25 May 2016
04 July 2016
ISEH 2016 & Geoinformatics 2016: Joint International Conference on Environment, Health, GIS and Agriculture
14 August 2016
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Science in the News
Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health
- Influence of clay minerals on sorption and bioreduction of arsenic under anoxic conditions 2015-12-01
Adsorption of As(V) on various clay minerals including kaolinite (KGa-1), montmorillonite (SWy-1) and nontronites (NAU-1 and NAU-2), and subsequent bioreduction of sorbed As(V) to As(III) by bacterium Shewanella putrefaciens strain CN-32 were investigated. Nontronites showed relatively higher sorption capacity for As(V) primarily due to higher iron oxide content. Freundlich equation well described the sorption of As(V) on NAU-1, NAU-2 and SWy-1, while As(V) sorption isotherm with KGa-1 fitted well in the Langmuir model. The bacterium rapidly reduced 50Â % of dissolved As(V) to As(III) in 2Â h, followed by its complete reduction (>ca. 98Â %) within 12Â h. In contrast, sorption of As(V) to the mineral surfaces interferes with the activity of bacterium, resulting in low bioreduction of As(V) by 27Â % for 5Â days of incubation. S. putrefaciens also promoted the reduction of Fe(III) present in the clay mineral to Fe(II). This study indicates that the sorption and subsequent bioreduction of As(V) on clay minerals can significantly influence the mobility of As(V) in subsurface environment.
- Determination of biomarkers for polycyclic aromatic hydrocarbons (PAHs) toxicity to earthworm ( Eisenia fetida ) 2015-12-01
Polycyclic aromatic hydrocarbon (PAH) compounds are persistent, carcinogenic, and mutagenic. When PAHs enter agricultural soils through sewage sludge, they pose an environmental risk to soil organisms, including earthworms. Therefore, we aimed to determine the toxic effects of PAHs on earthworms. Five PAHs were used: fluorene, anthracene, phenanthrene, fluoranthene, and pyrene. Only fluorene and phenanthrene exhibited toxicity (LC50 values 394.09 and 114.02Â gÂ Lâ1, respectively) against the earthworm Eisenia fetida. None of the other PAHs tested in this study enhanced the mortality of adult earthworm until the concentrations reached to 1000Â gÂ Lâ1. After exposure to PAHs, acetylcholinesterase (AChE) activity in E. fetida decreased in a concentration-dependent manner, and phenanthrene exhibited the strongest inhibitory effect on AChE, followed by fluorene. Activity of a representative detoxifying enzyme, carboxylesterase, was dramatically reduced in E. fetida exposed to all tested PAHs in comparison with that observed in the control test. The remaining glutathione S-transferase activity significantly decreased in E. fetida after exposure to PAHs. To profile small proteins <20Â kDa, SELDI-TOF MS with Q10 ProteinChips was used, and 54 proteins were identified as being significantly different from the control (pÂ =Â 0.05). Among them, the expressions of three proteins at 4501.8, 4712.4, and 4747.9Â m/z were only enhanced in E. fetida exposed to anthracene and pyrene. One protein with 16,174Â m/z was selectively expressed in E. fetida exposed to fluorene, phenanthrene, and fluoranthene. These proteins may be potential biomarkers for the five PAHs tested in E. fetida.
- Can abundance of methanogen be a good indicator for CH 4 flux in soil ecosystems? 2015-12-01
Methane, which is produced by methanogenic archaea, is the second most abundant carbon compound in the atmosphere. Due to its strong radiative forcing, many studies have been conducted to determine its sources, budget, and dynamics. However, a mechanistic model of methane flux has not been developed thus far. In this study, we attempt to examine the relevance of the abundance of methanogen as a biological indicator of methane flux in three different types of soil ecosystems: permafrost, rice paddy, and mountainous wetland. We measured the annual average methane flux and abundance of methanogen in the soil ecosystems in situ. The correlation between methane flux and the abundance of methanogen exists only under a specific biogeochemical conditions such as SOM of higher than 60Â %, pH of 5.6â6.4, and water-saturated. Except for these conditions, significant correlations were absent. Therefore, microbial abundance information can be applied to a methane flux model selectively depending on the biogeochemical properties of the soil ecosystem.