Ammonia and ammonium measurements from the southeastern United States

Twenty-four-hour integrated gaseous ${\mathrm{NH}}_3$ and fine particulate $({\mathrm{PM}}_{2.5}){\mathrm{NH}}_4^{+}$ were measured during 2004 at eight sites in the southeastern U.S. Mean ${\mathrm{NH}}_3$ concentrations for 2004 ranged from 2.44 ppbv at an urban-industrial site in North Birmingham, AL, to 0.23 ppbv at a rural-forested site near Centreville, AL. ${\mathrm{NH}}_3$ mixing ratios were found to be higher at urban sites than at nearby rural (or suburban sites) except for sites which were directly influenced by local sources. Only weak correlations with temperature were observed for ${\mathrm{NH}}_3$ at the sites; slightly greater correlations were observed for total ammonia $({\mathrm{NH}}_x={\mathrm{NH}}_3+{\mathrm{NH}}_4^{+})$ vs. temperature. A weak seasonal variation was observed for ${\mathrm{NH}}_3$ mixing ratios at all sites, with all but one site exhibiting biannual maxima in spring and late summer/fall. Mean ${\mathrm{PM}}_{2.5}$ ${\mathrm{NH}}_4^{+}$ concentrations ranged from $1.78\mathrm{\mu }\mathrm{g}{\mathrm{m}}^{-3}$ in Atlanta, GA, to $1.02\mathrm{\mu }\mathrm{g}{\mathrm{m}}^{-3}$ at Oak Grove, MS, and were more uniform across the network than ${\mathrm{NH}}_3$ mixing ratios, with only slightly larger values at urban sites as compared to nearby rural (or suburban) sites. All sites exhibited highest ${\mathrm{NH}}_x$ between July and September and lowest ${\mathrm{NH}}_x$ in November and December. The gaseous ${\mathrm{NH}}_3$ fraction $({\mathrm{NH}}_3/({\mathrm{NH}}_3+{\mathrm{NH}}_4^{+}))$ was observed to decrease with increasing values of ${\mathrm{PM}}_{2.5}$ ${\mathrm{SO}}_4^{2-}$ at all sites. At two rural-forested sites and two sites near the Gulf of Mexico, the ${\mathrm{NH}}_3$ gaseous fraction approached a relatively constant value of 5–10% as ${\mathrm{PM}}_{2.5}{\mathrm{SO}}_4^{2-}$ increased beyond 5–$7\mathrm{\mu }\mathrm{g}{\mathrm{m}}^{-3}$, suggesting that ${\mathrm{NH}}_3$ availability at these locations limits aerosol neutralization.     

Perennial observations of molecular hydrogen (H2) at a suburban site in Switzerland

Semi-continuous measurements of atmospheric molecular hydrogen $({\mathrm{H}}_2)$ and carbon monoxide (CO) were performed at a suburban sampling site in Switzerland from November 2002 to February 2005. The presented data provide information about time series, seasonal and diurnal cycles as well as sources and sinks in a suburban environment. Such records become increasingly important for the assessment of the effects of a possible future hydrogen economy on the environment. No significant trend of background ${\mathrm{H}}_2$ concentrations could be observed for the considered period. Seasonal cycles show the expected pattern with maxima in winter and minima in summer and autumn. When extracting the background ${\mathrm{H}}_2$ mixing ratios, the absolute levels as well as the seasonal amplitude agree well with literature data from semi-rural and remote sites. The ${\mathrm{H}}_2$ dry deposition velocity for summer days with low winds is estimated to be between $0.5\times {10}^{-4}$ to $1\times {10}^{-4}\mathrm{m}{\mathrm{s}}^{-1}$. Diurnal cycles are dominated by ${\mathrm{H}}_2$ emissions from nearby traffic. The influence of traffic-related emissions is also corroborated by a high ${\mathrm{H}}_2$ to CO correlation. Typical molar ${\mathrm{H}}_2$ to CO ratios from traffic were found to be 0.33 on a molar basis (ppb/ppb). A reduction of 37–62% in European anthropogenic ${\mathrm{H}}_2$ emissions is estimated for a period covering the last 25 years. Since the ambient ${\mathrm{H}}_2$ concentration did not decline during the same period, other simultaneous changes of sinks or sources of ${\mathrm{H}}_2$ must have compensated this reduction.     

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.     

