The long-term maintenance and renewal of Louisiana's wetlands cannot be accomplished without diversion of sediment laden water from the Mississippi and Atchafalaya Rivers. Because of ramifications for flood control, navigation, and established estuarine resource uses, such diversions, at least initially, are likely to be limited to structures that permit flow to be taken from the upper part of the water column. To evaluate the potential benefits from such diversions in terms of sediment introduction into the wetlands, and the possibility of abatement of wetland loss through small structures that could be implemented at a local level, an existing diversion by means of a siphon was investigated. The investigation focused on the White's Ditch Siphon, in Plaquemines Parish, Louisiana. Siphon operation was monitored for the 1989-1990 water year to determine water and sediment discharge characteristics and their relationship to those of the Mississippi River and to estuarine hydrology To determine sedimentation benefits to the adjacent marsh and the need for outfall management, sediment dispersal was evaluated and sediment deposition was compared for a site within the siphon outfall area and a control site. Results of the siphon monitoring are extended to larger scale diversions. On the basis of suspended load characteristicsmore » of the Mississippi River and the operational characteristics of a major structure, as related to the estuarine salinity regime and resource constraints, the extent to which such diversions are likely to offset subsidence and related wetland loss is evaluated.« less
Abstract The logarithm of the octanol/water partition coefficient has been widely used as the sole physicochemical property to define various types of biological activity, such as aquatic toxicity. In the present study, we derive a quantitative structure–activity relationship (QSAR) equation for the prediction of acute aquatic toxicity (48-h median effective concentration) of quaternary alkylammonium sulfobetaines to the aquatic invertebrate Daphnia magna Straus. The single-parameter approach described is also based on the hydrophobicity parameter, log P. The 17 zwitterionic compounds were considered for QSAR development. They have the general formula RN+(CH3)2(CH2)nSO3−, where n = 2 to 4, and were synthesized by reacting the corresponding N,N-dimethylamines with either sodium-2-chloroethanesulfonate (n = 2), 1,3-propanesultone (n = 3), or 1,4-butanesultone (n = 4). The R group was either a C6 to C12 alkyl chain, a phenylalkyl unit bearing a C1 to C4 chain, or a phenylpropyl unit with a C4 to C6 para-substituted alkyl group. Octanol/water partition coefficients were experimentally determined via a conventional stir-flask procedure, which was quantified using a reverse-phase, high-performance liquid chromatographic technique coupled with either an ultraviolet or an electrospray ionization mass spectrometry detection system. Median effective concentration values were also determined experimentally via a standard acute immobilization test recommended by Organisation for Economic Cooperation and Development (Paris, France) Guideline 202. The established QSAR equation for such zwitterionic compounds is consistent with the standard equation that normally defines the polar narcosis mode of toxic action.
Cigarette smoking has been associated with both the diagnosis of bacterial vaginosis (BV) and a vaginal microbiota lacking protective Lactobacillus spp. As the mechanism linking smoking with vaginal microbiota and BV is unclear, we sought to compare the vaginal metabolomes of smokers and non-smokers (17 smokers/19 non-smokers). Metabolomic profiles were determined by gas and liquid chromatography mass spectrometry in a cross-sectional study. Analysis of the 16S rRNA gene populations revealed samples clustered into three community state types (CSTs) ---- CST-I (L. crispatus-dominated), CST-III (L. iners-dominated) or CST-IV (low-Lactobacillus). We identified 607 metabolites, including 12 that differed significantly (q-value < 0.05) between smokers and non-smokers. Nicotine, and the breakdown metabolites cotinine and hydroxycotinine were substantially higher in smokers, as expected. Among women categorized to CST-IV, biogenic amines, including agmatine, cadaverine, putrescine, tryptamine and tyramine were substantially higher in smokers, while dipeptides were lower in smokers. These biogenic amines are known to affect the virulence of infective pathogens and contribute to vaginal malodor. Our data suggest that cigarette smoking is associated with differences in important vaginal metabolites, and women who smoke, and particularly women who are also depauperate for Lactobacillus spp., may have increased susceptibilities to urogenital infections and increased malodor.
