PCDD/F reduction in incinerator flue gas by adding urea to RDF feedstock

The effect of urea on PCDD/F formation in a pilot incinerator was studied by incinerating urea with refuse-derived fuel (RDF) at three concentrations (0.1%, 0.5% and 1.0%, of the fuel feed). A distinct reduction in both PCDD/F and chlorophenol concentrations could be noticed when urea was introduced into the system. Partial-least-square (PLS) analysis of the data showed the importance of certain chlorophenol isomers as PCDD/F precursors, pointing to the possibility that the impact point of the urea inhibitor could be before the precursor molecules, i.e. chlorophenols, have been formed.     

Reactions of compost-derived humic substances with lead, copper, cadmium, and zinc

Thermodynamic stability constants of the formation of complexes from the reactions of humic substances with various metals are usually used as parameters to judge the reactivities of both humic substances and metals. However, in calculating the thermodynamic stability constants, complicated processes for the acquisition of activities of components in reactions are absolutely inevitable. In this study, we investigated the average conditional concentration quotients of the complexes formed from the reaction of metals with humic substances and the relations of these quotients to thermodynamic stability constants. The characterized humic substances including HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) extracted from a swine compost were prepared to react with Pb, Cu, Cd, and Zn at 25 degrees C and at pH 4.00 and 6.50. Reactions of HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) with the four metals were carried out at 1:0.1, 1:0.5, 1:1, 1:5, and 1:10 ligand:metal stoichiometry. The concentrations of the free ions of Pb, Cu, Cd, and Zn in the reaction systems of metal-HA suspensions and metal-FA solutions were measured by anodic stripping voltammetry (ASV). The sequence of the average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals was FA(MW<1,000)>FA(MW>1,000)>HA(MW>1,000), showing the relative reactivities of the fractions of swine compost-derived humic substances. The sequence of reacting metals with humic substances was Pb>Cu>Cd>Zn, which is in good agreement with the sequence reported by judging the thermodynamic stability constants. The average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals were thus useful parameters that can be directly related to thermodynamic stability constants and other parameters.     

The joint action of sulphur dioxide and hydrogen fluoride on the yield and quality of wheat and barley

The effects of joint action of SO(2) and HF on the yield and quality of wheat and barley were studied by exposing them to combinations of <13,130 or 267 microg m(-3) SO(2) and 0.03 or 0.38 microg m(-3) HF in open top chambers for 90 days. At the concentrations used, SO(2) had greater effects than HF. All responses were marked by compensatory changes. The treatments had no effect on wheat yield, although SO(2) reduced shoot weight. SO(2) increased the growth and yield of barley, and HF or SO(2) increased the grain protein concentration of barley and wheat. The effects of mixtures of SO(2) and HF were complex, but often antagonistic, as the addition of HF counteracted the effect of SO(2) alone.     

Health effects of fine particulate air pollution: lines that connect

Efforts to understand and mitigate thehealth effects of particulate matter (PM) air pollutionhave a rich and interesting history. This review focuseson six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There hasbeen substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidiity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonaryhealth. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.     

Mobilization of soil organic matter by complexing agents and implications for polycyclic aromatic hydrocarbon desorption

Complexing agents are frequently used in treatment technologies to remediate soils, sediments and wastes contaminated with toxic metals. The present study reports results that indicate that the rate and extent of soil organic matter (SOM) as represented by dissolved natural organic carbon (DNOC) and polycyclic aromatic hydrocarbon (PAH) desorption from a contaminated soil from a manufactured gas plant (MGP) site can be significantly enhanced with the aid of complexing agents. Desorption of DNOC and PAH compounds was pH dependent, with minimal release occurring at pH 2-3 and maximal release at pH 7-8. At pH-6, chelate solutions were shown to dissolve large amounts of humic substances from the soil compared to controls. The complexing agents mobilized polyvalent metal ions, particularly Fe and Al from the soil. Metal ion chelation may disrupt humic (metal ion)-mineral linkages, resulting in mobilization of SOM and accompanying PAH molecules into the aqueous phase; and/or reduce the degree of cross-linking in the soil organic matter phase, which could accelerate PAH diffusion.     

Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

IntroductionCeramic,consistofearthymaterialslikeclaykaolin ,limestoneandsandglass .Ceramicmaterialsarenonmetalic ,inorganiccompoundsprimaryoxides ,alsocarbides ,nitridesandsilicides .Twotypesofbondingmechanismsoccurinceramicmaterial ,ionicandcovalent.Theo…     

近期和长远时段内北极生态系统结构受到的影响

生物在物种水平上对全球气候变暖和紫外线B(UV-B)辐射增强的反应受到其群落内其他物种以及生态系统内养分循环的调节,所有的这些反应将会导致生态系统结构的变化.根据高纬度地区坏境因子的可能变化而做的控制试验表明,由夏季变暖而引起苔原植被的变化要小于增加施肥而引起的变化,试验涉及的某些环境因子对北极生态系统的结构有非常强烈地影响,但是这些影响因地区而异,观测结果表明,处于最寒冷地区的植物群落和无脊椎动物群落对全球气候变暖和紫外线B辐射的增强反应最为强烈.尽管微生物量和养分储存量相对稳定,北极无脊椎动物群落还是很可能会对全球变暖产生迅速的反应.试验结果显示,加强紫外线B辐射会改变革兰氏阴性细菌和真菌的群落组成结构,但不会对植物群落的组成产生影响.由夏季气温升高而提高的植物生产力将会控制食物网的动态变化,以苔原植被和亚极地森林植物为基础的食物网中的营养流动会明显地影响到几种优势动物种群数量的周期性波动,在某些年分这些动物的种群数量会达到峰值.小型啮齿动物和食叶昆虫如秋毛虫种群数量的周期性变化则会影响苔原和森林苔原植物的组成结构和多样性,同时也会影响到一些专性捕食者和寄生虫的变化.在暖冬,雪表形成冰壳可能会减少旅鼠的植物食物来源,然而较深的雪也可以使它们免受雪地表面上捕食者对它们的捕食.在芬诺斯堪的亚地区,已有证据表明小型啮齿类动物群落结构和种群动态的显著变化会导致专门以小型啮齿类动物为食物的捕食者的数量减少.气候还可能改变昆虫在白桦森林生态系统中的作用,因为暖冬可以增加这些昆虫卵的成活率,并且扩大其分布范围.此外,在夏季困扰驯鹿的昆虫会由于夏季气候的变暖而扩大其分布范围、增加种群数量并且种群更为活跃;同时在另一方面也会对驯鹿不利,即那些昔日驯鹿/北美驯鹿的避难场所--冰川和未融的成片的雪--在这样温暖的夏季则可能会消失.     

近期和长远时段内北极生态系统功能受到的影响

长期以来,就营养物质和碳循环而言,北极生态系统降低了初级生产力；能量,水和温室气体交换的水平已引起了局部和区域性的小幅度降温.大气CO2中的碳沉积在广袤而寒冷的有机土壤中,冰雪覆盖的低矮植被产生高的反射率,都影响了局部气候.然而,北极生态系统功能的许多方面都对气候变化及其产生的生物多样性影响敏感.当前的北极气候导致了低的有机物质分解速率,因此,尽管有机物和元素输入量较低,但北极生态系统还是趋向于积累有机物和元素,土壤中氮和磷等可利用元素结果成为促进碳固定以及生物量和有机物进一步积累的关键性限制因素.气候变暖可能增加特别是土壤中的碳和元素的周转,起初可能导致元素的丢失,但最后会慢慢的恢复.在北极生态系统中,单个物种和物种多样性已经明显地影响了元素的输入和滞留,另一方面,从长远来看,尽管CO2和紫外线增加对植物组织化学、分解和氮固定的影响可能变得重要,但对整个生态系统来说,影响可能很小.碳循环的示踪气体主要形式是CO2和CH4,大多数碳以CO2的形式损失,这些CO2是由植物和土壤生物产生.来自潮湿苔原生态系统以CH4形式释放的碳大约是CO2形式的5％,而且在没有任何其他变化的情况下,对变暖作出响应.冬天过程和植物类型也影响CH4释放和能量在生物圈和大气之间的交换,因为反射率从冬末到夏天存在很大的变化,在冬末,雪反射了入射的大部分光线,在夏天,生态系统吸收了入射的大部分光线,所以在所有的陆地生态系统中,北极生态系统在能量交换方面表现出巨大的季节性变化.植被深刻地影响北极生态系统水和能量交换.在冰雪覆盖期间,反射率从苔原、森林苔原、落叶林、常绿林依次降低.灌木和树增加了雪的深度,反过来又使冬天的土壤温度增加,因此,由气候变化而引起的未来植被方面的变化很可能深远地改变区域的气候.