Effect of consortium bioaugmentation and biostimulation on remediation efficiency and bacterial diversity of diesel-contaminated aged soil.

This study aimed to evaluate the effects of consortium bioaugmentation (CB) and various biostimulation options on the remediation efficiency and bacterial diversity of diesel-contaminated aged soil. The bacterial consortium was prepared using strains D-46, D-99, D134-1, MSM-2-10-13, and Oil-4, isolated from oil-contaminated soil. The effects of CB and biostimulation were evaluated in various soil microcosms: CT (water), T1 (CB only), T2 (CB + NH4NO3 and KH2PO4, nutrients), T3 (CB + activated charcoal, AC), T4 (CB + nutrients + AC), T5 (AC + water), T6 (CB + nutrients + zero-valent iron nanoparticles, nZVI), T7 (CB + nutrients + AC + nZVI), T8 (CB + activated peroxidase, oxidant), T9 (AC + nZVI), and T10 (CB + nZVI + AC + oxidant). Preliminary evaluation of the bacterial consortium revealed 81.9% diesel degradation in liquid media. After 60 days of treatment, T6 demonstrated the highest total petroleum hydrocarbon (TPH) degradation (99.0%), followed by T1 (97.4%), T2 (97.9%), T4 (96.0%), T7 (96.0%), T8 (94.8%), T3 (93.6%), and T10 (86.2%). The lowest TPH degradation was found in T5 (24.2%), T9 (17.2%), and CT (11.7%). Application of CB and biostimulation to the soil microcosms decreased bacterial diversity, leading to selective enrichment of bacterial communities. T2, T6, and T10 contained Firmicutes (50.06%), Proteobacteria (64.69%), and Actinobacteria (54.36%) as the predominant phyla, respectively. The initial soil exhibited the lowest metabolic activity, which improved after treatment. The study results indicated that biostimulation alone is inadequate for remediation of contaminated soil that lacks indigenous oil degraders, suggesting the need for a holistic approach that includes both CB and biostimulation. Graphical Abstract.

Degradation of petroleum hydrocarbons in unsaturated soil and effects on subsequent biodegradation by potassium permanganate.

To date, the oxidation of petroleum hydrocarbons using permanganate has been investigated rarely. Only a few studies on the remediation of unsaturated soil using permanganate can be found in the literature. This is, to the best of our knowledge, the first study conducted using permanganate pretreatment to degrade petroleum hydrocarbons in unsaturated soil in combination with subsequent bioaugmentation. The pretreatment of diesel-contaminated unsaturated soil with 0.5-pore-volume (5%) potassium permanganate (PP) by solution pouring and foam spraying (with a surfactant) achieved the total petroleum hydrocarbon (TPH) removal efficiencies of 37% and 72.1%, respectively. The PP foam, when coupled with bioaugmentation foam, further degraded the TPH to a final concentration of 438 mg/kg (92.1% total reduction). The experiment was conducted without soil mixing or disturbance. The relatively high TPH removal efficiency achieved by the PP-bioaugmentation serial foam application may be attributed to an increase in soil pH caused by the PP and effective infiltration of the remediation agent by foaming. The applied PP foam increased the pH of the acidic soil, thus enhancing microbial activity. The first-order biodegradation rate after PP oxidation was calculated to be 0.068 d-1. Furthermore, 94% of the group of relatively persistent hydrocarbons (C18-C22) was removed by PP-bioaugmentation, as verified by chromatogram peaks. Some physicochemical parameters related to contaminant removal efficiency were also evaluated. The results reveal that PP can degrade soil TPH and significantly enhance the biodegradation rate in unsaturated diesel-contaminated soil when combined with bioaugmentation foam.

Application of a soil quality assessment system using ecotoxicological indicators to evaluate contaminated and remediated soils.

