Spatial variation of organochlorine pesticides and dissolved organic matter in urban closed lakes

Abstract

Closed lakes located in urban parks act as sinks of organochlorine pesticides (OCPs), which have been used, for decades, as insecticides, herbicides and fungicides. The closed lakes from Bucharest, Romania, are periodically managed to prevent eutrophication and accumulation of pollutants. However, it is not known if these practices reduce or enhance the legacy pollution with OCPs. The aim of this study was to explore the spatial variation of OCPs in closed lakes. The total concentration of OCPs in water and sediments ranged between 0.0176 and 37.1?µg/L, and between 122 to 1,890?ng/g, respectively. The concentrations of OCPs were compared with the consensus-based sediment quality guidelines (SQGs) in order to evaluate the ecological risks of sediments. The highest potential adverse effects were associated with γ-HCH exposure. Periodical draining and dredging of lakes lead to the resuspension of contaminants, increasing pesticide bioavailability and accumulation in sediments. In addition, we observed that fluorescent dissolved organic matter (DOM) might influence the OCPs cycle. The quantity and character of fluorescent DOM can provide further insight into OCPs degradation. Also, this study may help urban planners to determine the state of urban waters and to find the best solution for water management.     

高级氧化法脱除PVA浆料的清洁生产新工艺研究

为了研究高级氧化法脱除聚乙烯醇(PVA)浆料清洁生产新工艺的可行性,研究了3种高级氧化法UV/H2O2、UV/TiO2、Nafion-Fe2 /H2O2对含PVA溶液的氧化降解,其降解效果依次为:UV/H2O2＞Nafion-Fe2 /H2O2＞UV/TiO2.对于UV/H2O2法,PVA降解速率与H2O2的初始浓度成正相关,且H2O2浓度为2.95 mmol/L时14 min内就能使PVA的去除率达到98%;pH和温度对PVA的氧化降解效果影响不明显.在此基础上,对建立在高级氧化法基础上的退浆新工艺进行了探讨,结果表明,在65℃和75℃下,高级氧化法条件下的纯棉织物PVA退浆率分别达到70.16%和95.65%;该法不仅可以促进PVA从纯棉织物上的脱附,而且可以达到对PVA的较高降解效果,使得所排退浆废水的生化处理难度明显降低.     

氨氮浓度对活性炭深度处理工艺选择的影响

在广东省北江水源佛山段水质深度处理实验中,采用活性炭(GAC)和臭氧(O3)-生物活性炭(BAC)深度处理工艺,比较了两者对不同进水浓度下氨氮的去除效果,并对前加氯预处理工艺于氨氮的活性炭深度处理效果的影响进行了分析.结果表明:GAC和O3-BAC工艺对突发性氨氮污染具备耐冲击负荷能力.低氨氮浓度下,GAC和O3-BAC对氨氮的去除率接近(约40%),并随着进水氨氮浓度的增大而增加.两者出水中CHCl3浓度均未超标,但O3-BAC处理后的浓度更低.基于GAC工艺处理成本低于O3-BAC,建议优先采用GAC工艺.高氨氮浓度下,O3-BAC工艺除氨氮效果显著优于GAC,消毒后出水中CHCl3浓度也低于GAC的情况,建议优先采用O3-BAC工艺.若使氨氮去除率达最佳,则合适的氨氮浓度范围是:对O3-BAC工艺:0.57～0.62 mg/L,去除率高于93%.在0.43～0.62 mg/L时,去除率高于70%;对GAC工艺:0.5～0.57 mg/L,去除率介于70%～76.3%.O3-BAC工艺的适用范围宽.在合适浓度的沉淀池出水余氯下,可以在O3-BAC工艺前采用前加氯预处理工艺.     

Engineered and subsequent intrinsic in situ bioremediation of a diesel fuel contaminated aquifer

A diesel fuel contaminated aquifer in Menziken, Switzerland was treated for 4.5 years by injecting aerated groundwater, supplemented with KNO3 and NH4H2PO4 to stimulate indigenous populations of petroleum hydrocarbon (PHC) degrading microorganisms. After dissolved PHC concentrations had stabilized at a low level, engineered in situ bioremediation was terminated. The main objective of this study was to evaluate the efficacy of intrinsic in situ bioremediation as a follow-up measure to remove PHC remaining in the aquifer after terminating engineered in situ bioremediation. In the first 7 months of intrinsic in situ bioremediation, redox conditions in the source area became more reducing as indicated by lower concentrations of SO4(2-) and higher concentrations of Fe(II) and CH4. In the core of the source area, strongly reducing conditions prevailed during the remaining study period (3 years) and dissolved PHC concentrations were higher than during engineered in situ bioremediation. This suggests that biodegradation in the core zone was limited by the availability of oxidants. In lateral zones of the source area, however, gradually more oxidized conditions were reestablished again, suggesting that PHC availability increasingly limited biodegradation. The total DIC production rate in the aquifer decreased within 2 years to about 25% of that during engineered in situ bioremediation and remained at that level. Stable carbon isotope analysis confirmed that the produced DIC mainly originated from PHC mineralization. The total rate of DIC and CH4 production in the source area was more than 300 times larger than the rate of PHC elution. This indicates that biodegradation coupled to consumption of naturally occurring oxidants was an important process for removal of PHC which remained in the aquifer after terminating engineered measures.     

