Isolation and identification of an anti-algal compound from Artemisia annua and mechanisms of inhibitory effect on algae

The goals of this work were to isolate and identify an anti-algal compound from extracts of Artemisia annua and study its mode of action on Microcystis aeruginosa. The anti-algal compound was isolated from the extracts using column chromatography and activity-guided fractionation methods. Artemisinin with strong anti-algal activity was identified by gas chromatography-mass spectrometry and ¹H Nuclear Magnetic Resonance. The EC₅₀ of artemisinin on M. aeruginosa was 3.2 mg L⁻¹. Artemisinin decreased the soluble protein content and increased the superoxide dismutase activity and ascorbic acid content of M. aeruginosa, but exerted no effect on soluble sugar content. The results suggested the mode of action of artemisinin on algae may primarily be the increasing level of reactive oxygen species in algae cells. The results of our research could aid in the development of new anti-algal substances and lead to further study of mechanisms of inhibitory effect on algae.     

Aquivalence revisited--new model formulation and application to assess environmental fate of ionic pharmaceuticals in Hamilton Harbour, Lake Ontario

A model formulation based on "aquivalence", as defined in terms of activity is presented to estimate the multimedia fate of ionizing chemicals. The aquivalence approach is analogous to fugacity but aquivalence is applicable to neutral and ionizing compounds, and has been applied previously to speciating chemicals, notably metals. The new aquivalence-based mass-balance model treats ionizing organic compounds that exist as interconverting neutral and ionic species which are subject to fate processes at differing rates. The model is illustrated by application to four ionizing pharmaceuticals in Hamilton Harbour, Lake Ontario. At the system pH of 7.9-8.5, ibuprofen, gemfibrozil, and naproxen are expected to be almost entirely ionic and triclosan split between ionic and neutral forms. Measured seasonal surface water concentrations, which were 2-10 times lower in the late summer and fall than during spring, were used to solve for unknown values of chemical half-life in the water column due to degradation (photo- and bio-) of the ionizing and neutral forms and secondarily, ionic sorption coefficients of the ionizing forms. Model estimates of half-lives in the habour's water ranged from 11 to 77, 11 to 147 and 10 to 37 for ionic ibuprofen, gemfibrozil, and naproxen, respectively; and 4-22 days and 2-9 days for ionic and neutral triclosan, respectively, with the shortest half-lives in spring and the longest in summer.     

Antioxidant and metabolism responses to polyphenol stress in cyanobacterium Microcystis aeruginosa

Three common polyphenol compounds Gallic Acid (GA), Pyrogallic Acid (PA) and Catechol (CA) are known to have allelochemical-exhibiting inhibitory effects on the growth of the cyanobacterium Microcystis aeruginosa (M. aeruginosa). Metabolism and antioxidant responses in M. aeruginosa were investigated to elucidate the mechanism by which the three polyphenols inhibit algal growth. The inhibition effects of polyphenols were in the order of CA > PA > GA. The GA and CA exposures increased protein contents, superoxide dismutase (SOD) activity, catalase (CAT) activity and soluble sugar, especially for exposure to GA of 25 mg L^?1. Soluble sugar content increased significantly especially when exposed to CA for 72 h. When exposed to PA, protein content, and SOD and CAT activities initially increased but over longer treatment time the activities decreased, in contrast to sugar content. Our results suggest that PA exposure for longer periods of time may inhibit catabolism action, while CA exposure could induce more oxide stress than GA or PA. The overall study showed that polyphenol-induced oxidative damage might be responsible for polyphenol inhibition on M. aeruginosa growth. The increases in cellular antioxidant enzymes and soluble sugar may have been to counteract the oxidative stress.     

湖泊水动力模型外部输入条件不确定性和敏感性分析

以我国典型的大型浅水湖泊太湖为研究区域,采用国内外常用的环境流体动力学模型(EFDC),结合拉丁超立方取样(LHS)方法,研究湖泊水动力模型中4个重要的外部输入条件,即3个边界输入条件(出入湖流量、风速、风向)和1个初始输入条件(初始水位),对模型水动力模拟结果(水位、水龄以及流场)的影响与贡献.结果表明,初始水位的设定对模拟全湖水位和水龄产生决定性影响,不确定性的贡献率分别达到85.73%和66.125%,对垂向平均流速影响的贡献率只有3%;风速对表面流速模拟结果影响较大,贡献率达到58.70%,而对水位和水龄的贡献率分别为5.25%和3.00%.在垂向上,各层流速受外部输入条件不确定性的影响规律相似,贡献率排序为风速(55%~60%)>风向(10%~15%)>初始水位≈出入湖流量(1%~5%).因此在模拟大型浅水湖泊水动力过程时,可以根据不同的输出目标能够有针对性地提高外部输入条件的准确度,为提高模型精确度提供有效信息.     