The deterioration of soil quality owing to human activities results in adverse effects on the soil ecosystem. This study developed a systematic method to quantitatively evaluate soil quality based on physical, chemical, biological, and ecotoxicological indicators and proposed the soil quality assessment and management system. This system consists of step-by-step processes, including indicator classification, indicator measurement, scoring and weighting, and soil quality index (SQI) calculation. The novel strategy included the usage of authentic ecotoxicological indicators for realistically interpreting soil quality assessment results. This study used five ecotoxicological indicators, including earthworm survival, enzyme activities, nematode reproduction, plant germination and growth, soil algal biomass, and soil algal photosynthetic capacity. Relatively higher SQI values than those corresponding to the actual soil quality status would be obtained without considering the ecotoxicological indicators. We conclude that the use of ecotoxicological indicator can help in soil quality assessment even under extreme soil quality conditions, such as highly contaminated or physically and chemically remediated soils.

Soil infiltration capacity of chemical oxidants used for risk reduction of soil contamination.

Chemical oxidation has been applied to remove soil contaminants and thereby reduce human and ecological risks from contaminated sites. However, few studies have been conducted on the natural infiltration of oxidant solutions into unsaturated soil. Moreover, the infiltration capacity of oxidant solutions at various concentrations in unsaturated soil has not yet been studied. This study investigated the natural infiltration tendency of oxidant solutions like hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and sodium persulfate (Na2S2O8), in sand and sandy loam. Cumulative infiltration was recorded from a soil column equipped with a Mariotte reservoir. The infiltration rate, sorptivity, and unsaturated hydraulic conductivity were obtained from the cumulative infiltration results. Na2S2O8 showed the highest infiltration rate in both sand and sandy loam, and the infiltration of Na2S2O8 increased as the concentration was increased from 0.05 to 1%. However, the infiltration of KMnO4 and H2O2 solutions was governed more by chemical reaction behavior than by liquid physical properties or soil hydraulic properties. The production of oxides and gas due to reaction induced clogging in flow paths, resulting in less infiltration. Infiltration of H2O2 at concentrations greater than 0.5% was not observed in sand or sandy loam due to gas formation and swelling.

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.

Development of a bacterial consortium comprising oil-degraders and diazotrophic bacteria for elimination of exogenous nitrogen requirement in bioremediation of diesel-contaminated soil.

The purpose of this study was to develop an effective bacterial consortium and determine their ability to overcome nitrogen limitation for the enhanced remediation of diesel-contaminated soils. Towards this, various bacterial consortia were constructed using oil-degrading and nitrogen-fixing microbes. The diesel removal efficiency of various developed consortia was evaluated by delivering the bacterial consortia to the diesel-contaminated soils. The consortium Acinetobacter sp. K-6 + Rhodococcus sp. Y2-2 + NH4NO3 resulted in the highest removal (85.3%) of diesel from the contaminated soil. The consortium containing two different oil-degrading microbes (K-6 + Y2-2) and one nitrogen-fixing microbe Azotobacter vinelandii KCTC 2426 removed 83.1% of the diesel from the soil after 40 days of treatment. The total nitrogen content analysis revealed higher amounts of nitrogen in soil treated with the nitrogen-fixing microbe when compared with that of the soil supplemented with exogenous inorganic nitrogen. The findings in this present study reveal that the consortium containing the nitrogen-fixing microbe degraded similar amounts of diesel to that degraded by the consortium supplemented with exogenous inorganic nitrogen. This suggests that the developed consortium K-6 + Y2-2 + KCTC 2426 compensated for the nitrogen limitation and eliminated the need for exogenous nitrogen in bioremediation of diesel-contaminated soils.

Oil-degrading properties of a psychrotolerant bacterial strain, Rhodococcus sp. Y2-2, in liquid and soil media.

The aim of this study was to investigate oil-degrading ability of newly isolated strain Rhodococcus Y2-2 at low temperature. Rhodococcus sp. Y2-2 was isolated from oil-contaminated soil sampled at the end of winter using a newly developed transwell plate method. In the liquid phase, the oil-degradation efficiency of strain Rhodococcus sp. Y2-2 was about 84% with an initial concentration of 1500 ppm TPH (500 ppm each of kerosene, gasoline, and diesel) when incubated for 2 weeks under optimal conditions: 10 °C, pH 7, and 0.5 g L- 1 inoculum. In the soil phase, the isolate showed 80% oil degradation efficiency using glucose as a carbon source, with an initial concentration of 4000 ppm TPH and the addition of water during 14 days of incubation at 10 °C. Additionally, the degradation efficiency of the isolate was increased by the addition of mixture of surfactant alpha olefin sulfonate and gelatin, although strain Y2-2 also produced many biosurfactant components. This study shows Rhodococcus sp. Y2-2 can degrade oil components both in liquid and soil media by consuming kerosene, gasoline, and diesel as a carbon and energy source. Therefore, the crude oil-degrading ability of Rhodococcus sp. Y2-2 at low temperature provides proper bioremediation tool to clean up oil-contaminated sites especially in cold area or during winter season.

