Short-term exposure of the European sea bass Dicentrarchus labrax to copper-based antifouling treated nets: Copper bioavailability and biomarkers responses

We studied if the levels of copper released from antifouling treated nets used in finfish mariculture could affect the immune defense mechanism and/or induce oxidative stress in Dicentrarchus labrax, after short term exposure in laboratory experiments. Dissolved copper concentration released from the treated nets, copper bioavailability and a set of biomarkers responses were measured. Biomarkers included hemoglobin concentration, activities of lysozyme, total complement, respiratory burst, glutathione S-transferase and acetycholinesterase and concentration of thiobarbituric acid reactive substances. Results indicated elevated copper concentration in seawater (184 μg L⁻¹) but low concentration in muscle (1.5 μg g⁻¹) and liver (117 μg g⁻¹). Copper bioavailability was independent of copper complexes with dissolved organic carbon. However, formation of copper complexes with other matrices could neither be excluded nor justified. The released copper from the treated nets did not induce oxidative stress but affected the immediate immune defense mechanism of the exposed fish making them more easily vulnerable to diseases. Consequently, copper-based antifouling treated nets could be a risk factor for D. labrax health.     

Particulate matter emission rates from beef cattle feedlots in Kansas-reverse dispersion modeling

Open beef cattle feedlots emit various air pollutants, including particulate matter (PM) with equivalent aerodynamic diameter of 10 microm or less (PM10); however limited research has quantified PM10 emission rates from feedlots. This research was conducted to determine emission rates of PM10 from large cattle feedlots in Kansas. Concentrations of PM10 at the downwind and upwind edges of two large cattle feedlots (KS1 and KS2) in Kansas were measured with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2007 to December 2008. Weather conditions at the feedlots were also monitored. From measured PM10 concentrations and weather conditions, PM10 emission rates were determined using reverse modeling with the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). The two feedlots differed significantly in median PM10 emission flux (1.60 g/m2-day for KS1 vs. 1.10 g/m2-day for KS2) but not in PM10 emission factor (27 kg/1000 head-day for KS1 and 30 kg/1000 head-day KS2). These emission factors were smaller than published U.S. Environmental Protection Agency (EPA) emission factor for cattle feedlots.     

Acute toxicity of aromatic and non-aromatic fractions of naphthenic acids extracted from oil sands process-affected water to larval zebrafish

The toxicity of oil sands process-affected water (OSPW) has regularly been attributed to naphthenic acids, which exist in complex mixtures. If on remediation treatment (e.g., ozonation) or on entering the environment, the mixtures of these acids all behave in the same way, then they can be studied as a whole. If, however, some acids are resistant to change, whilst others are not, or are less resistant, it is important to establish which sub-classes of acids are the most toxic.     

Occurrence and fate of pesticides in four contrasting agricultural settings in the United States

Occurrence and fate of 45 pesticides and 40 pesticide degradates were investigated in four contrasting agricultural settings--in Maryland, Nebraska, California, and Washington. Primary crops included corn at all sites, soybeans in Maryland, orchards in California and Washington, and vineyards in Washington. Pesticides and pesticide degradates detected in water samples from all four areas were predominantly from two classes of herbicides--triazines and chloroacetanilides; insecticides and fungicides were not present in the shallow ground water. In most samples, pesticide degradates greatly exceeded the concentrations of parent pesticide. In samples from Nebraska, the parent pesticide atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] was about the same concentration as the degradate, but in samples from Maryland and California atrazine concentrations were substantially smaller than its degradate. Simazine [6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine], the second most detected triazine, was detected in ground water from Maryland, California, and Washington. Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] rarely was detected without its degradates, and when they were detected in the same sample metolachlor always had smaller concentrations. The Root-Zone Water-Quality Model was used to examine the occurrence and fate of metolachlor at the Maryland site. Simulations accurately predicted which metolachlor degradate would be predominant in the unsaturated zone. In analyses of relations among redox indicators and pesticide variance, apparent age, concentrations of dissolved oxygen, and excess nitrogen gas (from denitrification) were important indicators of the presence and concentration of pesticides in these ground water systems.     

