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301.
为了有效地清除城市小广告以及街头涂鸦,研制了一种针对热塑性丙烯酸树脂类手喷漆的乳液型脱漆剂。采用单因素实验法研究了有机溶剂的种类、用量,主、助溶剂的质量比,表面活性剂的种类、用量,甲酸的用量,对脱漆效率的影响。实验结果表明:脱漆剂的最佳组成为以乙酸丁酯为主溶剂,苯甲醇为助溶剂,十二烷基苯磺酸钠和OP-10复配为表面活性剂,甲酸为促进剂,石蜡为挥发抑制剂。当乙酸丁酯为27 g,苯甲醇为9 g,十二烷基苯磺酸钠为1 g,OP-10为1 g,甲酸为2 g,石蜡为6 g时脱漆效率最高。在最佳实验配方及其用量的条件下,1 mL脱漆剂所能擦除漆膜的面积为70.65 cm2。并且脱漆剂中水含量超过50%,其余组成部分均为低毒、挥发性不大的物质,易于生物降解,市售常见,成本低廉,符合绿色化学"高效、洁净、经济、环保"的要求。  相似文献   
302.
土壤温度上升对某些土壤化学性质的影响   总被引:2,自引:0,他引:2  
肖辉林  郑习健 《生态环境》2000,9(4):316-321
土壤温度变化导致微生物群落组成及其活性产生变化;某些微生物群落成员在较高温度时有能力代谢那些在较低温度时不能被利用的基质;因此,土壤温度上升将影响土壤生态系统中的C、N、S循环。大多数研究结果显示,温度对土壤溶液中的溶解态有机质和土壤有机磷组分有较大的影响。这些结论对预测全球气候变化对土壤的影响有重要的义。  相似文献   
303.
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Following intense overfishing in the 1970s, the western stock of Atlantic bluefin tuna (Thunnus thynnus) experienced a long period of depressed abundance, which has been attributed to failure of the population to periodically produce large numbers of juveniles, the western stock mixing with the more highly exploited eastern stock (fisheries in the Northeast Atlantic Ocean and Mediterranean Sea), and regime shift in the population's ecosystem resulting in lower replacement rates. To evaluate the presence of relatively strong years of juvenile production, we analyzed age structure from a recent sample of otoliths (ear stones) collected from the western stock (2011–2013, North Carolina, U.S.A., winter fishery). Mixing levels for the recent sample were analyzed using otolith stable isotopes to test whether age structure might be biased through immigration of eastern stock bluefin tuna. Age structure from historical samples collected from United States and Canadian fisheries (1975–1981) was compared with more recent samples (1996–2007) to examine whether demographic changes had occurred to the western stock that might have disrupted juvenile production. Relatively high juvenile production occurred in 2003, 2005, and 2006. Otolith stable isotope analysis showed that these recruitments were mostly of western stock origin. However, these high recruitments were >2‐fold less than historical recruitment. We found substantial age truncation in the sampled fisheries. Half the historical sample was >20 years old (mean age = 20.1 [SD 3.7]; skewness = ?0.3), whereas <5% of the recent sample was >20 years old (mean age = 13.4 [SD 3.8]; skewness = 1.3). Loss of age structure is consistent with changes in fishing selectivity and trends in the stock assessment used for management. We propose that fishing, as a forcing variable, brought about a threshold shift in the western stock toward lower biomass and production, a shift that emulates the regime shift hypothesis. An abbreviated reproductive life span compromised resilience by reducing the period over which adults spawn and thereby curtailing the stock's ability to sample year‐to‐year variability in conditions that favor offspring survival (i.e., storage effect). Because recruitment dynamics by the western stock exhibit threshold dynamics, returning it to a higher production state will entail greater reductions in exploitation rates.  相似文献   
304.
气相化学反应中的云盖效应   总被引:7,自引:0,他引:7  
王体健 《环境化学》1996,15(5):385-390
本文在CBM-I机理的基础上考虑了OH和HO2自由基对SO2的氧化作用和云对光解率的影响,定量研究了气相色化学反应中的云盖效应。结果表明,云的存在将改变整个反应体系的平衡,气态物对云的响应是非线的。  相似文献   
305.
