The uptake of cadmium and zinc by the bird-cherry oat aphid Rhopalosiphum padi (Homoptera:Aphididae) feeding on wheat grown on sewage sludge amended agricultural soil

A greenhouse trial investigated the uptake of cadmium and zinc by the bird-cherry oat aphid (Rhopalosiphum padi) feeding on wheat grown on sewage sludge amended soil. The trial was conducted at application rates of 0, 5, 7.5, 10, 15 and 20 tonnes ha(-1) dry solids. Concentrations of Cd and Zn were within current UK limits for potentially toxic elements in soils amended with sewage sludge. Cd and Zn in wheat plants were significantly greater than controls. Batches of aphids feeding on the wheat also showed a significant increase in the uptake of Cd and Zn. This study demonstrates a potential route of exposure to Cd and Zn for the predators of cereal aphids.     

Problems of quality designation in diffusely polluted urban streams - the case of Pymme's Brook, north London

Downstream patterns in the biology and bacteriology of Pymme's Brook (north London) between 1985 and 1992, are compared with the local Environment Agency (EA, England and Wales) quality classification of the site, revealing a considerable discrepancy. Although downstream contaminant dispersal patterns showed that at low flow the brook was less successful in absorbing contaminants at polluted surface water outfall (PSWO) entry points than it was at high flow (supporting the low flow strategy of contemporary audit schedules), this effect was found to vary downstream in response to reoxygenation from less polluted outfalls. Additionally, temporal variations in suspended solids, Escherichia coli counts, sediment-bound and soluble pollutant concentrations at low flow, and during two sampled storms, revealed that significant pollutant transfer was concentrated in the 'first flush' of storm events. A downstream survey of sediment-bound lead (Pb) found that concentrations in the bed sediments, which were likely to be mobilised during a first flush, were significantly higher than in solution. So, a complex pattern of downstream contaminant dispersal emerges, which varies with differing antecedent conditions, and through storms. These results indicate that: (1) the new General Quality Assessments (GQA) audit schedule proposed by the EA for England and Wales remains inappropriate for diffusely polluted, urban environments, because it omits routine E. coli counts and sediment-bound heavy metals; and that (2) when audit is based on chemical determinants alone, the choice of site and timing of audit excessively influence quality designations. Pre-audit planning surveys and more reliable alternatives to the use of chemical audit for urban watercourses, are discussed as possible ways forward for the design of quality audit schedules. Implications for the monitoring schedules in operation in other EU countries and the USA are also considered.     

Comparing estimates of fugitive landfill methane emissions using inverse plume modeling obtained with Surface Emission Monitoring (SEM), Drone Emission Monitoring (DEM), and Downwind Plume Emission Monitoring (DWPEM)

ABSTRACT

As part of the global effort to quantify and manage anthropogenic greenhouse gas emissions, there is considerable interest in quantifying methane emissions in municipal solid waste landfills. A variety of analytical and experimental methods are currently in use for this task. In this paper, an optimization-based estimation method is employed to assess fugitive landfill methane emissions. The method combines inverse plume modeling with ambient air methane concentration measurements. Three different measurement approaches are tested and compared. The method is combined with surface emission monitoring (SEM), above ground drone emission monitoring (DEM), and downwind plume emission monitoring (DWPEM). The methodology is first trialed and validated using synthetic datasets in a hand-generated case study. A field study is also presented where SEM, DEM and DWPEM are tested and compared. Methane flux during two-days measurement campaign was estimated to be between 228 and 350 g/s depending on the type of measurements used. Compared to SEM, using unmanned aerial systems (UAS) allows for a rapid and comprehensive coverage of the site. However, as showed through this work, advancement of DEM-based methane sampling is governed by the advances that could be made in UAS-compatible measurement instrumentations. Downwind plume emission monitoring led to a smaller estimated flux compared with SEM and DEM without information about positions of major leak points in the landfill. Even though, the method is simple and rapid for landfill methane screening. Finally, the optimization-based methodology originally developed for SEM, shows promising results when it is combined with the drone-based collected data and downwind concentration measurements. The studied cases also discovered the limitations of the studied sampling strategies which is exploited to identify improvement strategies and recommendations for a more efficient assessment of fugitive landfill methane emissions.

Implications: Fugitive landfill methane emission estimation is tackled in the present study. An optimization-based method combined with inverse plume modeling is employed to treat data from surface emission monitoring, drone-based emission monitoring and downwind plume emission monitoring. The study helped revealing the advantages and the limitations of the studied sampling strategies. Recommendations for an efficient assessment of landfill methane emissions are formulated. The method trialed in this study for fugitive landfill methane emission could also be appropriate for rapid screening of analogous greenhouse gas emission hotspots.     

Effect of mercury on the survival,respiration, and growth of postlarval white shrimp,Penaeus setiferus

The results of toxicity experiments have shown that a level of 17 ppb ionic mercury is acutely toxic (96-h LC₅₀) to postlarval white shrimp (Penaeus setiferus). In addition, the size of the shrimp, within the range tested (7 to 35 mm) did not significantly alter the toxicity values of mercury to this species. Fifty-seven days pre-exposure to low levels of mercury (0.5 and 1.0 ppb) had no effect on the acute toxicity (96-h LC₅₀) of mercury to the shrimp. The effect of chronic exposure to low levels of mercury on the respiratory rate, growth, and molting rate of postlarval P. setiferus was studied, and the results showed that 60 days exposure to 0.5 and 1.0 ppb mercury did not significantly affect any of these parameters for the postlarvae.     

A critical evaluation of combustible/explosible dust testing methods – Part 1

Tests were conducted by the Center for Agricultural Air Quality Engineering and Science (CAAQES) and by Safety Consulting Engineers Inc. (SCE) to determine if dust found in cotton gins (gin dust) would serve as fuel for dust explosions. In other words, is gin dust explosible? The laboratory tests used by CAAQES and SCE are very different. SCE used a totally enclosed 20 liter (L) chamber, flame from a 10,000 J (10 kJ) ignition source, reported that gin dust was a class ‘A’ explosible dust. CAAQES used a 28.3-L (1 ft³) chamber with diaphragm, a stationary coil as the igniter, video and pressure recordings of each test and concluded that gin dust was not explosible. SCE followed the protocols specified by ASTM E1226 and E1515. The only indicator used to determine whether a deflagration occurred during a test was pressure. If the pressure rise exceeded one bar gage (g) in a 20-L chamber test with a flame from a 10 kJ energy source as the igniter, it was assumed that a deflagration occurred in the chamber and the dust was classified as explosible (ASTM E1226-05, 2005). The CAAQES criterion for determining if a dust was explosible consisted of determining the minimum explosive concentration (MEC). If the MEC existed using the CAAQES test system, it was explosible! The criteria used with the CAAQES method for determining the MEC was to test concentrations starting at concentrations above the MEC and lowering the concentrations until at least one of the three tests at that concentration failed to result in a deflagration. The indicators of a deflagration were (1) bursting of a diaphragm, (2) flame front leaving the chamber and (3) characteristic pressure vs. time curve.It was concluded that the ASTM method of using only pressure as the indicator of a deflagration in a totally enclosed chamber would likely result of an “over-driven” test and an incorrect finding that gin dust was explosible. The result of CAAQES testing was that gin dust was not explosible.