkg-1 in different soils. Cyto-genotoxic assessment of A. cepa showed that extract of P. vittata treated soil had lower cyto-genotoxic effects as compared to untreated soil. A higher mitotic index (10%) while lower mitotic depression (29%), relative abnormality rate (10%), chromosomal aberrations (1%) and micronuclei (2%) were detected in root meristematic cells of A. cepa exposed to remediated soil extract in comparison to untreated soil. The studies provide a simple, rapid and economic cyto-genotoxicity bioassay tool for evaluating toxicity of contaminated soils of contaminated soils as well as revealed the phytoremdiation property of P. vittata against arsenic toxicity.

Two-step calculation method to enable the ecological and human health risk assessment of remediated soil treated through thermal curing

The centralized utilization of heavy-metal-contaminated soil has become the main strategy to remediate brownfield-site pollution. However, few studies have evaluated the ecological and human health risks of reusing these remediated soils. Considering Zn as the target metal, systematic pH-dependent leaching and the Community Bureau of Reference (BCR) extraction were conducted at six pH values (pH = 2, 4, 6, 8, 10, 12) for the remediated soil treated through thermal curing. The pH-dependent leaching results showed that with the formation of ZnCr2O4 spinel phases, the remediated soil exhibited strong inherent resistance to acidic attack over longer leaching periods. Furthermore, the BCR extraction results showed that the leaching agent pH value mainly affected the acid-soluble fraction content. Moreover, a strong complementary relationship was noted between the leaching and acid-soluble fraction contents, indicating that the sum of these two parameters is representative of the remediated soil risk value. Therefore, we proposed a two-step calculation method to determine the sum of the two heavy metal parameters as the risk value of remediated soil. In contrast to the traditional one-step calculation method, which only uses the leaching content as the risk value, this two-step calculation method can effectively avoid underestimating the risk of remediated soil.

Физиологическая активность рекультивированных аллювиальных почв при разном остаточном содержании нефтепродуктов

The respiratory activity parameters of various types of alluvial soils with different residual content of oil products were studied. The inhibitory effect of oil products on basal respiration in re-cultivated soils was not found. The substrate-induced respiration of most soils remained at the control level or decreased slightly. Soils differed significantly in the degree of resistance of their microbial pool to oil products. The microflora of alluvial soils is able to overcome the negative effects of high oil concentrations. In remediated soils, a strong effect of oil on the community of soil microorganisms was not found, while medium or low impact prevailed. Microbial communities of light alluvial soils showed more resistance to oil products. Restoration measures on alluvial meadow soils require more attention than remediation of alluvial bog and meadow soils.

Demonstration gardens with EDTA-washed soil. Part III: Plant growth, soil physical properties and production of safe vegetables

In previous reports large-scale EDTA-based soil washing using ReSoil® technology was demonstrated. In the current study, we established a vegetable garden with nine raised beds (4 × 1 × 0.5 m), three with original (contaminated) soil, three with remediated soil, and three with remediated soil vitalized by addition of vermicompost, earthworms, and rhizosphere inoculum. The garden was managed in 6 rotations between July 2018 and November 2019. Buckwheat was sown first as a green manure followed by spinach, lamb's lettuce, chicory, garlic, onion, leek, lettuce, carrot, kohlrabi and spinach again. Buckwheat growth on the remediated soil was reduced by half. Throughout the gardening process there were no remarkable differences in bulk density, hydraulic conductivity, available water capacity, and aggregate stability of the original and remediated soil. Biomass yield and plant performance, as measured by NDVI, also remained similar regardless of soil treatment. Remediation reduced Pb concentration in edible parts of vegetables from 76 (garlic) to 95% (kohlrabi), Zn concentration from 14 (lettuce) to 76% (first cutting of chicory), and Cd concentration from 33% (carrot) to 91% (leek and second cutting of chicory). The transfer of metals from soil to root and from root to shoot occurred in the order: Pb < Zn < Cd. The bioconcentration of toxic metals in edible plant parts was generally lower in the remediated soils. Application of ReSoil® technology and growing vegetables that exclude metals, especially Cd, has potential for safe food production on remediated soils. Vitalization had little effect on the properties of the remediated soil.

