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451.
Michael Rivera Bao Ha Leili Zamini Sonja Gamby Demar Pitter 《Journal of environmental science and health. Part. B》2019,54(1):54-60
We report on the rates of decomposition of a group of N-methylcarbamate (NMC) pesticides (carbaryl, carbofuran and propoxur) under pre-determined tropical field conditions. Rates of decomposition for three NMCs were determined at pH 7.08 and T?=?20?°C and pH 7.70 and T = 33?°C respectively, as follows: carbaryl (78?days and 69?days); carbofuran (143?days and 83?days) and propoxur (116?days and 79?days). Investigation on methods for removal of NMCs and their phenolic decomposition products shows that activated charcoal outperforms zeolite, alumina, diatomaceous earth, cellulose and montmorillonite clay in the removal of both NMCs and phenols from aqueous solution. Furthermore, metal complexation studies on the NMCs and phenols showed that Fe (III) forms a complex with isopropoxyphenol (IPP) within which the Fe:IPP ratio is 1:3, indicative of the formation of a metal chelate complex with the formula Fe(IPP)3. 相似文献
452.
Organic Farming and Soil Carbon Sequestration: What Do We Really Know About the Benefits? 总被引:1,自引:0,他引:1
Organic farming is believed to improve soil fertility by enhancing soil organic matter (SOM) contents. An important co-benefit
would be the sequestration of carbon from atmospheric CO2. Such a positive effect has been suggested based on data from field experiments though many studies were not designed to
address the issue of carbon sequestration. The aim of our study was to examine published data in order to identify possible
flaws such as missing a proper baseline, carbon mass measurements, or lack of a clear distinction between conventional and
organic farming practices, thereby attributing effects of specific practices to organic farming, which are not uniquely organic.
A total of 68 data sets were analyzed from 32 peer-reviewed publications aiming to compare conventional with organic farming.
The analysis revealed that after conversion, soil C content (SOC) in organic systems increased annually by 2.2% on average,
whereas in conventional systems SOC did not change significantly. The majority of publications reported SOC concentrations
rather than amounts thus neglecting possible changes in soil bulk density. 34 out of 68 data sets missed a true control with
well-defined starting conditions. In 37 out of 50 cases, the amount of organic fertilizer in the organic system exceeded that
applied in the compared conventional system, and in half of the cases crop rotations differed between systems. In the few
studies where crop rotation and organic fertilization were comparable in both systems no consistent difference in SOC was
found. From this data analysis, we conclude that the claim for beneficial effects of organic farming on SOC is premature and
that reported advantages of organic farming for SOC are largely determined by higher and often disproportionate application
of organic fertilizer compared to conventional farming. 相似文献
453.
中国CO_2地质封存与可持续发展 总被引:1,自引:0,他引:1
在全球气候变暖的自然趋势下,推行CO2地质封存项目对减缓气候变暖进程和我国实施可持续发展战略具有重要意义。本文概述了CO2在地质储层-盖层系统中的两种捕获机制:一是通过地层构造压力、地下水动力、流体密度差、盖层岩石毛细管压力及矿物(煤层)吸附等共同作用的物理捕获机制,另一种是通过水岩化学反应进行固碳的化学捕获机制。归纳了有利于长期安全封存CO2的地质条件和水文特征,结合文献资料指出我国CO2有效地质封存总容量可供中国CO2地质埋存使用1 000年以上。并从科学技术能力、人才储备、经济成本及效益预算、管理和运营体制等方面进行论证,认为我国实施CO2地质封存项目是切实可行的。结合我国不合理的能源消费结构及全球气候变暖、环境恶化可能产生的后果,阐述了CO2地质封存对我国实现节能减排、低碳经济等可持续发展战略的深远意义。建议我国尽快组织开展CO2地质封存相关科学理论、封存技术及基本框架和配套政策、法规研究,为我国应对全球气候变化提供足够的技术和人才储备。 相似文献
454.
吉林省农田黑土中Cd、Pb、As含量的空间分布特征 总被引:10,自引:1,他引:9
利用地统计学方法研究了吉林省黑土区耕层土壤(0~20cm)中Cd、Pb、As含量的空间结构及其分布特征.结果表明,研究区土壤Pb含量属中等程度的空间相关,而Cd、As含量属空间弱相关.3种元素含量的空间变异主要受人为的随机性因素的影响.利用半方差函数的分析结果经普通克立格插值得到了3种元素含量的空间分布图.结果显示,在空间分布上,受不同污染源的影响,土壤Cd、Pb、As含量表现出不同的分布特征.土壤Cd含量较高的地区主要分布于煤矿区周围;土壤Pb含量高的样点主要分布于城郊及公路两侧;煤矿区周围及城郊农田土壤中As含量相对较高. 相似文献
455.
