Bioremediation of trichloroethylene-contaminated groundwater using green carbon-releasing substrate with pH control capability

In this research, a sustainable substrate, termed green and long-lasting substrate (GLS), featuring a blend of emulsified substrate (ES) and modified rice husk ash (m-RHA) was devised. The primary objective was to facilitate the bioremediation of groundwater contaminated with trichloroethylene (TCE) using innovative GLS for slow carbon release and pH control. The GLS was concocted by homogenizing a mixture of soybean oil, surfactants (Simple Green™ and soya lecithin), and m-RHA, ensuring a gradual release of carbon sources. The hydrothermal synthesis was applied for the production of m-RHA production. The analyses demonstrate that m-RHA were uniform sphere-shape granules with diameters in micro-scale ranges. Results from the microcosm study show that approximately 83% of TCE could be removed (initial TCE concentration = 7.6 mg/L) with GLS supplement after 60 days of operation. Compared to other substrates without RHA addition, higher TCE removal efficiency was obtained, and higher Dehalococcoides sp. (DHC) population and hydA gene (hydrogen-producing gene) copy number were also detected in microcosms with GLS addition. Higher hydrogen concentrations enhanced the DHC growth, which corresponded to the increased DHC populations. The addition of the GLS could provide alkalinity at the initial stage to neutralize the acidified groundwater caused by the produced organic acids after substrate biodegradation, which was advantageous to DHC growth and TCE dechlorination. The addition of m-RHA reached an increased TCE removal efficiency, which was due to the fact that the m-RHA had the zeolite-like structure with a higher surface area and lower granular diameter, and thus, it resulted in a more effective initial adsorption effect. Therefore, a significant amount of TCE could be adsorbed onto the surface of m-RHA, which caused a rapid TCE removal through adsorption. The carbon substrates released from m-RHA could then enhance the subsequent dechlorination. The developed GLS is an environmentally-friendly and green substrate.

Bioremediation of hexavalent-chromium contaminated groundwater: Microcosm, column, and microbial diversity studies

Sulfate reducing bacteria (SRB) have the capability of bioreducing hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] under sulfate-reducing conditions for toxicity reduction. However, a high amount of sulfate addition would cause elevated sulfide production, which could inhibit the growth of SRB and result in reduced Cr(VI) bioreduction efficiency. A slow release reagent, viscous carbon and sulfate-releasing colloidal substrates (VCSRCS), was prepared for a long-lasting carbon and sulfate supplement. In the column study, VCSRCS was injected into the column system to form a VCSRCS biobarrier for Cr(VI) containment and bioreduction. A complete Cr(VI) removal was observed via the adsorption and bioreduction mechanisms in the column with VCSRCS addition. Results from X-ray diffractometer analyses indicate that Cr(OH)_3(s) and Cr₂O_3(s) were detected in precipitates, indicating the occurrence of Cr(VI) reduction followed by Cr(III) precipitation. Results from the Fourier-transform infrared spectroscopy analyses show that cell deposits carried functional groups, which could adsorb Cr. Addition of VCSRCS caused increased populations of total bacteria and dsrA, which also enhanced Cr(VI) reduction. Microbial diversity results indicate that VCSRCS addition resulted in the growth of Cr(VI)-reducing bacteria including Exiguobacterium, Citrobacter, Aerococcus, and SRB. Results of this study will be helpful in developing an effective and green VCSRCS biobarrier for the bioremediation of Cr(VI)-polluted groundwater.

Application of zeolitic imidazolate framework for hexavalent chromium removal: A feasibility and mechanism study