Environmental and socioeconomic impacts of pipeline transport interdiction in Niger Delta, Nigeria

Over the years, pipelines have been the most economic medium for transporting crude oil to production and distribution facilities in the Niger Delta area of Nigeria. However, damages to the pipelines in this area by interdiction have hampered the continuous flow of crude oil to the facilities. Consequently, the revenue of the government dwindles, and the environment is severely degraded. This study assesses the economic and environmental impacts of pipeline interdiction in the Niger Delta region. Data from National oil spills detection and response agency, Nigeria is used to map spatial distribution of oil spills using Kernel Density Estimation with Geographic Information System. Literature was assessed to synthesize the historical, socioeconomic, and environmental impacts of oil spills and pipeline interdiction. Soil samples were collected from study area to determine the types of hydrocarbon pollutants and their concentrations in comparison with uncontaminated sites in the area. Results show that the range of concentrations of total petroleum hydrocarbon (TPH) for the impacted soil (IMP) was 17.27–58.36 mg/kg; remediated soil (RS) was 11.73–50.78 mg/kg which were higher than the concentrations of 0.68 mg/kg in the control samples (CS). Polycyclic aromatic hydrocarbons (PAH) concentrations were in the range of 0.43–77.54 mg/kg for IMP, 0.42–10.65 mg/kg for RS, against CS value of 0.49 mg/kg while BTEX ranged between 0.02 – 0.38 mg/kg for IMP, 0.01–2.7 for RS against CS value of 0.01. The values of the PAH were higher than the limits of the Department of Petroleum Resources, Nigeria. This study also revealed that pipeline interdiction has affected the livelihood of the inhabitants of the study area and the revenue of the Nigerian government. The major hotspots for oil spills in the Niger Delta region are Bayelsa, Rivers and Delta states.

Mineralization of Organic Matter in Oil-Polluted and Remediated Oil-Polluted Soils in the Middle Taiga Zone of West Siberia under Laboratory Conditions

Mineralization of Organic Matter in Oil-Polluted and Remediated Oil-Polluted Soils in the Middle Taiga Zone of West Siberia under Laboratory Conditions

Durability of sorption of per- and polyfluorinated alkyl substances in soils immobilized using common adsorbents: 2. Effects of repeated leaching, temperature extremes, ionic strength and competing ions

Persistent use of aqueous film-forming foams containing per- and polyfluoroalkyl substances (PFASs) in firefighting has led to severe contamination of soil and aquifers at training sites, which makes remediation of such sites a necessity. We investigated the persistence of binding of PFASs to a mixed-mode remediation agent including repeated leaching, and the effects of competing ions and temperature extremes. The sorbent (RemBind®) was added to PFAS-contaminated soils and standard leaching procedures - the U.S. EPA Multiple Extraction Procedure and the U.S. EPA Leaching Environmental Assessment Framework were applied to quantify desorption of PFASs from remediated and unremediated soils. Possible desorption by competing anions such as orthophosphate (H2PO4−) and humic acid (HA) were assessed, and effects of temperature extremes and ionic strength were also investigated. These are the main environmental factors that could potentially affect desorption of PFASs over time at a typical site. Desorption of PFASs from unremediated soils was related to C-chain length with short-chain PFASs easily desorbed and leached. PFASs with carboxylic head groups leached faster than those with a sulfonic acid head group. The sorbent retained PFASs strongly and reduced desorption and leaching from remediated soils by 92 to 99.9%. There were no detrimental effects on desorption of PFASs from temperature extremes or changes in ionic strength. In remediated soils, effects of competing ions were also absent or minimal. However, in unremediated soils increasing concentrations of orthophosphate and HA increased leaching of some long-chain PFASs. While short-term laboratory desorption experiments cannot exactly mimic long-term field conditions, these results provide site owners and regulatory authorities with a high level of confidence that PFASs binding by RemBind® is predicted to be persistent in the long term. However, to give the greatest level of confidence, these simulations should be validated under field conditions for at least several years.

