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This work assessed both the fractionation and the seasonal mobility variations of Ga and In in systems impacted by acidic thermal waters. This was accomplished by performing thermodynamic calculations using the PHREEQC algorithm and by assessing the activity of acidophilic iron-oxidizing bacteria. The pH of the Kusatsu thermal waters in Gunma Prefecture, central Japan, is rapidly increased following the addition of a lime suspension. After an abrupt pH increase, under which conditions free ions of Ga and In and their complexes with Cl− and SO42− exist only in negligible quantities, the majority of dissolved Ga and In is removed by sorption onto suspended hydrous ferric oxides (HFOs). These HFOs are then transported to an artificial lake without significant sedimentation along the river. Subsequently, the suspended HFOs settle out and are added to sediments without significant fractionation between Ga and In. The Tamagawa thermal waters in Akita Prefecture, northeast Japan, are also treated with lime. However, complete neutralization requires mixing with some tributary streams, leading to a gradual downstream increase in pH. Dissolved Ga is, in general, sorbed by HFOs in upstream areas, leading to wide dispersal of Ga across the entire watershed. In comparison, In is transported to the lake inlet predominantly as a Cl− complex species without significant removal along the river, with the majority being precipitated in an artificial lake, where Cl− concentrations are too low to form stable complex species with In, and thus, dissolved In is sorbed by HFOs. As a result, In is effectively concentrated within downstream lakebed sediments, whereas Ga is dispersed along the river. Seasonal variations in Ga mobility within the Tamagawa field between snowmelt and low-flow seasons are primarily controlled by pH, because hydrolysis reactions of these metals, which are related to sorption reactions, tend to occur in the upstream regions in the snowmelt season. However, under warmer conditions, HFO formation preferably occurs due to the activity of acidophilic iron-oxidizing bacteria. Thus, under similar pH variations, dissolved Ga is more effectively removed by HFOs during warmer seasons. On the contrary, because HFOs are abundantly formed in low-flow season, even under colder conditions, before In hydrolysis reaction starts to occur, In mobility is less affected by water temperature and then bacterial activity.

Mangroves constitute valuable coastal resources that are vulnerable to oil pollution. One of the major processes to remove oil from contaminated mangrove sediment is microbial degradation. A study on heavy oil- and hydrocarbon-degrading bacterial consortia from mangrove sediments in Okinawa, Japan was performed to evaluate their capacity to biodegrade and their microbial community composition. Surface sediment samples were obtained from mangrove sites in Okinawa (Teima, Oura, and Okukubi) and enriched with heavy oil as the sole carbon and energy source. The results revealed that all enriched microbial consortia degraded more than 20% of heavy oil in 21 days. The K1 consortium from Okukubi site showed the most extensive degradative capacity after 7 and 21 days. All consortia degraded more than 50% of hexadecane but had little ability to degrade polycyclic aromatic hydrocarbons (PAHs). The consortia were dominated by Pseudomonas or Burkholderia. When incubated in the presence of hydrocarbon compounds, the active bacterial community shifted to favor the dominance of Pseudomonas. The K1 consortium was a superior degrader, demonstrating the highest ability to degrade aliphatic and aromatic hydrocarbon compounds; it was even able to degrade heavy oil at a concentration of 15%(w/v). The dominance and turn-over of Pseudomonas and Burkholderia in the consortia suggest an important ecological role for and relationship between these two genera in the mangrove sediments of Okinawa.

The aims of this study were to identify the bacteria responsible for the rapid degradation of aromatic hydrocarbons, and to determine the roles of bacterial species in the microbial consortium. The population changes of the four major bacterial groups, namely Burkholderia spp., Achromobacter spp./Alcaligenes spp., Cupriavidus spp., and Rhodanobacter spp. in the Y consortium that preferentially degraded petroleum oil-derived aromatic hydrocarbons were assessed using quantitative real-time polymerase chain reaction (q-PCR). P-xylene was used as a representative aromatic compound, decane as a representative aliphatic compound, p-xylene-decane as a representative hydrocarbon mixture, and kerosene as a representative petroleum-based oil. The results showed that the remarkable increase of Burkholderia spp. coincided with the rapid degradation of aromatic hydrocarbons in kerosene, and p-xylene in single and dual-substrate cultures. Cupriavidus spp. significantly increased when decane was rapidly depleted. Achromobacter spp.,/Alcaligenes spp., and Rhodanobacter spp. were initially inhibited by the presence of aromatic hydrocarbons and seemed not to be active in hydrocarbon degradation, but utilized the metabolic products. This work provided an alternative way to explain the contribution of different microbial species in the degradation of hydrocarbon fractions. The behavior of the consortium is of interest in the context of the bioremediation of the more toxic aromatic hydrocarbons in environments contaminated by petroleum products.