Sphingobium naphthae sp. nov., with the ability to degrade aliphatic hydrocarbons, isolated from oil-contaminated soil.

A light yellow-coloured, Gram-stain-negative, non-motile and rod-shaped bacterium, designated strain K-3-6T, capable of degrading aliphatic hydrocarbons was isolated from oil-contaminated soil of Biratnagar, Morang, Nepal. It was able to grow at 15-45 °C, at pH 5.0-9.5 and with 0-6 % (w/v) NaCl. Based on 16S rRNA gene sequence analysis, strain K-3-6T belongs to the genus Sphingobium and is closely related to Sphingobium olei IMMIB HF-1T (98.4 % similarity), Sphingobium abikonense NBRC 16140T (98.3 %), Sphingobium rhizovicinum CC-FH12-1T (97.9 %), Sphingobium lactosutens DS20T (97.9 %), Sphingobium amiense NBRC 102518T (97.2 %), Sphingobium phenoxybenzoativorans SC_3T (97.2 %) and Sphingobium fontiphilum Chen16-4T (97.0 %). The predominant respiratory quinone was ubiquinone-10 and the major polyamine was spermidine. The polar lipid profile revealed the presence of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphatidyldimethylethanolamine, sphingoglycolipid and phosphatidylmonomethylethanolamine. The predominant fatty acids of strain K-3-6T were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C14 : 0, C16 : 0 and C14 : 0 2-OH. The genomic DNA G+C content was 65.6 mol%. Levels of DNA-DNA relatedness between strain K-3-6T and S. olei IMMIB HF-1T, S. abikonense NBRC 16140T, S. lactosutens DS20T, S. rhizovicinum CC-FH12-1T, S. amiense NBRC 102518T and S. fontiphilum Chen16-4T were 34.0, 33.3, 28.7, 26.3, 29.0 and 22.3 %, respectively. The morphological, physiological, chemotaxonomic and phylogenetic analyses clearly distinguished this strain from its closest phylogenetic neighbours. Thus, strain K-3-6T represents a novel species of the genus Sphingobium, for which the name Sphingobium naphthae sp. nov. is proposed. The type strain is K-3-6T (=KEMB 9005-449T=KACC 19001T=JCM 31713T).

Exoenzyme activity in contaminated soils before and after soil washing: ß-glucosidase activity as a biological indicator of soil health.

It is essential to remediate or amend soils contaminated with various heavy metals or pollutants so that the soils may be used again safely. Verifying that the remediated or amended soils meet soil quality standards is an important part of the process. We estimated the activity levels of eight soil exoenzymes (acid phosphatase, arylsulfatase, catalase, dehydrogenase, fluorescein diacetate hydrolase, protease, urease, and ß-glucosidase) in contaminated and remediated soils from two sites near a non-ferrous metal smelter, using colorimetric and titrimetric determination methods. Our results provided the levels of activity of soil exoenzymes that indicate soil health. Most enzymes showed lower activity levels in remediated soils than in contaminated soils, with the exception of protease and urease, which showed higher activity after remediation in some soils, perhaps due to the limited nutrients available in remediated soils. Soil exoenzymes showed significantly higher activity in soils from one of the sites than from the other, due to improper conditions at the second site, including high pH, poor nutrient levels, and a high proportion of sand in the latter soil. Principal component analysis revealed that ß-glucosidase was the best indicator of soil ecosystem health, among the enzymes evaluated. We recommend using ß-glucosidase enzyme activity as a prior indicator in estimating soil ecosystem health.

Rapid in situ assessment for predicting soil quality using an algae-soaked disc seeding assay.