456.
净化去除酸性废水中不同价态砷的研究 总被引:9,自引:0,他引:9
根据净化含砷废水的铁盐中和法.通过理论分析和实验表明,在Fe/As=0.5—6.0范围内,铁盐中和法对废水中3价砷的去除率较其对5价砷的去除率平均低约60%,证实了废水中的3价砷较5价砷难于去除。氧化剂选择研究表明,对于含砷量高的酸性废水,采用漂白粉[Ca(C10)2]氧化其中的3价砷最为适宜。对于含砷782.5mg/L,pH=1的酸性废水,采用氧化-铁盐中和法经一级处理后,废水中含砷量即可低于8mg/L.除砷率大于99%,二级处理后出水中砷含量即可低于国家排放标准(0.5mg/L)。 相似文献
457.
Elizabeth Ramlal Denys Yemshanov Glenn Fox Daniel McKenney 《Journal of environmental management》2009
This study explores the economic attractiveness of afforestation as a strategy for the joint production of fibre, carbon storage and biosolids (treated municipal sewage sludge) disposal for municipalities in Southern and Central Ontario, Canada. We use a spatial, stochastic model, the Canadian Forest Service Afforestation Feasibility Model (CFS-AFM), to simulate a range of spatial biosolids application scenarios in hybrid poplar afforestation projects. Results suggest that such joint afforestation strategies could be financially attractive. Significant cost savings can be expected through decreases in transportation distances and avoided waste disposal fees. Sensitivity analysis is used to examine the effects of variations in critical model parameters on net present values. Our findings indicate that waste disposal savings from application of biosolids on hybrid poplar plantations combined with incentives for landowners to sequester carbon can easily compete with agricultural land rental values in some regions of Ontario. Social acceptance of this kind of activity, however, may be an impediment to adoption. 相似文献
458.
Mehdi Zeidouni Mehran Pooladi-Darvish David Keith 《International Journal of Greenhouse Gas Control》2009,3(5):600-611
Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO2. Among various mechanisms, CO2 can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO2. Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the reservoir in the vicinity of the wellbore, and can lead to reduction in injectivity. The amount of salt precipitation and the region in which it occurs may be important in CO2 storage operations if salt precipitation significantly reduces injectivity. Here we develop an analytical model, as a simple and efficient tool to predict the amount of salt precipitation over time and space. This model is particularly useful at high injection velocities, when viscous forces dominate.First, we develop a model which treats the vaporization of water and dissolution of CO2 in radial geometry. Next, the model is used to predict salt precipitation. The combined model is then extended to evaluate the effect of salt precipitation on permeability in terms of a time-dependent skin factor. Finally, the analytical model is corroborated by application to a specific problem with an available numerical solution, where a close agreement between the solutions is observed. We use the results to examine the effect of assumptions and approximations made in the development of the analytical solution. For cases studied, salt saturation was a few percent. The loss in injectivity depends on the degree of reduction of formation permeability with increased salt saturation. For permeability-reduction models considered in this work, the loss in injectivity was not severe. However, one limitation of the model is that it neglects capillary and gravity forces, and these forces might increase salt precipitation at the bottom of formation particularly when injection rate is low. 相似文献
459.
Regular ingestion of soils could pose a potential health threat due to long-term toxic element exposure. In order to estimate
the human bioavailability quotients for As and heavy metals, 12 urban roadside soil samples were collected and analyzed for
As, Pb, Cu, Zn, Ni, Co, and Cr using Simple Bioavailability Extraction Test (SBET). The quantities of As, Pb, Cu, Zn, Ni,
Co, and Cr leached from soils within the simulated human stomach for 1 h indicated, on average, 27.3, 71.7, 40.4, 59.3, 17.7,
27.2 and 5.6% bioavailability, respectively. Significant positive correlations were observed between the amounts leached using
SBET and the total amounts dissolved with HNO3-HCl-HF acid mixtures. Stepwise multiple regression analysis indicated that the amounts leached with SBET for As, Pb, Zn,
Ni, and Co were not related to any of the physic-chemical parameters measured (i.e., soil texture, pH, total organic matter).
These results may be valuable for providing input data for risk assessment at sites subject to anthropogenic soil contamination. 相似文献
460.
土壤和底质中砷形态分析前处理技术 总被引:2,自引:0,他引:2
利用可溶性砷(包括有机砷、砷的无机含氧化合物)和硫化砷的特性进行砷的形态分析。在2mol/L盐酸中提取可溶性砷,与硫化砷进行分离,分别测定总砷和可溶性砷后差值为硫化砷,在9mol/L硫酸-碘化钾溶液中用苯萃取砷的无机含氧化合物与有机砷进行分离,可分别测定有机砷的砷的无机含氧化合物。 相似文献