Larval viability and heterozygote deficiency in populations of marine bivalves: evidence from pair matings of mussels

Using a pressurized temperature gradient, which rapidly equilibrates bacteria to a wide range of temperature and pressures, temperature ranges for growth and survival of Vibrio harveyi (strain B 392) were found to narrow with increasing pressures. Both temperature and pressure ranges were greater in an enriched seawater medium than in unenriched seawater. Using a kinetics apparatus, V. harveyi was also exposed to gradual changes in temperature and pressure, simulating a particle sinking at approximately 200 m d^-1 from surface waters (17 °C; 1 bar pressure) to 3 400 m (4°C; 340 bars pressure). With gradual temperature changes, cells were able to grow and survive at lower temperatures than they had in rapid equilibration experiments. Gradual pressurization, however, did not increase pressure tolerance. Under all experimental conditions, the combined effects of low temperatures and high pressures were lethal for V. harveyi. It is hypothesized that temperature and pressure stratify the ocean into regions of growth, survival, and death for V. harveyi, and perhaps other bacteria.     

DGT富集-乙基化GC-CVAFS测定天然水体中的甲基汞

利用薄膜扩散技术(DGT)原位富集天然水体中的甲基汞,溶剂洗脱后进入水相连行乙基化反应,与气相色谱(GC)联用,冷原子荧光光谱法(CVAFS)测定.实验结果显示,26"(3条件下在超纯水中放置24 h,典型DGT单元的最低检出限为0.014 ng/L;延长放置时闻或者减少扩散层厚度,可以得到更低的检测限.相对标准偏差＜...     

A chemical residue survey in relation to the 1930 spruce budworm spray program in New Brunswick (Canada)

Abstract

This paper describes the results from a pesticide residue survey conducted in relation to the 1980 spraying of insecticides in New Brunswick (Canada) to preserve the coniferous forest from an on‐going spruce buciworm infestation. A total of 465 water and air samples were collected from 12 sites throughout the Province.

In water, fenitrothion was usually detected at about the same time that spraying occurred in the immediate area of the sites. The maximum that was ever detected was 2 0.0 ppb and persistence was usually United to a few days except in a small pond where fenitrothion was detected for a total of 18 consecutive days. Aminofenitrothion was also detected at a maximum of 8.0 ppb.

Fenitrothion was only detected occasionally in air samples the maximum being 1.2 ng/dm³. However, aminofenitrothion was present in several air samples at c. maximum of 12.0 ng/dm ³.     

Anti-diffusion and source identification with the ‘RAW’ scheme: A particle-based censored random walk

This paper presents a novel methodology for time reversal in advective-diffusive pollutant transport in groundwater systems and other environmental flow systems (specifically: time reversal of diffusive terms). The method developed in this paper extends previous particle-based approaches like the Reversed Time Particle Tracking Method of Bagtzoglou [6]. The reversal of the ‘diffusive’ and/or ‘macrodispersive’ component of pollutant migration is especially under focus here. The basis of the proposed scheme for anti-diffusion is a continuous time, censored, non-local random walk capable of tracking groundwater solute concentration profiles over time while conserving the (reverse) Fickian properties of the anti-diffusing particle cloud in terms of moments. This scheme is an alternative to the direct solution of the eulerian concentration-based diffusion PDE, which is notoriously unstable in reverse time. Our analysis leads to the conclusion that an adaptive time stepping scheme—with decreasing time step—is necessary in order to maintain a constant amount of anti-diffusion (the reverse form of Fick’s law). Specifically, we study the relations between the following parameters: time step evolution vs. time (or vs. number of steps); variance evolution (decrease rate); total time (or number of steps) required to reach a fully anti-diffused solution. The proposed approach is shown to be quite efficient; typically, for every ten time steps, one to two orders of magnitude reduction of the dispersion width of the plume can be attained. Furthermore, the method is shown to be asymptotically exact for reverse Fickian diffusion. The method is applied with success to several situations involving the diffusive transport of a conservative solute in the following cases: (i) Single source recovery in one-dimensional space with constant diffusion parameters (this example serves as a validation test for the theory); (ii) Single source recovery in two-dimensional space with constant isotropic diffusion (this example also serves as a test for the theory); (iii) Multiple source recovery in two-dimensional space, assuming isotropic diffusion. It is expected that the methodology tested in this paper is applicable more generally to complex environmental pollution problems involving multiple sources, anisotropic hydrodynamic dispersion, and space-time variable advection-diffusion flow systems; the modeling of reverse diffusion/dispersion in such systems is currently under investigation.     