The soil quality of remediated land is altered and this land consequently exerts unexpected biological effects on terrestrial organisms. Therefore, field evaluation of such land should be conducted using biological indicators. Algae are a promising new biological indicator since they are a food source for organisms in higher soil trophic levels and easily sampled from the soil. Field evaluation of soil characteristics is preferred to be testing in laboratory conditions because many biological effects cannot be duplicated during laboratory evaluations. Herein, we describe a convenient and rapid algae-soaked disc seeding assay for assessing soil quality in the field based on soil algae. The collection of algae is easy and rapid and the method predicts the short-term quality of contaminated, remediated, and amended farm and paddy soils. The algae-soaked disc seeding assay is yet to be extensively evaluated, and the method cannot be applied to loamy sand soil in in situ evaluations. The algae-soaked disc seeding assay is recommended for prediction of soil quality in in situ evaluations because it reflects all variations in the environment. The algae-soaked disc seeding assay will help to develop management strategies for in situ evaluation.

Simultaneous detection of bioavailable arsenic and cadmium in contaminated soils using dual-sensing bioreporters.

Whole-cell bioreporters (WCBs) have attracted increasing attention during the last few decades because they allow fast determination of bioavailable heavy metals in contaminated sites. Various WCBs to monitor specific heavy metals such as arsenic and cadmium in diverse environmental systems are available. However, currently, no study on simultaneous analysis of arsenic and cadmium has been reported, even though soils are contaminated by diverse heavy metals and metalloids. We demonstrated herein the development of dual-sensing WCBs to simultaneously quantify bioavailable arsenic and cadmium in contaminated sites by employing the promoter regions of the ars and znt operons as separate metal-sensing domains, and egfp and mcherry as reporter genes. The dual-sensing WCBs were generated by inserting two sets of genes into E. coli DH5α. The capability of WCBs was successfully proved to simultaneously quantify bioavailable arsenic and cadmium in amended Landwirtschaftliche Untersuchungs und Forschungsanstalt (LUFA) soils, and then, it was applied to contaminated field soils collected from a smelter area in Korea. As a result, it was noticed that the bioavailable portion of cadmium was higher than that of arsenic while the absolute amount of bioavailable arsenic and cadmium level was opposite. Since both cadmium and arsenic were assessed from the same E. coli cells, the data obtained by using dual-sensing WCBs would be more efficient and convenient than that from comparative WCB assay. In spite of advantageous aspects, to our knowledge, this is the first report on a dual-sensing WCB for rapid and concurrent quantification of bioavailable arsenic and cadmium in contaminated soils.

Aquabacterium olei sp. nov., an oil-degrading bacterium isolated from oil-contaminated soil.

Strain NHI-1T is a Gram-negative, motile, non-spore-forming bacterium isolated from oil-contaminated soil in South Korea. The strain was able to grow by using gasoline, diesel and kerosene as energy and carbon sources. After incubation for 14 days, cells (1 g l- 1) degraded approximately 58 % of oil present at concentration of 1500 p.p.m. at pH 8 and 28 °C. Strain NHI-1T grew well under aerobic conditions, with optimal growth at pH 7-9 and 28 °C-37 °C but grew poorly in the presence of ≥ 0.5 % NaCl. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the closest relatives of strain NHI-1T were Aquabacterium fontiphilum CS-6T (97.96 % sequence similarity), Aquabacterium parvum B6T (96.39 %), Aquabacterium commune B8T (95.76 %), Aquabacterium limnoticum ABP-4T (95.72 %) and Aquabacterium citratiphilum B4T (95.25 %). DNA-DNA relatedness was 41-53 % between strain NHI-1T and its closest type strains. The major fatty acids present in strain NHI-1T were summed feature 3 (C16 : 1ω7c/C16 : 1ω6c, 44.5 %), summed feature 8 (C18 : 1ω7c/C18 : 1ω6c, 21.5 %) and C16 : 0 (16.2 %), and the predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, diphosphatidylglycerol and uncharacterized aminophospholipids. Strain NHI-1T was distinguishable from other members of genus Aquabacterium based on phenotypic, chemotaxonomic and genotypic characteristics. Therefore, strain NHI-1T represents a novel species of the genus Aquabacterium for which the name Aquabacterium olei sp. nov. is proposed. The type strain is NHI-1T ( = KEMB 9005-082T = KACC 18244T = NBRC 110486T).

