Investigating the affinities and persistence of VX nerve agent in environmental matrices

Laboratory experiments were conducted to determine environmental variables that affect the affinities and persistence of the nerve agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) at dilute concentrations in environmental matrices. Quantitative analyses of VX and its degradation products were performed using LC-MS. Batch hydrolysis experiments demonstrated an increasing hydrolysis rate as pH increased, as shown in previous studies, but also indicated that dissolved aqueous constituents can cause significant differences in the absolute hydrolysis rate. Adsorption isotherms from batch aqueous experiments revealed that VX has a high affinity for hydrophobic organics, a moderate affinity for montmorillonite clay, and a very low affinity for an iron-oxyhydroxide soil mineral, goethite. The adsorption on goethite was increased with the presence of dissolved organic matter in solution. VX degraded rapidly when dried onto goethite, when specific adsorption was forced. No enhanced degradation occurred with goethite in small amounts of water. These results suggest that aqueous conditions have important controls on VX adsorption and degradation in the environment and a more mechanistic understanding of these controls is needed in order to enable accurate predictions of its long-term fate and persistence.     

国外水资源保护区域化和流域化管理发展趋势——探讨我国水资源保护管理体制建设

一、前言 目前国际上水环境保护战略正在从水经济工程战略(即“谁污染谁治理”等环保方针政策)向水环境生态战略(即以资源开发为起点,调节控制物质循环中的污染源,综合协调社会经济和环境生态的平衡,确保其永续的同步发展)过渡.其主要标志是:美国的河系水质规划和环境影响评价;日本的     

First evaluation of the Brazilian microorganisms biocatalytic potential

The biocatalytic potential of two novel Brazilian strains of Aspergillus niger and Rhodotorula glutinis, revealed enantioselective epoxide hydrolase activity in the asymmetrization of meso-epoxide and monosubstituted epoxides respectively. These two types of oxirane derivatives are not usually good substrates for biocatalytic enantioselective conversion.     

Effects of an industrial effluent on plant colonization and on the germination and post-germinative growth of seeds of terrestrial and aquatic plant species

Major oil sands industrial companies are located in the Athabasca Oil Sands Deposit in northeastern Alberta, Canada. During the process used to extract light crude oil (via hot water digestion and flotation), gypsum is usually added to produce consolidated tails (CT) and CT release water. The vast volumes of process-treated waters (effluent) are held within large dyked tailings ponds. Toward testing viable options for reclamation, various hummock-wetlands systems have been constructed; in addition, natural wetlands (inhabited by obligate wetland plant species) have become established as a result of seeping of the effluents held within the large dyked ponds. Vegetation surveys conducted on and around the industrial site revealed that the constructed wetlands associated with the dyke drainage (effluent treated with phosphorous) and consolidated tails (CT; effluent treated with gypsum) had low biodiversity and were not invaded by many aquatic plants. Although the natural wetland was also not invaded by many aquatic species, it was found to be as diverse as the reference wetlands (i.e. off-site wetlands not exposed to the effluents). Exposure to oil sands effluents had an inhibitory effect on the germination (percent and/or rate) of several plant species (tomato, clover, wheat, rye, pea, reed canary grass, loblolly pine); clover and tomato seed germination were most affected. Two treatments in particular (effluents from the natural on-site wetland and the CT constructed wetland), delayed germination, and also led to reduced fresh weight of seedlings of tomato, wheat, clover and loblolly pine. The osmolarities of the effluents associated with the natural on-site wetland and CT constructed wetland were 712 and 728 mOs/kg, respectively; substituting these effluents with solutions of polyethylene glycol of the same osmotic potentials had a greater inhibitory effect on germination rate. The negative effects of the effluents on seed germination may account for the paucity of aquatic species that invaded the oil sands impacted wetlands. This factor will also be critical in determining the long-term feasibility of hummock-wetland systems.     

