Precipitation chloride at West Point,NY: Seasonal patterns and possible contributions from non-seawater sources

Chloride derived from the atmosphere can be a valuable tracer in ecosystem and watershed processes. For these purposes and other environmental studies, it is important to establish temporal patterns and sources for ${\mathrm{Cl}}^{-}$ in wet deposition. Weekly composite precipitation samples have been analyzed by the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) at West Point, NY during 1981–2003, although systematic contamination of precipitation ${\mathrm{Na}}^{+}$ significantly perturbed data for ${\mathrm{Na}}^{+}$ prior to 1998. Chloride and sodium ion seasonal wet deposition were highest in winter and lowest in summer through most of the record, probably as a result of more frequent marine-trajectory storms in winter. During 1998–2003, the period of highest quality ${\mathrm{Na}}^{+}$ data, the ratio of $[{\mathrm{Cl}}^{-}]/[{\mathrm{Na}}^{+}]$ was significantly higher than average in summer and lower in winter. Higher summer $[{\mathrm{Cl}}^{-}]/[{\mathrm{Na}}^{+}]$ occurred consistently throughout the record, often reaching values four times the seawater ratio. Based on the ratio of $[{\mathrm{Cl}}^{-}]/[{\mathrm{Na}}^{+}]$ in seawater $(1.16)\sim 16\%$ of annual wet deposition of ${\mathrm{Cl}}^{-}$ during 1998–2003 was in excess of that for surface seawater. Additionally, a minor terrestrial dust ${\mathrm{Na}}^{+}$ component was approximated, which had the net effect of increasing annual excess ${\mathrm{Cl}}^{-}$ wet deposition to $\sim 22\%$ ($2.56\mathrm{mEq}{\mathrm{m}}^{-2}$ or $0.90\mathrm{kg}{\mathrm{ha}}^{-1}$) of the mean annual ${\mathrm{Cl}}^{-}$ wet deposition at West Point ($11.9\mathrm{mEq}{\mathrm{m}}^{-2}$ or $4.2\mathrm{kg}{\mathrm{ha}}^{-1}$). Consistent with plausible sources of non-seawater ${\mathrm{Cl}}^{-}$, we attribute excess ${\mathrm{Cl}}^{-}$ wet deposition to HCl emission from coal fired generating stations, HCl emissions from domestic and industrial waste incineration and to HCl formation in the regional atmosphere from reactions of sea-salt aerosols with S and N acidic gases.     

Coarse particulate matter concentrations from residential outdoor sites associated with the North Carolina Asthma and Children's Environment Studies (NC-ACES)

Coarse particulate matter (PM${}_{10\text{-}2.5})$ concentration data from residential outdoor sites were collected using portable samplers as part of an exposure assessment for the North Carolina Asthma and Children's Environment Studies (NC-ACES). PM${}_{10\text{-}2.5}$ values were estimated using the differential between independent PM${}_{10}$ and PM${}_{2.5}$ collocated MiniVol measurements. Repeated daily 24-h integrated PM${}_{10}$ and PM${}_{2.5}$ residential outdoor monitoring was performed at a total of 26 homes during September 2003–June 2004 in the Research Triangle Park, NC area. This effort resulted in the collection of 73 total daily measurements. This assessment was conducted to provide data needed to investigate the association of exposures to coarse particle PM mass concentrations with observed human health effects. Potential instrument bias between the differential MiniVol methodology and a dichotomous sampler were investigated. Results indicated that minimal bias of PM${}_{10\text{-}2.5}$ mass concentration estimates (slope $=$ 0.8, intercept $=0.36\mathrm{\mu }$g m${}^{-3})$ existed between the dichotomous and differential MiniVol procedures. Residential outdoor PM${}_{10\text{-}2.5}$ mass concentrations were observed to be highly variable across measurement days and ranged from 1.1 to $12.6\mathrm{\mu }$g m${}^{-3}$ (mean of $5.4\mathrm{\mu }$g m${}^{-3})$. An average correlation coefficient of $r=0.75$ existed between residential outdoor PM${}_{10\text{-}2.5}$ mass concentrations and those obtained from the central ambient monitoring site. Temporal and spatial variability of PM${}_{10\text{-}2.5}$ mass concentrations during the study were observed and are described in this report.     

Observation and origin of organochlorine compounds and polycyclic aromatic hydrocarbons in the free troposphere over central Europe

On Zugspitze (2670 m a.s.l.), Alps, higher concentrations were observed during a winter than during a summer measurement campaign of PAHs, chlorobenzenes (43.6 vs. 2.0 pg m⁻³) and DDTs (3.7 vs. 1.2 pg m⁻³), while hexachlorocyclohexanes and PCBs were found at similar levels. The PCB, HCH and DDT levels are among the lowest ever reported from outside the Arctic. Mostly lower levels were found in samples collected in summer than in winter despite a significant boundary layer air influence, but no such influence on samples collected during the winter campaign. Boundary layer influence was quantified by Lagrangian particle dispersion model retroplume analyses. Photochemical lifetimes corresponding to k_OH < 1.5 × 10⁻¹² cm³ molec⁻¹ s⁻¹ are found for p,p′-DDT, k_OH < 0.75 × 10⁻¹² cm³ molec⁻¹ s⁻¹ for p,p′-DDE and k_OH < 1.0 × 10⁻¹² cm³ molec⁻¹ s⁻¹ for p,p′-DDD.     

