Aquatic toxicity of glyphosate-based formulations: comparison between different organisms and the effects of environmental factors

Glyphosate-based herbicides (e.g. Roundup) are extensively used in the aquatic environment, but there is a paucity of data on the toxicity of the formulated products and the influences by environmental factors. In this study, the acute toxicity of technical-grade glyphosate acid, isopropylamine (IPA) salt of glyphosate, Roundup and its surfactant polyoxyethylene amine (POEA) to Microtox bacterium (Vibrio fischeri), microalgae (Selenastrum capricornutum and Skeletonema costatum), protozoa (Tetrahymena pyriformis and Euplotes vannus) and crustaceans (Ceriodaphnia dubia and Acartia tonsa) was examined and the relative toxicity contributions of POEA to Roundup were calculated. The effects of four environmental factors (temperature, pH, suspended sediment and algal food concentrations) on the acute toxicity of Roundup to C. dubia were also examined. Generally, the toxicity order of the chemicals was: POEA>Roundup>glyphosate acid>IPA salt of glyphosate, while the toxicity of glyphosate acid was mainly due to its high acidity. Microtox bacterium and protozoa had similar sensitivities towards Roundup toxicity (i.e. IC50 from 23.5 to 29.5 mg AE/l). In contrast, microalgae and crustaceans were 4-5 folds more sensitive to Roundup toxicity than bacteria and protozoa. Except photosynthetic microalgae, POEA accounted for more than 86% of Roundup toxicity and the toxicity contribution of POEA was shown to be species-dependent. Increase in pH (6-9) and increase of suspended sediment concentration (0-200 mg/l) significantly increased the toxicity of Roundup to C. dubia, but there were no significant effects due to temperature change and food addition.     

An anaerobic bioreactor allows the efficient degradation of HCH isomers in soil slurry

The insecticide gamma-hexachlorocyclohexane (gamma-HCH or lindane), which has been extensively used for agricultural and medical purposes, presents high persistence and toxicity to the environment and low solubility. This study intends to assess the efficiency of an anaerobic reactor to degrade HCH isomers contained in soil slurry cultures. This study was developed in two phases: experiments in flasks to optimize the process parameters, and assessment of the slurry process in the anaerobic slurry reactor operated for an approximate period of a year. The influence of different environmental conditions was evaluated: the HCH concentration (25-100 mg HCH kg-1), the type of substrate (volatile fatty acids or starch), the sludge concentration (2-8 g VSS l-1) and the replacement of spiked soil to simulate a fed-batch operation (10-50%). The best results were obtained when the reactor was operated with a sludge concentration of 8 g VSS l-1, starch concentration of 2 g COD l-1 and soil replacements of 10-20%. Under these conditions, alpha- and gamma-HCH were completely degraded after 10d while nearly 90% beta- and delta-HCH were removed only after 50 d. According to the obtained results related to the total degradation of the HCH isomers and the degradation rates, especially high for alpha- and gamma-HCH, the anaerobic slurry reactor appears to be a good alternative for the degradation of the HCH isomers present in polluted soil.     

Enzymatic degradation of anthracene, dibenzothiophene and pyrene by manganese peroxidase in media containing acetone

The high hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) greatly hamper their degradation in liquid media. The use of an organic solvent can assist the degradative action of ligninolytic enzymes from white rot fungi. The enzymatic action of the enzyme manganese peroxidase (MnP) in media containing a miscible organic solvent, acetone (36% v/v), was evaluated as a feasible system for the in vitro degradation of three PAHs: anthracene, dibenzothiophene and pyrene. These compounds were degraded to a large extent after a short period of time (7, 24 and 24h, respectively), at conditions maximizing the MnP-oxidative system. The initial amount of enzyme present in the reaction medium was determinant for the kinetics of the process. The order of degradability, in terms of degradation rates was as follows: anthracene>dibenzothiophene>pyrene. The intermediate compounds were determined using gas chromatography-mass spectrometry and the degradation mechanisms were proposed. Anthracene was degraded to phthalic acid. A ring cleavage product of the oxidation of dibenzothiophene, 4-methoxybenzoic acid, was also observed.     