Durability of sorption of per- and polyfluorinated alkyl substances in soils immobilised using common adsorbents: 1. Effects of perturbations in pH

The global problem of groundwater being contaminated with per- and polyfluoroalkyl substances (PFASs) originating from highly contaminated soils has created a need to remediate these locations. In situ immobilisation of PFASs in soil by applying sorbents is often a preferred low-cost technique to reduce their mobility and leaching to groundwater, but the long-term efficacy of sorbents has not yet been investigated. In this study, the longevity of remediation of two different soils by two common sorbents (RemBind®, and pulverized activated carbon, Filtrasorb™ 400) was assessed. Regulatory agencies often rely on standardised leaching procedures to assess the risk of contaminant mobility in soils. Hence, the Australian Standard Leaching Procedure and the U.S. EPA Leaching Environmental Assessment Framework were applied to quantify the desorption/leaching of a wide range of PFASs from unremediated and remediated soils under a range of pH conditions (pH 2 to 12). Ease of desorption and subsequent leaching from the unremediated soils was related to C-chain length; while short-chain PFASs were easily desorbed and leached, long-chain PFASs were more difficult to desorb. Desorption of long-chain PFASs was also pH dependent in unremediated soils, with desorption being greater at high pH. Both sorbents retained PFASs strongly in the remediated soils (> 99% for most PFASs) across a broad range of pH conditions, with only small differences between the sorbents in terms of efficacy. Both sorbents showed better retention of PFASs under low pH conditions. Remediation of PFAS-contaminated soils with these sorbents could be considered robust and durable in terms of changes in soil pH, with little risk of subsequent PFASs desorption under normal environmental pH conditions. Ultimately, to give regulators and site owners the greatest level of confidence that immobilisation is stable for the longer term, it should also be tested under repeated cycles of leaching and under different conditions.

Changes in Soil Health with Remediation of Petroleum Hydrocarbon Contaminated Soils Using Two Different Remediation Technologies

For sustainable soil management, there is an increasing demand for soil quality, resilience, and health assessment. After remediation of petroleum hydrocarbon (PHC)-contaminated soils, changes in the physicochemical and ecological characteristics of the soil were investigated. Two kinds of remediation technologies were applied to contaminated soils: land farming (LF) and high temperature thermal desorption (HTTD). As a result of total petroleum hydrocarbons (TPH), PHC-contaminated soils were efficiently remediated by LF and HTTD. The soil health could not be completely recovered after the removal of pollutants due to adverse changes in the soil properties, especially in soil enzyme activities. Therefore, monitoring is necessary for accurate estimation of soil ecotoxicity and effective remediation, and additional soil management, such as fertilizer application or organic amendments, is needed to restore soil heath. In the case of HTTD, soil ecological properties are severely changed during the remediation process. The decision to reuse or recycle remediated soils should reflect changes in soil quality. HTTD is a harsh remediation method that results in deterioration of soil fertility and ecological functions. Alternatives, such as low-temperature thermal desorption or additional soil management using fertilizer or organic amendments, for example, are needed.

Changes in Soil Properties after Soil Washing of Metal-contaminated Soil near the former Janghang Smelter

Objectives : Changes in soil properties after washing of metal-contaminated soil near the former Janghang Smelter were investigated in this study. Contaminated input soils and remediated output soils were sampled from three different soil washing plants and analyzed for soil physical and chemical properties. Soil quality was evaluated by the soil fertilization guideline suggested by the Korea Rural Development Administration (KRDA). This study revealed the necessity of soil quality management for the remediated soil as an ecosystem member.Methods : Three soil washing plants (1OU, 2OU, 3OU) were commonly divided into the five steps: 1) the particle separation (crushing and grinding etc.) → 2) soil particle classification (big stone, fine soil, minimal fine soil) → 3) chemical washing (fine soil) → 4) neutralization of washed soil (lime) → 5) return-back to the original position. The separating minimum particle diameters of the 1OU, 2OU, and 3OU washing processes were 5 µm, 20 µm, and 10 µm, respectively, and the chemical washing solutions used were respectively 0.1 M H2SO4, 0.5 M H2SO4/0.5 M H3PO4, and 0.1 N NaOH-Na2CO3 (alkali reduction). Soils were collected before and after washing, air-dried, sieved with &lt; 2 mm and analyzed for soil texture, bulk density, aggregate stability (AS), water holding capacity (WHC), pH, electrical conductivity (EC), organic matter content (OM), total nitrogen (TN), available phosphate (AvP), cation exchange capacity (CEC), exchangeable cations (potassium, calcium, magnesium, sodium).Results and Discussion : Sandy soil showed a big change in soil texture before and after soil washing, while there was no change in soil texture for fine soil. Sandy soil showed an increase in bulk density, a decrease in WHC, and a decrease in AS. The pH of remediated soil was affected by the type of washing chemical. The acidic washing processes (1OU, 2OU) resulted in low pH soils, while an alkali reduction process (3OU) showed high pH soil. The soil OM, TN, AvP and CEC decreased after soil washing. In the case of silty paddy soil, OM and TN were significantly reduced by washing. The most important change in soil property after washing was EC. After soil washing, the soil electrical conductivity increased sharply in all OUs : 1OU 0.51 → 6.21 ds/m, 2OU 1.09 → 3.73 ds/m, 3OU 0.99 → 9.30 ds/m. The EC values of the contaminated soil before washing were all less than 2 ds/m, which is an appropriate agricultural level. However, EC was significantly increased after washing, implying a strong salty soil level. The soil quality evaluation results before and after washing showed that the soil quality of heavy-metal contaminated soil was apparently degraded by washing. The number of soil property in the optimal range before washing (contaminated soil) was 10, but the number decreased to 5 after washing (remediated soil).Conclusions : Soil quality may be significantly changed after soil washing. The most noticeable change was the significant increase in the EC of soil and the soil health should be restored first to recycle the remediated soil. The important causes of changes in the soil quality were the separation of fine soil particles containing relatively high heavy metals from the bulk soil, soil disturbance by chemical washing solution and addition of high salts such as coagulants and pH adjust. Soil management schemes considering soil health should be soon prepared to restore the remediated soil back as an ecosystem member.