Pharmaceuticals in STP effluents and their solar photodegradation in aquatic environment

The presence of pharmaceutical compounds in surface waters is an emerging environmental issue. Sewage treatment plants (STPs) are recognized as being the main point discharge sources of these substances to the environment. A monitoring campaign of STP effluents was carried out in four European countries (Italy, France, Greece and Sweden). More than 20 individual pharmaceuticals belonging to different therapeutic classes were found. For six selected pharmaceuticals (carbamazepine, diclofenac, clofibric acid, ofloxacin, sulfamethoxazole and propranolol) present in the STP effluents, the persistence towards abiotic photodegradation was evaluated submitting them to solar experiments at 40° N latitude during spring and summer. Based on experimentally measured quantum yields for the direct photolysis in bi-distilled water, half-life times (t_1/2) at varying seasons and latitude were predicted for each substance. In salt- and organic-free (bi-distilled) water carbamazepine and clofibric acid are characterized by calculated half-life times of the order of 100 days at the highest latitudes (50° N) in winter, whereas under the same conditions sulphamethoxazole, diclofenac, ofloxacin and propranolol undergo fast degradation with t_1/2 respectively of 2.4, 5.0, 10.6 and 16.8 days. For almost all studied compounds, except propranolol the presence of nitrate ions in aqueous solutions results in a reduction of t_1/2. When present, humic acids act as inner filters towards carbamazepine and diclofenac, and as photosensitizers towards sulphamethoxazole, clofibric acid, oflaxocin and propranolol.     

Chloroform in the environment: occurrence,sources, sinks and effects

The chloroform flux through the environment is apparently constant at some 660±220 Gg yr⁻¹ (±1σ) and about 90% of the emissions are natural in origin: the largest single source being in offshore sea water (contributing 360±90 Gg yr⁻¹), with soil processes the next most important (220±100 Gg yr⁻¹). Other natural sources, mainly volcanic and geological, account for less than 20 Gg yr⁻¹. The non-natural sources total 66±23 Gg yr⁻¹ and are much better characterised than the natural sources. They are predominantly the result of using strong oxidising agent on organic material in the presence of chloride ion, a direct parallel with the natural processes occurring in soils.

Chloroform partitions preferentially into the atmosphere; the equilibrium distribution is greater than 99% and the average global atmospheric concentration has been calculated to be 18.5 pmol mol⁻¹. Atmospheric oxidation, the principal removal process, is approximately in balance with the identified source fluxes. Chloroform is widely dispersed in the aquatic environment (even naturally present in some mineral waters). Consequently, it is also widely dispersed in the tissue of living creatures and in foodstuffs but there is little evidence of bioaccumulation and the quantities in foodstuffs and drinking water are not problematical for human ingestion at the highest concentrations found. Definitive studies have shown that current environmental concentrations of chloroform do not present an ecotoxicological risk, even to fish at the embryonic and larval stages when they are most susceptible.

By virtue of the very small amounts that actually become transported to the stratosphere, chloroform does not deplete ozone materially, nor is it a photochemically active volatile organic compound (VOC). It has a global warming potential that is less than that of the photochemically active VOCs and is not classed as a greenhouse gas.     

Biotechnology to develop innovative syntheses using CO2

We present an overview of possible biotechnological applications for using carbon dioxide for the synthesis of chemicals. These approaches are very appealing as they contribute to the implementation of new synthetic methodologies that reduce waste and make a better use of carbon and energy. Several synthetic approaches will be considered including both the incorporation of the whole COO moiety or its reduction to other C₁ molecules. Each option will be discussed making a comparison between the natural and artificial process in order to highlight the possibility to learn from Nature and develop useful mimetic or enzymatic systems.     

Ce-based catalysts used in advanced oxidation processes for organic wastewater treatment: A review

Refractory organic pollutants in water threaten human health and environmental safety, and advanced oxidation processes (AOPs) are effective for the degradation of these pollutants. Catalysts play vital role in AOPs, and Ce-based catalysts have exhibited excellent performance. Recently, the development and application of Ce-based catalysts in various AOPs have been reported. Our study conducts the first review in this rapid growing field. This paper clarifies the variety and properties of Ce-based catalysts. Their applications in different AOP systems (catalytic ozonation, photodegradation, Fenton-like reactions, sulfate radical-based AOPs, and catalytic sonochemistry) are discussed. Different Ce-based catalysts suit different reaction systems and produce different active radicals. Finally, future research directions of Ce-based catalysts in AOP systems are suggested.     

The dynamic development of bacterial community following long-term weathering of bauxite residue

Bauxite residue is the industrial waste generated from alumina production and commonly deposited in impoundments. These sites are bare of vegetation due to the extreme high salinity and alkalinity, as well as lack of nutrients. However, long term weathering processes could improve residue properties to support the plant establishment. Here we investigate the development of bacterial communities and the geochemical drivers in bauxite residue, using Illumina high-throughput sequencing technology. Long term weathering reduced the pH in bauxite residue and increased its nutrients content. The bacterial community also significantly developed during long term weathering processes. Taxonomic analysis revealed that natural weathering processes encouraged the populations of Proteobacteria, Chloroflexi, Acidobacteria and Planctomycetes, whereas reducing the populations of Firmicutes and Actinobacteria. Redundancy analysis (RDA) indicated that total organic carbon (TOC) was the dominant factors affecting microbial structure. The results have demonstrated that natural weathering processes improved the soil development on the abandoned bauxite residue disposal areas, which also increased our understanding of the correlation between microbial variation and residue properties during natural weathering processes in Bauxite residue disposal areas.