Spatial and temporal distributions of mercury species ...

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... Daniele Borrini 2, Giordano Montegrossi 1, Franco Tassi 2, Orlando Vaselli 2,. Antonio ... m) producing wells discharge water at up to 50 and 90 ~ respectively.
Vol. 25 (Suppl.) 2006

CHINESE JOURNAL OF GEOCHEMISTRY

147

Sulfur species variation controlled by sulfate reducing bacteria (SRB) in sediments of Lake Erhai Xiaobing LIANG 1, Tae Seok Ahn 2, Mingyi WANG 1, Youzhi ZHAO a 1Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002,China 2Department of Envionmental Science, KangwangNational University, Chunchon, Korea

Sulfate reduction bacteria (SRB) are widespread in freshwater sediments and control the transformation of sulfur species. Sediment samples were collected from Lake Erhai in southwestern China. The sediment cores were cut to 1 cm-long segments, using the designed equipment under anaerobic conditions. SRB at different sediment depths were quantified by '~lle methods of fluorescence in-situ hybridization (FISH) and direct counting. At the same time, specific primers were chosen to amplify the 16 s rRNA genes from six main groups of SRB. 8042~ in sediment pore waters was analyzed using the anion chromatograph. SO was detected by HPLC. Other sulfur species, such as H2S, FeS and FeS2 were determined by chemical methods. In spring, SRB were distributed vertically at 2-15 cm depth, from 0.95• cells/g of sediments in Lake Erhai. The peak appeared at 11 cm depth. Three SRB groups detected are Desulfotomaculum, Desulfobulbus and Desulfococcus- Desulfonema-Desulfosarcina. However, in autumn, SRB increased to 2.54x 104-46.82 x 104 cells/g of sediments. SRB were distributed vertically at 2-19 cm depth and the peak appeared at 7-8 cm depth. Four SRB groups were found in autumn, one more group of Desulfovibrio-Desulfomicrobium than in spring. 8042 concentrations were low in 4cm of surface layer sediments in spring, averaging 1.2 mg/L. It increased from 5 cm and peak appeared at 7-8 cm depth. So had high contents in suspend layer (6.37 mg/g). However, SO42"concentrations were low as 2.2 mg/L in suspend layer sediments in spring. It increased from 4 cm and peak appeared at 8 cm depth. So had the same trend as in spring but lower contents. High contents were found in the suspend layer (0.38 mg/g). Vertical distribution of SRB was quite different in different seasons. There were also different SRB groups in each season. More SRB groups were distributed in sediments of autumn than of spring in Lake Erhai. SRB at different sediment depths controlled the variation of sulfate at each sediment depth.

Key words sulfur; sulfate reducing bacteria; sediment; Lake Erhai

Spatial and temporal distributions of mercury species and controlling factors in Hongfeng Reservoir, Guizhou, China Tianrong H E 1, X i n b i n F E N G 1, G u a n g l e Q I U 1, W e i y a n g B A I 1, Z h o n g g e n L I 1, Julia L U 2 1State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Science, Guiyang 550002, China 2 Department of Chemistry andBiology, Ryerson University, 350 VictoriaSt., Toronto, ON. Canada

The Hongfeng Reservoir was built in 1960 and is an alkaline, hyper-eutrophic and seasonal anoxic reservoir due to the contamination from domestic and industrial wastewaters. The water samples at deferent depths from two sampling sites were collected from November 2003 to September 2004 using metal clean protocols. Total Hg (THg), reactive Hg (RHg), dissolved total Hg (DHg), dissolved gaseous mercury (DGM) were measured by gold trap pre-concentration and CVAFS detection. Methyl mercury was measured by distillation followed by aqueous phase ethylation, precollection on a Tenax, isothermal gas chromatography and cold vapor atomic fluorescence detection. There was no discernible seasonal trend (about 8 rig/L) in THg concentration based on the average information developed during the four cruises except for high concentrations at bottom and water-sediment interface in May and September 2004. On the other hand, particulate mercury (PHg) and methyl mercury have discernible seasonal variability. Proportion of PHg increased from 29% in February 2004 to 50% in May 2004. In November 2003, February and May 2004 methyl mercury concentrations were relative low and increased with depth (from 0.13 to 0.40 rig/L). In September 2004, methyl mercury concentrations increased from 0.14 ng/L in the epilimnion to 0.99 ng/L in the hypolirnnion. DGM concentrations varied from 0.024 to 0.11 ng/L and decreased with depth. The concentrations of dissolve organic carbon, suspend solids, total Hg, and methyl mercury all were higher at Houwu than at Daba in spring, summer and autumn, but there were no evident differences at two sample sites in Feb.2004. This may be attributed to low temperature in winter and fishing farm's work decreased. This suggested that other pollutants such as N, P from fishing farm and other waste water at Houwu may have changed the distribution pattern of Hg in the reservoir.