Diffusive Gradient in thin film technique as tool for assessment of metal availability and kinetics of resupply in remediated soils

This study focussed on the efficacy of two treatments, commercial-hardwood biochar and Delonix regia pods biomass, an agricultural waste, as amendment to tropical soils contaminated with lead, copper and cadmium ions; the use of Diffusive Gradient in Thin Films Technique (DGT) and measurement of soil solution concentration as means to assess the available concentration of the metals, lead, copper and cadmium ions, during and after the remediation treatment was carried out. Furthermore, Soil dynamics predicted from values of the labile partition coefficient (Kd), response time to depletion (Tc) and rates of exchange or desorption (k-1) of metal ions between soil solid phase and soil solution were also obtained using the DGT-induced fluxes in soils (DIFS) model.The heavy metal labile pool size in the soil and their kinetics of resupply in the biochar and Delonix regia amended soils were determined. The experimental results showed that the biochar-treated soils have the highest distribution coefficient, Kd, values in all the soils and for all metals considered. The depletion time (Tc) and desorption rate constant, k-1, values also revealed that the biochar treated soils would be depleted faster than the Delonix regia treated soils. Thus results from this work has shown that dynamics of metals in soils should be considered after treatment of contaminated soils.

Fe1-xS/biochar combined with thiobacillus enhancing lead phytoavailability in contaminated soil: Preparation of biochar, enrichment of thiobacillus and their function on soil lead

Properly increasing mobility of heavy metals could promote phytoremediation of contaminated soil. Fe1-xS/biochar was successfully prepared from sawdust with loading pyrrhotite (Fe1-xS) at a pyrolysis temperature of 550 °C. Thiobacillus were successfully adsorbed and enriched on the surface of Fe1-xS/biochar. Microbial growth for 36 d supported by bio-oxidization of Fe1-xS decreased the system pH from 4.32 to 3.50, increased the ORP from 298 to 487 mV, and the Fe3+ release reached 25.48 mg/g, enhancing the oxidation and leaching of soil Pb. Finally, Fe1-xS/biochar and Thiobacillus were simultaneously applied into Pb-contaminated soil for 60 d, the soil pH decreased from 7.83 to 6.72, and the exchangeable fraction of soil Pb increased from 22.86% to 37.19%. Ryegrass planting for 60 d in Pb-contaminated soil with Fe1-xS/biochar and Thiobacillus showed that the Pb content in shoot and root of ryegrass increased by 55.65% and 73.43%, respectively, confirming an obvious increase of phytoavailability of soil Pb. The relative abundance of Thiobacillus in remediated soil significantly increased from 0.06% to 34.55% due to the addition of Fe1-xS/biochar and Thiobacillus. This study provides a novel approach for regulating the Pb phytoavailability for phytoremediation of Pb-contaminated soil.