Chemical speciation and partitioning of trace metals (Cd, Co, Cu, Ni, Pb) in the lower Athabasca river and its tributaries (Alberta, Canada)

Concentrations of Cd, Co, Cu, Ni and Pb were measured in particulate and dissolved phases at 11 sites located upstream and near Athabasca oil sands development. The in situ discrimination between non-labile and labile dissolved metals was done using diffusive gradients in thin-films (DGT) devices. The DGT-labile fraction of Co and Ni was 30% lower near development sites whereas Cu, Cd and Pb showed minor changes spatially. It was found that an 8-fold increase in dissolved organic matter (DOM) near development induced a rapid decrease in DGT-labile metals. Dissolved metal concentrations were used along with DOM, major ions, nutrients, pH and conductivity to calculate the distribution of dissolved metal species using the speciation model WHAM. Labile-DGT metal concentrations agreed well with WHAM-predicted concentrations. It was also found that a significant amount of metals were associated with the non-DGT labile fraction (i.e. colloidal DOM) and colloid abundance was more important than suspended particulate matter abundance in influencing metal mobility near Athabasca oil soils development. Since changes in colloidal DOM levels are likely to be the result of surface mining activities, this confirms the serious effects of oil sands activities on metal biogeochemical cycles in the lower Athabasca River.     

Winter quiescence and spring awakening of the Eastern oyster Crassostrea virginica at its northernmost distribution limit

To test the hypothesis that oysters, Crassostrea virginica, from the northernmost part of the species range in the Gulf of St. Lawrence (48°N) open their valves at lower temperatures than those reported for more southern oysters, Hall element sensors were used to monitor their gaping behaviour. These observations were made in a flow-through system and the temperature, salinity and relative fluorescence of unfiltered seawater were monitored. Photoperiod was controlled (15?h dark:9?h light) and light levels were measured but not closely controlled. Gaping behaviour was followed from February to June 2010 (113?days) and from April to May 2011 (34?days) and was classified into three successive phases: quiescent, awakening and active. Although valves were either closed or slightly open during the quiescent phase (maximum gape angle?=?0.49°, SE?=?0.04), they abruptly opened to maximum angles of about 5.88° (SE?=?0.29) during the awakening phase. Moreover, there was noticeable synchrony amongst individuals, since approximately one-half of the monitored population awoke within a 6.6-h period in both study years. Correlative analyses identified temperature as a factor influencing valve movement, and oysters awakened when temperatures were 0.2–4.0?°C (mean?=?2.2, SE?=?0.2). Oysters exerted their maximal gape angle as soon as temperatures reached 2.8–6.6?°C (mean?=?4.8, SE?=?0.2). During the active phase, valves remained open 68.6?% (2010) and 79.7?% (2011) of the time. An unexpected result was the observation of a diurnal rhythm in valve openness whereby the openness was greatest near the end of the afternoon and least in the early morning.     

Identification of Workers at Increased Risk of Infection During a COVID-19 Outbreak in a Meat Processing Plant,France, May 2020

Food and Environmental Virology - On 13 May 2020, a COVID-19 cluster was detected in a French processing plant. Infected workers were described. The associations between the SARS-CoV-2 infection...     

Toxicity assessment of the maize herbicides S-metolachlor,benoxacor, mesotrione and nicosulfuron,and their corresponding commercial formulations,alone and in mixtures,using the Microtox® test

The Microtox® test, using the prokaryote Vibrio fischeri, was employed to assess the toxicity of the maize herbicides S-metolachlor, benoxacor, mesotrione and nicosulfuron, and their formulated compounds: Dual Gold Safeneur®, Callisto® and Milagro®; alone and in mixtures. For each compound we obtained original IC₅₀ values, with consistent higher toxicities for formulated compounds compared to active ingredients alone. Mixtures of the four herbicides, prepared according to application doses encountered in agriculture, were found to be toxic at a lower concentration than single molecules. Mesotrione and nicosulfuron mixture appeared to be highly toxic to V. fischeri, however, this recommended post-emergence combination for maize crops got its toxicity decreased in formulated compound mixtures, suggesting that chemical interactions could potentially reduce the toxicity. Data comparisons to theoretical models showed a good prediction of mixture toxicity by Concentration Addition concept. Results seemed to exclude any synergistic effects on V. fischeri for the tested herbicide mixtures. Additional work coupling these bioassay data to ecosystemic level studies (aquatic and soil compartments) and data on additives and degradation products toxicity, will help to fill the gap in our knowledge of the environmental impact of these xenobiotics and in the choice of a more sustainable use of pesticides.