This study examined the effects of water temperature and the origin (terrestrial vs marine) and light history of chromophoric dissolved organic matter (CDOM) on the apparent quantum yields of carbon monoxide (CO) photoproduction for water samples collected along a salinity gradient (salinity range: 0-33) in the St. Lawrence estuarine system (Canada). The solar insolation-weighted mean apparent quantum yield of CO (phico) decreased as much as fourfold with increasing salinity and showed a strong positive correlation with the dissolved organic carbon-specific absorption coefficient at 254 nm. This suggests that terrestrial CDOM is more efficient at photochemically producing CO than is marine algae-derived CDOM and that aromatic moieties are likely involved in this photoprocess. CDOM photobleaching, mainly at the very early stage, dramatically decreased phico (by up to 6.4 times) for low-salinity samples, but photobleaching had little effect on the most marine sample. For a 20 degree C increase in temperature, phico increased by approximately 70% for low-salinity samples and 30-40% for saline samples. This study demonstrates that water temperature, as well as the CDOM's origin and light history, strongly affect the efficiency of CO photoproduction. These factors should be taken into account in modeling the photochemical fluxes of CO and other related CDOM photoproducts on varying spatiotemporal scales.

Background: To date, a systematic review of the evidence regarding the association

This is the first study of the involvement of CYP2E1, GSTM1 and GSTT1 genetic polymorphisms in ATDH using a nested case-control population-based prospective cohort design. We could not confirm positive associations of genetic polymorphisms of CYP2E1 RsaI, CYP2E1 DraI, GSTM1 null and GSTT1 null with ATDH reported by various groups, in our Chinese TB population.

South China Sea (SCS) is the largest Western Pacific marginal sea. However, microbial studies have never been performed in the cold seep sediments in the SCS. In 2004, "SONNE" 177 cruise found two cold seep areas with different water depth in the northern SCS. Haiyang 4 area, where the water depth is around 3000 m, has already been confirmed for active seeping on the seafloor, such as microbial mats, authigenic carbonate crusts and bivalves. We investigated microbial abundance and diversity in a 5.55-m sediment core collected from this cold seep area. An integrated approach was employed including geochemistry and 16S rRNA gene phylogenetic analyses. Here, we show that microbial abundance and diversity along with geochemistry profiles of the sediment core revealed a coupled reaction between sulphate reduction and methane oxidation. Acridine orange direct count results showed that microbial abundance ranges from 10 5 to 10 6 cells/g sediment (wet weight). The depth-related variation of the abundance showed the same trend as the methane concentration profile. Phylogenetic analysis Production and hosting by Elsevieravailable at www.sciencedirect.com China University of Geosciences (Beijing) GEOSCIENCE FRONTIERS journal homepage: www.elsevier.com/locate/gsf GEOSCIENCE FRONTIERS 3(3) (2012) 301e316indicated the presence of sulphate-reducing bacteria and anaerobic methane-oxidizing archaea. The diversity was much higher at the surface, but decreased sharply with depth in response to changes in the geochemical conditions of the sediments, such as methane, sulphate concentration and total organic carbon. Marine Benthic Group B, Chloroflexi and JS1 were predominant phylotypes of the archaeal and bacterial libraries, respectively. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

Based on magnetotelluric (MT) array data, we have obtained the first three‐dimensional (3‐D) electrical resistivity model at the Gaoligong intracontinental block boundary in southeastern Tibetan Plateau where the Quaternary intraplate Tengchong volcanism and seismic activities occur. Comparing with results of previous geophysical studies in the area, our MT model clearly reveals three conductive bodies in the depth ranges of 10–30 km in the Tengchong volcano area, which we interpret as three middle‐lower crustal magma chambers associated with the Tengchong volcanism. Seismogenic faults in the Gaoligong Shear Zone (GLGSZ) are characterized by subvertical conductive zones bounded by resistive upper crustal layer on both sides. Earthquakes of moderate magnitudes near the GLGSZ have all occurred within the conductive fault zones at the bottom of the upper resistive crust. More importantly, one large resistive body was imaged at middle‐lower crustal depth beneath the GLGSZ, which seems to block the previously proposed horizontal crustal channel flow along this intracontinental block boundary. Our 3‐D model indicates that crustal channel flow could take place east of the GLGSZ. The current study provides evidence from electrical resistivity structure for the middle‐lower crustal magma chambers in the Tengchong volcano area and detailed 3‐D electrical structure of crustal channel flow in this active tectonic region.