Psychrobacillus soli sp. nov., capable of degrading oil, isolated from oil-contaminated soil.

A novel, aerobic, psychrotolerant, Gram-stain-positive, endospore-forming strain, NHI-2(T), was isolated from oil-contaminated soil near a gas station in Mongolia. This strain was characterized by motile rods and grew over a wide range of temperatures ( -2 to 40 °C) with optimal growth at 28-30 °C. It tolerated salt concentrations of up to 7% over a five-day incubation period. Analysis of 16S rRNA gene sequence indicated that strain NHI-2(T) belongs to the genus Psychrobacillus. Sequence similarity between NHI-2(T) and members of the genus Psychrobacillus with validly published names ranged from 97.83 to 98.18%. DNA-DNA hybridization indicated less than 70% relatedness to reference strains within the genus. The G+C content of the genomic DNA was 36 mol%. This strain contained MK-8 as a predominant isoprenoid menaquinone. NHI-2(T) had ornithine in the cell wall similar to reference strains of the genus Psychrobacillus. The major fatty acids present in NHI-2(T )were anteiso-C15 : 0 (51.0%), iso-C15 : 0 (9.1%) and anteiso-C17 : 0 (8.0%). The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. These data highlight that the phenotype of strain NHI-2(T) differs from that of related species in terms of chemotaxonomic properties and genotype characteristics. Therefore, this strain is proposed as a representative of a novel species, named Psychrobacillus soli. The type strain is NHI-2(T) ( = KEMB 9005-135(T) = KACC 18243(T) = NBRC 110600(T)).

Filtration of fullerene and copper oxide nanoparticles using surface-modified microfilters.

This study evaluated the filtration of engineered nanoparticles of fullerene and copper oxide (CuO) from water by using surface-modified microsized filters. The surfaces of microsized filters of cellulose acetate and glass fibers were coated with cationic and anionic surfactants to give them positively and negatively charged surfaces, respectively. Uncoated microfilters removed 30% of a fullerene suspension, while no nanosized CuO suspension was removed. Cationic surfactant-coated filters enhanced the removal efficiency up to 70% for the fullerene suspension, while the anionic surfactant-coated filters could not remove fullerene at all. The positively charged filters with cationic surfactant coating could easily adsorb negatively charged fullerenes on their surfaces. However, none of the surfactant-coated filters removed the CuO nanoparticles because the nanoparticles were not affected by the electrical charge of the filtration medium. The Hamaker constants of nanoparticles interacting with the filter materials in water were calculated to study these interactions. The Hamaker constant of fullerene interacting with cellulose acetate in water, 4.68E - 21 J, was higher than that of interacting with quartz in water, 2.59E - 21 J. However, the Hamaker constants of CuO interacting with quartz and cellulose acetate in water were both negative values, implying repulsive van der Waals interactions. The curves of potential energy of interaction between nanoparticles and the various filter media implied that the nanoparticles were very stable in water, and so, natural deposition of nanoparticles on the filters would not occur. Therefore, electrical bonding and hydrophobic interactions were the forces dominating fullerene removal by positively charged filters.

Enhanced isolation and culture of highly efficient psychrophilic oil-degrading bacteria from oil-contaminated soils in South Korea.

It is known that isolation of oil-degrading bacterial strains is difficult at low temperatures, and the biodegradation efficiency of oil-contaminated soil is significantly reduced in cold weather. In this study, 14 strains were isolated from oil-contaminated soil that grew well at 10°C by using a newly developed culture method. 11 of the 14 isolates were successfully cultured in mineral salts medium containing 1,500 ppm of oil components, 500 ppm each kerosene, gasoline, and diesel as carbon sources, at 10°C for 2 weeks. The oil degradation efficiencies of these 11 isolates ranged from 36% to 100%, as measured by total petroleum hydrocarbon (TPH) degradation analyses. Three strains (Pseudomonas simiae G1-10O, P. taiwanensis Y1-4, and P. koreensis Gwa2) displayed complete degradation (100%), and six others (R frederiksbergensis G2-2, P arsenicoxydans Y2-1, R umsongensis Gwa3, P. migulae Gwa5, RhodococcusjialingiaeY 1-l , and R. qingshengii Y2-2) showed relatively high degradation efficiencies (> 70%). This study suggests that these isolates can be effectively utilised in thetreatment of oil-contaminated soil in landfarming, especially during winter.