The mechanisms and effectiveness of using zeolitic imidazolate framework (ZIF-8) [a sub-family of metal-organic framework (MOF)] particles on hexavalent chromium [Cr(VI)] removal were evaluated. The ultrasonic mixing method was applied for the preparation of ZIF-8, and chemicals used for ZIF-8 synthesis included ammonium hydroxide, zinc nitrate hexahydrate, and 2-methylimidazole. ZIF-8 particle had a clear rhombic dodecahedron morphology shape and a strong peak intensity with high crystallinity. The adsorption capacity (AC) of ZIF-8 was 30.3 mg of Cr(VI)/g of ZIF-8 [Cr(VI) = 50 mg/L]. The AC of Cr(VI) raised to 34.3 mg/g under acidic conditions (pH = 5), and the AC dropped to below 13.7 mg/g with a pH range from 7 to 11. It could be because of the competitive effects between CrO₄ ^2- and hydroxide ions for adsorption locations of ZIF-8. Cr(VI) removal relied on the amount of Cr(VI) adsorbed on the particles of ZIF-8, and the mechanisms of Cr(VI) adsorption by ZIF-8 included chemical/physical processes and the rate-limiting step was the chemical adsorption. A fraction of sorbed Cr(VI) was reduced to Cr(III), and thus, ZIF-8 could serve as a reducing agent during Cr(VI) reduction. Cr(VI) was removed effectively from the water phase by ZIF-8 via adsorption and reduction mechanisms. PRACTITIONER POINTS: ZIF-8 particles had an adsorption capacity of 30.33 mg of Cr(VI)/g of ZIF-8. Cr(VI) sorption by ZIF-8 has chemical (rate-limiting step) and physical processes. ZIF-8 can serve as a reducing agent for Cr(VI) reduction. Cr(VI) can be removed by ZIF-8 via the adsorption and reduction mechanisms.

Application of iron/aluminum bimetallic nanoparticle system for chromium-contaminated groundwater remediation

When the nanoscale zero valent iron (nZVI) is used for the reduction of hexavalent chromium (Cr⁶⁺) to trivalent chromium (Cr³⁺) in groundwater, the reduction efficiency is decreased due to the passivation of reactive sites by precipitation. The bimetallic nanoparticle (BNP) can be created with the addition of the second metal to achieve a higher activity and reduce the occurrence of the ferrous/ferric hydroxide precipitation. In this study, the iron-coated aluminum (Fe/Al) BNP and aluminum-coated iron (Al/Fe) BNP systems were designed for remediating Cr⁶⁺-contaminated groundwater. The chemical liquid-phase deposition and co-reduction method was applied to produce BNPs. Cr⁶⁺ removal rate by Fe/Al BNPs was directly proportional to the saturation concentration and reactive sites, which caused a higher Cr⁶⁺ removal rate. The pseudo-first-order kinetic model could be used to describe the Cr⁶⁺ adsorption mechanism by Fe/Al BNPs. Results show that Fe/Al BNPs and Al/Fe BNPs could reduce Cr⁶⁺ to Cr³⁺, and the removal efficiencies for Cr⁶⁺ were 1.47 g/g BNP and 0.07 g/g BNP, respectively. Detection of Cr³⁺ in the aqueous phase was observed during the Cr⁶⁺ removal process. Results from X-ray diffraction (XRD) analysis confirmed that Cr(OH)₃ was present on the surface of BNPs. Main mechanisms caused Cr⁶⁺ removal included reduction, precipitation, and adsorption. The reduction of Cr⁶⁺ produced OH^-, which created alkaline environment and facilitated the formation of chromium hydroxide precipitates [Cr(OH)₃]. Thus, the migration of Cr³⁺ was prevented and the environmental risk was reduced. BNP had a higher activity and stability, and it was applicable for Cr⁶⁺-contaminated site remediation.

Growth inhibition of sulfate-reducing bacteria for trichloroethylene dechlorination enhancement

Trichloroethylene (TCE) is a frequently found organic contaminant in polluted-groundwater. In this microcosm study, effects of hydrogen-producing bacteria [Clostridium butyricum (Clostridium sp.)] and inhibitor of sulfate-reducing bacteria (SRB) addition on the enhancement of TCE dechlorination were evaluated. Results indicate that Clostridium sp. supplement could effectively enhance TCE reductive dechlorination (97.4% of TCE removal) due to increased hydrogen concentration and Dehalococcoides (DHC) populations (increased to 1 × 10⁴ gene copies/L). However, addition of Clostridium sp. also caused the increase in dsrA (dissimilatory sulfide reductase subunit A) (increased to 2 × 10⁸ gene copies/L), and thus, part of the hydrogen was consumed by SRB, which would limit the effective application of hydrogen by DHC. Control of Clostridium sp. addition is a necessity to minimize the adverse impact of Clostridium sp. on DHC growth. Ferric citrate caused the slight raise of the oxidation-reduction state, which resulted in growth inhibition of SRB. Molybdate addition inhibited the growth of SRB, and thus, the dsrA concentrations (dropped from 4 × 10⁷ to 9 × 10⁵ gene copies/L) and sulfate reduction efficiency were decreased. Increased DHC populations (increased from 8 × 10³ to 1 × 10⁵ gene copies/L) were due to increased available hydrogen (increased from 0 to 2 mg/L), which enhanced TCE dechlorination (99.3% TCE removal). Metagenomic analyses show that a significant microbial diversity was detected in microcosms with different treatments. Clostridium sp., ferric citrate, and molybdate addition caused a decreased SRB communities and increased fatty acid production microbial communities (increased from 4.9% to 20.2%), which would be beneficial to the hydrogen production and TCE dechlorination processes.