A comparative study on metal sorption by brown seaweed

This study compared the sorption of Ag, Cd, Co, Cd, Mn, Ni, Pb and Zn by a Ca-treated Sargassum biomass at pH 5.0, under low and high ionic strength (IS) conditions. The sorption isotherms of As [As(V)] and Cr [Cr(III) and Cr(VI)] were also determined at low IS. The isotherm data for the eight cationic metals and Cr(III) were well fitted by Langmuir equations. Generally, the maximum metal uptake (Umax) followed: Cr(III) > Pb approximately Cu > Ag approximately Zn approximately Cd > Ni approximately Mn approximately Co > Cr(VI) > As(V) at low IS and Pb > Cu > Co > Mn approximately Cd > Zn approximately Ag > Ni at high IS. As(V) did not bind to the seaweed at pH 5.0. The results indicated that sorption of Pb was not affected by the increasing IS, though the percentage of free Pb ions in the water was greatly reduced as predicted by the speciation model. High IS lowered Umax by 10-36% (except Co and Pb), and lowered the affinity constant of the metal by 33-91% for all cationic metals, as compared to low IS. Moreover, the removal efficiency of the cationic metals and Cr decreased exponentially with initial metal concentrations and was lower at high IS. Ion-exchange was the mechanism responsible for the cationic metal sorption onto the seaweed, and Na ion interfered with the cationic metal binding through electrostatic interaction. In conclusion, this study showed the differential binding capacity of the Sargassm biomass for different metals and oxidation states and the differential effects of IS. According to the present results, Sargassum may be considered a good biosorbent for cationic metals (especially Pb) in both low and high-salt containing wastewater.     

Operator-splitting errors in coupled reactive transport codes for transient variably saturated flow and contaminant transport in layered soil profiles

One possible way of integrating subsurface flow and transport processes with (bio)geochemical reactions is to couple by means of an operator-splitting approach two completely separate codes, one for variably-saturated flow and solute transport and one for equilibrium and kinetic biogeochemical reactions. This paper evaluates the accuracy of the operator-splitting approach for multicomponent systems for typical soil environmental problems involving transient atmospheric boundary conditions (precipitation, evapotranspiration) and layered soil profiles. The recently developed HP1 code was used to solve the coupled transport and chemical equations. For steady-state flow conditions, the accuracy was found to be mainly a function of the adopted spatial discretization and to a lesser extent of the temporal discretization. For transient flow situations, the accuracy depended in a complex manner on grid discretization, time stepping and the main flow conditions (infiltration versus evaporation). Whereas a finer grid size reduced the numerical errors during steady-state flow or the main infiltration periods, the errors sometimes slightly increased (generally less than 50%) when a finer grid size was used during periods with a high evapotranspiration demand (leading to high pressure head gradients near the soil surface). This indicates that operator-splitting errors are most significant during periods with high evaporative boundary conditions. The operator-splitting errors could be decreased by constraining the time step using the performance index (the product of the grid Peclet and Courant numbers) during infiltration, or the maximum time step during evapotranspiration. Several test problems were used to provide guidance for optimal spatial and temporal discretization.     

Comparison of the role of the sea club-rush Scirpus maritimus and the sea rush Juncus maritimus in terms of concentration, speciation and bioaccumulation of metals in the estuarine sediment

The capability of Scirpus maritimus and of Juncus maritimus to accumulate metals and the role of each plant on the physico-chemical composition of sediments, from Douro river estuary (NW Portugal), were investigated through a year of plants' life. The contents of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined (by atomic absorption spectrophotometry) in sediment, rhizosediments (those in contact with each plant roots and rhizomes) and different tissues of S. maritimus and of J. maritimus. Both plants influenced the sediment composition (concentrating metals around its roots) and were able to bioaccumulate Cd, in spite of some seasonal variations in the metal levels in the system (both in rhizosediments and plants' roots). Therefore, both plants showed to have potential for Cd phytostabilization. S. maritimus could also concentrate Pb in its roots, probably by sorption on the root surface in (hydr)oxide forms, therefore, denoting capability for Pb phytostabilization.     

