The role of black carbon as a catalyst for environmental redox transformation

Black carbon (BC) is an important class of geosorbents that control the fate and transport of organic pollutants in soil and sediment. We previously demonstrated a new role of BC as an electron transfer mediator in the abiotic reduction of nitroaromatic and nitramine compounds by Oh and Chiu (Environ Sci Technol 43:6983–6988, 2009). We proposed that BC can catalyze the reduction of nitro compounds because it contains microscopic graphitic (graphene) domains, which facilitate both sorption and electron transfer. In this study, we assessed the ability of different types of BC—graphite, activated carbon, and diesel soot—to mediate the reduction of 2,4-dinitrotoluene (DNT) and 2,4-dibromophenol (DBP) by H₂S. All three types of BC enhanced DNT and DBP reduction. H₂S supported BC-mediated reduction, as was observed previously with a thiol reductant. The results suggest that BC may influence the fate of organic pollutants in reducing subsurface environments through redox transformation in addition to sorption.

     

Dechlorination of polychlorinated biphenyl congeners by anaerobic microorganisms from river sediment.

The microbial dechlorination of seven kinds of polychlorinated biphenyls (PCBs) by anaerobic microorganisms from river sediment was investigated. Dechlorination rates were found to be affected by the chlorine level of PCB congeners; dechlorination rates decreased as chlorine levels increased. Dechlorination rates were fastest under methanogenic conditions and slowest under nitrate-reducing conditions. The addition of individual electron donors (acetate, pyruvate, and lactate) enhanced the dechlorination of PCB congeners under methanogenic and sulfate-reducing conditions but delayed the dechlorination of PCB congeners under nitrate-reducing conditions. PCB congener dechlorination also was delayed by the addition of various polycyclic aromatic hydrocarbons (PAHs) under three reducing conditions and by surfactants, such as brij30, triton SN70, and triton N101. The results suggest that methanogen, sulfate-reducing bacteria, and nitrate-reducing bacteria all are involved in the dechlorination of PCB congeners.     

Photoacoustic infrared spectroscopy for conducting gas tracer tests and measuring water saturations in landfills

Gas tracer tests can be used to determine gas flow patterns within landfills, quantify volatile contaminant residence time, and measure water within refuse. While gas chromatography (GC) has been traditionally used to analyze gas tracers in refuse, photoacoustic spectroscopy (PAS) might allow real-time measurements with reduced personnel costs and greater mobility and ease of use. Laboratory and field experiments were conducted to evaluate the efficacy of PAS for conducting gas tracer tests in landfills. Two tracer gases, difluoromethane (DFM) and sulfur hexafluoride (SF₆), were measured with a commercial PAS instrument. Relative measurement errors were invariant with tracer concentration but influenced by background gas: errors were 1-3% in landfill gas but 4-5% in air. Two partitioning gas tracer tests were conducted in an aerobic landfill, and limits of detection (LODs) were 3-4 times larger for DFM with PAS versus GC due to temporal changes in background signals. While higher LODs can be compensated by injecting larger tracer mass, changes in background signals increased the uncertainty in measured water saturations by up to 25% over comparable GC methods. PAS has distinct advantages over GC with respect to personnel costs and ease of use, although for field applications GC analyses of select samples are recommended to quantify instrument interferences.     

First detection of enteric adenoviruses genotype 41 in recreation spring areas of Taiwan

Environmental Science and Pollution Research - Human adenoviruses (HAdVs) are DNA viruses found in recreational water, such as water parks and swimming pools. Human adenovirus 41 (HAdV-41) is the...     

Female reproductive biology and oocyte development of the red frog crab,Ranina ranina,off Hachijojima,Izu Islands,Japan

Speciments of the red frog crab, Ranina ranina, examined in this study were collected off Hachijojima, Japan from 1987–1988 and 1990–1991. Ovigerous females occurred from May to September, and their carapace length ranged from 61.8 to 102.1 mm. Minimum size at the maturity was estimated to be 50 to 60 mm carapace length. The lobule-type ovary had a longitudinal ovarian cavity at the center. Germinal zones were located along the sides of the cavity. Oogenesis was divided into five main and ten detailed stages: proliferation (oogonium); previtellogenesis (bouquet, early chromatin nucleolus, late chromatin nucleolus); primary vitellogenesis (oil globule and yolk granule); secondary vitellogenesis (primary yolk platelet, secondary yolk platelet and prematuration); and maturation (maturation) stages. Vitellogenesis started at the oil globule stage when weakly positive periodic acid-Schiff granules appear in the cytoplasm. Based on the gonadosomatic index and histological changes in ovary, the reproductive cycle was divided into five stages: multiplication, from December to January; developing, from February to March; ripe in April and early May; spawning, from late May to August; and recovery, from August to November. Each crab spawned more than once during the spawning season.     

