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931.
Matthew Daly 《Local Environment》2017,22(11):1358-1377
Many intentional communities worldwide, such as ecovillages and co-housing communities, have explicit goals of living in an environmentally sustainable manner, and are taking conscious steps towards these goals in response to the widely discussed unsustainability of the global sociotechnical system. There are numerous claims from researchers and community members, in the academic and grey literature, that intentional communities are making significant improvements towards sustainability goals, particularly in terms of environmental impact. However, actual measures of progress, with evidence supporting these claims, are relatively scarce. This paper presents the findings of a systematic review of quantitative studies of the environmental impact of intentional communities, including comparisons with relevant “mainstream” communities. The review focused on the two indicators that are most commonly reported in studies of the impact of intentional communities – the ecological footprint and the carbon footprint. This review was undertaken as there is a lack of literature reviews that comprehensively compile existing quantitative studies about intentional communities. In total, the review identified 16 separate studies covering 23 communities and 30 footprint measurements, with publication dates ranging from 2000 to 2014. This is a greater number of studies than in any other literature review of this topic. Taken as a whole, these compiled studies provide strong support for claims of greater environmental sustainability within these communities, and reinforce the need for greater research and exploration of the role sustainability-oriented intentional communities can play in the transition to more sustainable sociotechnical systems. 相似文献
932.
Does the Temporal Resolution of Precipitation Input Influence the Simulated Hydrological Components Employing the SWAT Model? 下载免费PDF全文
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
933.
934.
Part V—sorption of pharmaceuticals and personal care products 总被引:5,自引:0,他引:5
Background, aim, and scope Pharmaceuticals and personal care products (PPCPs) including antibiotics, endocrine-disrupting chemicals, and veterinary pharmaceuticals
are emerging pollutants, and their environmental risk was not emphasized until a decade ago. These compounds have been reported
to cause adverse impacts on wildlife and human. However, compared to the studies on hydrophobic organic contaminants (HOCs)
whose sorption characteristics is reviewed in Part IV of this review series, information on PPCPs is very limited. Thus, a
summary of recent research progress on PPCP sorption in soils or sediments is necessary to clarify research requirements and
directions.
Main features We reviewed the research progress on PPCP sorption in soils or sediments highlighting PPCP sorption different from that of
HOCs. Special function of humic substances (HSs) on PPCP behavior is summarized according to several features of PPCP–soil
or sediment interaction. In addition, we discussed the behavior of xenobiotic chemicals in a three-phase system (dissolved
organic matter (DOM)–mineral–water). The complexity of three-phase systems was also discussed.
Results Nonideal sorption of PPCPs in soils or sediments is generally reported, and PPCP sorption behavior is relatively a more complicated
process compared to HOC sorption, such as the contribution of inorganic fractions, fast degradation and metabolite sorption,
and species-specific sorption mechanism. Thus, mechanistic studies are urgently needed for a better understanding of their
environmental risk and for pollution control.
Discussion Recent research progress on nonideal sorption has not been incorporated into fate modeling of xenobiotic chemicals. A major
reason is the complexity of the three-phase system. First of all, lack of knowledge in describing DOM fractionation after
adsorption by mineral particles is one of the major restrictions for an accurate prediction of xenobiotic chemical behavior
in the presence of DOM. Secondly, no explicit mathematical relationship between HS chemical–physical properties, and their
sorption characteristics has been proposed. Last but not least, nonlinear interactions could exponentially increase the complexity
and uncertainties of environmental fate models for xenobiotics. Discussion on proper simplification of fate modeling in the
framework of nonlinear interactions is still unavailable.
Conclusions Although the methodologies and concepts for studying HOC environmental fate could be adopted for PPCP study, their differences
should be highly understood. Prediction of PPCP environmental behavior needs to combine contributions from various fractions
of soils or sediments and the sorption of their metabolites and different species.
Recommendations and perspectives More detailed studies on PPCP sorption in separated soil or sediment fractions are needed in order to propose a model predicting
PPCP sorption in soils or sediments based on soil or sediment properties. The information on sorption of PPCP metabolites
and species and the competition between them is still not enough to be incorporated into any predictive models. 相似文献
935.
