Pyrethroid residue dynamics in insects depends on the circadian clock

Many factors may affect pesticide effectiveness against pests. One of the factors that should be considered is circadian rhythmicity. In this study, we evaluated daily variations in pyrethroid susceptibility in the house cricket, Acheta domesticus L. Crickets were exposed to a standard dose of ß-cyfluthrin at different times of a day, and pesticide residue levels were evaluated using gas chromatography. Results demonstrate that the time of pyrethroid disappearance is correlated with the circadian clock, with the highest decomposition rate at night. Furthermore, crickets also showed the highest resistance to the insecticide at night, expressed as a high survival rate. Moreover, ß-cyfluthrin induced significant changes in thermal preferences of intoxicated crickets. This is the first report showing that pyrethroid residue levels in the crickets' body depend on its circadian clock.     

Hydrogeological study of an anti-tank range

The Arnhem Anti-Tank Range (Canadian Forces Base [CFB] Valcartier, Canada, in operation since the 1970s) has been characterized, including the drilling, installation, and characterization of 25 wells and a ground-penetrating radar survey. The observed particular features of this site include highly variable flow velocities (from < 3 to 1200 m/yr) and transient flow regime in the regional aquifer below the contaminant source zone of the impact area, sharp flow direction shifts, discontinuous stratigraphy and a local perched aquifer. A transient ground water flow model permitted us to understand how the complex hydrogeological setting shapes contaminant transport in the regional aquifer. The model explains the highly variable energetic material (EM) concentrations measured in the plume with peaks associated to spring and to a lesser extent to fall recharge events. As a conclusion from this work, the authors suggest that the characterization of contaminant sources on slopes should extend over all seasons to be sure to detect potential transient flow conditions and variable contaminant concentrations.     

Life cycle inventory for an organic swine waste treatment system

Journal of Material Cycles and Waste Management - The aim of this study was to analyze the efficiency of a system of treatment of organic swine waste as a management tool in the transformation of...     

Sensitized photooxygenation of mononitrophenols in micellar media

The singlet molecular oxygen‐mediated photooxidation of simple nitrophenols was studied in micellar (CTAB) alkaline solutions.

A different behaviour for the values of the overall rate constant (K_t ) and the reactive rate constant (K_t ) in the interaction nitrophenol‐singlet molecular oxygen was observed as a function of surfactant concentration. The former decreases as [CTAB] increases, from values of 1–3 × 10⁹ M^–1 s^–1 in the absence of surfactant to values at least one order of magnitude lower at [CTAB] ～0.1 M. Parallel, k_t remains practically unaffected, in values of the order of 10⁶ — 10⁷ M^–l s^–1, depending on the particular nitrophenol, within the same [CTAB] range. The quantum yield of nitrophenols photooxidation reaches a maximum at [CTAB] ～0.1 M.

The results are discussed in terms of a combination of causes, the polarity of the nitrophenolic microenvironment being the driving effect. The implication of the results on environmental decontamination are also analyzed.     

Effect of selenium on the growth of Lemna minor

The effect of selenium on the vegetative reproduction of cultured Lemna minor was investigated. Cultures were grown for 28 days at a temperature of 23 ± 3°C and under a constant (24 h) light cycle. Growth was monitored every seven days. The growth of L. minor was inhibited at high concentrations (>5mg/L [Se]), but stimulated at low concentrations (0.2—2mg/L [Se]). This stimulation of growth at low selenium concentrations has significant implications for the use of selenium enriched superphosphate fertilisers on selenium deficient pastures.