Effect of surfactants on persistence of azadirachtin-A (neem based pesticide)

Photostability of azadirachtin-A, a neem based pesticide, was studied in the presence of non-ionic surfactants. Surfactants such as Span-80, Atlox 3400B, Tween-80, Agrimul 52B, and Agrimul N4S enhanced the rate of photodegradation of azadirachtin-A, whereas surfactants such as Triton-X, Emulsol CFA, Tween-20, Emulsol MAS, and Emulsol-N-33 decreased the rate of degradation. Emulsol-N-33 was found to be the most effective surfactant, as half life of azadirachin-A in the presence of Emulsol-N-33 was found to be 94.93 min in comparison to 48 min for azadirachtin-A alone under UV light.     

Differences in accumulation of PAHs and metals on the leaves of Tiliaxeuchlora and Pyrus calleryana

The accumulation of substances associated with PM2.5 [polycyclic aromatic hydrocarbons (PAHs) and metals] on leaves of Pyrus calleryana (pear) and Tiliaxeuchlora (linden) along an urban road was investigated. These species have similar leaf morphology and were exposed to the identical environmental conditions. The accumulation of both PAHs and metals per leaf area was significantly higher on linden leaves than on pear leaves.     

A Note on the Emission of Nitrogen Oxides from Silage in Opened Bunker Silos

The evolution of NO_x from grass and maize silages wasmeasured using chemiluminescence in samples kept in airtightcontainers, in the silos and in a 750 kg mass removed to a mixer waggon. Measurements were made on the grass and maizesilos in two consecutive years. The results show that thereis continuous evolution of NO_x after silos have been opened and that high concentrations persist in the mass whichare rapidly released on agitation at the feed-out. The maximumrecorded concentrations of NO and NO₂ were 1985 and 152 ppbv respectively. These values are orders of magnitude greaterthan for rural background levels and exceed the maximum hourlyexposure of 50 ppbv for NO₂ recommended by the UK expertpanel for quality standards.     

Quantifying 137Cs aggregated transfer coefficients in a semi-natural woodland ecosystem adjacent to a nuclear reprocessing facility

Radiocaesium (137Cs) activity concentrations and aggregated transfer factors (Tag values) were calculated for vascular plants, fungal fruiting bodies and invertebrates in a semi-natural Picea sitchensis woodland (Lady Wood) adjacent to the British Nuclear Fuels plc. reprocessing facility at Sellafield, Cumbria, UK. The Tag values for vascular plants ranged from 7.1 x 10(-4) - 1.9 x 10(-2) m2 kg(-1), the maximum value being for Pteridium aquilinum. Fungal fruiting bodies had higher Tag values (1.9 x 10(-3) - 1.8 x 10(-1) m2 kg(-1)) than vascular plants, with a maximum value for Mycena galericulata. None of the activity concentrations for edible foodstuffs collected within this study (fungi and berries) exceeded the EC recommended limits of 137Cs in foodstuffs grown within the UK. The invertebrate community sampled during the study had Tag values ranging from 3.4 x 10(-4) to 1.3 x 10(-2) m2 kg(-1). There were no systematic differences in 137Cs activity concentration between invertebrate guilds, or between seasonal cohorts within guilds. The invertebrates in Lady Wood were exposed to a dose from 137Cs (internal gamma + beta and external gamma) ranging between 4.37 x 10(-4) and 6.40 x 10(-4) mGy day(-1). Including dose from radionuclides other than 137Cs and accounting for uncertainties due to the relative biological effectiveness of differing radionuclides could increase total dose by approximately an order of magnitude. These dose rates are at least three orders of magnitude lower than the 1 mGy d(-1) level at which harm may be caused to terrestrial biota, hence the risk to the invertebrate community from the effects of ionising radiation in Lady Wood is low.     

Fate of phosphorus in dairy wastewater and poultry litter applied on grassland

Large and repeated manure applications can exceed the P sorption capacity of soil and increase P leaching and losses through subsurface drainage. The objective of this study was to evaluate the fate of P applied with increasing N rates in dairy wastewater or poultry litter on grassland during a 4-yr period. In addition to P recovery in forage, soil-test phosphorus (STP) was monitored at depths to 180 cm in a Darco loamy sand (loamy, siliceous, semiactive, thermic Grossarenic Paleudults) twice annually. A split-plot arrangement of a randomized complete block design comprised four annual N rates (0, 250, 500, and 1000 kg ha(-1)) for each nutrient source on coastal bermudagrass [Cynodon dactylon (L.) Pers.] over-seeded with ryegrass (Lolium multiflorum L. cv. TAM90). Increasing annual rates of N and P in wastewater and poultry litter increased P removal in forage (P = 0.001). At the highest N rate of each nutrient source, less than 13% of applied P was recovered in forage. The highest N rates delivered 8 times more P in wastewater or 15 times more P in poultry litter than was removed in forage harvests during an average year. Compared with controls, annual P rates up to 188 kg ha(-1) in dairy wastewater did not increase STP concentrations at depths below 30 cm. In contrast, the highest annual P rate (590 kg ha(-1)) in poultry litter increased STP above that of controls at depth intervals to 120 cm during the first year of sampling. Increases in STP at depths below 30 cm in the Darco soil were indicative of excessive P rates that could contribute to nonpoint-source pollution in outflows from subsoil through subsurface drainage.     

