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151.
最近 ,小型倾斜河流中的阶梯形鱼道建筑以它的简易与实用而变得日益重要。在这种鱼道中出现的滚动流将产生波涌 ,并继续向下传播 ,而且它的周期性滚动可能会严重危害鱼道。因此 ,我们着手研究了它的严重性以便设计者在设计鱼道时能考虑这些因素。由实验证实滚动流源于阶梯形鱼道的上游。滚动流在稳定流与半平滑流间转变 ,它在一定时间间隔内不断地从稳定流变成半平滑流 ,又从半平滑流变成稳定流。它的流量值随着阶梯形水道的几何形状变形而呈现上下限。流量值和时间间隔均随着水池长度的增加而增加。 相似文献
152.
Chhay Leaksmy Reyad Md Amjad Hossain Suy Rathny Islam Md Rafiqul Mian Md Manik 《Journal of Material Cycles and Waste Management》2018,20(3):1761-1770
Journal of Material Cycles and Waste Management - In the developing countries, the inadequacy of basic waste data is a significant obstacle for municipal solid waste management. To evaluate an... 相似文献
153.
Murshed Muntasir Rahman Md. Aminur Alam Md Shabbir Ahmad Paiman Dagar Vishal 《Environmental science and pollution research international》2021,28(36):49967-49988
Environmental Science and Pollution Research - Environmental sustainability has become a major concern for policymakers across the globe. In this regard, understanding the factors responsible for... 相似文献
154.
155.
岩溶区不同水体有机氯农药对比研究 总被引:1,自引:0,他引:1
为研究岩溶区地下水、地表水之间有机氯农药的差异,用气相色谱-微池电子捕获检测器(GC-μECD)分析了水中OCPs含量.结果表明:研究区水样中有机氯农药检出率达100%.OCPs浓度范围32.13~319.53ng/L,均值为134.17ng/L.OCPs浓度季节差异明显,枯水期高于丰水期.水井(sj)中OCPs,DDTs、HCHs浓度均大于水池(sc).通过采样点间的对比可知,雨季水池、水井间OCPs含量相当,旱季水池小于水井.水池、水井间DDTs、HCHs对比没有明显的季节性,表现为水池的DDTs含量小于水井,但HCHs含量大于水井.水井中的OCPs、DDTs、HCHs的最小值与水池相比均表现出了滞后性.地表水与地下水有机氯农药表现出的差异,是由于两采样点的环境不同.通过比值法得出HCHs来自于混合源,地表水的比值更能准确的反映出HCHs的来源.DDTs可能来自于混合DDTs,且为历史残留,降解环境为好氧环境.水井中DDTs、HCHs百分比组成由于土壤的影响发生了变化. 相似文献
156.
M. J. Watts T. S. Barlow M. Button S. K. Sarkar B. D. Bhattacharya Md. Aftab Alam A. Gomes 《Environmental geochemistry and health》2013,35(1):13-25
This paper documents the concentration of total arsenic and individual arsenic species in four soft-bottom benthic polychaetes (Perenereis cultifera, Ganganereis sootai, Lumbrinereis notocirrata and Dendronereis arborifera) along with host sediments from Sundarban mangrove wetland, India. An additional six sites were considered exclusively for surface sediments for this purpose. Polychaetes were collected along with the host sediments and measured for their total arsenic content using inductively coupled plasma mass spectrometry. Arsenic concentrations in polychaete body tissues varied greatly, suggesting species-specific characteristics and inherent peculiarities in arsenic metabolism. Arsenic was generally present in polychaetes as arsenate (AsV ranges from 0.16 to 0.50 mg kg?1) or arsenite (AsIII ranges from 0.10 to 0.41 mg kg?1) (30–53 % as inorganic As) and dimethylarsinic acid (DMAV <1–25 %). Arsenobetaine (AB < 16 %), and PO4-arsenoriboside (8–48 %) were also detected as minor constituents, whilst monomethylarsonic acid (MAV) was not detected in any of the polychaetes. The highest total As (14.7 mg kg?1 dry wt) was observed in the polychaete D. arborifera collected from the vicinity of a sewage outfall in which the majority of As was present as an uncharacterised compound (10.3 mg kg?1 dry wt) eluted prior to AB. Host sediments ranged from 2.5 to 10.4 mg kg?1 of total As. This work supports the importance of speciation analysis of As, because of the ubiquitous occurrence of this metalloid in the environment, and its variable toxicity depending on chemical form. It is also the first work to report the composition of As species in polychaetes from the Indian Sundarban wetlands. 相似文献
157.