An Approach for Evaluating the Effectiveness of Various Ozone Air Quality Standards for Protecting Trees

We demonstrate an approach for evaluating the level of protection attained using a variety of forms and levels of past, current, and proposed Air Quality Standards (AQSs). The U.S. Clean Air Act requires the establishment of ambient air quality standards to protect health and public welfare. However, determination of attainment of these standards is based on ambient pollutant concentrations rather than prevention of adverse effects. To determine if a given AQS protected against adverse effects on vegetation, hourly ozone concentrations were adjusted to create exposure levels that “just attain” a given standard. These exposures were used in combination with a physiologically-based tree growth model to account for the interactions of climate and ozone. In the evaluation, we used ozone concentrations from two 6-year time periods from the San Bernardino Mountains in California. There were clear differences in the level of vegetation protection achieved with the various AQSs. Based on modeled plant growth, the most effective standards were the California 8-hr average maximum of 70 ppb and a seasonal, cumulative, concentration-weighted index (SUM06), which if attained, resulted in annual growth reductions of 1% or less. Least effective was the 1-hr maximum of 120 ppb which resulted in a 7% annual reduction. We conclude that combining climate, exposure scenarios, and a process-based plant growth simulator was a useful approach for evaluating effectiveness of current or proposed air quality standards, or evaluating the form and/or level of a standard based on preventing adverse growth effects.     

Identification of key parameters controlling dissolved oxygen migration and attenuation in fractured crystalline rocks

In the crystalline rocks of the Canadian Shield, geochemical conditions are currently reducing at depths of 500-1000 m. However, during future glacial periods, altered hydrologic conditions could potentially result in enhanced recharge of glacial melt water containing a relatively high concentration of dissolved oxygen (O2). It is therefore of interest to investigate the physical and geochemical processes, including naturally-occurring redox reactions, that may control O2 ingress. In this study, the reactive transport code MIN3P is used in combination with 2k factorial analyses to identify the most important parameters controlling oxygen migration and attenuation in fractured crystalline rocks. Scenarios considered are based on simplified conceptual models that include a single vertical fracture, or a fracture zone, contained within a rock matrix that extends from the ground surface to a depth of 500 m. Consistent with field observations, Fe(II)-bearing minerals are present in the fractures (i.e. chlorite) and the rock matrix (biotite and small quantities of pyrite). For the parameter ranges investigated, results indicate that for the single fracture case, the most influential factors controlling dissolved O2 ingress are flow velocity in the fracture, fracture aperture, and the biotite reaction rate in the rock matrix. The most important parameters for the fracture zone simulations are flow velocity in the individual fractures, pO2 in the recharge water, biotite reaction rate, and to a lesser degree the abundance and reactivity of chlorite in the fracture zone, and the fracture zone width. These parameters should therefore receive increased consideration during site characterization, and in the formulation of site-specific models intended to predict O2 behavior in crystalline rocks.     

Spawning behaviour and sex hormone levels in adult and precocious brown trout (Salmo trutta L.) males and the effect of anosmia

Summary. In the present experiment the behaviour and endocrine status of males of the brown trout, Salmo trutta L., (Salmoniformes: Salmonidae) were studied when males were kept in a stream tank with a nest digging female. Groups of mature adult males and precocious intact or anosmic male parr were placed with the nesting female so that the group resembled a natural spawning situation with big anadromous fish acting as dominant males and precocious parr acting as “sneakers”. A control experiment was also run with only males without a female present. In intact parr there were significant positive correlations between the per cent of the total observation time spent with a female, milt volume, and plasma concentration of 17α, 20β-dihydroxy-4-pregnen-3-one. Anosmic parr had significantly lower volumes of strippable milt and gonadal steroid hormone levels compared with intact parr. However, no differences were found in the control experiment. Significantly fewer anosmic parr attended and courted the nesting female and those anosmic fish that attended the female had significantly lower plasma levels of gonadal hormones. Intact parr also displayed a greater number of agonistic acts against other parr without any difference in fighting ability. No differences in aggression occured in the control experiment. In adult males together with a female, post-experimental gonadal steroid hormone levels were higher than pre-experimental levels. Positive correlations between aggression and androgen hormone levels were observed in adult males. No differences in plasma hormone levels were observed between adult males and intact precocious males. The results show that olfactory occlusion results in low steroid hormone levels and milt volumes in precocious males placed in a spawning situation. The courting behaviour was also affected by anosmia. Odours from the nesting female may have caused the enhanced plasma hormone levels and stimulated the males to attend the female. Received 15 May 1997; accepted 29 June 1997.     

Polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Bizerte Lagoon,Tunisia: levels,sources, and toxicological significance

To assess the status of polycyclic aromatic hydrocarbon (PAH) contamination in sediments from the Bizerte Lagoon (northern Tunisia), 18 surface sediment samples were collected in March 2011 and analyzed for 14 US Environmental Protection Agency priority PAHs by high-performance liquid chromatography. The total concentrations of the 14 PAHs (ΣPAHs) ranged from 16.9 to 394.1 ng g^?1 dry weight (dw) with a mean concentration of 85.5 ng g^?1 dw. Compared with other lagoons, coasts, and bays in the world, the concentrations of PAHs in surface sediments of the Bizerte Lagoon are low to moderate. The PAHs’ composition pattern was dominated by the presence of four-ring PAHs (45.8 %) followed by five-ring (26.8 %) and three-ring PAHs (12.7 %). The PAH source analysis suggested that the main origin of PAHs in the sediments of the lagoon was mainly from pyrolytic sources. According to the numerical effect-based sediment quality guidelines of the USA, the levels of PAHs in the Bizerte Lagoon should not exert adverse biological effects. The total benzo[a]pyrene toxicity equivalent values calculated for the samples varied from 3.1 to 53.7 ng g^?1 dw with an average of 10.6 ng g^?1 dw.     

Molecular Transport of Xylene Through Palm Pressed Fibre Filled Low Density Polyethylene: Role of Fibre Content,Alkali Treatment and Particle Size

We report in this paper the transport of an aromatic solvent, xylene through palm pressed fibre filled low density polyethylene composites studied at three different temperatures (40, 60, and 80 °C) by conventional weight-gain method. The diffusion parameters were investigated with special reference to the effect of fibre content, temperature and particle size. The effect of alkali treatment on solvent uptake was also analyzed. The transport coefficients of diffusion, permeation and sorption were determined to evaluate the influence of interface bonding on transport properties. The van’t Hoff relationship was used to determine the thermodynamic parameters and was found that the estimated free energies of sorption were all positive, indicating non-spontaneity of the solubility of PPF/LDPE composites. The first order kinetic rate constant and swelling parameters were also evaluated.     

Restoration ecology of riverine wetlands: II. An example in a former channel of the Rhône River

Riverine wetlands, which provide numerous valuable functions, are disappearing in floodplains of a channelized European river. A restoration project has been proposed by scientists to restore a former braided channel of the Rhône River by the removal of fine organic sediments in order to enhance groundwater supply. A precise and intensive prerestoration monitoring program during one year (including comparison with a reference channel) has taken into account several variables and ecological performance indicators measured at various spatial and temporal scales. Three restoration techniques were then suggested, taking into account two characteristics of ecosystem functions for increasing restoration success and self-sustainability: (1) the riparian forest as well as the shores must be preserved or disturbed as little as possible; and (2) the upstream alluvial plug must be preserved to prevent direct supply of nutrientrich water from the Rhône River. Among the three restoration options proposed, it was not possible to carry out the less ecologically disturbing one as it was considered too expensive, time consuming, and difficult to realize. A precise and intensive postrestoration monitoring program, conducted over two years, demonstrated restoration success but also unpredicted problems, such as a locally thick layer of fine organic sediment. As long as a self-sustainable state is not achieved, this monitoring should be continued. Afterwards, a less precise and less intensive long-term monitoring should enable the detection of future events that may influence ecosystem changes.