  总被引:1,自引:0,他引:1  
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   
306.
南方某氟化学工业园四氟乙烯(TFE)和聚四氟乙烯(PTFE)的年生产量均达万吨以上,大量氟化学品的生产可能对周围环境产生一定的危害.本文以该氟化学工业园为研究对象,对其周边地区的水体、沉积物中的11种全氟化合物(PFASs)含量进行监测,并首次对植物树叶和树皮中PFASs含量进行测定.结果表明,与树皮相比,树叶对环境中PFASs具有更强的富集能力;水、沉积物、树叶和树皮中最主要的PFASs均是全氟辛酸(PFOA).地表水中PFOA浓度均值为675.9 ng·L-1,最高浓度达1503 ng·L-1;沉积物中PFOA浓度均值为1.11 ng·g-1(干重,下同),最高浓度为2.58 ng·g-1;树叶和树皮中的PFOA浓度均值分别为22.18和15.43 ng·g-1,最高浓度分别为168.6和89.67 ng·g-1.  相似文献   
307.
水中甲苯、对二甲苯磁化-光解耦合过程动力学研究   总被引:5,自引:0,他引:5       下载免费PDF全文
以甲苯、对二甲苯两种典型苯系污染物为研究对象, 对其在水中的紫外光解(UV)、磁化-紫外光解(PM-UV)进行了过程动力学比较研究, 结果证实高强度永久磁场(>0.1T)有促进光解的效应, 并阐述了磁场通过影响污染物光解时, 自由基对系间跃迁速度的变化而影响反应速度的作用机理。  相似文献   
308.
    
A one‐step strategy to obtain a high‐performance catalyst from Cr(VI)‐containing wastewater by the photoreduction process is described. ZrO2 is employed as a wide bandgap and high conduction‐band photocatalyst to reduce, capture, and immobilize Cr(VI) ions under UV light irradiation. The byproduct of this step is used as a catalyst for the CO2 reverse water‐gas shift (RWGS) reaction. The total Cr content in water decreases to 0.0413 mg L−1 in 3 h, fulfilling the strictest wastewater standard. The soluble Cr(VI) species is converted into Cr(0) and Cr(III), and fixed on the ZrO2 surface to form Cr@ZrO2 as a byproduct with highly dispersed Cr species. Using this byproduct as a catalyst for the RWGS reaction results in almost thermal equilibrium conversion under 500 °C with 100% CO selectivity. This environment‐friendly and economic strategy is very promising for controlling heavy metal pollution and comprehensive CO2 utilization.  相似文献   
309.
赵家兴  陈景文  张思玉  尉小旋 《环境化学》2011,30(12):1975-1982
以磺胺嘧啶为模型化合物,基于量子化学密度泛函理论(DFT),通过结构优化及相互作用能的计算,预测Mg^2+与磺胺嘧啶形成1:1配合物的结构.结果表明,Mg^2+和磺酰胺基的N和0原子配位,同时结合一个水分子;配合物磺酰胺基的键长、键角和二面角发生明显变化.基于含时密度泛函理论(TD-DFT)方法,计算磺胺嘧啶及其配合物...  相似文献   
310.
A field project encompassing wet-only rainwater sampling was initiated as a bilateral Fiji/Australia activity. Normally, biweekly samples were collected, using a wet-only rainwater sampler, and analysed for H+, Na+, K+, Mg2+, NH4 +, Cl, NO3 , SO4 2–, PO4 3-, methane sulphonic acid, oxalic acid, formic acid and acetic acid. The pH of the rainwater ranged between 5.730 and 4.480 with an average value of 5.176, slightly lower than the pH of unpolluted rainwater saturated with atmospheric CO2(pH = 5.650). Na+and Clwere the major ions with average concentrations of 98.15 M and 109.57 M respectively. There is an excellent correlation between the cation sum (average 147.71 eq L-1) and the anion sum (average 142.12 eq L-1) attesting to the quality of the data generated. This paper presents the detailed results of the study for a relatively clean remote island site in Suva, Fiji, latitude 18° 09 S, longitude 178° 27 E, height 6 m, and outlines prospects for further work.  相似文献   
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