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431.
Hai Chen David López-Carr Yan Tan Jing Xi Xiaoying Liang 《Regional Environmental Change》2016,16(4):1147-1159
Analyzing the interaction between environmental policies and farmers’ responses to them is an important dimension to understand regional agro-ecosystem sustainability. We examine land-use outcomes of perhaps the largest government-planned rural reforestation program in the history of humankind, China’s “Grain for Green” (GFG) policy from 1999 to 2006. Specifically, we simulate household responses to the GFG policy in Western China’s Shaanxi Province, a region experiencing acute climate and land change-related environmental degradation. We develop a “farmer group decision-making model” to simulate the probability of land-use change. Elevation, slope, and farm household characteristics emerge as key factors influencing farmers’ land-use decisions and subsequent land-use patterns. Land reversion and abandonment in the study area have been significantly affected by the GFG program. Policy recommendations suggest potential avenues to enhance the effectiveness of the GFG program and to improve the efficient use of under-used farmland. Results may help inform the Chinese government as it crafts policy guiding a coupled rural migration and reforestation program of unprecedented scale. 相似文献
432.
以处理生活污水的平板膜-生物反应器为依托,通过将进水调配成30、200和500 mg/L 3种不同的钙离子浓度,考察钙离子对短期膜污染的影响。结果表明,随着钙离子浓度的增加,TMP增长趋势变小,膜污染得到缓解;钙离子浓度为200 mg/L时,膜的渗透性最好,而过高的钙离子浓度并不利于降低膜污染。钙离子的投加强化了生物絮凝作用,可以降低SMP和LB-EPS的含量,主要通过降低外部阻力减缓膜污染;投加钙离子也可以增加絮体的大小,较大的絮体形成的泥饼有更好的过滤性,然而过高的钙离子浓度会使无机颗粒的量增加,造成平均粒径下降,将会加重内部污染,进而加剧膜污染。 相似文献
433.
434.
Fan W Cui M Liu H Wang C Shi Z Tan C Yang X 《Environmental pollution (Barking, Essex : 1987)》2011,159(3):729-734
The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO2 remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L−1 nano-TiO2, the (LC50) of Cu2+ concentration observed to kill half the population, decreased from 111 μg L−1 to 42 μg L−1. Correspondingly, the level of metallothionein decreased from 135 μg g−1 wet weight to 99 μg g−1 wet weight at a Cu2+ level of 100 μg L−1. The copper was found to be adsorbed onto the nano-TiO2, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO2 may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins. 相似文献
435.
436.
采用H2O2浸渍的修饰方法对ACF进行化学改性,并利用氮吸附等温线和XPS(X-ray photoelectron spectroscopy)的方法对ACF样品进行表征。通过在反应床上开展吸附实验,由此测定改性前后ACF脱除VOC(甲苯作为VOC的代表物)的效果,同时考察氧气、温度、水蒸气等因素对ACF脱除甲苯的影响。研究发现,改性使得ACF样品比表面积和孔容略有降低,但表面含氧官能团含量增加,吸附甲苯的能力也因此增强。当模拟烟气中O2浓度为5%时,ACF脱除VOC效果达到最佳,超过5%之后,氧的促进效果不再明显;温度40℃为最佳吸附温度;当烟气中加入水蒸气时,ACF对VOC的脱除效率降低。 相似文献
437.