White birch (Betula papyrifera Marshall) foliar litter decomposition in relation to trace metal atmospheric inputs at metal-contaminated and uncontaminated sites near Sudbury, Ontario and Rouyn-Noranda, Quebec, Canada

Decomposition of white birch (Betula papyrifera Marshall) foliar litter was examined at metal-contaminated and uncontaminated sites established along gradients of soil Cu, Ni, Pb and Zn concentrations near Sudbury, Ontario and Rouyn-Noranda, Quebec. Over an 18-month study period, a significantly lower rate of litter mass loss was observed at the Sudbury contaminated site (S1) than at the uncontaminated site (S2). This result was not duplicated at corresponding sites (RN1, RN2) in Rouyn-Noranda, despite similar levels of soil metal contaminants and atmospheric inputs. Concentrations of metals in litter increased at all sites with time. However, the greatest litter Cu and Ni concentrations were observed at S1 (188 and 192 microg/g, respectively), a result of substantial net gains of these elements from atmospheric inputs. On a per hectare basis, Cu accumulation in litter at S1 approached recommended application rates of Cu as copper sulphate for control of fungal diseases in agricultural operations, indicating that the current rate of Cu smelter emissions in Sudbury may cause the observed impairment of decomposition.     

STREAM MEANDER RESTORATION1

ABSTRACT: Stream meander restoration designs currently used by many state and local government agencies are often based on empirical equations, such as those developed by Leopold and Wolman (1957; 1960). In order to assess the suitability of these equations and propose alternative strategies, 18 sites in Central Maryland were selected and data on channel planform, cross-sections, sediments, and spacing and sizing of the pools and riffles were collected and analyzed to characterize the channel type in the study area. A large bias was found comparing the meander parameters measured to those computed using the Leopold and Wolman equations for the streams in central Maryland. Based on these results, appropriate empirical equations for the study area that can assist in stream restoration designs were investigated. An additional approach that can assist in stream restoration consists of the application of a detailed stream reconnaissance to verify that the restoration project is consistent with the natural form and processes of the river.     

Optimizing Liquid Effluent Monitoring at a Large Nuclear Complex

Effluent monitoring typically requires a large number of analytes and samples during the initial or startup phase of a facility. Once a baseline is established, the analyte list and sampling frequency may be reduced. Although there is a large body of literature relevant to the initial design, few, if any, published papers exist on updating established effluent monitoring programs. This paper statistically evaluates four years of baseline data to optimize the liquid effluent monitoring efficiency of a centralized waste treatment and disposal facility at a large defense nuclear complex. Specific objectives were to: (1) assess temporal variability in analyte concentrations, (2) determine operational factors contributing to waste stream variability, (3) assess the probability of exceeding permit limits, and (4) streamline the sampling and analysis regime. Results indicated that the probability of exceeding permit limits was one in a million under normal facility operating conditions, sampling frequency could be reduced, and several analytes could be eliminated. Furthermore, indicators such as gross alpha and gross beta measurements could be used in lieu of more expensive specific isotopic analyses (radium, cesium-137, and strontium-90) for routine monitoring. Study results were used by the state regulatory agency to modify monitoring requirements for a new discharge permit, resulting in an annual cost savings of US $223,000. This case study demonstrates that statistical evaluation of effluent contaminant variability coupled with process knowledge can help plant managers and regulators streamline analyte lists and sampling frequencies based on detection history and environmental risk.     

Simplified method for detecting tritium contamination in plants and soil

Cost-effective methods are needed to identify the presence and distribution of tritium near radioactive waste disposal and other contaminated sites. The objectives of this study were to (i) develop a simplified sample preparation method for determining tritium contamination in plants and (ii) determine if plant data could be used as an indicator of soil contamination. The method entailed collection and solar distillation of plant water from foliage, followed by filtration and adsorption of scintillation-interfering constituents on a graphite-based solid phase extraction (SPE) column. The method was evaluated using samples of creosote bush [Larrea tridentata (Sessé & Moc. ex DC.) Coville], an evergreen shrub, near a radioactive disposal area in the Mojave Desert. Laboratory tests showed that a 2-g SPE column was necessary and sufficient for accurate determination of known tritium concentrations in plant water. Comparisons of tritium concentrations in plant water determined with the solar distillation-SPE method and the standard (and more laborious) toluene-extraction method showed no significant difference between methods. Tritium concentrations in plant water and in water vapor of root-zone soil also showed no significant difference between methods. Thus, the solar distillation-SPE method provides a simple and cost-effective way to identify plant and soil contamination. The method is of sufficient accuracy to facilitate collection of plume-scale data and optimize placement of more sophisticated (and costly) monitoring equipment at contaminated sites. Although work to date has focused on one desert plant, the approach may be transferable to other species and environments after site-specific experiments.