A comparison of contaminant dynamics in arctic and temperate fish: A modeling approach

In order to compare the abilities of arctic and temperate fish to accumulate PCBs we conduct a metabolic analysis to determine how process rates in a mathematical fish contaminant model change with temperature. We evaluate the model by applying the original and adapted models to estimate PCB concentrations in lake trout (Salvelinus namaycush) in Trout Lake, Ontario, Canada, and in arctic char (Salvelinus alphinus) in Lake ?yangen, in the Norwegian high arctic. Modeled concentrations are, for the most part, within 50% of mean measured values and are comparable to the error associated with the fish data. In order to evaluate differences in fish bioaccumulation processes, the model is applied to hypothetical arctic and temperate systems, assuming the same contaminant input values in water and diet. The model predicts that temperate salmonids are able to biomagnify PCBs 6-60% more than arctic salmonids. For all congeners, the lower BMF(MAX) of arctic fish contribute to their lower concentrations. For congeners with log K(ow) < 6.0, the lower concentrations in arctic fish are also attributed to faster loss due to gill ventilation. Faster growth rates for temperate fish reduce the difference in bioaccumulation for congeners with log K(ow) > 7.0. These processes are controlled by the influence of lipid in the fish and their diet as well as the dependence of growth on temperature. We suggest that fish models originally calibrated for temperate systems may be directly applied to arctic lakes after accounting for the lipid content of the fish and their diet as well as water temperature.     

Toxicity and regulations of food nanomaterials

Environmental Chemistry Letters - Food nanotechnology has been rapidly growing in last decade due to the unique properties of nanomaterials. Nonetheless, the presence of nanomaterials in food...     

The Mass and Energy Exchange of a Tibetan Glacier: Distributed Modeling and Climate Sensitivity

Most glaciers in the Tibetan Plateau (TP) are not closely monitored for mass balance (MB) due to their inaccessibility, which makes it difficult to better understand the dynamics of glacial advancement or retreat. Surface energy budget, MB, and the resulting melt runoff were calculated for Zhadang glacier (5,710 m above sea level) of the central TP. Energy balance was calculated on 30‐m square grids for the summers of 2007 and 2008. On average, net radiation dominated the total energy source (66%) while the residual was supplied by sensible heat flux. More than 67% of the energy sink was available for melting on the glacier. Thus, less than 33% of the total energy was consumed by latent heat flux. A large and a slightly negative summer MB were calculated for the 2007 and 2008 summers, respectively. The high sensitivity of the glacier to air temperature may indicate that the lower than average seasonal temperature was more important than the increased precipitation for the slightly negative MB in the summer of 2008. Comparisons of glacial melt runoff indicated that rainfall and snowmelt were the dominant contribution to total runoff in the glacierized basin and the ice melting is also very important. Glacial melt calculation provides a basis for quantifying glacial melt‐runoff contribution to the river streamflow in the TP.     

Decomposition of trifluoromethane in a dielectric barrier discharge non-thermal plasma reactor

The decomposition of trifluoromethane (CHF₃) was carried out using non-thermal plasma generated in a dielectric barrier discharge (DBD) reactor. The effects of reactor temperature, electric power, initial concentration and oxygen content were examined. The DBD reactor was able to completely destroy CHF₃ with alumina beads as a packing material. The decomposition efficiency increased with increasing electric power and reactor temperature. The destruction of CHF₃ gradually increased with the addition of O₂ up to 2%, but further increase in the oxygen content led to a decrease in the decomposition efficiency. The degradation pathways were explained with the identified by-products. The main by-products from CHF₃ were found to be COF₂, CF₄, CO₂ and CO although the COF₂ and CF₄ disappeared when the plasma were combined with alumina catalyst.     

离子色谱/质谱联用分析水和食品中的高氯酸盐

摘要用离子色谱／质谱联用(IC／MS)测定低ppb水平高氯酸根离子的方法．IC／MS是根据EPA方法314开发出来的,原方法用Ic分离电导检测,检测范围为1ppb．IC／MS在整个测定范围内,高氯酸盐回收率不受干扰基质的影响．在饮料和废水中0．5和1ppb添加水平的测定回收率为90％-105％,方法检测限(DML)低于100ppt．