Quantifying Asian and biomass burning sources of mercury using the Hg/CO ratio in pollution plumes observed at the Mount Bachelor observatory

Total airborne mercury (TAM) and carbon monoxide (CO) were measured in 22 pollution transport “events” at Mt. Bachelor Observatory (MBO), USA (2.8 km asl) between March 2004 and September 2005. Submicron particulate scattering (${\sigma }_{\mathrm{sp}})$, ozone (${\mathrm{O}}_3)$, and nitrogen oxides (${\mathrm{NO}}_y)$ were also measured and enhancement ratios for each chemical and aerosol species with CO were calculated. Events were categorized based on their source regions, which were determined by a combination of back trajectories, satellite fire detections, chemical and aerosol enhancement ratios, and meteorology. The mean $\mathrm{\Delta }\mathrm{TAM}/\mathrm{\Delta }\mathrm{CO}$ values for each source region are: East Asian industrial ($0.0046\pm 0.0013\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=10$ events, 236 h), Pacific Northwest U.S. (PNW) biomass burning ($0.0013\pm 0.008\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=7$ events, 173 h), and Alaska biomass burning ($0.0014\pm 0.0006\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=3$ events, 96 h). The $\mathrm{\Delta }\mathrm{TAM}/\mathrm{\Delta }\mathrm{CO}$ means from Asian long-range transport (ALRT) and biomass burning events are combined with previous estimates of CO emissions from Chinese anthropogenic, global biomass burning, and global boreal biomass sources in order to estimate the emissions of gaseous elemental mercury (GEM) from these sources. The GEM emissions that we calculate here are: Chinese anthropogenic ($620\pm 180\mathrm{t}{\mathrm{y}}^{-1}$), global biomass burning $(670\pm 330\mathrm{t}{\mathrm{y}}^{-1})$, and global boreal biomass burning $(168\pm 75\mathrm{t}{\mathrm{y}}^{-1})$, with errors estimated from propagating the uncertainty in the mean enhancement ratios and CO emissions. A comparison of our results with published mercury (Hg) emissions inventories reveals that the Chinese GEM emissions from this study are higher by about a factor of two, while our estimate for global biomass burning is consistent with previous studies.     

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.     

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.     

好氧颗粒污泥的特点及其研究进展

综述了好氧颗粒污泥的基本特征和微生物相、好氧颗粒污泥形成的主要影响因素及其颗粒化反应器等。好氧颗粒污泥是近几年发现的在好氧条件下自发形成的细胞自身固定化过程 ,是生物膜特殊的生长形式。颗粒污泥具有良好的沉降性能、较高的生物量和在高容积负荷条件下降解高浓度有机废水的良好生物活性。污泥颗粒化过程是一个多阶段的过程 ,取决于废水组成及其操作条件的选择。在气提式内循环间歇反应器 (internalcirculatesequencingbatchairliftreac tor ,ICSBAR )中易于培养出性能良好的好氧颗粒污泥。     

铁炭微电解-MAP沉淀法联合预处理垃圾渗滤液

采用铁炭微电解-磷酸氨镁(MAP)沉淀法对垃圾渗滤液进行预处理,实验结果表明,铁炭比为5∶1,pH值为3,反应时间为3 h时,铁炭微电解的COD的去除率为47.5%;在投加药剂n(Mg2+)∶n(PO43-)∶n(NH4+)为1.4∶1∶1,pH值为9,反应时间为1 h的条件下,垃圾渗滤液氨氮去除率达到79.7%。     

Photochemistry and environment IV- Photochemical behaviour of monochlorophenols in dilute aqueous solution

The photochemical behaviour of chlorophenols is different to that of non-halogenated phenols. In the former, the first step is a C-Cl bond scission, which is not influenced by oxygen. Chlorine is converted into hydrochloric acid. For monochlorophenols, the position of the chlorine on the ring strongly influences the transformation. In the molecular form, 2-chlorophenol is converted into pyrocatechol. In the anionic form however, it is reduced in a cyclopentadienic acid which dimerizes according to a Diels-Alder reaction. The irradiation of 3-chlorophenol leads to resorcinol whatever the pH. This would appear to suggest a photohydrolysis mechanism. With 4-chlorophenol, the photochemical conversion is not so specific. Hydroquinone is formed (mainly in aerated solution), along with polyphenolic oligomers. A radical mechanism is proposed.