A dechlorinating consortium (designated as TES-1 culture) able to convert trichloroethene (TCE) to ethene was established from TCE-contaminated groundwater. This culture had the ability of complete dechlorination of TCE within about one month. From the clone library analysis of 16S rRNA gene, this culture was mainly composed of fermentation bacteria, such as Clostridium spp., and Desulfitobacterium spp. known as facultative dechlorinator. PCR using specific primers for Dehalococcoides spp. and the dehalogenase genes confirmed that the culture contained the Dehalococcoides spp. 16S rRNA gene and three dehalogenase genes, tceA, vcrA and bvcA. Dechlorination experiments using cis-dichloroethene (cis-DCE) at concentrations of 37-146 μM, revealed that the gene copy numbers of tceA, vcrA, and bvcA increased up to 10⁷ copy/mL, indicating that Dehalococcoides spp. containing these three dehalogenase genes were involved in cis-DCE dechlorination. However, in the culture to which 292 μM of cis-DCE was added, only the tceA gene and the Dehalococcoides spp. 16S rRNA gene increased up to 10⁷ copy/mL. The culture containing 292 μM of cis-DCE also exhibited about one tenth slower ethene production rate compared to the other cultures.

Numerous studies on the biodegradation of petroleum products using total petroleum hydrocarbons (TPH) have been carried out; however, the biodegradation of equivalent carbon number (EC) based hydrocarbon fractions in mineral oil has attracted little attention. This study investigated the ability of a microbial consortium to degrade the EC fractions in kerosene, which was used as a representative mineral oil. Based on the cloning and sequencing of the 16S rRNA gene, the microbial community was predominantly identified as Betaproteobacteria of the genera Achromobacter , Alcaligenes , and Cupriavidus . Degradation experiments in sealed 120-ml vials containing 1% (w v −1 ) kerosene revealed that aromatic fractions were degraded faster than aliphatic fractions. Aromatic fractions EC >7–8 and EC >8–10 were completely degraded after three days while aliphatic fractions EC >6–8 and EC >8–10 were only partially degraded. The aromatic EC >10–12 fraction was the third most degraded, and the aliphatic EC >10–12 and EC >12–16 fractions were the least degraded fractions. The first-order rate constants for the aromatic fractions ranged from 0.12 d −1 to 0.51 d −1 and from 0.06 d −1 to 0.32 d −1 for the aliphatic fractions. The microbial consortium preferentially utilized aromatic fractions, which are more toxic than aliphatic fractions. This finding is useful when considering risk-based bioremediation: A microbial community could potentially degrade the more toxic aromatic hydrocarbon components in petroleum-contaminated environments.

The pathways and kinetics of trichloroethylene (TCE) degradation in aerobic pyrite suspension were investigated. The detection of hydroxyl radical in aqueous pyrite suspension suggested that TCE was degraded by this strong oxidant The reaction pathways of TCE degradation were proposed in which the degradation of TCE to formic acid and finally to CO2 was the main route. Degradation of TCE to oxalic acid and to dichloroacetic acid were found as minor pathways. Degradation rates of TCE to formic acid, glyoxylic acid, and dichloroacetic acid were obtained using kinetic model at 1.2 x 10(-2), 9.8 x 10(-4) and 4.6 x 10(-4) h(-1), respectively.

The transformation of trichloroethylene (TCE) in natural mineral iron disulfide (pyrite) aqueous suspension under different oxygen conditions was investigated in laboratory batch experiments. TCE transformation was pursued by monitoring its disappearance and products released with time. The effect of oxygen was studied by varying the initial dissolved oxygen concentration (DO(i)) inside each reactor. Transformation rates depended strongly on DO(i) in the system. In anaerobic pyrite suspension, TCE did not transform as it did under aerobic conditions. The transformation rate increased with an increase in DO(i). The TCE transformation kinetics was fitted to a pseudo-first-order reaction with a rate constant k (h(-1)) varying from 0.004 to 0.013 for closed systems with DO(i) varying from 0.017 to 0.268 mmol/L under the experimental conditions. In the aerobic systems, TCE transformed to several organic acids including dichloroacetic acid, glyoxylic acid, oxalic acid, formic acid, and finally to CO2 and chloride ion. Dichloroacetic acid was the only chlorinated intermediate found. Both TCE and the pyrite surface were oxidized in the presence of O2. Oxygen consumption profiles showed O2 was the common oxidant in both TCE and pyrite oxidation reactions. Ferric ion cannot be used as an alternative oxidant to oxygen for TCE transformation.

