钛基锡锑电极电催化氧化处理硝基苯废水

采用钛基锡锑(Sn-Sb/Ti)电极作为氧化阳极,不锈钢为阴极,电催化氧化降解废水中硝基苯。实验结果表明,处理硝基苯废水的最佳条件为:电流密度25 mA/cm~2;Na_2SO_4作为电解质,加入量15g/L;极板间距2 cm;溶液初始pH 6。在此最佳条件下,硝基苯去除率大于95%,TOC去除率大于80%,表明Sn-Sb/Ti阳极能有效去除废水中有机污染物。     

微电解法预处理咖啡因生产废水及机理研究

采用微电解法预处理咖啡因生产废水,考察了进水pH、反应时间、进水浓度、铁炭比等因素对废水处理效果的影响。实验结果表明;进水为pH3、反应时间为60min、原水进水(COD16585mg/L,BOD53814mg/L,ρ(氨氮)640mg/L)、铁炭比(堆积体积比)为1∶1时,废水的COD去除率为46.8%,氨氮去除率为62.6%,脱色率为93.5%,并对重金属有良好的去除效果。气相色谱-质谱分析结果表明,微电解可以将废水中的含氮杂环物质转化为胺类和脲类等链状易生物降解的小分子物质。     

水利工程建设对环境影响的探讨

随着现代工程技术的不断发展,大规模的水利工程建设,为国民经济建设发挥了巨大作用,但同时也对环境造成了影响和危害,因此,如何兴利避害,充分发挥水利工程为人类造福的优势,减少其对环境的不利影响,是我们必须考虑的问题。从水利工程对环境的影响进行探讨并对环境保护提出了建议。     

Ambient sulfur dioxide,nitrogen dioxide,and ammonia at ten background and rural sites in China during 2007–2008

We present two years (January 2007–December 2008) of atmospheric SO₂, NO₂ and NH₃ measurements from ten background or rural sites in nine provinces in China. The measurements were made on a monthly basis using passive samplers under careful quality control. The results show large geographical and seasonal variations in the concentrations of these gases. The mean SO₂ concentration varied from 0.7 ± 0.4 ppb at Waliguan on Qinghai Plateau to 67.3 ± 31.1 ppb at Kaili in Guizhou province. The mean NO₂ concentration ranged from 0.6 ± 0.4 ppb at Waliguan to 23.9 ± 6.9 ppb at Houma in southern Shanxi. The mean NH₃ concentration ranged from 2.8 ± 3.0 ppb at Shangdianzi in northeastern Beijing to 13.7 ± 8.4 ppb at Houma. At most sites, SO₂ and NO₂ peaked in winter and reached minima in summer, while NH₃ showed maximum values in summer and lower values in cold seasons. On the whole, the geographical distributions of the observed gas concentrations are consistent with those of emissions. The ground measurements of SO₂ and NO₂ are contrasted to the SCIAMACHY SO₂ and OMI NO₂ tropospheric columns, respectively. Although the satellite data can capture the main features of emissions and concentrations of SO₂, they do not reflect the variations of SO₂ in the surface layer. The situation is better for the case of NO₂. The OMI NO₂ columns capture the geographical differences in the ground NO₂ and correlate fairly well with the ground levels of NO₂ at six of the ten sites.     

China's natural wetlands: past problems, current status, and future challenges

Natural wetlands, occupying 3.8% of China's land and providing 54.9% of ecosystem services, are unevenly distributed among eight wetland regions. Natural wetlands in China suffered great loss and degradation (e.g., 23.0% freshwater swamps, 51.2% costal wetlands) because of the wetland reclamation during China's long history of civilization, and the population pressure and the misguided policies over the last 50 years. Recently, with an improved understanding that healthy wetland ecosystems play a vital role in her sustainable economic development, China started major efforts in wetland conservation, as signified by the policy to return reclaimed croplands to wetlands, the funding of billions of dollars to restore degraded wetlands, and the national plan to place 90% of natural wetlands under protection by 2030. This paper describes the current status of the natural wetlands in China, reviews past problems, and discusses current efforts and future challenges in protecting China's natural wetlands.     

CH4 and N2O emissions from Spartina alterniflora and Phragmites australis in experimental mesocosms

Spartina alterniflora, a perennial grass with C(4)-photosynthesis, shows great invading potential in the coastal ecosystems in the east of China. We compared trace gas emissions from S. alterniflora with those from a native C(3) plant, Phragmites australis, by establishing brackish marsh mesocosms to experimentally assess the effects of plant species (S. alterniflora vs. P. australis), flooding status (submerged vs. non-submerged), and clipping (plants clipped or not) on trace gas emissions. The results show that trace gas emission rates were higher in S. alterniflora than P. australis mesocosms due to the higher biomass and density of the former, which could fix more available substrates to the soil and potentially emit more trace gases. Meanwhile, trace gas emission rates were higher in non-submerged than submerged soils, suggesting that water might act as a diffusion barrier in the brackish marsh mesocosms. Interestingly, methane (CH(4)) emission rates were lower in clipped non-submerged mesocosms than in non-clipped submerged mesocosms, but nitrous oxide (N(2)O) emissions were enhanced. CH(4) emissions were significantly correlated with the plant biomass and stem density (R(2)>0.48, P<0.05) for both species, suggesting that both the two species might play important roles in CH(4) production and transport and also act as suppliers of easily available substrates for the methanogenic bacteria in wetland ecosystems. N(2)O emissions, however, were not significantly correlated with plant biomass and density (P>0.05).     