Mohammed Mahabubur Rahman Jiro Tsukamoto Md. Motiur Rahman Aogu Yoneyama Kamal Mohammad Mostafa 《Chemistry and Ecology》2013,29(6):540-553
Lignin is a major component of plant litter. In this review, we found lignin comprises a complex class of organic compounds whose concentration differs greatly both between and within plant species. There are many analytical methods for detecting the composition and structure of lignins. As lignins are enormously complex compounds, chemical assay is difficult and different methods vary with the results. Lignin plays a significant role in the carbon cycle, sequestering atmospheric carbon into the living tissues of woody perennial vegetation. It has also great effects on nitrogen dynamics of forest ecosystems as well as other ecological processes. Lignin is one of the most slowly decomposing components of dead vegetation, contributing a major fraction of the material that becomes humus as it decomposes. Lignin is highly correlated with decomposition of litter. Thus, there is evidence that the lignin concentration is a more influential factor than the other chemical concentrations, in determining the rate of leaf litter decomposition of different forest ecosystems. Although a great number of researchers have addressed lignin's role in litter decomposition, still there are many aspects of lignin biogeochemistry that are not known. This lack of information hinders complete amalgam of lignin effects on litter decomposition processes and dynamics of nutrient cycling. 相似文献
158.
A pot experiment was conducted to evaluate the potential effects of arbuscular mycorrhizal fungi (AMF) on growth, nutrient uptake, and inoculation effectiveness on Phragmites japonica. Spores of AMF strains (Gigaspora margarita Becker &; Hall) were collected from the commercial product ‘Serakinkon’. Four treatments, namely, natural soil (NS), natural soil inoculated by AM fungi, sterilised soil (SS) inoculated by AM fungi, and SS without AM fungi inoculation were selected to determine the effects of applied and indigenous AMF on P. japonica. The average colonisation level of P. japonica was 24–33%, whereas no colonisation was found in the SS. AMF colonisation increased the chlorophyll content (r?=?0.84, p?.01), plant dry mass (r?=?0.89, p?.01), and N, P, K, Mg, and Fe concentration of the plant's roots, stems, and leaves when AMF was applied with natural and SS. In all cases, maximum values were found when the plants were applied with NS in combination with AMF, but Ca concentration decreased as the colonisation level increased. Mn concentration decreased in the roots, but increased in the leaves. Cu concentration was not significantly affected by treatments. N-loss minimisation from the soil was significant when the colonisation level was high. 相似文献
159.
Haq Fazal Yu Haojie Wang Yang Wang Li Mehmood Sahid Haroon Muhammad Bilal-Ul-Amin Fahad Shah Uddin Md. Alim Shen Di 《Journal of Polymers and the Environment》2021,29(8):2676-2685
Journal of Polymers and the Environment - Succinylated starches (SS) were prepared by the reaction of normal starch (NS) and porous starch (PS) with succinic anhydride (SA) in the presence of DMF... 相似文献
160.
Yusaku?SakataEmail author Thallada?Bhaskar Md. Azhar?Uddin Akinori?Muto Toshiki?Matsui 《Journal of Material Cycles and Waste Management》2003,5(2):113-124
Dehalogenation is a key technology in the feedstock recycling of mixed halogenated waste plastics. In this study, two different methods were used to clarify the effectiveness of our proposed catalytic dehalogenation process using various carbon composites of iron oxides and calcium carbonate as the catalyst/sorbent. The first approach (a two-step process) was to develop a process for the thermal degradation of mixed halogenated waste plastics, and also develop dehalogenation catalysts for the catalytic dehydrochlorination of organic chlorine compounds from mixed plastic-derived oil containing polyvinyl chloride (PVC) using a fixed-bed flow-type reactor. The second approach (a single-step process) was the simultaneous degradation and dehalogenation of chlorinated (PVC) and brominated (plastic containing brominated flame retardant, HIPS–Br) mixed plastics into halogen-free liquid products. We report on a catalytic dehalogenation process for the chlorinated and brominated organic compounds formed by the pyrolysis of PVC and brominated flame retardant (HIPS–Br) mixed waste plastics [(polyethylene (PE), polypropylene (PP), and polystyrene (PS)], and also other plastics. During dehydrohalogenation, the iron- and calcium-based catalysts were transformed into their corresponding halides, which are also very active in the dehydrohalogenation of organic halogenated compounds. The halogen-free plastic-derived oil (PDO) can be used as a fuel oil or feedstock in refineries. 相似文献