Integrated assessment modeling of atmospheric pollutants in the Southern Appalachian Mountains: Part II. Fine particulate matter and visibility

As part of the Southern Appalachian Mountains Initiative, a comprehensive air quality modeling system was developed to evaluate potential emission control strategies to reduce atmospheric pollutant levels at the Class I areas located in the Southern Appalachian Mountains. Six multiday episodes between 1991 and 1995 were simulated, and the skill of the modeling system was evaluated. Two papers comprise various parts of this study. Part I details the ozone model performance and the methodology that was used to scale discrete episodic pollutant levels to seasonal and annual averages. This paper (part II) addresses issues involved with modeling particulate matter (PM) and its relationship to visibility. For most of the episodes, the fractional error was approximately 50% or less for the major constituents of the fine PM (i.e., sulfate [SO4] and organics) in the region. The mean normalized errors and fractional errors are generally larger for the NO3 and soil components, but these components are relatively small. Variations in modeling bias with pollutant levels were also examined. The model showed a systematic overestimation for low levels and an underestimation for high levels for most PM species. For ammonium, the model showed better performance at lower SO4 concentrations when the measured SO4 was assumed to be completely neutralized (ammonium sulfate) and better performance at higher SO4 concentrations when the partially neutralized (ammonium bisulfate) assumption was made. The contributions of various components of PM to reductions in visibility were also calculated; SO4 was found to be the major contributor.     

浅析加油站施工现场HSE管理

HSE管理体系在石化销售系统内运行多年，现已逐渐被员工充分理解。但是在加油站的施工现场，由于作业人员是施工单位雇用，并非石化系统员工，如何将HSE管理理念传授给非石化系统人员，在现场有效实施HSE管理，是本文探讨的核心内容。     

“重奖围剿食人鱼”错在短视思维

7月7日,有广西柳州市民称在柳江遭3条食人鱼袭击。柳州官方随后宣布,欢迎市民沿江垂钓参与围剿食人鱼,市民抓到食人鱼每条可获1000元奖励。据报道,围捕第一天共抓获几十斤鲤鱼、鳜鱼,但一条食人鱼都没有抓到。有网友质疑,政府部门"泛娱乐化"处理生态问题。(7月11日《新华网》)血红的眼睛,锯齿状的牙齿,迅速的游动时隐进没,暗中窥伺着每一     

三峡工程运行后洞庭湖水环境变化及影响分析

以入湖水系、湖体、出湖口为研究区域,基于20多年的监测数据,运用水质单因子评价、综合营养状态指数(∑TLI)等评价方法,系统地分析了洞庭湖水文、水质、营养化状态的时空变化规律,探讨三峡工程运行后洞庭湖水环境变化及原因。结果表明:(1)洞庭湖入湖水量及沙量均明显降低、水位变幅减小。(2)透明度(SD)、总氮(TN)、总磷(TP)、浮游植物等指标的时空分异特征较为明显,4个指标年均值均总体呈上升趋势,其中,SD、浮游植物种类数量及密度自三峡工程运行后变化尤为明显。西洞庭湖的SD高于南洞庭湖,东洞庭湖的SD最低。ρ(TP)在湖体最高,ρ(TN)则在湖体最低。(3)入湖水系水质最好,出湖口水质最差。入湖水系水质一直维持在Ⅱ～Ⅲ类之间,水质良好;出湖口、湖体水质自三峡工程运行后以Ⅳ～Ⅴ类为主,变劣趋势明显。湖体富营养化日趋严重,东洞庭湖的富营养程度稍高于西洞庭湖和南洞庭湖。(4)初步认为:洞庭湖水文水动力环境条件的变化,整体上对水质产生一定的不利影响,对湖体富营养化有一定的促进作用。