Field application of bio-foam spray to reduce ammonia emission from ammonia-rich swine manure piles.

In this study, the first field-scale application of a bio-foam spray (a mixture of microbes and a surfactant) for the reduction of ammonia emitted from manure was investigated on six field swine manure piles. The objective of this study was to evaluate the odor suppression ability of bio-foam and odor degradation ability of odor-degrading bacteria loaded in the surfactant foam after covering manure piles. The size of field manure piles tested in this study ranged from 27 to 300 m3. Bio-foam spraying completely suppressed the release of the major odor component, ammonia (NH3), and odor-degrading bacteria in the bio-foam aided in the degradation of NH3 in field swine manure piles. On average, 85.7-100% of NH3 was reduced after 24-48 h of serial bio-foam spray application on the swine manure surface, while the control showed 25-42%. The reduction efficiency of NH3 by the bio-foam application was affected by the bio-foam spray frequency, ambient temperature, ventilation of the field facility, and upward airflow to the pile. The reduction in surface emission of NH3 also reduced the ambient air concentration of NH3 at the gate of the compost facility. NH3 gas measurements at a depth of 50 cm indicated that NH3-degrading bacteria infiltrated the manure and were active in biodegradation. Finally, the measured effectiveness of bio-foam application as shown by this study indicates that sprinkling bio-foam via specialized rotating sprinklers may be an efficient and uniform method for the delivery of bio-foam to wide field areas within composting facilities.

Case report: Pembrolizumab as an alternative to atezolizumab following a severe infusion reaction.

The emergence of immune-checkpoint inhibitors (ICIs) has revolutionized the field of oncology, providing promising results in various malignancies. However, ICIs can sometimes lead to severe injection reactions, requiring alternative treatment options. In this case report, we introduce a case of a severe infusion reaction induced by atezolizumab. After atezolizumab infusion, the patient experienced symptoms that were suggestive of anaphylactic shock, including chest tightness, low blood pressure, and loss of consciousness, all of which were restored by immediate administration of steroid, antihistamine, and epinephrine. When selecting a new ICI, we were concerned about cross-reactivity with atezolizumab. As such, we conducted a skin test to establish the underlying mechanism of the previous reaction to atezolizumab infusion, the results of which were highly suggestive of Ig-E-mediated hypersensitivity. The skin test for pembrolizumab, another ICI, was negative. Therefore, we replaced atezolizumab with pembrolizumab, and the infusion proceeded safely. To date, the patient has undergone 13 cycles of pembrolizumab, and the disease has remained stable. This case demonstrates that patients who exhibit severe injection reactions to ICIs can continue treatment safely, without cross-reactions, with alternative ICIs. This case will help provide patients who have experienced drug-related hypersensitivity reactions with a choice to use alternative ICIs, thus expanding their options for chemotherapy.

Changes in the health of metal-contaminated soil before and after stabilization and solidification.

