Analysis of some organochlorine pesticides in an urban atmosphere (Strasbourg, east of France)

High volume samples of urban air have been collected in Strasbourg, a big city situated in the east of France, for the evaluation of the contamination by organochlorine pesticides. Pesticides (p,p'-DDT, p,p'-DDD, p,p'-DDE, aldrin, dieldrin, endrin, gamma-HCH, cis-chlordane, trans-chlordane, alpha-endosulfan, beta-endosulfan, hexachlorobenzene, heptachlor and some of their metabolites: alpha-HCH, 2,4'-DDT, 2,4'-DDD and 2,4'-DDE) were analysed by GC-ECD. Prior to analysis, samples were Soxhlet extracted with a mixture of n-hexane/methylene chloride. The analysis of samples collected in 2001 (n = 6), 2002 (n = 7) and 2003 (n = 5) shows that alpha-HCH and gamma-HCH were detected in all samples (between 0.05 and 4 ng m(-3) and between 0.01 and 1 ng m(-3), respectively) along with aldrin and dieldrin at lower concentrations (between 0.01 and 0.08 ng m(-3) and between 0.02 and 0.09 ng m(-3), respectively). Other pesticides were detected very randomly at very low concentrations. The calculation of the alpha/gamma-HCH ratio shows that hexachlorocyclohexane measured in the atmosphere have a local origin and come probably from contaminated soil by volatilisation. alpha and beta-endosulfan were practically not detected in samples collected in 2001 and 2002 while they were always measured in the gas phase in samples from 2003. This observation can be explained by an increase of volatilisation with the increase of the air temperature. In July, temperature were higher (between 17 and 30 degrees C in climatic station) than in March-May 2001 and 2002 (between 2 and 19 and between 2 and 10, respectively).     

Dynamics of fipronil residue in vegetable-field ecosystem

Fipronil insecticide has been widely used to control vegetable pests in China recently. The research was conducted to evaluate the fate of fipronil in vegetable-field ecosystem and provide the scientific basis of using this insecticide. Developed on the analytical methods of fipronil residue and its four metabolisms, the degradation dynamics of their residue in a vegetable and the soil of the vegetable fields was studied. The results showed that (1) degradation of fipronil was faster in pakchoi (half-life 2.6 days) than in soil (half-life 7.3 days); (2) degradation reaction occurred in soil was governed mainly by photodegradation and oxidization accompanying with production of the metabolites, MB46513 and MB46136. Reduction and hydrolyzation played little role in the degradation process. In pakchoi, degradation was mainly contributed by reduction though oxidization and hydrolyzation occurred simultaneously. The metabolite products were MB45950, MB46136 and RPA200766; (3) the final residue in pakchoi was at a level of 0.003 mg kg⁻¹, which was much lower than the USA’s upper limit of 0.04 mg kg⁻¹ in rice. Therefore, a dosage of 24 g hm⁻² was suggested and considered as safe to human beings and animals.     

Pesticide vapours in confined atmospheres. Determination of dichlorvos by SPME-GC-MS at the microg m(-3) level

A method based on SPME is described for assessing the gaseous dichlorvos concentration in confined atmospheres like a greenhouse after a pesticide application. Sampling was made by using SPME with PDMS fibres immersed into a 250 mL sampling flask into which air samples were dynamically pumped from the analysed atmosphere. Sampling duration was 40 min and samples were then analysed by GC-MS. Calibration was performed from a vapour saturated air sample and gas phase diluted samples, and this procedure afforded a curve with a regression coefficient (R2) higher than 0.98. The repeatability of these measurements was observed with an RSD of 2.5%. This analysis procedure was then applied for the determination of gaseous dichlorvos concentrations versus time, in the atmosphere of an experimental 8 m2 and 20 m3 greenhouse. The pesticide was sprayed according to real cultivation conditions and measurements were made from 2 up to 74 h after application affording observed concentrations in the range of decades and hundreds of microg m(-3) (corresponding limits of detection and quantification were found at the level of a few microg m(-3)).     

EVALUATING THE EFFECTIVENESS OF A FIXED WELLHEAD DELINEATION: REGIONAL CASE STUDY 1

The 1996 Safe Drinking Water Act amendments mandated that every state must determine the hydrogeologic origin of each public drinking water system and assess the degree to which each system may be adversely affected by potential sources of contamination. Wisconsin delineated and assessed one specific class of systems, transient noncommunity drinking water wells, with the least stringent standards of all governed system types. This study evaluates the effectiveness of Wisconsin's arbitrarily fixed radius approach used in determining susceptibility to potential contamination from 1,872 transient noncommunity ground water wells. Nearly 28 percent of the wells with contaminated water did not have any recorded potential sources of contamination within the delineation radii. Additionally, regression models derived from potential contaminant inventories within the delineation radii could not accurately predict actual incidences of water contamination. Differences between observed and expected frequencies of contamination further suggest that some transient noncommunity systems should probably be delineated with larger and more sophisticated methods that would account for varying geology and contaminant susceptibility. The majority of contamination cases without recorded potential sources of contamination within the delineation radii were in a karst area. Subsequently, the arbitrarily fixed radius delineation method should not be used in areas with karst aquifers.     

THE HUDSON BAY AIR MASS TYPE–SOME CLIMATOLOGICAL IMPLICATIONS

A substantial percentage of days with below normal temperatures in central Illinois during May and June (1956-1965) appear to be associated with polar air masses which traverse the Hudson Bay area before entering the Midwest. January departures, in contrast, are related to polar air masses that enter the United States near the Mackenzie River in western Canada. The general influences of the Hudson Bay area on climate are discussed.     