Application of γ-PGA as the primary carbon source to bioremediate a TCE-polluted aquifer: A pilot-scale study

The effectiveness of using gamma poly-glutamic acid (γ-PGA) as the primary carbon and nitrogen sources to bioremediate trichloroethene (TCE)-contaminated groundwater was studied in this pilot-scale study. γ-PGA (40 L) solution was injected into the aquifer via the injection well (IW) for substrate supplement. Groundwater samples were collected from monitor wells and IW and analyzed for TCE and its byproducts, geochemical indicators, dechlorinating bacteria, and microbial diversity periodically. Injected γ-PGA resulted in an increase in total organic carbon (TOC) (up to 9820 mg/L in IW), and the TOC biodegradation caused the formation of anaerobic conditions. Increased ammonia concentration (because of amine release from γ-PGA) resulted in the neutral condition in groundwater, which benefited the growth of Dehalococcoides. The negative zeta potential and micro-scale diameter of γ-PGA allowed its globule to distribute evenly within soil pores. Up to 93% of TCE removal was observed (TCE dropped from 0.14 to 0.01 mg/L) after 59 days of γ-PGA injection, and TCE dechlorination byproducts were also biodegraded subsequently. Next generation sequence (NGS) analyses were applied to determine the dominant bacterial communities. γ-PGA supplement developed reductive dechlorinating conditions and caused variations in microbial diversity and dominant bacterial species. The dominant four groups of bacterial communities including dechlorinating bacteria, vinyl chloride degrading bacteria, hydrogen producing bacteria, and carbon biodegrading bacteria.

Assessment of PM2.5 and PAH content in PM2.5 emitted from mobile source gasoline-fueled vehicles in concomitant with the vehicle model and mileages

This study investigates the PM_2.5 emission and analyses the PAHs content in PM_2.5 emitted from gasoline-fueled vehicles. Outflow from the vehicles appear to be the ultimate source of PAHs in metro urban communities since the emission from gasoline vehicle increases the wellbeing hazard due to contiguity of exposure to gasoline exhaust. In this study, fifteen vehicles were randomly taken for sampling, where sixteen priority PAHs concentration were investigated. The study was performed on the vehicles with different Euro standard emission by taking into consideration the European legislative levels for vehicles on the toxic gaseous emission. Among all the PAHs outflow components of PM_2.5 radiated in the exhaust of gasoline engines, the average concentration of total PAHs discharged was 0.377ng/L-fuel, while the total BaPeq concentration was 0.00993ng/L-fuel.

Copper promotes E. coli laccase-mediated TNT biotransformation and alters the toxicity of TNT metabolites toward Tigriopus japonicus

Although laccase is involved in the biotransformation of 2,4,6-trinitrotoluene (TNT), little is known regarding the effect of E. coli laccase on TNT biotransformation. In this study, E. coli K12 served as the parental strain to construct a laccase deletion strain and two laccase-overexpressing strains. These E. coli strains were used to investigate the effect of laccase together with copper ions on the efficiency of TNT biotransformation, the variety of TNT biotransformation products generated and the toxicity of the TNT metabolites. The results showed that the laccase level was not relevant to TNT biotransformation in the soluble fraction of the culture medium. Conversely, TNT metabolites varied in the insoluble fraction analyzed by thin-layer chromatography (TLC). The insoluble fraction from the laccase-null strain showed fewer and relatively fainter spots than those detected in the wild-type and laccase-overexpressing strains, indicating that laccase expression levels were interrelated determinants of the varieties and amounts of TNT metabolites produced. In addition, the aquatic invertebrate Tigriopus japonicus was used to assess the toxicity of the TNT metabolites. The toxicity of the TNT metabolite mixture increased when the intracellular laccase level in strains increased or when purified E. coli recombinant Laccase (rLaccase) was added to the culture medium. Thus, our results suggest that laccase activity must be considered when performing microbial TNT remediation.

