Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland

Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m × 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m × 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides.     

Mechanisms of biodegradation of dibenzoate plasticizers

Biodegradation mechanisms were elucidated for three dibenzoate plasticizers: diethylene glycol dibenzoate (D(EG)DB), dipropylene glycol dibenzoate (D(PG)DB), both of which are commercially available, and 1,6-hexanediol dibenzoate, a potential green plasticizer. Degradation studies were done using Rhodococcus rhodochrous in the presence of pure alkanes as a co-substrate. As expected, the first degradation step for all of these systems was the hydrolysis of one ester bond with the release of benzoic acid and a monoester. Subsequent biodegradation of the monobenzoates of diethylene glycol (D(EG)MB) and dipropylene glycol (D(PG)MB) was very slow, leading to significant accumulation of these monoesters. In contrast, 1,6-hexanediol monobenzoate was quickly degraded and characterization of the metabolites indicated that the biodegradation proceeded by way of the oxidation of the alcohol group to generate 6-(benzoyloxy) hexanoic acid followed by β-oxidation steps. This pathway was blocked for D(EG)MB and D(PG)MB by the presence of an ether function.The use of a pure hydrocarbon as a co-substrate resulted in the formation of another class of metabolites; namely the esters of the alcohols formed by the oxidation of the alkanes and the benzoic acid released by hydrolysis of the original diesters. These metabolites were biodegraded without the accumulation of any intermediates.     

Lingual and biting responses to prey chemicals by ingestively naive scincid lizards: discrimination from control chemicals,time course,and effect of method of stimulus presentation

Summary. We tested responses to prey chemicals by lizard hatchlings of an oviparous species and neonates of a viviparous species, neither of which had never eaten. Both species responded more strongly to prey chemicals than to odorous and odorless control stimuli presented on cotton swabs. Although only a few species have been examined, all that have been tested have an innate capacity for prey chemical discrimination, suggesting that this innate response to prey chemicals is widespread among lizards that use the lingual-vomeronasal system to locate and identify prey. Innate prey chemical discrimination has the great advantage of permitting lizards lacking prior experience with food to respond appropriately to chemical cues associated with food. Both species discriminated prey chemicals from control substances at age three days, earlier than previously known. Our data hint that Mabuya macularia may be capable of discrimination on its day of birth, but further study is needed to determine the exact onset. A stronger tendency to attack swabs bearing prey chemicals by Scincella lateralis than by M. macularia may be explained by differences in defensiveness near an experimenter or by differences in the importance of visual prey cues for confirmation of chemical cues in the natural habitats of these species. In M. macularia responses to the control stimuli declined over days of testing, suggesting habituation, but responses to prey chemicals did not habituate by the third day of testing, which is interpreted as a possible adaptive response to permit location of food. In the standard method of stimulus presentation, a cotton swab bearing a chemical stimulus is placed anterior to a lizard's snout. We tested a new method in which the swab was placed in continuous contact with the lizard's anterior labial scales. The new method elicited significantly stronger responses from M. macularia. We discuss reasons for this finding and applications for the new method. Received 2 September 1999; accepted 15 December 1999     

Study of biological stabilization processes of cattle and poultry manure by thermogravimetric analysis and (13)C NMR

The biological stabilization process of cattle and poultry manure was studied using thermogravimetric analysis and (13)C nuclear magnetic resonance. The stabilization processes carried out were composting, anaerobic digestion and a mixed process (partly aerobic, partly anaerobic). It was observed from the analyzed samples that the biological stabilization processes reduce the volatile content of the bio-wastes and increase the degree of aromaticity. The stabilization of cattle manure by means of aerobic processes was able to further oxidize and enriched in aromatic compounds the bio-waste when compared with the digestion process. On the other hand, the stabilization of poultry manure resulted in a greater aromatization under the digestion process. Stabilized samples with a high degree of aromaticity presented a lower volatile content accompanied by a reduction in the intensity of the differential thermogravimetry peak registered under an inert atmosphere, indicative of the thermal decomposition of the organic matter. The thermal decomposition of all the analyzed materials (fresh and stabilized samples) commenced at around 200 degrees C but for the digested poultry manure, which decomposition initiated close to 250 degrees C. All stabilized samples yielded a lower degree of volatilization to that one observed in fresh samples.     

Prevalence of work-family conflict: Are work and family boundaries asymmetrically permeable?