Conjugation of artificial humic acids with inorganic soil matter to restore land for improved conservation of water and nutrients

AbstractArtificial soil (AS) with a dark–brown appearance and high soil organic matter (SOM) was manufactured under hydrothermal conditions from poor sandy landfill using the 'hydrothermal humification process.' This approach may retrosynthesize the natural clay–humin complex, which is the main contributor for water and ion binding in fertile, natural soils. The structure and morphology of as‐created organic–inorganic composites was examined, and it was shown that the as‐created artificial SOM (A‐SOM) indeed tightly binds to the mineral surfaces, thus creating remediated soil or more general AS. A‐SOM does not change the bulk structure of the involved inorganic minerals but activates their surface. Depending on the biomass used as the starting product, the high effectivity of synthetic humification improves the organic carbon and nitrogen content when compared with the employed sandy soil (SS). The composition was adjusted to be comparable with a reference sample of cultivated soil (2.92% in C content and 7.8% in SOM) to enable a fair referencing. We then analyzed the most frequently used soil quality indicators for agricultural land use and found strong water retention and nutrient conservation, which reflects the successful restoration of mineral–humus conjugation. Pure ASs provide superior performance in the analyzed series, whereas simulated soils (mixture of SS and AS) still exhibit satisfactory capacities of water and ion bonding. The values were found to be very similar to cultivated soils sampled from Germany and Harbin, China.

Soil Quality Assessment Based on Different Properties of Remediated Soil Affected by Various Organic Amendments

Remediated soil can be one of valuable resources for sustainable agriculture after improving its quality and properties with proper treatments. Therefore, this study was conducted to estimate changes in soil properties and soil quality for improving remediated soil contaminated with petroleum as affected by the applications of various organic amendments as soil conditioners including biochar (BC), charcoal (CC), and livestock manure compost (LC). Two remediated soils, remediated soil A and B (RSA and RSB) that previously contaminated with different concentrations of total petroleum hydrocarbons, were alkaline soils with up to 8.5 of soil pH, very low soil organic matter (SOM) contents and available phosphate (available P2O5) concentrations, and very high exchangeable Ca concentrations. Thus, these soils had very unfavorable conditions for crop growth. RSA and RSB were treated with BC, CC, and LC in levels of 0.0%, 1.0%, and 5.0% on dry weight bases. The remediated soils treated with organic soil conditioners were incubated for 2, 4, 8 and 16 weeks at room temperature (24 ± 2°C). SOM contents increased with all the treatments. In particular, SOM in RSB increased up to 19.5 g kg-1 with BC 5.0% treatment (BC5, 16-week), which was 2 times higher than that in both RSA and RSB soils without BC applications (Control soils). Also, available P2O5 concentrations increased to 24.9 mg kg-1 (RSA, 16-week), and 17.0 mg kg-1 (RSB, 8-week) with BC5. However, available P2O5 concentration in the remediated soils was very lower than that of the optimal value for cultivating crops suggested by National Institute of Agricultural Sciences in the Republic of Korea. Available P2O5 was negatively correlated with soil pH (p < 0.01) and exchangeable Ca (p < 0.01). Soil quality index (SQI) and weight additive soil quality index (SQIW) were positively correlated with SOM (p < 0.01). The mean value of soil quality indices were 39.3, 56.0, 40.0, and 54.5 for RSA Control, RSA BC5, RSB Control, and RSB BC5, respectively. The highest soil quality index was found in the remediated soil with BC treatment. The remediated soils require the immediate solution for the poor soil quality, and thus should need methodical and continuous management. Soil quality index (SQI) and weight additive soil quality index (SQIW) of the two remediated soils (RSA and RSB) as influenced by the applications of various organic amendments. Treatment† RSA RSB SQI SQIW SQI SQIW Control 39.3 d‡ 32.6 d 40.0 d 32.4 c BC1 45.5 bc 39.5 bc 45.0 bc 37.2 bc BC5 56.0 a 51.0 a 54.5 a 47.6 a CC1 43.0 cd 36.6 cd 42.5 cd 35.6 bc CC5 48.0 b 42.7 b 47.5 b 40.9 b LC1 39.3 d 32.6 d 41.3 cd 34.0 c LC5 48.0 b 42.7 b 47.5 b 40.5 b †Control, no treated; BC1, 1% of biochar treated; BC5, 5% of biochar treated; CC1, 1% of charcoal treated; CC5, 5% of charcoal treated; LC1, 1% of livestock manure compost treated; LC5, 5% of livestock manure compost treated. ‡Numbers followed by the different letter within a column are significantly different at p <0.05 by Duncan's multiple range test.

