Continuous-flow column study of reductive dehalogenation of PCE upon bioaugmentation with the Evanite enrichment culture

A continuous-flow anaerobic column experiment was conducted to evaluate the reductive dechlorination of tetrachloroethene (PCE) in Hanford aquifer material after bioaugmentation with the Evanite (EV) culture. An influent PCE concentration of 0.09 mM was transformed to vinyl chloride (VC) and ethene (ETH) within a hydraulic residence time of 1.3 days. The experimental breakthrough curves were described by the one-dimensional two-site-nonequilibrium transport model. PCE dechlorination was observed after bioaugmentation and after the lactate concentration was increased from 0.35 to 0.67 mM. At the onset of reductive dehalogenation, cis-dichloroethene (c-DCE) concentrations in the column effluent exceeded the influent PCE concentration indicating enhanced PCE desorption and transformation. When the lactate concentration was increased to 1.34 mM, c-DCE reduction to vinyl chloride (VC) and ethene (ETH) occurred. Spatial rates of PCE and VC transformation were determined in batch-incubated microcosms constructed with aquifer samples obtained from the column. PCE transformation rates were highest in the first 5 cm from the column inlet and decreased towards the column effluent. Dehalococcoides cell numbers dropped from approximately 73.5% of the total Bacterial population in the original inocula, to about 0.5% to 4% throughout the column. The results were consistent with estimates of electron donor utilization, with 4% going towards dehalogenation reactions.     

Reduced analytical availability of polychlorinated biphenyls (PCB's) in colored surface water

It has been generally accepted, during the last few decades, that the dissolved natural organic matter in water [DNOM] appearing as yellow brownish color, has become more and more "polluted" by inorganic and organic micro-pollutants. Due to the complexing properties of NOM, lipophilic organic micro-pollutants, such as, PCBs will be mobilized into water together with the DNOM. A mixture of eight PCBs, with Cl-content from tri-Cl to hepta-Cl, was added to solutions of ten different DNOMs. The DNOMs were aqua's solutions of RO-(reverse osmosis)-isolated material, having approximately the same concentration of carbon. After a contact time of three days, standard analytical PCB-method was used to determine the recovery of the added PCBs. The results show that the analytical availability of the added PCB was significantly reduced in the presence DNOM, compared to distilled water. The percentage loss in recovery of PCB increased with the content of Cl, in mean, from 3%/mg C for tri-Cl to 9%/mg C for hepta-Cl. The results also suggest that the analytical recovery of PCB was affected by the quality and the nature of the organic matter. For example the longer the DNOMs had been in the aquatic phase, the less efficient they are attached to the PCBs.     

Über einen Mechanismus der Transpirationserniedrigung durch ätherische Öle

The Science of Nature -     

COVID-19: From health crises to food security anxiety and policy implications

Like the rest of the world, African countries are reeling from the health, economic and social effects of COVID-19. The continent’s governments have responded by imposing rigorous lockdowns to limit the spread of the virus. The various lockdown measures are undermining food security, because stay at home orders have among others, threatened food production for a continent that relies heavily on agriculture as the bedrock of the economy. This article draws on quantitative data collected by the GeoPoll, and, from these data, assesses the effect of concern about the local spread and economic impact of COVID-19 on food worries. Qualitative data comprising 12 countries south of the Sahara reveal that lockdowns have created anxiety over food security as a health, economic and human rights/well-being issue. By applying a probit model, we find that concern about the local spread of COVID-19 and economic impact of the virus increases the probability of food worries. Governments have responded with various efforts to support the neediest. By evaluating the various policies rolled out we advocate for a feminist economics approach that necessitates greater use of data analytics to predict the likely impacts of intended regulatory relief responses during the recovery process and post-COVID-19.     