Vinicius F. Farjalla André M. Amado Albert L. Suhett Frederico Meirelles-Pereira 《Environmental science and pollution research international》2009,16(5):531-538
Background, aim, and scope Dissolved humic substances (HS) usually comprise 50–80% of the dissolved organic carbon (DOC) in aquatic ecosystems. From
a trophic and biogeochemical perspective, HS has been considered to be highly refractory and is supposed to accumulate in
the water. The upsurge of the microbial loop paradigm and the studies on HS photo-degradation into labile DOC gave rise to
the belief that microbial processing of DOC should sustain aquatic food webs in humic waters. However, this has not been extensively
supported by the literature, since most HS and their photo-products are often oxidized by microbes through respiration in
most nutrient-poor humic waters. Here, we review basic concepts, classical studies, and recent data on bacterial and photo-degradation
of DOC, comparing the rates of these processes in highly humic ecosystems and other aquatic ecosystems.
Materials and methods We based our review on classical and recent findings from the fields of biogeochemistry and microbial ecology, highlighting
some odd results from highly humic Brazilian tropical lagoons, which can reach up to 160 mg C L−1.
Results and discussion Highly humic tropical lagoons showed proportionally lower bacterial production rates and higher bacterial respiration rates
(i.e., lower bacterial growth efficiency) than other lakes. Zooplankton showed similar δ13C to microalgae but not to humic DOC in these highly humic lagoons. Thus, the data reviewed here do not support the microbial
loop as an efficient matter transfer pathway in highly humic ecosystems, where it is supposed to play its major role.
In addition, we found that some tropical humic ecosystems presented the highest potential DOC photo-chemical mineralization
(PM) rates reported in the literature, exceeding up to threefold the rates reported for temperate humic ecosystems. We propose
that these atypically high PM rates are the result of a joint effect of the seasonal dynamics of allochthonous humic DOC input
to these ecosystems and the high sunlight incidence throughout the year. The sunlight action on DOC is positive to microbial
consumption in these highly humic lagoons, but little support is given to the enhancement of bacterial growth efficiency,
since the labile photo-chemical products are mostly respired by microbes in the nutrient-poor humic waters.
Conclusions HS may be an important source of energy for aquatic bacteria in humic waters, but it is probably not as important as a substrate
to bacterial growth and to aquatic food webs, since HS consumption is mostly channeled through microbial respiration. This
especially seems to be the case of humic-rich, nutrient-poor ecosystems, where the microbial loop was supposed to play its
major role. Highly humic ecosystems also present the highest PM rates reported in the literature. Finally, light and bacteria
can cooperate in order to enhance total carbon degradation in highly humic aquatic ecosystems but with limited effects on
aquatic food webs.
Recommendations and perspectives More detailed studies using C- and N-stable isotope techniques and modeling approaches are needed to better understand the
actual importance of HS to carbon cycling in highly humic waters. 相似文献
936.
Jan Bernd Barhorst Roland Kubiak 《Environmental science and pollution research international》2009,16(5):582-589
Background, aim and scope The use of sodium hypochlorite (HYP) in viticulture results in effluents which are contaminated with halogenated substances.
These disinfection by-products (DBPs) can be quantified as group parameter ‘adsorbable organic halogens’ (AOX) and have not
been determined in effluents of viticulture yet. The substances that are detected as AOX are unknown. The AOX can be composed
of harmless substances, but even toxic contaminants. Thus, it is impossible to assess ecological impacts. The aim of this
study is to determine the quantification of AOX and DBPs after the use of HYP. This will be helpful to reduce environmental
pollution by AOX.
Materials and methods The potential of HYP to generate AOX was determined in laboratory-scale experiments. Different model solutions were treated
with HYP according to disinfection processes in viticulture and conditions of AOX formation in effluents were simulated. AOX
were quantified using the flask-shaking method and identified DBPs were investigated by gas chromatography–mass spectrometry.
Results Treatment with HYP resulted in the formation of AOX. The percentage conversion of HYP to AOX was up to 11%. Most important
identified DBPs in viticulture are chloroform, dichloroacetic acid and trichloroacetaldehyde. In addition, the formation of
carbon tetrachloride (CT), 1,1,1-trichloropropanone, 2,4-dichlorobenzoic acid and 2-chloro-/2,4-dichlorophenylacetic acid
was investigated. It was demonstrated that reaction temperature, concentration of HYP and type of organic matter have important
influence on the formation of chlorinated DBPs.