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CHINESE JOURNAL OF GEOCHEMISTRY

Vol. 25 (Suppl.) 2006

Key words Hongfeng Reservoir; mercury species; methyl mercury; distribution

The Tianjin geothermal field (northeastern China): Geochemistry and implications for possible plugging phenomena Angelo Minissale 1, Daniele Borrini 2, Giordano Montegrossi 1, Franco Tassi 2, Orlando Vaselli 2, Antonio Delgado Huertas 3, Wanqing C H E N G 4, Jincheng Y A N G 4, X u z h o u C H E N G 5 1 CNR-Institute of Geosciences and Earth Resources, Via G La Pira, 4-50121 Florence, Italy e Department of Eacth Sciences, l~a G La Pira, 4-50121 Florence, Italy 3 Estacirn Experimental del Zaidin (CSIC), Prof. Albareda 1, 18008 Granada, Spain 4 Tianfin Aode Renewable Energy Research Institute, Tianjin 300381, China 5 Institute of Nuclear andNew Energy Technology, Tsinghua University, Beijing 100084, China

The low-enthalpy geothermal system of Tianjin is located in and around the City of Tianjin (China), in the NE part of the North China plain, a tectonic depression affected by subsidence since the Neogene. The regional aquifer system is from the top to the bottom, as follows: (1) the "Quaternary aquifer", in continental sediments; (2) the "Tertiary aquifer", in the continental depositional series; (3) the "Lower Palaezoic-Sinian aquifer", in Ordovician-Sinian calcareous rocks. Shallow (300-600 m) and deep (up to 2600 m) producing wells discharge water at up to 50 and 90 ~ respectively. Exhausted fluid re-injection started in the 90's. Subsequently, a reduction in the injection process was observed, suggesting that sealing or plugging occurred in the reservoir(s). The present work, based on chemical and isotopic data on fluids and minerals from productive and re-injection wells, describes the causes of the permeability reduction at the bottom hole of the re-injection wells. Geochemical data processing using speciation codes indicates that: (1) sealing caused by precipitation of both calcite or amorphous silica is very unlike; (2) the saturation indices for several Fe and Zn sulfides and hydroxides are very positive, although fluids have neutral pH and low temperature (Fe- and Zn-rich minerals are present mainly as transported solids); (3) pipes, casings, heat exchangers and steel frames are made of low-quality Fe and show evident oxidation effects; casings and producing liners in the wells are likely in the same conditions; (4) thermal fluids sampled in summer, when most wells are shut down, are characterized by more negative redox potential and lower pH than those collected in winter, probably because in summer there is less casing-hot water interaction and, consequently, Fe-oxidation in the casing is reduced. Accordingly, the plugging problem does not seem to be a natural process related to the chemical characteristics of the produced fluid. It is, on the contrary, possibly induced by the oxidation of casings, pumps, pipes, etc. However, it is not quantitatively relevant and the installation of mechanical filters and the utilization for future wells of better quality casings and iron frames may prevent any plugging process.

Key words Tianjin; low enthalpy; sealing and plugging; fluid geochemistry; geochemical modeling

Three-Gorges Reservoir "Aigae Bioom" ConditionsmAn investigation Haiyun W A N G 1'2, Lei H U A N G 1, N i n g Z O U 1, Shenggao C H E N G 1 t EnvironmentalAssessment Institute, China University of Geosciences, Wuhan 430074, China 2 Department of Environment Engineering, Three Gorges University, Yichang 443002, China

The Three-Gorges Reservoir lies in the west of China where economic development is at low level. The construction of water conservancy cannot only boost economy of local agriculture, but also make local ecosystem become unstable in a period of time. The Three-Gorges Reservoir has begun storing water for 3 years from June 2003, "algae bloom" is a particular pollutant in the course of super water conservancy. By monitoring the disquisitive "algae bloom" in the Three-Gorges Reservoir, from points of view of circulation, water character, weather, temperature, abundant azote, abundant phosphor, accrue spend, pH, delay glide. It is confmned that especially different interactional colligate courses including water character state of affairs, human character, physics chem. abe warfare course, sedimentation, adsorb and abc warfare, bring about "algae bloom". The conclusion shows that "algae bloom" happened in the Three-Gorges Reservoir is not only a simple physical-chemical process, but also an integrated process including water conservancy, literae humaniores, ph~csics, chemistry, biologic deposition, absorption, release and decomposing. Peculiar hydrological regime of the reservoir is an important condition for "algae bloom". The depths in different positions are also unbalanced, making different vegetations of algae in different tributaries in the same season and air temperature, which is an