Absorption and translocation of 2,4-D in plants of Memora peregrina

The objective of this work was to evaluate absorption and translocation of the herbicide 2,4-D in plants of Memora peregrina. The herbicide 2,4-D was used alone with the formulation DMA 806 BR and associated with the herbicide picloram in the commercial product Padron. Levels of radioactivity on the treated leaves were determined in sample obtained after washing them with methanol and chloroform at different times after the application of the radiolabelled formulation (1, 2, 4, 8, 24, and 48 h). Translocation was evaluated by cutting plants between stem and root. The parts obtained were: root, stem, leaf treated, leaves above the leaf treated, leaves below the leaf treated, and leaf opposite of the leaf treated. These parts were weighted, dried, ground, burnt, and radioactivity in the samples was determined. The results suggest that the translocation of the radioactive herbicide 2,4-D was insignificant in plants of M. peregrina in the two treatments evaluated. Absorption of 14C 2,4-D in the treatment with DMA 806 BR and the mixture of DMA 806 BR plus Padron had the same behavior. These observations explain the inefficient control obtained with this herbicide in plant species under study.     

试论城市生活垃圾的治理及其利用

一、前言哪里有人的踪迹,哪里就有垃圾,高耸入云的珠穆朗玛峰上也留有登山队员的废弃物。然而,当前城市生活垃圾在我国,乃至世界已构成一大公害。 1.它侵占大量土地。以北京市为例,     

“全国水系污染与保护科技信息网第二届理事会第一次会议”在杭州召开

“全国水系污染与保护科技信息网第二届理事会第一次会议”于1996年10月17日至19日在杭州市举行.本网第二届理事会第一次会议理事或代表,以及特邀代表等共计30余人参加了会议.本次会议的主要议程是:(1)上届理事会总结第一届理事会成立以来的工作;(2)选举第二届理事会领导成员;(3)聘任本网理事会名誉理事长、顾问;(4)聘任本网网刊《水系污染与保护》第二届编辑委员会编委;(5)讨论修改《全国水系污染与保护科技信息网章程》;(6)商定召开“第十一次全国水系污染与保护科技信息网交流会暨本网工作会议”及庆祝本网成立20周年等有关事宜.会议还对《全国水系污染与保护科技信息网章程》进行了修订完善,待本网办公室集中各方面意见后,提交给本网第十一次工作会议审议通过.     

The release of phosphorus to porewater and surface water from river riparian sediments

Sediments can be both a source and a sink of dissolved phosphorus (P) in surface water and shallow groundwater. Using laboratory mesocosms, we studied the influence of flooding with deionized water and simulated river water on P release to solution using sediment columns taken from a riparian wetland. The mesocosm incubation results showed that rather than retaining nutrients, sediments in the riparian zone may be a significant source of P. Concentrations of dissolved P in porewater reached more than 3 mg L(-1) and in surface water over 0.8 mg L(-1) within a month of sediment inundation. The reductive dissolution of P-bearing iron (Fe) oxides was the likely mechanism responsible for P release. Dissolved P to Fe molar ratios in anaerobic samples were approximately 0.45 when columns were flooded with water that simulated the chemistry of the adjacent river. This suggests there was insufficient Fe in the anaerobic samples to precipitate all P if the solutions were oxygenated or transported to an aerobic environment. If the anaerobic wetland solutions were delivered to oxygenated rivers and streams adjacent to the riparian zone, the equilibrium concentration of P in these systems could rise. The timing of P release was inversely related to the nitrate (NO3-) concentration in floodwater. This indicates that in riparian zones receiving low nitrate loads, or where NO3- loads are being progressively reduced, the risk of dissolved P release may increase. These findings present particular challenges for restoration and management in riparian areas.     

Inferring evolutionary signals from ecological data in a plant-pathogen metapopulation

We followed the dynamics of local epidemics in three populations of a natural plant-pathogen system for four sequential years. We characterize the overwintering process with spatial statistics and use a stochastic, spatially explicit, modeling approach with Bayesian parameter estimation to study the spread of the infection during the growing season. Our modeling approach allows us to infer coevolutionary signals from spatiotemporal data on pathogen prevalence. Most importantly, we are able to assess the distribution of resistant hosts within the distribution of all host plants. We show that resistant hosts occur in areas with high pathogen encounter rates, and that the occurrence of resistance correlates with overwintering probability of the pathogen. The estimates for essentially all model parameters are characterized by a large amount of variation over the years and the populations. While the variation in the fraction of resistant hosts and in the force of infection is to a large extent explained by the population, the other model parameters (two parameters describing the shape of the dispersal kernel) vary essentially in an unpredictable manner, suggesting that much of the variation may occur at very fine spatial and temporal scales.