Volatile organic compounds (VOCs) in urban atmosphere of Hong Kong

The assessment of volatile organic compounds (VOCs) has become a major issue of air quality network monitoring in Hong Kong. This study is aimed to identify, quantify and characterize volatile organic compounds (VOCs) in different urban areas in Hong Kong. The spatial distribution, temporal variation as well as correlations of VOCs at five roadside sampling sites were discussed. Twelve VOCs were routinely detected in urban areas (Mong Kok, Kwai Chung, Yuen Long and Causeway Bay). The concentrations of VOCs ranged from undetectable to 1396 microg/m3. Among all of the VOC species, toluene has the highest concentration. Benzene, toluene, ethylbenzene and xylenes (BTEX) were the major constituents (more than 60% in composition of total VOC detected), mainly contributed from mobile sources. Similar to other Asian cities, the VOC levels measured in urban areas in Hong Kong were affected both by automobile exhaust and industrial emissions. High toluene to benzene ratios (average T/B ratio = 5) was also found in Hong Kong as in other Asian cities. In general, VOC concentrations in the winter were higher than those measured in the summer (winter to summer ratio > 1). As toluene and benzene were the major pollutants from vehicle exhausts, there is a necessity to tighten automobile emission standards in Hong Kong.     

Environmental Monitoring of Benzene and Alkylated Benzene from Vehicular Emissions

The volatile organic pollutants from direct vehicular exhaust were trapped with activated charcoal, desorbed with carbon disulphide and analysed by GC/MS with tert-butyl benzene as an internal standard. A comparative study was made from the exhaust of 1000 cc, 1300 cc, 1600 cc cars, pickup, lorry(diesel), 125 cc and 70 cc motorbikes. The level of pollutants emitted were in the following order, motorbike(petrol) car(petrol) pickup(petrol) lorry(diesel). The range of highest emission (125 cc motorbike) to the lowest emission (lorry(diesel)) was of the order of 102 for benzene, 6×102 for ethyl benzene, 5×102 for toluene and 3×102 for xylenes. Among cars, those fitted with catalytic convertors emitted a lower level of benzene (2 to 3 times) when compared with those without catalytic convertors. Similar studies on the air in air-conditioned buses, non air-conditioned buses and three metres from the edge of the road shows that they have the same pollutant level. The level of these pollutant as compared to those from direct car exhaust are of the order of 102 times less for benzene, xylene and toluene and 103 times less for ethylbenzene. The levels of benzene, toluene, ethylbenzene and xylenes by the road side and in the buses were found to be lower than the exposure limits of ACGIH, OSHA and EH40.     

Constituents of volatile organic compounds of evaporating essential oil

Essential oils containing aromatic compounds can affect air quality when used indoors. Five typical and popular essential oils—rose, lemon, rosemary, tea tree and lavender—were investigated in terms of composition, thermal characteristics, volatile organic compound (VOC) constituents, and emission factors. The activation energy was 6.3–8.6 kcal mol^?1, the reaction order was in the range of 0.6–0.8, and the frequency factor was 0.01–0.24 min^?1. Toluene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, n-undecane, p-diethylbenzene and m-diethylbenzene were the predominant VOCs of evaporating gas of essential oils at 40 °C. In addition, n-undecane, p-diethylbenzene, 1,2,4-trimethylbenzene, m-diethylbenzene, and 1,2,3-trimethylbenzene revealed high emission factors during the thermogravimetric (TG) analysis procedures. The sequence of the emission factors of 52 VOCs (137–173 mg g^?1) was rose ≈ rosemary > tea tree ≈ lemon ≈ lavender. The VOC group fraction of the emission factor of aromatics was 62–78%, paraffins were 21–37% and olefins were less than 1.5% during the TG process. Some unhealthy VOCs such as benzene and toluene were measured at low temperature; they reveal the potential effect on indoor air quality and human health.     

Emission factor of exhaust gas constituents during the pyrolysis of zinc chloride immersed biosolid

Pyrolysis enables ZnCl₂ immersed biosolid to be reused, but some hazardous air pollutants are emitted during this process. Physical characteristics of biosolid adsorbents were investigated in this work. In addition, the constituents of pyrolytic exhaust were determined to evaluate the exhaust characteristics. Results indicated that the pyrolytic temperature was higher than 500 °C, the specific surface area was >900 m²/g, and the total pore volume was as much as 0.8 cm³/g at 600 °C. For non-ZnCl₂ immersed biosolid pyrolytic exhaust, VOC emission factors increased from 0.677 to 3.170 mg-VOCs/g-biosolid with the pyrolytic temperature increase from 400 to 700 °C, and chlorinated VOCs and oxygenated VOCs were the dominant fraction of VOC groups. VOC emission factors increased about three to seven times, ranging from 1.813 to 21.448 mg/g for pyrolytic temperatures at 400–700 °C, corresponding to the mass ratio of ZnCl₂ and biosolid ranging from 0.25–2.5.