Exposure to perchlorate is widespread in the United States and many studies have attempted to character the perchlorate exposure by estimating the average daily intakes of perchlorate. These approaches provided population-based estimates, but did not provide individual-level exposure estimates. Until recently, exposure activity database such as CSFII, TDS and NHANES become available and provide opportunities to evaluate the individual-level exposure to chemical using exposure surveillance dataset. In this study, we use perchlorate as an example to investigate the usefulness of urinary biomarker data for predicting exposures at the individual level. Specifically, two analyses were conducted: (1) using data from a controlled human study to examine the ability of a physiologically based pharmacokinetic (PBPK) model to predict perchlorate concentrations in single-spot and cumulative urine samples; and (2) using biomarker data from a population-based study and a PBPK model to demonstrate the challenges in linking urinary biomarker concentrations to intake doses for individuals. Results showed that the modeling approach was able to characterize the distribution of biomarker concentrations at the population level, but predicting the exposure-biomarker relationship for individuals was much more difficult. The type of information needed to reduce the uncertainty in estimating intake doses, for individuals, based on biomarker measurements is discussed. 相似文献
438.
Shabir A. Dar Hui Tan Aaron D. Peacock Peter Jaffe Lucie N'Guessan Kenneth H. Williams Sarah Strycharz‐Glaven 《补救:环境净化治理成本、技术与工艺杂志》2013,23(2):31-49
Analysis of the physiological status of subsurface microbial communities generally relies on the study of unattached microorganisms in the groundwater. These approaches have been employed in studies on bioremediation of uranium‐contaminated groundwater at a study site in Rifle, Colorado, in which Geobacter species typically account for over 90 percent of the microbial community in the groundwater during active uranium reduction. However, to develop efficient in situ bioremediation strategies it is necessary to know the status of sediment‐associated microorganisms as well. In order to evaluate the distribution of the natural community of Geobacter during bioremediation of uranium, subsurface sediments were packed into either passive flux meters (PFMs) or sediment columns deployed in groundwater monitoring wells prior to acetate injection during in situ biostimulation field trials. The trials were performed at the Department of Energy's (DOE's) Rifle Integrated Field Research Challenge site. Sediment samples were removed either during the peak of Fe(III) reduction or the peak of sulfate reduction over the course of two separate field experiments and preserved for microscopy. Direct cell counts using fluorescence in situ hybridization (FISH) probes targeting Geobacter species indicated that the majority of Geobacter cells were unattached during Fe(III) reduction, which typically tracks with elevated rates of uranium reduction. Similar measurements conducted during the sulfate‐reducing phase revealed the majority of Geobacter to be attached following exhaustion of more readily bioavailable forms of iron minerals. Laboratory sediment column studies confirmed observations made with sediment samples collected during field trials and indicated that during Fe(III) reduction, Geobacter species are primarily unattached (90 percent), whereas the majority of sulfate‐reducing bacteria and Geobacter species are attached to sediment surfaces when sulfate reduction is the predominant form of metabolism (75 percent and 77 percent, respectively). In addition, artificial sediment experiments showed that pure cultures of Geobacter uraniireducens, isolated from the Rifle site, were primarily unattached once Fe(III) became scarce. These results demonstrate that, although Geobacter species must directly contact Fe(III) oxides in order to reduce them, cells do not firmly attach to the sediments, which is likely an adaptive response to sparsely and heterogeneously dispersed Fe(III) minerals in the subsurface. © 2013 Wiley Periodicals, Inc. 相似文献
439.
多环芳烃类化合物(PAHs)是环境中普遍存在的持久性有毒有机污染物,因具有强烈的"三致"作用,业已引起各国环境科学工作者的广泛关注,PAHs污染土壤的修复也已成为环境科学与工程领域的研究热点。以菲为PAHs的代表,研究了黑麦草/苜蓿间作对多环芳烃(菲)污染土壤的修复效应。通过温室盆栽模拟实验,观察到5 mg/kg和50 mg/kg污染水平没有明显抑制黑麦草和苜蓿的生长;黑麦草/苜蓿间作促进了植物对土壤菲的吸收,且间作体系根系富集系数大于单作;土壤中菲的可提取浓度随时间的延长逐渐减少,在菲重度污染土壤上,黑麦草/苜蓿间作修复效果明显优于单作,菲去除率可高达90.53%。因此,对于重度PAHs污染土壤该体系是一种有实际应用价值的间作修复体系。 相似文献
440.