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961.
In California, the growing popularity of urban agriculture (UA) has unfolded against a backdrop of historic drought. While UA is often celebrated as an urban sustainability strategy, it must be able to persist during drought if it is to perform these functions. Using Santa Clara County – the geographic core of Silicon Valley – as a case study, we use interviews and surveys to explore the implications of drought for UA. We show how developing an understanding of water access for UA during a drought requires examining the social and institutional context of water management and use. In metropolitan California, the highly decentralised water supply system combined with the diverse institutional arrangements that support UA create an uneven landscape of water access. Consequently, the pressure to change water-consuming practices – that is, the stress that institutional drought responses place on different water users – is geographically and socially differentiated. Among UA water users, responses to drought have also varied, in part because the possibilities for change are constrained by the sociotechnical arrangements of UA sites and the different purposes of UA. 相似文献
962.
Public participation in water decision-making is an accepted and expected practice. It is expected to lead to better decisions and ensure fairness by satisfying peoples' understanding of democracy and their “right” to participate in decisions that affect them. However, despite years of experience and “best practices”, governing bodies at all levels struggle to implement successful, genuine participation that leads to fair decisions. Ultimately, decision-making about natural resources such as water is a process that takes place in a wider power context where some groups have greater access to sources of power and entitlements. This research applies a “Social Justice Framework” (SJF) to examine the experiences of different stakeholder groups in making their voices heard during water reform processes in the Murray–Darling Basin in Australia. The experiences of croppers and graziers in two different floodplains show how historical advantages and disadvantages affect the power balance between different stakeholder groups and their ability to participate in and influence water decision-making. Applying the three components of the SJF, distributive, procedural and interactive justice, in water decision-making should lead to greater equity in distribution and underline the importance of good governance in decision-making processes. 相似文献
963.
Does the Temporal Resolution of Precipitation Input Influence the Simulated Hydrological Components Employing the SWAT Model?
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Andreas Bauwe Sara Tiedemann Petra Kahle Bernd Lennartz 《Journal of the American Water Resources Association》2017,53(5):997-1007
This study aimed to evaluate the influence of sub‐daily precipitation time steps on model performance and hydrological components by applying the Green and Ampt infiltration method using the Soil and Water Assessment Tool (SWAT). Precipitation was measured at a resolution of 0.1 mm and aggregated to 5‐, 15‐, 30‐, and 60‐min time steps. Daily discharge data over a 10‐year period were used to calibrate and validate the model. Following a global sensitivity analysis, relevant parameters were optimized through an automatic calibration procedure using SWAT‐CUP for each time step. Daily performance statistics were almost equal among all four time steps (NSE ≈ 0.47). Discharge mainly consisted of groundwater flow (55%) and tile flow (42%), in reasonable proportions for the investigated catchment. In conclusion, model outputs were almost identical, showing simulations responded nearly independently of the chosen precipitation time step. This held true for (1) the selection of sensitive parameters, (2) performance statistics, (3) the shape of the hydrographs, and (4) flow components. However, a scenario analysis revealed that the precipitation time step becomes important when saturated hydraulic conductivities are low and curve numbers are high. The study suggests that there is no need in using precipitation time steps <1 h for lowland catchments dominated by soils with a low surface runoff potential if daily flow values are being considered. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series. 相似文献
964.
The study aims to compare the detection of 16S rRNA gene of Dehalococcoides species and the microcosm study for biotransformation in predicting reductive dechlorination of chlorinated ethenes in ground water at hazardous waste sites. A total of 72 ground water samples were collected from 12 PCE or TCE contaminated sites in the United States. The samples were analyzed and used to construct microcosms in the laboratory. The results showed that the presence of Dehalococcoides DNA was well associated with dechlorination to ethene in the field. Nearly half of the wells where Dehalococcoides DNA was detected had ethene as a dechlorination end product. In comparison, for ground water samples of 16 wells where ethene was detected, ethene was produced in 11 of the corresponding microcosms. For most microcosms, during two years of incubation, dechlorination was less extensive than that observed in the field. 相似文献
965.
Jussi Kosonen Leif Kronberg 《Environmental science and pollution research international》2009,16(5):555-564
Background, aim and scope Each year, large quantities of pharmaceuticals are consumed worldwide for the treatment and prevention of human and animal
diseases. Although the drugs and the metabolites observed in the wastewaters and in the environment are present at concentrations
several orders of magnitude lower than the concentrations required to exert their effects in humans or animals, their long-term
impact on the environment is commonly not known. In this study, the occurrence of six antihistamines, which are used for the
relief of allergic reactions such as hay fever, was determined in sewage treatment plants wastewaters and in recipient river
waters.
Materials and methods The occurrence of the antihistamines cetirizine, acrivastine, fexofenadine, loratadine, desloratadine and ebastine in sewage
treatment plants wastewaters and in recipient river waters was studied. The analytical procedure consisted of solid-phase
extraction of the water samples followed by liquid chromatography separation and detection by a triple-quadrupole mass spectrometer
in the multiple reaction mode.
Results Cetirizine, acrivastine and fexofenadine were detected in both influent and effluent wastewater samples at concentration levels
ranging from about 80 to 220 ng/L, while loratadine, desloratadine and ebastine could not be detected in any samples. During
sewage treatment, the concentration of the antihistamines dropped by an average of 16–36%. Furthermore, elevated concentrations
of antihistamines were observed in samples collected during the season of most intensive plant pollen production, i.e. in
May. In the river water samples, the relative pattern of occurrence of cetirizine, acrivastine and fexofenadine was similar
to that in the wastewater samples; although the concentration of the compounds was substantially lower (4–11 ng/L). The highest
concentrations of the studied drugs were observed near the discharging point of the sewage treatment plant.