Emulsified polycolloid substrate biobarrier for benzene and petroleum-hydrocarbon plume containment and migration control - A field-scale study

The objective of this field-scale study was to assess the effectiveness of applying an emulsified polycolloid substrate (EPS; containing cane molasses, soybean oil, and surfactants) biobarrier in the control and remediation of a petroleum-hydrocarbon plume in natural waters. An abandoned petrochemical manufacturing facility site was contaminated by benzene and other petroleum products due to a leakage from a storage tank. Because benzene is a petroleum hydrocarbon with a high migration ability, it was used as the target compound in the field-scale study. Batch partition and sorption experiment results indicated that the EPS to water partition coefficient for benzene was 232 mg/mg at 25 °C. This suggests that benzene had a higher sorption affinity to EPS, which decreased the benzene concentrations in groundwater. The EPS solution was pressure-injected into three remediation wells (RWs; 150 L EPS in 800 L groundwater). Groundwater samples were collected from an upgradient background well, two downgradient monitor wells (MWs), and the three RWs for analyses. EPS injection increased total organic carbon (TOC) concentrations (up to 786 mg/L) in groundwater, which also resulted in the formation of anaerobic conditions. An abrupt drop in benzene concentration (from 6.9 to below 0.04 mg/L) was observed after EPS supplementation in the RWs due to both sorption and biodegradation mechanisms. Results show that the EPS supplement increased total viable bacteria and enhanced bioremediation efficiency, which accounted for the observed decrease in benzene concentration. The first-order decay rate in RW1 increased from 0.003 to 0.023 d^-1 after EPS application. Injection of EPS resulted in significant growth of indigenous bacteria, and 23 petroleum-hydrocarbon-degrading bacterial species were detected, which enhanced the in situ benzene biodegradation efficiency. Results demonstrate that the EPS biobarrier can effectively contain a petroleum-hydrocarbon plume and prevent its migration to downgradient areas, which reduces the immediate risk presented to downgradient receptors.

Application of an emulsified polycolloid substrate biobarrier to remediate petroleum-hydrocarbon contaminated groundwater

Emulsified polycolloid substrate (EPS) was developed and applied in situ to form a biobarrier for the containment and enhanced bioremediation of a petroleum-hydrocarbon plume. EPS had a negative zeta potential (-35.7 mv), which promoted its even distribution after injection. Batch and column experiments were performed to evaluate the effectiveness of EPS on toluene containment and biodegradation. The EPS-to-water partition coefficient for toluene (target compound) was 943. Thus, toluene had a significant sorption affinity to EPS, which caused reduced toluene concentration in water phase in the EPS/water system. Groundwater containing toluene (18 mg/L) was pumped into the three-column system at a flow rate of 0.28 mL/min, while EPS was injected into the second column to form a biobarrier. A significant reduction of toluene concentration to 0.1 mg/L was observed immediately after EPS injection. This indicates that EPS could effectively contain toluene plume and prevent its further migration to farther downgradient zone. Approximately 99% of toluene was removed after 296 PVs of operation via sorption, natural attenuation, and EPS-enhanced biodegradation. Increase in total organic carbon and bacteria were also observed after EPS supplement. Supplement of EPS resulted in a growth of petroleum-hydrocarbon degrading bacteria, which enhanced the toluene biodegradation.

Using poly-glutamic acid as soil-washing agent to remediate heavy metal-contaminated soils

The extraction efficiency of heavy metals from soils using three forms of gamma poly-glutamic acid (γ-PGA) as the washing agents was investigated. Controlling factors including agent concentrations, extraction time, pH, and liquid to soil ratio were evaluated to determine the optimum operational conditions. The distribution of heavy metal species in soils before and after extraction processes was analyzed. Up to 46 and 74% of heavy metal removal efficiencies were achieved with one round and a sequential extraction process using H-bonding form of γ-PGA (200 mM) with washing time of 40 min, liquid to solid ratio of 10 to 1, and pH of 6. Major heavy metal removal mechanisms were (1) γ-PGA-promoted dissolution and (2) complexation of heavy metal with free carboxyl groups in γ-PGA, which resulted in heavy metal desorption from soils. Metal species on soils were redistributed after washing, and soils were remediated without destruction of soil structures and productivity.