划船和航行活动对波罗的海群岛区域鱼类补充的影响

我们研究了划船和航行活动对在严格意义上的西北波罗的海的斯德哥尔摩群岛海域近岸鱼类补充的影响.这种影响可以通过对毗邻下述地区的小湾的变态幼鱼的取样来量化:①中型客船摆渡的路线;②小型划艇的停泊处(小码头);③参照区域.以植物为主要食物的鱼类受到划船和航行活动的负面影响;不以植物为主要食物的鱼类受到划船和航行活动的正面影响.当欧鲌在疏浚码头数量较多时,白斑狗鱼的幼鱼在参照区域数量也显著增多.尽管沿摆渡路线数量有减少的趋势,但对河鲈来说,无法确定具有统计意义的模式.许多近岸鱼类需要依靠沉水植被作为产卵和幼鱼的底质、结构性的庇护所与觅食的生境.我们的研究结论是,划船和航行活动对沉水植被的覆盖面和高度将造成负面影响,尤其是对轮藻属和眼子菜的负面影响,可能导致幼鱼群落的改变.     

Simulated marine respirometry of biodegradable polymers

Eleven microorganisms were isolated from several temperate marine locations in the northeast Altantic coast of the United States and one tropical location in the Pacific Ocean (Hawaii) for the purpose of developing a rapid and accurate method of screening biodegradable materials for their susceptibility to mineralization. The materials evaluated in this study included chemically modified starch, amylose and pullulan, poly(3-hydroxybutyrate-co-valerate), (PHB/V), cellulose acetate, and a modified lignin/styrene. Some of the soluble, unmodified, biologically produced substrates such as starch, pullulan, and amylose mineralized rapidly. In general, the synthetic, insoluble polymers and the chemically modified polymers, such as acetylated and chlorinated amylose and pullulan, mineralized more slowly, although the ultimate mineralization of some of the substituted polysaccharides equaled or exceeded that of the unmodified substrate. The insoluble bacterial polyester, PHB/V, degraded rapidly after a short induction period. Initial respiration rate data, in general, could not be used as a predictor of ultimate mineralization. It was found that the cumulative level of carbon dioxide evolved signifies the minimum extent of biodegradation of the substrate, and the oxygen consumed is a good indicator of the maximum extent of substrate degradation.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.     

Agricultural chemical exposure in small farmers in Guyana

A study of self-reported injury from agricultural chemical exposure was conducted in farmers in rural Guyana. One hundred and ninety agricultural workers were studied, of which 167 (88%) were male. Morbidity from agricultural chemical exposure was common, with 87 farmers (46%) reporting having experienced at least one episode of illness after agricultural chemical exposure. Relatively few of the farmers sought medical assistance for their symptoms, with only 20 farmers (11%) visiting a local doctor and only two farmers (1%) reporting going to a hospital for treatment. Local farmer use of protective equipment was limited. Pyrethroids and herbicides paraquat and glyphosate were the most commonly used agricultural chemicals in the population studied. Data showed that exposure to agricultural chemicals remains frequent, with incidence of severe injury requiring less frequent medical attention.     

Bioremediation of benzene-, MTBE- and ammonia-contaminated groundwater with pilot-scale constructed wetlands

In this pilot-scale constructed wetland (CW) study for treating groundwater contaminated with benzene, MTBE, and ammonia-N, the performance of two types of CWs (a wetland with gravel matrix and a plant root mat) was investigated. Hypothesized stimulative effects of filter material additives (charcoal, iron(III)) on pollutant removal were also tested. Increased contaminant loss was found during summer; the best treatment performance was achieved by the plant root mat. Concentration decrease in the planted gravel filter/plant root mat, respectively, amounted to 81/99% for benzene, 17/82% for MTBE, and 54/41% for ammonia-N at calculated inflow loads of 525/603 mg/m²/d, 97/112 mg/m²/d, and 1167/1342 mg/m²/d for benzene, MTBE, and ammonia-N. Filter additives did not improve contaminant depletion, although sorption processes were observed and elevated iron(II) formation indicated iron reduction. Bacterial and stable isotope analysis provided evidence for microbial benzene degradation in the CW, emphasizing the promising potential of this treatment technique.