How the redox state of tobacco 'Bel-W3' is modified in response to ozone and other environmental factors in a sub-tropical area?

This study intended to determine whether the redox state in plants of Nicotiana tabacum ‘Bel-W3’ fluctuates in response to the environmental factors in a sub-tropical area contaminated by ozone (São Paulo, SE - Brazil) and which environmental factors are related to this fluctuation, discussing their biomonitoring efficiency. We comparatively evaluated the indicators of redox state (ascorbic acid, glutathione, superoxide dismutase, ascorbate peroxidase, and glutathione reductase) and leaf injury in 17 field experiments performed in 2008. The redox state was explained by the combined effects of chronic levels of O₃ and meteorological variables 4-6 days prior to the plant sampling. Moderate leaf injury was observed in most cases. The redox state of tobacco decreases few days after their placement in the sub-tropical environment, causing them to become susceptible to oxidative stress imposed by chronic doses of O₃. Its bioindicator efficiency would not be diminished in such levels of atmospheric contamination.     

Exposure of an anoxic and contaminated canal sediment: Mobility of metal(loid)s

A derelict canal contains an estimated 9800 tonnes of anoxic sediment with highly elevated concentrations of trace elements. Lack of maintenance, reduced water levels and vegetation colonization threaten the stability of pollutants by removing existing waterlogged reduced conditions. A column leaching study of the sediment under increasingly oxidized conditions showed reductions in As mobility but increased heavy metal concentrations. In a reduced state, As mobility was higher (as a consequence of enhanced Fe and organic carbon solubility) whilst heavy metal concentrations in leachates were lower (due to markedly higher pH). Over 10 contiguous wetting and drying cycles, the consequences were profound; all trace elements were continuously leached with enhanced flushing of Fe, As, Zn and Cu. This raises concern over possible mobilization of pollutants to the wider environment, including groundwater. Options for management to stabilize contaminants are discussed that point to the importance of limiting water flow through the sediment.     

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m³ year^− 1) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH₄⁺, NO₃⁻, turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L^− 1, max. 5.58 mg L^− 1), in addition to dissolved Fe, NH₄⁺, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes.Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.     

The impact of eutrophication on the biogeochemical cycling of mercury species in a reservoir: a case study from Hongfeng Reservoir, Guizhou, China

The mercury distribution and speciation in the water column were investigated from November 2003 to September 2004. The distribution and concentrations of total mercury (THg) and particulate mercury (PHg) showed that algae had a large capacity to bind mercury in late spring (e.g. in May). It is shown that dissolved gaseous mercury (DGM) concentrations may also be affected by algae activities. The MeHg profile in the water column at a highly eutrophied site in Hongfeng Reservoir demonstrated that most of the MeHg was produced in the hypolimnion, whereas the MeHg profile pattern at another site with less eutrophication indicated that MeHg in water was largely ascribed to release from sediment. In September, the outflow of the reservoir was enriched with MeHg, which was 5.5 times higher than that in the inflows. The discharge of MeHg-concentrated water from the anoxic hypolimnion in the reservoir may pose a risk to downstream fauna.     

集约化柑橘种植抑制土壤磷循环微生物活性

微生物是调节土壤磷循环的关键驱动力.阐明土壤解磷菌的微生物矿化过程对于提高植物养分吸收率和作物产量具有重要意义.通过测定柑橘园与毗邻的自然林地土壤编码碱性磷酸酶基因（phoD）丰度、解磷细菌群落多样性和土壤无机磷组分,探究柑橘种植对土壤微生物获取磷策略的影响机制.结果表明,柑橘种植导致土壤pH下降,土壤有效磷累积,ω（有效磷）平均值高达112 mg·kg^-1,显著高于毗邻的自然林地（3.7 mg·kg^-1）.柑橘种植也会影响土壤磷素组成,柑橘土壤含有较高的可溶态磷（CaCl₂-P）、柠檬酸提取态磷（Citrate-P）和矿物结合态磷（HCl-P）.自然林地土壤各磷组分均显著低于柑橘土壤,而phoD基因丰度和碱性磷酸酶活性显著高于柑橘土壤.高通量测序结果表明,柑橘土壤解磷细菌Shannon指数（4.61）显著低于自然林地（5.35）,群落结构也有别于自然林地.柑橘种植改变了土壤解磷菌的群落组成,自然林地变形菌门的相对丰度显著低于柑橘土壤.土壤有效磷含量与碱性磷酸酶活性呈显著负相关,表明土壤高磷累积抑制土壤解磷细菌的活性.柑橘种植改变了土壤微生物对磷的获取策略,在柑橘园中,土壤微生物主要依赖外源磷,而自然林地土壤微生物主要以微生物分泌碱性磷酸酶矿化有机磷来获取磷的方式满足其生长需求.     