Discussion The percentage conversion of HYP to AOX was similar to other published studies. Although a correlation of single compounds
and AOX is difficult, chloroform was the predominant AOX. Generation of the volatile chloroform should be avoided due to possible
adverse effects. The generation of dichloroacetic acid is of minor importance on account of biodegradation. Trichloroacetaldehyde
and 1,1,1-trichloropropanone are weak mutagens and their formation should be avoided.
Conclusions The generation of AOX and chlorinated DBPs can be minimised by reducing the concentrations of the organic materials in the
effluents. The removal of organic matter before disinfection results in a decreased formation of AOX. HYP is an effective
disinfectant; therefore, it should be used at low temperatures and concentrations to reduce the amount of AOX. If possible,
disinfection should be accomplished by the use of no chlorine-containing agents. By this means, negative influences of HYP
on the quality of wine can also be avoided.
Recommendations and perspectives Our results indicate that HYP has a high potential to form AOX in effluents of viticulture. The predominant by-products are
chloroform, dichloroacetic acid and trichloroacetaldehyde. In further research, wastewaters from a winery and the in- and
outflows of two sewage treatment plants were sampled during vintage and analysed. These results will be discussed in a following
paper. 相似文献
937.
938.
重金属元素在冻土与融土中迁移的对比试验 总被引:1,自引:0,他引:1
随着寒区经济的发展,冻土地区的矿山开采活动不断加剧,随之产生的重金属污染问题也越来越严重.冻土地区生态环境脆弱,一旦受到破坏就很难恢复.针对此问题,室内模拟了尾矿矿渣在冻土与融土中的填埋及其对填埋场周边土体的影响,通过检测填埋场各处土壤的温度、含水量以及重金属元素的含量,发现温度和水分对重金属元素的迁移影响很大.土壤温度越低,重金属元素的迁移越慢;在温度梯度的作用下,重金属元素均随着水分从土体的暖端向冷端迁徙并聚集于冻结锋面.重金属元素在冻土中的迁移比融土中慢,表明冻土环境不利于重金属元素的迁移.在土壤质地、温度和含水量等相同的情况下,Zn的迁移性较强,Pb和Cu的迁移性相对较弱. 相似文献
939.
Viivi Hassinen Veli-Matti Vallinkoski Sirpa Kärenlampi 《Environmental pollution (Barking, Essex : 1987)》2009,157(3):922-930
Metal uptake and its effect on foliar metallothionein 2b (MT2b) mRNA levels were studied in hybrid aspen (Populus tremula × tremuloides) in field conditions. The trees were planted on a site contaminated with several metals, including cadmium (mean 5.1 mg kg−1), chromium (80 mg kg−1), copper (180 mg kg−1), nickel (81 mg kg−1), vanadium (240 mg kg−1) and zinc (520 mg kg−1). Of the ten trace elements analyzed, only Cd and Zn accumulated in the leaves with maximal foliar concentrations of 35 and 2400 mg kg−1 (dry weight), respectively. There was a strong correlation between Cd and Zn concentrations and bioaccumulation factors (concentration in plant/soil) in the leaves, branches and roots, suggesting similar transport mechanisms for these two metals. The levels of MT2b correlated with Cd and Zn concentrations in the leaves, demonstrating that increased MT2b expression is one of the responses of hybrid aspen to chronic metal exposure. 相似文献
940.
Jason A. Dittman James B. Shanley George R. Aiken Janet E. Towse 《Environmental pollution (Barking, Essex : 1987)》2009,157(6):1953-1956
Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THgd), DOC concentration and DOC composition, and UV254 absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive correlation of THgd to DOC (r2 = 0.87), but progressively stronger correlations of THgd with the hydrophobic acid fraction (HPOA) of DOC (r2 = 0.91) and with UV254 absorbance (r2 = 0.92). The strength of the UV254 absorbance-THgd relationship suggests that optical properties associated with dissolved organic matter may be excellent proxies for THgd concentration in these streams. Ease of sample collection and analysis, the potential application of in-situ optical sensors, and the possibility for intensive monitoring over the hydrograph make this an effective, inexpensive approach to estimate THgd flux in drainage waters. 相似文献