Retained nitrate, hydrated sulfates, and carbonaceous mass in federal reference method fine particulate matter for six eastern U.S. cities

Material balance of fine particulate matter (PM2.5) measured with the Federal Reference Method (FRM) is developed for one rural and five urban locations in the eastern half of the United States using routine Speciation Trends Network (STN) and FRM chemical measurements and thermodynamic models. The Aerosol Inorganics Model is used to estimate retained particle bound water, and an ammonium nitrate evaporation model is used to estimate nitrate concentrations retained on the Teflon-membrane filter of the FRM. To address large uncertainties in carbonaceous mass calculated from STN carbon measurements, retained carbonaceous mass is derived by material balance between PM2.5 FRM mass and estimates of its non-carbon constituents. The resulting sulfate, adjusted nitrate, derived water, inferred carbonaceous material balance approach (SANDWICH) is compared with reconstructed fine mass (RCFM) using the Interagency Monitoring of Protected Visual Environments monitoring program equation. For this study, the SANDWICH method resulted in approximately 21-27% higher sulfate mass and approximately 24-85% lower nitrate mass. The combined mass associated with sulfates and nitrates, however, are well within +/- 10% of the proportion derived using the more traditional RCFM method. The discrepancies between SANDWICH and measurement-derived carbonaceous mass vary from -21% to +56% on an annual basis and are attributed in part to urban-rural source influences and uncertainties in estimating FRM-retained carbonaceous mass.     

Adding complex trophic interactions to a size-spectral plankton model: Emergent diversity patterns and limits on predictability

A new model in the NPZ (nutrient-phytoplankton-zooplankton) style is presented, mechanistically simple but with 40 size classes each of phytoplankton (1-20 μm) and small zooplankton (2.1-460 μm), in order to resolve one level of trophic interactions in detail. General, empirical allometric relationships are used to parameterize both the optimal prey size and size selectivity for each grazer class, as is rarely done. This inclusion of complex predator-prey linkages and realistic prey preferences yields a system with an emergent pattern of phytoplankton diversity consistent with global ocean observations, i.e., a parabolic relationship between diversity (as measured by the Shannon evenness) and biomass. It also yields significant long-term time evolution, which places limits on the extent to which the community response to nutrient forcing can be predicted from forcing in a pragmatic sense. When a simple annual cycle in nutrient supply is repeated exactly for many years, transient fluctuations up to a factor of two in spring bloom magnitude persist for 10-20 years before a stable seasonal biomass cycle is achieved. When the amplitude of the nutrient-supply annual cycle is given a random interannual modulation, these long-lived transients add significant noise to a 100-year correlation between annual-mean nutrient supply and annual-mean biomass. This noise is 20% of total interannual variance in the model base case, and ranges from 0% to 40% depending on the grazer size selectivity. In general, unpredictability on the bloom timescale is damped when food-web complexity is increased by making grazers less selective, while unpredictability on the interannual scale shows the opposite pattern, increasing with increasing food-web complexity up to a high threshhold, past which community structure and biomass time evolution both suddenly simplify. These results suggests a new strategy for ensemble ecosystem forecasting and uncertainty estimation, analogous to methods common in circulation and climate modeling, in which internal variability (predator-prey interactions in the biological case; eddies and climate-system oscillations in the physical case) are resolved and quantified, rather than suppressed.     

Determination of response of real-time SidePak AM510 monitor to secondhand smoke, other common indoor aerosols, and outdoor aerosol

The amount of light scattered by airborne particles inside an aerosol photometer will vary not only with the mass concentration, but also with particle properties such as size, shape, and composition. This study conducted controlled experiments to compare the measurements of a real-time photometer, the SidePak AM510 monitor (SidePak), with gravimetric mass. PM sources tested were outdoor aerosols, and four indoor combustion sources: cigarettes, incense, wood chips, and toasting bread. The calibration factor for rescaling the SidePak measurements to agree with gravimetric mass was similar for the cigarette and incense sources, but different for burning wood chips and toasting bread. The calibration factors for ambient urban aerosols differed substantially from day to day, due to variations in the sources and composition of outdoor PM. A field evaluation inside a casino with active smokers yielded calibration factors consistent with those obtained in the controlled experiments with cigarette smoke.     

A further case with a small supernumerary marker chromosome (sSMC) derived from chromosome 1—evidence for high variability in mosaicism in different tissues of sSMC carriers

A prenatally ascertained case with a de novo small supernumerary marker chromosome (sSMC) derived from chromosome 1 is reported. Due to a fetal heart defect the parents decided in favour of an induced abortion. Postmortem, a molecular cytogenetic study on eleven formalin fixed, paraffin-embedded tissues of the fetus was performed, to further characterize the levels of mosaicism of the sSMC(1). sSMC presence varied between 13 and 62% within different tissues of sSMC carriers. This finding is something common in sSMC carriers and could explain why up to the present no clinical correlations for sSMC mosaicism and clinical outcome in the corresponding carriers could be established. Copyright © 2007 John Wiley & Sons, Ltd.     

A review of the significance and formation of chlorinated N-organic compounds in water supplies including preliminary studies on the chlorination of alanine,tryptophan, tyrosine,cytosine, and syringic acid

Nitrogenous organic compounds are of environmental significance because of their potential as both trihalomethane (THM) and nonpurgeable organic halide (NPOX) precursors. They additionally lead to falsely positive tests for free available chlorine (FAC) and are components in the reaction of chlorine to form dihaloacetonitriles (DHANs). A large number of naturally occurring nitrogenous compounds additionally react readily with aqueous chlorine exerting significant chlorine demand. Such reactions generally involve the substitution of chlorine for hydrogen on a nitrogen atom. Additionally, N-chloroorganic materials may be produced even when the precursor concentration is low owing to the rapid specific rate of formation. While previous attention has been largely focused on nonpolar chlorinated organic contaminants such as THMs, the wide distribution of N-organic compounds in water, as well as their general reactivity towards aqueous chlorine, warrant further attention and study to this group of materials. Preliminary studies on the chlorination of several N-organic compounds at a few chlorine-to-compound molar ratios at pH 7 and 4.7 over several reaction intervals are presented. NPOX formation was quite rapid and comprised the greatest proportion of the total organic halide formed for the conditions studied.     

Constructed Wetland Treatment of Nitrates: Removal Effectiveness and Cost Efficiency

A constructed wetland (CW) was strategically placed to treat nitrates in groundwater as part of a watershed‐based farmer engagement process. Using stream water quality data collected before and after installation, this CW was found to reduce stream concentrations of nitrogen from nitrate (NO₃‐N) during the growing season by about 0.14 mg/l at mean streamflow, a 17% reduction. Based upon realistic ecological and economic assumptions, about 80 kg of NO₃‐N were removed annually by the CW at a cost of around US$30/kg. This per unit cost is at the low range of small wastewater treatment plant costs for nitrates, but higher than the costs of reduced fertilizer application.