紫外光作用下氯酚的矿化程度比较

有关氯酚污染物光化学降解的研究,已有报道。ＨｕａｎｇＣＰ的工作较有系统性,他研究了四类深度化学氧化过程,检测指标是氯酚浓度。本文研究了在紫外光以及其它因素作用下,氯酚混合溶液的矿化程度,以溶液总有机磷浓度ＴＯＣ作为指标。所得结论,对于含有氯酚废水的治理,具有指导意义;对于难降解     

Use of headspace SPME-GC-MS for the analysis of the volatiles produced by indoor molds grown on different substrates

An automated headspace solid phase microextraction method followed by GC-MS analysis was used to evaluate and compare the in vitro production of microbial volatile organic compounds (MVOCs) on malt extract agar, plasterboard and wallpaper. Five fungal strains were isolated from the walls of water-damaged houses and identified. In addition, four other common molds were studied. In general, MVOC production was the highest on malt extract agar. On this synthetic medium, molds typically produced 2-methylpropanol, 2-methylbutanol and 3-methylbutanol. On wallpaper, mainly 2-ethylhexanol, methyl 2-ethylhexanoate and compounds of the C8-complex such as 1-octene-3-ol, 3-octanone, 3-octanol and 1,3-octadiene were detected. The detection of 2-ethylhexanol and methyl 2-ethylhexanoate indicates an enhanced degradation of the substrate by most fungi. For growth on plasterboard, no typical metabolites were detected. Despite these metabolite differences on malt extract agar, wallpaper and plasterboard, some molds also produced specific compounds independently of the used substrate, such as trichodiene from Fusarium sporotrichioides and aristolochene from Penicillium roqueforti. Therefore, these metabolites can be used as markers for the identification and maybe also mycotoxin production of these molds. All five investigated Penicillium spp. in this study were able to produce two specific diterpenes, which were not produced by the other species studied. These two compounds, which remain unidentified until now, therefore seem specific for Penicillium spp. and are potentially interesting for the monitoring of this fungal genus. Further experiments will be performed with other Penicillium spp. to study the possibility that these two compounds are specific for this group of molds.     

Assessment of dissolved heavy metal in the Yangtze River estuary and its adjacent sea, China

The purpose of this paper is to determine the concentrations of dissolved heavy metals namely mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu) and to investigate the relationships between nutrients (nitrate-nitrogen and phosphate) and dissolved heavy metals. For this purpose, the concentrations of dissolved heavy metals were measured through 51 voyages form 1984 to 2006 in the Yangtze river estuary and its adjacent sea. Results analysis showed that dissolved heavy metals were not the main pollutants in the Yangtze river estuary, and the main source of heavy metal contamination was industrial wastewater from terrestrial pollution during the past 20 years. Heavy metal values showed significant abundance in the south branch of the Yangtze River estuary and Hangzhou Bay. In addition, Pb showed negative correlation with nutrients, while the positive correlations between Hg, Cd, and nutrients were shown. The obtained molar ratios, $\Delta \mbox{Cd}/\Delta \mbox{N} = 1.68 \times 10^{-5}$ and $\Delta \mbox{Cd}/\Delta \mbox{P} = 1.66 \times 10^{-4}$ , are close to those in plankton, showing the biogeochemical behavior and process of dissolved cadmium.     

Assessment of toxic heavy metals in urban lake sediments as related to urban stressor and bioavailability

Aquatic pollution pose a serious challenge to the scientific community worldwide, since lakes or reservoirs find multifarious use and most often their water is used for drinking, bathing, irrigation, and aquaculture. Nine metals and several physicochemical parameters, from four sampling sites in a tropical lake receiving the discharges from a thermal power plant, a coal mine, and a chlor-alkali industry, were studied from 2004 to 2005. Pertaining to metal pollution, the site most polluted with heavy metals was Belwadah, i.e., waters and sediments had the highest concentration of all the metals examined. The reference site was characterized by the presence of low concentrations of metals in waters and sediments. Following the water quality monitoring, 2-month field phytoremediation experiments were conducted using large enclosures at the discharge point of different polluted sites of the lake. During field phytoremediation experiments using aquatic macrophytes, marked percentage reduction in metals concentrations were recorded. The percentage decrease for different metals was in the range of 25% to 67.90% at Belwadah (with Eichhornia crassipes and Lemna minor), 25% to 77.14% at Dongia nala (with E. crassipes, L. minor and Azolla pinnata), and 25% to 71.42% at Ash pond site of G.B. Pant Sagar (with L. minor and A. pinnata). Preliminary studies of polluted sites are useful for improved microcosm design and for the systematic extrapolation of information from experimental ecosystems to natural ecosystems.