This paper describes about microbial diversity in an iron oxidation tank of an AMD treatment plant established at an abandoned sulphur mine in Japan. Since the mining operation was stopped, this mine has produced strong acidic mine drainage, pH 1.8, including a high concentration of ferrous iron, 301mg/L, and the flow rate was about 4m3/min. In 2006, a pilot scale microbial iron oxidizing system was installed to remove total iron more easily from the AMD by oxidizing ferrous iron to ferric iron. From the start of this pilot operation, microbial diversity in the iron oxidation tank was investigated using a PCR-DGGE method for about two months. In the PCR, V3 region of 16S rRNA gene for Bacteria was amplified. The profiles of DGGE showed that there were three dominant species in the iron oxidation tank through the experimental period. Number of bands on DGGE profiles decreased with dates of sampling so that the microbial population became less diverse because of the iron oxidizing operation. There was a wide variety of bacterial species of even though conditions were strongly acidic.

This paper describes a fundamental examination of a quicklime mixing treatment combined with carbon dioxide ventilation for the remediation process of soils polluted with volatile organic compounds (VOCs). The quicklime mixing treatment is widely applied to remove volatile pollutants in soils using the heat of reaction with quicklime and pore water. To maintain a higher temperature and to ensure that most of the VOCs are volatilized, quicklime is usually mixed at a ratio of 10% with soils in this treatment. However, a surplus of added quicklime results in higher (alkaline) soil pH and causes serious damage to the soil ecosystems. To solve this problem, the simultaneous ventilation of carbon dioxide during quicklime mixing with polluted soil was examined. Under these conditions calcium hydroxide is generated by the reaction of quicklime with pore water; the calcium hydroxide then reacts with carbon dioxide to produce additional heat of reaction. It is expected that the heat from the second reaction can be used for the pollutant treatment, allowing the amount of quicklime addition for the treatment to be reduced. Laboratory experiments showed that more than half of the calcium hydroxide was changed to calcium carbonate when the mixed soil sample was ventilated by carbon dioxide, using mixing ratios of 5% quicklime and 5% water in the soil. The maximum soil temperature reached with this treatment was the same as that for the treatment using 10% quicklime. Scale-up experiments confirmed the effectiveness of using carbon dioxide ventilation.

Polycyclic aromatic hydrocarbons (PAHs) have polluted soil and groundwater widely and for long term because of their low solubility at normal temperature. Several microorganisms, such as Pseudomonas sp., Sphigomonas sp., a white‐rot fungus and so on, being able to decompose PAHs, have been isolated and researched. This study reported to investigate biodegradation of low molecule PAH by isolated bacteria from light oil polluted soil. 12 isolates were obtained from a light oil polluted soil using naphthalene, fluorene and anthracene as sole carbon source, of which 4 isolates grew with naphthalene, 4 isolates did with fluorene and 4 isolates did with anthracene. Among them 3 isolates showed the ability to degrade phenanthrene additionally. These phenanthrene degradation and growth rates were almost same as that of S. yanoikuyae (DSM6900), which is the typical bacteria of PAHs degrader. Therefore, the isolate seemed to have an expectation for PAHs degradation.

An anaerobic mixed microbial culture was enriched from soil and groundwater taken from a site contaminated with trichloroethene (TCE). This enrichment culture could dechlorinate TCE sequentially to cis‐dichloroethene (cis‐DCE), vinyl chloride (VC), and ethene rapidly within 2 weeks. This enrichment culture could utilize various organic compounds, such as methanol, ethanol, and sodium acetate and so on, as electron donor. This culture had maintained high ability of TCE dechlorination for about 3 years since the start of enrichment cultivation. The optimum pH value for the dechlorination activity of this culture, which reacts from TCE to ethene, was 6.7. However above the pH value 7.1, it lost the dechlorination ability of cis‐DCE and VC. So cis‐DCE was remained at that pH conditions. From the DNA sequencing analysis of 16SrRNA gene, this enrichment culture includes Dehalococcoides sp. which has the ability to dechlorinate TCE to VC completely with hydrogen. It suggested that this Dehalococcoides sp. takes part in the dechlorination of chloroethenes.