Discussion The highest concentrations of antihistamines in STP wastewaters correlate with the outbreak of allergic reaction caused by
high amounts of plant pollens in the air. The analysis results of the river water samples show that the antihistamines are
carried far away from the effluent discharge points. They may account for a part of the mix of pharmaceuticals and of pharmaceutical
metabolites that occur downstream of STPs.
Conclusions Antihistamines are poorly degraded/eliminated under the biological treatment processes applied in the wastewater treatment
plants and, consequently, they are continuously being discharged along with other drugs to the aquatic environment.
Recommendations and perspectives As a huge quantity and variety of drugs and their metabolites are continuously discharged to rivers and the sea, the compounds
should be considered as contaminants that may possess risks to the aquatic ecosystem. Further studies are urgently needed
on the environmental fate of the antihistamines and other pharmaceuticals in the aquatic environment. These studies should
be concerned with the stability of the compounds, their transformation reactions and the identity of the transformation products,
the distribution of drugs and their uptake and effects in organisms. On the basis of these studies, the possible environmental
hazards of pharmaceuticals may be assessed. 相似文献
966.
沸石联合微生物固定化去除微污染水体中氨氮的研究 总被引:5,自引:0,他引:5
将沸石联合经过驯化的活性污泥微生物固定化,通过静态实验.考察了不同粒径沸石及不同组分固定化方法对沸石联合微生物固定化去除氨氮的影响;通过动态实验,考察了沸石联合微生物固定化去除微污染水体中低浓度氨氮的机制.结果表明,活性污泥经过16 d的驯化,氨氮去除率为90%以上;沸石吸附氨氮为快速吸附,粒径<0.5 mm的沸石的吸附容量明显大于其他粒径的沸石;不同组分固定化小球对氨氮的去除效率不同,各组分均有贡献,吸附容量依次为:沸石固定化小球>沸石联合微生物固定化小球>微生物固定化小球;沸石联合微生物固定化去除微污染水体中低浓度氨氮可分为4个阶段,即沸石吸附阶段、吸附饱和及微生物适应阶段、硝化作用明显加强和沸石部分再生阶段、微生物作用良好和沸石进一步再生阶段,最终沸石吸附与生物再生处于良好的动态平衡中,氨氮去除率达到60%左右. 相似文献
967.
以天然矿物质沸石、细砂及煤渣取代传统滤料构建复合基质生态床,表面种植景观植物,采用下向流-上向流运行方式修复北方景观水体。分别进行静态实验及不同循环速率下的动态实验,考察对水体污染物去除过程。结果表明,2种运行方式下对水体NH+4-N去除率都在85%以上,其中以1 h为循环周期的运行方式去除率达97%,较静态提高12.8%;TN去除率最高为84%;TP去除不稳定,过程缓慢。煤渣层对NH+4-N的去除效果差,硝化作用不彻底与反硝化作用的加强使下层出水NH+4-N 、NO-2-N及NO-3-N浓度均高于上层。提高循环速率有利于对氮的去除。 相似文献
968.
基于超临界水氧化过程的能源环境系统设计 总被引:2,自引:0,他引:2
阐述了超临界水氧化过程的工艺路线,介绍了超临界水氧化过程的特点,提出了基于超临界水氧化过程的能源环境系统,设计了几种热量与能量回收系统程的耦合工艺,为提高超临界水氧化过程的经济性奠定了基础。 相似文献
969.
Agata Szygua Eric Guibal María Ario Palacín Montserrat Ruiz Ana Maria Sastre 《Journal of environmental management》2009,90(10):2979-2986
Chitosan (a biopolymer) is an aminopolysaccharide that can be used for the treatment of colored solutions by coagulation–flocculation (as an alternative to more conventional processes such as sorption). Acid Blue 92 (a sulfonic dye) was selected as a model dye for verifying chitosan's ability to treat textile wastewater. A preliminary experiment demonstrated that chitosan was more efficient at color removal in tap water than in demineralized water, and that a substantially lower concentration of chitosan could be used with tap water. Dye removal reached up to 99% under optimum concentration; i.e., in terms of the acidic solutions and the stoichiometric ratio between the amine groups of the biopolymer and the sulfonic groups in the dye. The flocs were recovered and the dye was efficiently removed using alkaline solutions (0.001–1 M NaOH solutions) and the biopolymer, re-dissolved in acetic acid solution, was reused in a further treatment cycle. 相似文献
970.
A method for quality screening is suggested to detect volatile impurities in inorganic coagulants that are used for drinking water treatment. Static headspace gas chromatography with mass spectrometry detection (HS–GCMS) is sensitive and selective to detect volatiles in low concentrations. This study has discovered that volatile organic impurities are detectable in ferric and aluminium-based coagulants which are used for drinking water treatment. For ferric chloride, 2-propanol was detected at a level of 17–24 μg ml−1, acetone at 0.7–1.7 μg ml−1, 1,1,1-trichloroacetone at 0.02–0.04 μg ml−1, trichloromethane at 0.01–0.02 μg ml−1 and toluene at 0.01–0.12 μg ml−1. For ferric chloride sulfate, acetone was detected at a level of 0.12 μg ml−1, 1,1,1-trichloroacetone at 0.06–0.08 μg ml−1, trichloromethane at 0.13–0.23 μg ml−1, bromodichloromethane at 0.04–0.06 μg ml−1 and dibromochloromethane at 0.04–0.05 μg ml−1. For aluminium hydroxide chloride, only trichloromethane was detectable, but below the method detection limits (MDL). Although the concentrations of these impurities in commercial coagulants are low, this observation is important and should have impact on water industries for them to pay attention to the chemicals they are using for drinking water production. 相似文献