Stabilization is popularly employed to remediate metal-contaminated soils. It involves the absorption and precipitation of heavy metals to reduce their solubility, movement characteristics, or risk and toxicity. This study aimed to conduct a soil health assessment to determine changes in the health of metal-contaminated soil before and after the application of five stabilizers (acid mine drainage sludge (AMDS), coal mine drainage sludge (CMDS), steel slag, lime, and cement). Soil health assessment, including three soil functions, namely soil productivity, soil stability, and soil biodiversity, evaluated the physical, chemical, and biological indicators (total 16 indicators). Soil health index (SHI) of soil function was calculated by multiplying each indicator score by the weighting factor of each indicator. Total SHI was obtained by summing the three soil-function SHI. Total SHI of the stabilized and test soils followed the order as control soil (1.90) > heavy metal-contaminated soil (1.55) > CMDS-stabilized soil (1.29) > steel slag-stabilized soil (1.29) > AMDS-stabilized soil (1.26) > cement-stabilized soil (0.74) > lime-stabilized soil (0.67). Total SHI of the initial heavy metal-contaminated soil was evaluated as 'normal', before the stabilizer was applied; however, most of the stabilized soils became 'bad' after application of the stabilizers. Furthermore, soils stabilized by cement and lime showed very poor soil health. The results implied that changes in physical and chemical soil properties occurred due to the disturbance caused by the mixing of stabilizers, and ions eluted from the stabilizers could deteriorate soil health further. The findings indicated that soil treated with stabilizers is not suitable for agricultural purposes. Overall, the study suggested that stabilized soil from metal-contaminated sites should be covered with clean soil or monitored for some time before deciding its future agricultural use.

Construction of a chemical ranking system of soil pollution substances for screening of priority soil contaminants in Korea.

The Korean government recently proposed expanding the number of soil-quality standards to 30 by 2015. The objectives of our study were to construct a reasonable protocol for screening priority soil contaminants for inclusion in the planned soil quality standard expansion. The chemical ranking system of soil pollution substances (CROSS) was first developed to serve as an analytical tool in chemical scoring and ranking of possible soil pollution substances. CROSS incorporates important parameters commonly used in several previous chemical ranking and scoring systems and the new soil pollution parameters. CROSS uses soil-related parameters in its algorithm, including information related to the soil environment, such as soil ecotoxicological data, the soil toxic release inventory (TRI), and soil partitioning coefficients. Soil TRI and monitoring data were incorporated as local specific parameters. In addition, CROSS scores the transportability of chemicals in soil because soil contamination may result in groundwater contamination. Dermal toxicity was used in CROSS only to consider contact with soil. CROSS uses a certainty score to incorporate data uncertainty. CROSS scores the importance of each candidate substance and assigns rankings on the basis of total scores. Cadmium was the most highly ranked. Generally, metals were ranked higher than other substances. Pentachlorophenol, phenol, dieldrin, and methyl tert-butyl ether were ranked the highest among chlorinated compounds, aromatic compounds, pesticides, and others, respectively. The priority substance list generated from CROSS will be used in selecting substances for possible inclusion in the Korean soil quality standard expansion; it will also provide important information for designing a soil-environment management scheme.

Degradation of petroleum hydrocarbons in soil via advanced oxidation process using peroxymonosulfate activated by nanoscale zero-valent iron.

Recently, the use of nanoscale zero-valent iron (nZVI) for removal of organic contaminants from aqueous and soil system has increased. In this study, we employ nZVI to activate peroxymonosulfate (PMS) for the degradation of total petroleum hydrocarbons (TPHs) in aged diesel-contaminated soil. Upon PMS activation by nZVI, PMS produces more highly reactive oxygen species (ROS) in both aqueous solution and soil compared to other compounds (PMS/Co(II)), as determined by electron paramagnetic resonance spectroscopy. Thus, nZVI is an effective catalyst for PMS activation, leading to the efficient degradation of diesel oil in soil compared to other catalysts and oxidants. The optimal concentrations of PMS and nZVI were found to be 3 and 0.2%, respectively, showing the best degradation efficiency (61.2% in 2 h). The observed TPH degradation was retarded (up to 19.1-37% efficiency) in the presence of radical scavengers, such as tert-butyl alcohol, nitrobenzene, ethyl alcohol, and isopropyl alcohol. These results also demonstrate that ROS (hydroxyl and sulfate free radicals) are generated via PMS activation by nZVI. Moreover, more than 96% of TPH can be degraded by sequential applications of PMS/nZVI. Factors affecting TPH degradation, namely PMS/nZVI concentration, soil:solution ratio, soil pH, activators, and oxidants, are also analyzed. The results demonstrate that TPH is degraded to below the residential soil quality limit using PMS/nZVI based on the advanced oxidation process (AOP), which is therefore an effective option for chemical remediation of diesel-contaminated soils over a wide range of pH.