Organochlorine pesticide in fresh and pasteurized cow's milk from Kampala markets

Fresh and pasteurized milk samples from Kampala markets were analyzed for organochlorine pesticides using a gas chromatograph equipped with an electron capture detector. Five organochlorine pesticides, namely; aldrin, dieldrin, endosulfan, lindane, DDT and its metabolites were detected in the milk samples and confirmed with a gas chromatograph equipped with a mass spectrometer [GC-MS]. The mean values are expressed in mg kg⁻¹ milk fat (mf) basis. The mean concentration in the fresh milk (n = 54) were: 0.026 ± 0.003 mg kg⁻¹ mf; 0.002 ± 0.0003 mg kg⁻¹, below the detection limit; 0.007 ± 0.003 mg kg⁻¹, 0.009 ± 0.002 mg kg⁻¹ milk fat for lindane, endosulfan dieldrin and aldrin, respectively. The mean concentrations of p,p′-DDE; p,p′-DDT and o,p′-DDT were 0.009 ± 0.002 mg kg⁻¹; 0.033 ± 0.007 mg kg⁻¹ and 0.008 ± 0.001 mg kg⁻¹ mf, respectively in the fresh milk samples.In the pasteurized milk samples (n = 47), the mean concentrations recorded were: 0.008 ± 0.003 mg kg⁻¹, 0.025 ± 0.004 mg kg⁻¹, and 0.007 ± 0.001 mg kg⁻¹, respectively for p,p′-DDE; p,p′-DDT and o,p′-DDT.Alpha and beta-endosulfan recorded the concentration below the detection limit and the mean of 0.022 ± 0.001 mg kg⁻¹ mf, 0.005 ± 0.002 mg kg⁻¹ mf, and 0.006 ± 0.0002 mg kg⁻¹ mf, respectively for lindane, dieldrin and aldrin. Although, most of the residues detected were above the residue limits set by the FAO/WHO (2008), bioaccumulation of these residues is likely to pose health risks to the consumers of milk in Uganda.     

The effects of parametric uncertainties in simulations of a reactive plume using a Lagrangian stochastic model

A combined Lagrangian stochastic model with micro-mixing and chemical sub-models is used to investigate a reactive plume of nitrogen oxides (NO_x) released into a turbulent grid flow doped with ozone (O₃). Sensitivities to the model input parameters are explored for different source NO_x scenarios. The wind tunnel experiments of Brown and Bilger (1996) provide the simulation conditions for the first case study where photolysis reactions are not included and the main uncertainties occur in parameters defining the turbulence scales, source size and reaction rate of NO with O₃. Using nominal values of the parameters from previous studies, the model gives a good representation of the radial profile of the conserved mean scalar ${\overline{\Gamma }}_{{\text{NO}}_{\text{x}}}$ although slightly over predicts peak mean NO₂ concentrations ${\overline{\Gamma }}_{{\text{NO}}_{\text{2}}}$ compared to the experiments. The high dimensional model representation (HDMR) method is used to investigate the effects of uncertainties in model inputs on the simulation of chemical species concentrations. For this scenario, the Lagrangian velocity structure function coefficient has the largest impact on simulated ${\overline{\Gamma }}_{{\text{NO}}_{\text{x}}}$ profiles. Photolysis reactions are then included in a chemical scheme consisting of eight reactions between species NO, O, O₃ and NO₂. Independent and interactive effects of 22 input parameters are studied for two source NO_x scenarios using HDMR, including turbulence parameters, temperature dependant rate parameters, photolysis rates, temperature, fraction of NO in total NO_x at the source and background ozone concentration [O₃]. For this reactive case, the variance in the predicted mean plume centre ${\overline{\Gamma }}_{{\text{O}}_{\text{3}}}$ is caused by parameters describing both physical (mixing time-scale coefficient) and chemical processes (activation energy for the reaction O₃+NO). The variance in predicted plume centre ${\overline{\Gamma }}_{{\text{NO}}_{\text{2}}}$ and root mean square NO₂ concentration ${\gamma }_{{\text{NO}}_{\text{2}}}^{\prime }$, is strongly influenced by the fraction of NO in the source NO_x, and to a lesser extent the mixing time-scale coefficient. Adjusting the latter gives improved agreement with the Brown and Bilger experiment. Some weak parameter interactions are observed.