Hydrogeochemical Disparities and Constraints of Water Produced from Various Coal Seams in the Baode Block, Ordos Basin, China.

The hydrogeochemical characteristics of coalbed water play a crucial role in assessing the production level of coalbed methane (CBM) due to its involvement in the entire process of CBM generation, migration, accumulation, and extraction. To investigate variations in hydrochemical characteristics and controlling factors among different coal seams, a representative CBM field (Baode block) within the Ordos basin in China was chosen as a target. We have systematically collected produced water samples from coal seams of the Permian Shanxi Formation (P1s) and Taiyuan Formation (P1t). Tests and analyses were conducted on conventional cation and anions, trace elements, pH value, total dissolved solids (TDS), stable isotopes of hydrogen and oxygen in water, and inorganic carbon (δD, δ18O, and δ13CDIC). The findings indicate that the P1s coal seam primarily contains HCO3-Na type water, while the P1t coal seam consists of Cl-Na and HCO3-Na types of water. The disparity in water types between P1s and P1t can be attributed to interactions between water and rocks. The isotopic compositions of δD, δ18O, and δ13CDIC suggest that the sampled coalbed waters originate from atmospheric precipitation, with subsequent microbial activity. It is suggested that TDS content along with bicarbonate concentration can serve as effective indicators for determining high productivity due to weaker hydraulic conditions and a more enclosed water environment in P1t coal seams; threshold values being >1000 mg/L for TDS and >10 mequiv/L for bicarbonate concentration. Additionally, microbial activity is found to be more widespread in P1t compared to P1s. Principal component analysis reveals a significantly higher contribution of conventional ions toward TDS content observed within the P1t coal seam compared to that of P1s coal seam, accompanied by alterations in pH control parameters. The water produced from the P1s coalbed is primarily controlled by evaporite and silicate weathering/dissolution coupled with substantial cation exchange. Conversely, the water in the P1t coalbed is mainly influenced by silicate weathering/dissolution as well as evaporative concentration, with a limited occurrence of cation exchange. Moreover, there are distinct disparities in ion sources between P1s and P1t. These research findings provide a scientific foundation for assessing the development potential of CBM and optimizing extraction systems within similar CBM areas.

Evidence of Coal Biodegradation from Coalbed-Produced Water - A Case Study of Dafosi Gas Field, Ordos Basin, China.

Bioconversion of coal to methane occurs in the coalbed aquifer environment. To investigate the evidence of coal biodegradation from coalbed-produced water, we collected six field water samples from the Dafosi gas field and prepared one laboratory-simulated water sample and one indoor anaerobic microbial degradation sample with the highest compound concentration as the two reference standards. Gas chromatography-mass spectrometry was used to detect the organic compound type, concentration, and differences in the biomarker compound sensitivity. Results indicate that extracted organic matter from coalbed-produced water samples can be evidence of biodegradation. Variations in range compounds (such as n-alkanes, tri- and pentacyclic terpenes, and steranes) and their sensitivity confirmed active microbial degradation in the studied area. A positive correlation between the n-alkanes content in the coalbed-produced water and the stable carbon isotope value of methane further verifies that the n-alkanes are primary substrates for maintaining microbial activity. Therefore, evidence including n-alkanes, tri- and pentacyclic terpenes, steranes, unresolved complex mixtures, and stable carbon isotope composition of methane contribute to biogenic methane generation in situ. Our limited data suggest that managing soluble organic matter in the coalbed-produced water may provide a viable route for coal biodegradation since most microorganisms survive within the coal seam water.

[Correlation of bacterial diversity in rot Chinese cabbage with the habitat].

OBJECTIVE: To investigate the diversity of bacteria in soft rot Chinese cabbage and analyze their correlation with rhizosphere bacteria, we analyzed the bacterial population structures of soft rot Chinese cabbage and the rhizosphere in different habitat. METHODS: Based on the initial medium and artificial Chinese cabbage medium, we isolated the bacteria from soft rot tissues and rhizospheric soils from two typical habitats. According to the analysis of 16S rRNA gene sequence homology, we identified the isolated strains and analyzed the strains population structure. RESULTS: The total bacteria in soft rot tissues were 4.0 x 10(8) cell g(-1) and 1.2 x 10(11) cell g(-1), the number of pure strains were 56 and 85, the dominant strains were Curtobacterium flaccumfaciens pv. flaccumfaciens and Pseudomonas spp. (P. hibiscicola, P. taiwanensis, P. tuomuerensis, P. mosselii). The total bacteria in rhizospheric soils were 2.7 x 10(5) cell g(-1) and 6.2 x 10(7) cell g(-1), the number of pure strains were 36 and 70, the dominant strains were Bacillus megatherium and Pseudomonas spp. (P. plecoglossicida, P. hibiscicola, P. parafulva, P. monteilii, P. geniculata). CONCLUSION: The methods used in this study were effective in analyzing bacterial diversity in soft rot Chinese cabbage and the results correlated well with the soil bacteria analysis, suggesting that soft rot Chinese cabbage may be induced by various environmental bacteria. Our results infer that soft rot of Chinese cabbage might be pathogen-complex, and provide the clues for the mechanism study and protection.