Abstract. Rates and apparent quantum yields of photomineralization (AQY DOC ) and photomethanification (AQY CH 4 ) of chromophoric dissolved organic matter (CDOM) in Saguenay River surface water were determined at three widely differing dissolved oxygen concentrations ([O 2 ]) (suboxic, air saturation, and oxygenated) using simulated-solar radiation. Photomineralization increased linearly with CDOM absorbance photobleaching for all three O 2 treatments. Whereas the rate of photochemical dissolved organic carbon (DOC) loss increased with increasing [O 2 ], the ratio of fractional DOC loss to fractional absorbance loss showed an inverse trend. CDOM photodegradation led to a higher degree of mineralization under suboxic conditions than under oxic conditions. AQY DOC determined under oxygenated, suboxic, and air-saturated conditions increased, decreased, and remained largely constant with photobleaching, respectively; AQY DOC obtained under air saturation with short-term irradiations could thus be applied to longer exposures. AQY DOC decreased successively from ultraviolet B (UVB) to ultraviolet A (UVA) to visible (VIS), which, alongside the solar irradiance spectrum, points to VIS and UVA being the primary drivers for photomineralization in the water column. The photomineralization rate in the Saguenay River was estimated to be 2.31 × 10 8 mol C yr −1 , accounting for only 1 % of the annual DOC input into this system.Photoproduction of CH 4 occurred under both suboxic and oxic conditions and increased with decreasing [O 2 ], with the rate under suboxic conditions ∼ 7-8 times that under oxic conditions. Photoproduction of CH 4 under oxic conditions increased linearly with photomineralization and photobleaching. Under air saturation, 0.00057 % of the photochemical DOC loss was diverted to CH 4 , giving a photochemical CH 4 production rate of 4.36 × 10 −6 mol m −2 yr −1 in the Saguenay River and, by extrapolation, of (1.9-8.1) × 10 8 mol yr −1 in the global ocean. AQY CH 4 changed little with photobleaching under air saturation but increased exponentially under suboxic conditions. Spectrally, AQY CH 4 decreased sequentially from UVB to UVA to VIS, with UVB being more efficient under suboxic conditions than under oxic conditions. On a depth-integrated basis, VIS prevailed over UVB in controlling CH 4 photoproduction under air saturation while the opposite held true under O 2 -deficiency. An addition of micromolar levels of dissolved dimethyl sulfide (DMS) substantially increased CH 4 photoproduction, particularly under O 2 -deficiency; DMS at nanomolar ambient concentrations in surface oceans is, however, unlikely a significant CH 4 precursor. Results from this study suggest that CDOM-based CH 4 photoproduction only marginally contributes to the CH 4 supersaturation in modern surface oceans and to both the modern and Archean atmospheric CH 4 budgets, but that the photochemical term can be comparable to microbial CH 4 oxidation in modern oxic oceans. Our results also suggest that anoxic microniches in particulate orga...

Based on six cruises from March to September in 2016, we investigated monthly distributions of dissolved organic matter (DOM) and ancillary water chemistry parameters in a mariculture area in the Northern Yellow Sea, where summertime hypoxia and seawater acidification were observed. The most severe oxygen depletion (hypoxia covered approximately one-third of the aquaculture area) and the largest pH decrease (8.07 ± 0.05 in surface layer vs. 7.66 ± 0.07 in bottom layer) were revealed in August. Concentration of dissolved organic carbon (DOC) and the absorption properties of chromophoric DOM (CDOM) were used to characterize DOM. Results showed that DOM mainly originated from marine in situ processes. In March, a DOM pool with the lowest DOC concentration of 211 ± 23 µmol L −1 and nearly uniform optical characteristics were presented in the well-mixed water column. In August, however, DOC increased to 361 ± 29 µmol L −1 in the surface layer and 342 ± 25 µmol L −1 in the bottom layer. Two non-linear relationships between the absorption coefficient at 355 nm [a CDOM (355)] and the absorption spectral slope over 275-295 nm (S 275−295) were revealed. According to modeling results, the non-linear relationships were mostly caused by the conservative mixing of a refractory CDOM pool with a freshly produced CDOM pool. Apparent oxygen utilization in August was positively related to DOC, but not to a CDOM (355) and S 275−295 , presumably due to multiple sources of CDOM in bottom waters. Both a CDOM (355) and S 275−295 respond largely to decreasing pH; however, they would be less affected by ocean acidification since this process leads to a limited pH decline.

[1] We investigated the thermal (dark) production of carbon monoxide (CO) from dissolved organic matter (DOM) in the water column of the St. Lawrence estuarine system in spring 2007. The production rate, Q co , decreased seaward horizontally and downward vertically. Q co exhibited a positive, linear correlation with the abundance of chromophoric dissolved organic matter (CDOM). Terrestrial DOM was more efficient at producing CO than marine DOM. The temperature dependence of Q co can be characterized by the Arrhenius equation with the activation energies of freshwater samples being higher than those of salty samples. Q co remained relatively constant between pH 4-6, increased slowly between pH 6-8 and then rapidly with further rising pH. Ionic strength and iron chemistry had little influence on Q co . An empirical equation, describing Q co as a function of CDOM abundance, temperature, pH, and salinity, was established to evaluate CO dark production in the global coastal waters (depth < 200 m). The total coastal CO dark production from DOM was estimated to be from 0.46 to 1.50 Tg CO-C a À1 (Tg carbon from CO a À1 ). We speculated the global oceanic (coastal plus open ocean) CO dark production to be in the range from 4.87 to 15.8 Tg CO-C a À1 by extrapolating the coastal water-based results to blue waters (depth > 200 m). Both the coastal and global dark source strengths are significant compared to the corresponding photochemical CO source strengths (coastal: $2.9 Tg CO-C a À1 ; global: $50 Tg CO-C a À1