Changes in soil properties after remediation influence the performance and survival of soil algae and earthworm

Previous research on soil remediation focused on soil properties and not on its effects on soil ecosystems. The present study investigated the adverse effects of soil physicochemical changes due to remediation on the biological indicators Chlorococcum infusionum and Chlamydomonas reinhardtii (algae) and Eisenia andrei (earthworm). Soil physicochemical properties, concentrations of total, bioavailable, and water-soluble heavy metals in soil were measured before and after remediation. Changes in soil pH, electrical conductivity, total nitrogen, and total phosphorous immediately after soil remediation were the primary causes of the biomass and photosynthetic activity inhibition observed in C. infusionum and C. reinhardtii, and the survival, normality, and burrowing behavior decrease observed in E. andrei in remediated soils showing dramatic changes in those properties. These findings suggest that remediated soils need some time to recover before restoring their functions, although heavy metals are no longer contaminating the soil.

Assessment of Concentrations and Ecological Risk of Heavy Metals at Resident and Remediated Soils of Uncontrolled Mining Site at Dareta Village, Zamfara, Nigeria

This study determined the levels of some heavy metals at resident and remediated soils of uncontrolled gold mining activities with a view to providing information on the extent of contamination and ecological risk to the resident area. The soil samples were collected from two site at the resident and one remediated soil, and analyzed for metals (Cr, Ni, Pb, Fe, Cu, Cd and Mn) using Atomic Absorption spectrophotometer (AAS). The concentrations of heavy metals (mg/kg) in residents samples ranged from 1.500-13.30 (Cr), 0.0001-0.05 (Ni), 0.18-3.754 (Pb), 0.0003-0.10 (Fe), 0.0005-0.88 (Cu), 0.0009-0.27 (Cd) and 0.0003-0.0035 (Mn) and for the remediated sample are 12.3000, 0.0001, 1.1989, 0.0002, 0.0006, 0.0003, and 0.0003 for Cr, Ni, Pb, Fe, Cu, Cd and Mn respectively. The calculated geo-accumulation index (Igeo) shows that the soil samples fall under unpolluted to moderately pollute for all the studied metals with respect to all studied sites. Pollution Load Index values (PLI>1) were all less than 1 for each metals in all studied sites, thus indicating perfection. The contamination factor (Cf) and degrees of contamination (Cd) of the soil samples were very slightly contaminated to slightly contaminated with Cr and Cd; The ecological risk results revealed that site A, B and Remediated samples were fall under low ecological risk index with values of 0.28, 10.28 and 0.33 respectively. The contaminations of these studied metals may not add ecological risk to the local environment. Keywords : Assessment, Ecological risk Heavy Metals, Uncontrolled Mining

The bio-mitigation of acetochlor in soil using Rhodopseudomonas capsulata in effluent after wastewater treatment

The bio-mitigation of acetochlor and improvement of fertility in soil using Rhodopseudomonas capsulata (R. capsulata) in effluent was investigated in this research. Acetochlor content and cytochrome P450 monooxygenase activity were tested using the HPLC method. EthB gene regulation was measured by RT-PCR. It was observed that acetochlor was not degraded under the control group. The addition of effluent containing R. capsulata and residual organics degraded acetochlor efficiently and re-mediated soil fertility. Acetochlor mitigation reached 100% after 5 days under the optimal group (2000 mg/L). Interestingly, the acetochlor began to be degraded after day 1 of inoculation. Further research indicated that EthB gene was expressed after the first day of inoculation. Subsequently, the cytochrome P450 monooxygenase was synthesized to degrade acetochlor under EthB gene regulation. Analysis revealed that EthB and cytochrome P450 monooxygenase were inducible gene expressions and enzyme. The acetochlor as stimulus signal induced EthB expression through signal transduction pathway. This process took 1 day for R. capsulata, as they were ancient bacteria. However, the organics in soil and the control group were deficient, which could not maintain R. capsulata growth for over 1 day. The residual organics in effluent provided sufficient carbon sources and energy for R. capsulata under four effluent groups. The new method completed the remediation of acetochlor pollution and the improvement of soil fertility and soybean processing wastewater treatment simultaneously, as well as realizing the resource reutilization of wastewater and R. capsulata as sludge.