Temperature dependence of Henry's law constants of metolachlor and diazinon

A dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube has been used to determine experimentally the Henry's law constants (HLC) of two pesticides: metolachlor and diazinon. The measurements were conducted over the temperature range 283-301 K. At 293 K, HLCs values are (42.6+/-2.8) x 10(3) (in units of M atm(-1)) for metolachlor and (3.0+/-0.3)x10(3) for diazinon. The obtained data were used to derive the following Arrhenius expressions: HLC=(3.0+/-0.4) x 10(-11) exp((10,200+/-1,000)/T) for metolachlor and (7.2+/-0.5) x 10(-15) exp((11,900+/-700)/T) for diazinon. At a cumulus cloud temperature of 283 K, the fractions of metolachlor and diazinon in the atmospheric aqueous phase are about 57% and 11% respectively. In order to evaluate the impact of a cloud on the atmospheric chemistry of both studied pesticides, we compare also their atmospheric lifetimes under clear sky (tau(gas)), and cloudy conditions (tau(multiphase)). The calculated multiphase lifetimes (in units of hours) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): metolachlor, 0.4 (2.9); diazinon, 1.9 (5.0).     

Seasonal changes in eicosanoid metabolism in the brown bear

Polyunsaturated fatty acids (PUFAs) exert several important functions across organ systems. During winter, hibernators divert PUFAs from oxidation, retaining them in their tissues and membranes, to ensure proper body functions at low body temperature. PUFAs are also precursors of eicosanoids with pro- and anti-inflammatory properties. This study investigated seasonal changes in eicosanoid metabolism of free-ranging brown bears (Ursus arctos). By using a lipidomic approach, we assessed (1) levels of specific omega-3 and omega-6 fatty acids involved in the eicosanoid cascade and (2) concentrations of eicosanoids in skeletal muscle and blood plasma of winter hibernating and summer active bears. We observed significant seasonal changes in the specific omega-3 and omega-6 precursors. We also found significant seasonal alterations of eicosanoid levels in both tissues. Concentrations of pro-inflammatory eicosanoids, such as thromboxane B2, 5-hydroxyeicosatetraenoic acid (HETE), and 15-HETE and 18-HETE, were significantly lower in muscle and/or plasma of hibernating bears compared to summer-active animals. Further, plasma and muscle levels of 5,6-epoxyeicosatrienoic acid (EET), as well as muscle concentration of 8,9-EET, tended to be lower in bears during winter hibernation vs. summer. We also found lower plasma levels of anti-inflammatory eicosanoids, such as 15dPGJ₂ and PGE₃, in bears during winter hibernation. Despite of the limited changes in omega-3 and omega-6 precursors, plasma and muscle concentrations of the products of all pathways decreased significantly, or remained unchanged, independent of their pro- or anti-inflammatory properties. These findings suggest that hibernation in bears is associated with a depressed state of the eicosanoid cascade.