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321.
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
322.
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
323.
324.
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
325.
木棉基活性炭纤维吸附性能的研究 总被引:1,自引:0,他引:1
采用浸渍(NH4)2HPO4化学活化法650℃时制备得到3种新型木棉基活性炭纤维,即只浸渍不预氧化方法处理的AK1(activated kapok),先浸渍后预氧化的AK-2和先预氧化后浸渍的AK-3。利用制备得到的活性炭纤维处理苯酚和亚甲基蓝的模拟废水,AK-2具有苯酚最大吸附量(137.00 mg/g),AK-1具有亚甲基蓝最大吸附量(274.11 mg/g)。吸附苯酚时,在静态平衡实验中,更符合Freundlich吸附等温线;在动力学实验中,更符合准一级反应。吸附亚甲基蓝时,在静态平衡实验中,AK-1更符合Langmuir模型,AK-2 、AK-3更符合Freundlich吸附等温线;在动力学实验中,更符合准二级反应。 相似文献
326.
三氯生在碳纳米管上的吸附 总被引:3,自引:2,他引:1
药品和个人护理用品(PPCPs)已成为一个引起广泛关注的新的环境问题。采用碳纳米管(CNTs)对水溶液中的三氯生进行吸附处理,考察了碳纳米管粒径及用量、温度、pH、振荡时间等因素对三氯生去除率的影响。研究结果表明,碳纳米管能快速吸附水中的三氯生,粒径较小的碳纳米管可获得较高的三氯生去除率;低温有利于吸附反应的进行;pH在6.5~7.0时,三氯生的去除率可达97%。三氯生在碳纳米管上的吸附可以很好地用Langmuir和Freundlich吸附等温方程进行描述。 相似文献
327.
固定化假单胞菌降解油烟废气的研究 总被引:1,自引:0,他引:1
将从受油烟废气污染严重的土壤中分离筛选的具有较强降解油烟能力的假单胞菌利用活性炭为填料吸附固定后制成填料床生物反应器。实验考察了进气浓度、气体流量、气体停留时间、容积负荷等对油烟去除率的影响,初步研究了生物反应器的抗冲击能力。结果表明,活性炭填料对菌体具有良好的吸附能力,当油烟进气浓度小于100 mg/L,气体流速小于8 L/h,停留时间大于30 s,容积负荷为2.6~18.9 g油烟废气/(m3·h),生物反应器的降解效率可达到95%以上,且活性炭填料床反应器具有较强的抗冲击能力。 相似文献
328.
329.
F. Boudrahem F. Aissani-Benissad H. Aït-Amar 《Journal of environmental management》2009,90(10):3031-3039
Lignocellulosic materials are good precursors for the production of activated carbon. In this work, coffee residue has been used as raw material in the preparation of powder activated carbon by the method of chemical activation with zinc chloride for the sorption of Pb(II) from dilute aqueous solutions.The influence of impregnation ratio (ZnCl2/coffee residue) on the physical and chemical properties of the prepared carbons was studied in order to optimize this parameter. The optimum experimental condition for preparing predominantly microporous activated carbons with high pore surface area (890 m2/g) and micropore volume (0.772 cm3/g) is an impregnation ratio of 100%. The developed activated carbon shows substantial capability to sorb lead(II) ions from aqueous solutions and for relative impregnation ratios of 75 and 100%, the maximum uptake is practically the same. Thus, 75% represents the optimal impregnation ratio.Batch experiments were conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), solution pH, ionic strength and temperature. The maximum uptake of lead(II) at 25 °C was about 63 mg/g of adsorbent at pH 5.8, initial Pb(II) concentration of 10 mg/L, agitation speed of 200 rpm and ionic strength of 0.005 M. The kinetic data were fitted to the models of pseudo-first order and pseudo-second order, and follow closely the pseudo-second order model. Equilibrium sorption isotherms of Pb(II) were analyzed by the Langmuir, Freundlich and Temkin isotherm models. The Freundlich model gives a better fit than the others.Results from this study suggest that activated carbon produced from coffee residue is an effective adsorbent for the removal of lead from aqueous solutions and that ZnCl2 is a suitable activating agent for the preparation of high-porosity carbons. 相似文献
330.
In this paper, Loofa egyptiaca (LE), an agricultural plant cultivated in Egypt, was used to prepare low-cost activated carbon (LEC1 and LEC2) adsorbents. The adsorbents (LE, LEC1 and LEC2) were evaluated for their ability to remove direct blue 106 dye from aqueous solutions. Batch mode experiments were conducted using various parameters such as pH, contact time, dye concentration and adsorbent concentration. The surface chemistry of LE, LEC1 and LEC2 was analyzed by scanning electron microscopy (SEM). The experimental data were examined using Langmuir, Freundlich, Temkin and Harkins–Jura isotherms. The results showed that the adsorption of direct blue 106 was maximal at the lowest value of pH (pH = 2). Removal efficiency was increased with an increase in dye concentration and a decrease in amount of adsorbent. Maximum adsorption capacity was found to be 57.14, 63.3 and 73.53 mg/g for LE, LEC1 and LEC2 respectively. Kinetics were also investigated using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The experimental data fitted very well with the pseudo-first-order and pseudo-second-order kinetic models. The results indicate that LE, LEC1 and LEC2 could be employed as adsorbents for the removal of direct blue dye from aqueous solutions. 相似文献