A Bayesian hierarchical model of Antarctic fur seal foraging and pup growth related to sea ice and prey abundance

We created a Bayesian hierarchical model (BHM) to investigate ecosystem relationships between the physical ecosystem (sea ice extent), a prey measure (krill density), predator behaviors (diving and foraging effort of female Antarctic fur seals, Arctocephalus gazella, with pups) and predator characteristics (mass of maternal fur seals and pups). We collected data on Antarctic fur seals from 1987/1988 to 1994/1995 at Seal Island, Antarctica. The BHM allowed us to link together predators and prey into a model that uses all the data efficiently and accounts for major sources of uncertainty. Based on the literature, we made hypotheses about the relationships in the model, which we compared with the model outcome after fitting the BHM. For each BHM parameter, we calculated the mean of the posterior density and the 95% credible interval. Our model confirmed others' findings that increased sea ice was related to increased krill density. Higher krill density led to reduced dive intensity of maternal fur seals, as measured by dive depth and duration, and to less time spent foraging by maternal fur seals. Heavier maternal fur seals and lower maternal foraging effort resulted in heavier pups at 22 d. No relationship was found between krill density and maternal mass, or between maternal mass and foraging effort on pup growth rates between 22 and 85 days of age. Maternal mass may have reflected environmental conditions prior to the pup provisioning season, rather than summer prey densities. Maternal mass and foraging effort were not related to pup growth rates between 22 and 85 d, possibly indicating that food was not limiting, food sources other than krill were being used, or differences occurred before pups reached age 22 d.     

Turbulent flow over a D-section bluff body: a numerical benchmark

Environmental Fluid Mechanics - A numerical benchmark of different turbulence closures was performed to investigate the turbulent wake flow behind a submerged D-shaped bluff body. The numerical...     

Species-specific variation in cuttlebone δ13C and δ18O for three species of Mediterranean cuttlefish

Stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes in cuttlebones of three species of Mediterranean cuttlefish (Sepia elegans, S. officinalis, and S. orbignyana) with different life histories were contrasted. Cuttlebone δ¹³C and δ¹⁸O were quantified at both the core and edge (representing early life and recent deposition, respectively) for all three species sampled from the southern Adriatic Sea in 2010 (n = 28). For S. officinalis, cuttlebone δ¹³C and δ¹⁸O values were both lower relative to S. elegans and S. orbignyana at the core by approximately 1.0–2.0 and 3.0 ‰, respectively. Differences between core and edge in cuttlebone δ¹³C and δ¹⁸O were also observed for S. officinalis with observed values at the cuttlebone edge (recent) exceeding core (early life) values by 2.5 ‰ for δ¹³C and 1.4 ‰ for δ¹⁸O. Differences in isotopic composition across S. officinalis cuttlebones are possibly reflective of ontogenetic migrations from nearshore nurseries (lower seawater δ¹³C and δ¹⁸O values) to offshore overwintering habitats (higher seawater δ¹³C and δ¹⁸O values). Overall, results from this study suggest that cuttlebone δ¹³C and δ¹⁸O hold promise as natural tags for determining the degree of spatial connectivity between nearshore and offshore environments used by cuttlefish.     

Hierarchical Bayesian Modelling of plant colonisation by winged aphids: Inferring dispersal processes by linking aerial and field count data

Understanding and modelling insect pest dispersal is an important prerequisite for designing integrated pest management programs. Nevertheless, studies investigating the dispersal of small insects in natural conditions remain scarce mainly because of the difficulty of tracking the movements of these organisms. Here we propose to use Hierarchical Bayesian Modelling (HBM) framework to gain knowledge on hidden processes that cannot be observed directly in natura, such as insect landing and insect mortality, through the definition of latent variables. An HBM describing crop colonization by winged aphids was fitted to a large dataset of field observations issued from a long term survey at a wide scale of both aerial and field densities of the bird cherry-oat aphid Rhopalosiphum padi. This study provides the first evidence that suction trap data are reliable proxies of aphid colonizing rates in cereal fields in autumn and can be a nice alternative to the very time-consuming crop sampling. The proportion of winged aphids landing in cereal fields is shown to vary between regions according to the degree of investment of local R. padi population in sexual reproduction. Results also indicate that under autumnal field conditions, less than 5% of winged aphids survive more than 10 days after landing. This HBM provides the basis of a predictive model for aphid crop colonization that fully accounts for all sources of uncertainty. It should be of great value to improve the trust of users in any decision making systems.     

Restoration of a Canadian Prairie Wetland with Agricultural and Municipal Wastewater

3 /day (800,000 US gallons) of municipal wastewater and beef processing wastewater. A large nongovernmental organization hastened restoration with a development process that outlined restoration goals and management objectives to satisfy a dual mandate of wastewater treatment and wildlife habitat creation. In 1995, after five years of wastewater additions, the basins had been refilled and the surrounding uplands had been acquired and restored. The Frank Lake Conservation Area currently provides high-quality habitat for a variety of wildlife in a region where many of the native plants and animals species have been lost due to habitat loss and fragmentation. The success of upland and water management strategies is reflected in the increase of target species' abundance and richness: 50 shorebird species, 44 waterfowl species, 15 raptor species, and 28 other new bird species have returned to the marsh since restoration. As well, significant N and P reduction occurs as waters flow through the first basin of the marsh. The management strategies of this project that satisfied a dual mandate serve as a model to guide managers of other large-scale wetland restoration projects.