This study tested Pleck's (1977) hypothesis concerning gender differences in the relative permeability of work and family boundaries. Data were obtained from a randomly drawn community sample of 631 employed adults (278 men; 353 women). Respondents reported that work interfered with family life (W→F conflict) more frequently than family life interfered with work (F→W conflict). These results suggest that work and family boundaries are indeed asymmetrically permeable with family boundaries being more permeable than work boundaries. However, there was no evidence of gender differences in the pattern of asymmetry, indicating that the dynamics of work and family boundaries may operate similarly among men and women. Implications for future research are discussed.     

RESEARCH: Warmwater Stream Bank Protection and Fish Habitat: A Comparative Study

/ Fishes and their habitats were sampled in Harland Creek, Mississippi, for 3 years to compare the relative value of three types of bank treatment in an incised, warmwater stream. Semiannual samples were collected from 10 reaches: 3 reaches protected by each of the three types of protection (longitudinal stone toe, stone spurs, and dormant willow posts) and an unprotected, slowly eroding bend. Protection of concave banks of bends had no measurable effect on the habitat quality of downstream riffles. Although bends and adjacent downstream riffles were faunistically similar at the species level, catostomids and centrarchids were more dominant in pools and smaller cyprinids more dominant in riffles. Reaches with willow posts were slightly deeper than the others, most likely because of geomorphic factors rather than bank treatment. Mean water surface widths in reaches stabilized with stone spurs were 40% to 90% greater than for other treatments, and current velocities were greatest in reaches with stone toe. Patterns of fish abundance and species diversity did not differ significantly among treatments. However, principal components analysis indicated that the fish species distribution associated with the untreated reference site was distinct. Reaches stabilized with stone spurs supported significantly higher densities of large fish and higher levels of fish biomass per unit channel length than reaches with other bank treatments, generally confirming previous research in the region. Initial costs for spurs were comparable to those for stone toe and about three times greater than for willow posts.     

Lead in grass in the Scottish uplands: deposition or uptake?

If it is assumed that the Pb collected in grass samples is derived mainly from atmospheric deposition then grass samples can be used as a convenient and easily analysed monitor for Pb deposition, in particular to establish the isotopic composition of current deposition in remote locations. As some studies have demonstrated a strong correlation between soil and grass Pb concentrations, it was considered important to establish the proportion of soil Pb in the grasses used to monitor atmospheric deposition at upland locations in Scotland. Consideration of earlier studies provided evidence that very little, if any, Pb in grass was derived from soil. Lead isotope analysis, by thermal ionisation mass spectrometry, of grasses grown on soils spiked with enriched (207)Pb in the field situation allowed the relative contribution of atmospheric deposition and soil to the grass Pb to be calculated. In most cases, >80% of Pb in grass was derived from atmospheric deposition and in recent years this value was >90%. Recalculation of the (206)Pb/(207)Pb ratio in grass samples showed that there was very little error in the results, published previously, which were based on the assumption that all the Pb collected with grass was derived from the atmosphere. The trends established by measuring the (206)Pb/(207)Pb ratio in grasses were confirmed and remain valid.     

Evaluating toxicity of Asana XL (esfenvalerate) amendments in agricultural ditch mesocosms

Agricultural ditches primarily serve to remove and store excess water associated with irrigation and storm events. The ability of these ecosystems to mitigate potential contaminants is not well understood. Five sites along a 650-m agricultural ditch located in the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were used to measure fate and effects of an esfenvalerate (insecticide) exposure. Following a 0.64-cm simulated storm event, samples were collected from water and sediments and analyzed spatially from five sites and temporally from 0.5 h to 56 d. Results of aqueous toxicity bioassays indicated that lethality progressed downstream throughout all sampling intervals, while sediment toxicity bioassays only elicited biological responses at the point of pesticide application to the ditch (0 m). Significant reductions in survival of Ceriodaphnia dubia and Pimephales promelas in water were measured at the 0-, 20-, and 80-m sites following application. Ten-day solid phase sediment testing of Chironomus tentans indicated persistent toxicity only at the point of application (0 m) and throughout 56 d (mean=14.4% survival). No lethality or significant reduction in midge growth was measured for remaining downstream sites. These measurements were used to evaluate the potential of agricultural ditches to reduce potential deleterious effects of contaminants in agricultural drainage systems that precede receiving streams.