Microbially Mediated Redox Cycling at the Oxic–Anoxic Boundary in Sediments: Comparison of Animal and Plants Habitats

Microorganisms are responsible for the bulk of transformations that occur in surficial sediments. They are most active at redox boundaries where they can benefit from access to various oxidants and reductants generated during redox cycling events. To illustrate the dynamics of microbially mediated processes, especially those involving sulfur and metal cycles, processes were compared in habitats either bioturbated by a capitellid worm or inhabited by a salt marsh grass. The presence of macrofauna and macroflora greatly altered the three-dimensional array of redox gradients in sediments, but the type and form of reductants and oxidants provided varied greatly; clastic sedimentary infauna subducted solid phase organic material and iron oxides, whereas plant roots released dissolved organic matter and oxygen. These differences resulted in a bioturbated system that exhibited a rapid sulfur cycle (residence time of minutes), but a slower iron cycle (days), whereas vegetation caused a slow sulfur cycle and rapid iron cycle. Alteration of sediments by higher life forms also greatly affected the composition and relative abundances of sedimentary bacteria, even on short time scales. Although redox cycling at interfaces can be somewhat predictable, variations in response to biological and physical perturbations demonstrated wide differences in the dynamics of redox-mediated processes.     

Enhancement of photocatalytic efficiency by in situ fabrication of BiOBr/BiVO4 surface junctions

Surface junctions between Bi OBr and BiVO_4 were synthesized. The BiOBr/BiVO_4 with 1 wt.%of Bi OBr exhibited the highest photocatalytic activity in the degradation of Rh B under visible-light irradiation. It was found that the highly efficient adsorption of Rh B molecules via the electrostatic attraction between Br-and cationic \N(Et)_2 group played a key role for the high photocatalytic activities of BiOBr/BiVO_4. This efficient adsorption promoted the N-deethylation of Rh B and thus accelerated the photocatalytic degradation of Rh B.Moreover, the metal-to-metal charge transfer(MMCT) mechanism was proposed, which revealed the concrete path paved with Bi–O–Bi chains for the carrier migration in BiOBr/BiVO_4. The interaction between photoexcited Rh B* and the Bi~(3+) in BiVO_4 provided the driving force for the migration of photo-generated carriers along the Bi–O–Bi chains. This work has not only demonstrated the important role of efficient adsorption in the photocatalytic degradation of organic contaminants, but also developed a facile strategy to improve the efficiency of photocatalysts.     

生物炭对滨海湿地盐碱土壤碳氮循环的影响

滨海湿地盐碱土壤在全球碳氮循环及调节气候变化中起着重要作用。环境友好型土壤改良剂生物炭（Biochar,BC）在缓解气候变化和促进农业可持续发展方面前景巨大。然而,现有研究多关注BC对滨海湿地盐碱土壤中温室气体排放及土壤氮素流失的影响,缺乏其对滨海湿地盐碱土壤碳氮循环的深入研究和系统总结。本文综合分析了施用BC对滨海湿地盐碱土壤植被碳库、有机碳库、有机碳矿化及生物固氮、硝化、反硝化、矿化、氨损失等碳氮循环过程的影响和可能机制。指出未来应关注长期野外研究,利用宏基因组等现代分子生物技术,阐明BC对土壤碳氮循环影响的分子生物学机制,以期为滨海湿地生态系统的修复与功能保育提供理论依据。     

Assessing effects of aerobic and anaerobic conditions on phosphorus sorption and retention capacity of water treatment residuals

Water treatment residuals (WTRs) are the by-products of drinking water clarification processes, whereby chemical flocculants such as alum or ferric chloride are added to raw water to remove suspended clay particles, organic matter and other materials and impurities. Previous studies have identified a strong phosphorus (P) fixing capacity of WTRs which has led to experimentation with their use as P-sorbing materials for controlling P discharges from agricultural and forestry land. However, the P-fixing capacity of WTRs and its capacity to retain sorbed P under anaerobic conditions have yet to be fully demonstrated, which is an issue that must be addressed for WTR field applications. This study therefore examined the capacity of WTRs to retain sorbed P and sorb further additional P from aqueous solution under both aerobic and anaerobic conditions. An innovative, low cost apparatus was constructed and successfully used to rapidly establish anoxic conditions in anaerobic treatments. The results showed that even in treatments with initial solution P concentrations set at 100 mg l(-1), soluble reactive P concentrations rapidly fell to negligible levels (due to sorption by WTRs), while total P (i.e. dissolved + particulate and colloidal P) was less than 3 mg l(-1). This equated to an added P retention rate of >98% regardless of anaerobic or aerobic status, indicating that WTRs are able to sorb and retain P in both aerobic and anaerobic conditions.     

川渝地区农业生态系统氧化亚氮排放

基于县级农业活动水平数据及区域氮循环模型IAP-N方法,并根据地理特征、环境气候条件及地区行政区划将川渝地区划分成4个亚区,详细估算了1990~2004年川渝地区农业生态系统氧化亚氮(N2O)的排放及其时空分布状况.结果表明,川渝地区1990~1994、1995~1999、2000~2004年农业生态系统N2O年平均排放量(以纯氮量计)分别为52.3、58.2、62.0 Gg/a,其中55%来自农田直接排放.3个时期农田直接排放量分别为29.6(7.6~63.3)、33.0(8.4~71.8)、34.0(8.5~75.8)Gg/a,农田直接排放通量分别为4.73、5.39、6.11 kg/(hm2.a).农田旱作是农田N2O直接排放的主要源,水旱轮作对农田N2O直接排放的贡献也很大.川渝地区农业生态系统N2O排放量以及农田N2O排放通量,1995~1999年期间比1990~1994年期间增长幅度较大;2000~2004年期间,农田N2O排放通量增长速度未呈现减缓趋势,但由于耕地面积减少,农田N2O排放量增长呈现停滞状态.川渝地区农业生态系统N2O主要排放地区分布在成都平原和重庆地区,各区域的N2O排放源贡献各...