Application of a long-lasting colloidal substrate with pH and hydrogen sulfide control capabilities to remediate TCE-contaminated groundwater

A long-lasting emulsified colloidal substrate (LECS) was developed for continuous carbon and nanoscale zero-valent iron (nZVI) release to remediate trichloroethylene (TCE)-contaminated groundwater under reductive dechlorinating conditions. The developed LECS contained nZVI, vegetable oil, surfactants (Simple Green™ and lecithin), molasses, lactate, and minerals. An emulsification study was performed to evaluate the globule droplet size and stability of LECS. The results show that a stable oil-in-water emulsion with uniformly small droplets (0.7 μm) was produced, which could continuously release the primary substrates. The emulsified solution could serve as the dispensing agent, and nZVI particles (with diameter 100-200 nm) were distributed in the emulsion evenly without aggregation. Microcosm results showed that the LECS caused a rapid increase in the total organic carbon concentration (up to 488 mg/L), and reductive dechlorination of TCE was significantly enhanced. Up to 99% of TCE (with initial concentration of 7.4 mg/L) was removed after 130 days of operation. Acidification was prevented by the production of hydroxide ion by the oxidation of nZVI. The formation of iron sulfide reduced the odor from produced hydrogen sulfide. Microbial analyses reveal that dechlorinating bacteria existed in soils, which might contribute to TCE dechlorination.

The search for human osteoporosis genes

Osteoporosis is the most prevalent metabolic bone disease and a major clinical and public health problem. Heredity plays an important and well-established role in determining the lifetime risk of this disease. Major efforts are currently underway to identify the specific genes and their allelic variations that contribute to the heritable component to osteoporosis. A number of laboratories are using quantitative trait locus (QTL) methods of genome scanning in families and animal models to identify candidate genomic regions and, ultimately, the genes and genetic variations that lead to osteoporosis. Several chromosomal regions of the human genome have now been linked to osteoporosis-related phenotypes. Although the specific genes contributing to the majority of these linkage signals have not been identified, two positional candidate genes have now been identified: low density lipoprotein receptor-related protein 5 (LRP5) and bone morphogenetic protein 2 (BMP2). A number of QTL has also been identified by cross-breeding strains of mice with variable bone density and several of these QTL have been fine mapped, providing a rich new base for understanding osteoporosis. Genetic association analyses have also provided evidence for a modest relationship between allelic variants in several biological candidate genes and bone mass and the risk of fracture. These ongoing animal and human studies will provide a continuing source of new insight into the genetic regulation of bone and mineral metabolism and the molecular etiology of osteoporosis. The new insight that will emerge from this ongoing research should lead to new ways of diagnosing, preventing and treating the growing clinical and public health problem of osteoporosis.

Spermatozoan morphology of four species of bivalve (Heterodonta, Veneridae) from Taiwan

Using transmission and scanning electron microscopy, the mature spermatozoa of four bivalves of the family Veneridae--Gafrarium tumidum and Circe scripta (Circinae), Pitar sulfureum (Pitarinae) and Gomphina aequilatera (Tapetinae)--are described for the first time and compared with those of other bivalves, particularly other heterodonts. As our observations show, the spermatozoa of these four species are of the primitive type or ect-aquasperm form. The head contains a slightly curved nucleus with a short cone-shaped acrosome. The structure of the acrosome is typical of heterodont bivalves and two major components of the acrosomal vesicle material can be distinguished. The midpiece exhibits four or five mitochondria which surround the proximal and the distal centrioles. Variation in the shape and dimensions of the acrosomal vesicle and nucleus is substantial in these four Veneroidea species.

Retinoic acid syndrome induced by arsenic trioxide in treating recurrent all-trans retinoic acid resistant acute promyelocytic leukemia

Arsenic Trioxide (As2O3) is an effective agent for treating acute promyelocytic leukemia achieving a complete remission rate of about 60% to 90%. It is similar to all-trans retinoic acid (ATRA) when treating acute promyelocytic leukemia (APL), because both agents have limited side effects compared to conventional chemotherapy, although the treatment period is more prolonged. During treatment, both agents may induce leukocytosis, and in patients taking ATRA, leukocytosis appears to be related to the development of retinoic acid syndrome (RAS). We report here a case of APL treated with ATRA in combination with chemotherapy 3 years earlier. During treatment, an episode of RAS with fever, edema, pericardiac effusion etc. was encountered. Recently, she had a relapse of leukemia, and As2O3 therapy was used. Leukocytosis developed again, and symptoms of fever, skin rash, edema resembling a RAS also developed, which was quickly relieved by steroid administration in a manner resembling response to RAS.