Response of a grassland ecosystem to air pollutants. IV. The chemical climate: concentrations of relevant non-criteria pollutants (trace gases and aerosols)

The concentrations of sulphur dioxide, nitric acid, nitrous acid, hydrogen chloride, ammonia and sulphate, nitrate, chloride and ammonium in aerosols were measured continuously for two years at the rural site of Rotenkamp near Braunschweig in south-east Lower Saxony. The level of air pollution registered is typical for rural areas near industrial areas in Central Europe. Long-range transport of polluted air masses from Saxony-Anhalt and Saxony affects air quality when high-pressure areas over Eastern Europe result in easterly winds and reduced vertical exchange due to low inversion layers.     

Reevaluating Epidemiological Monitoring

For a two-year period, the chemistry of daily precipitation samples for a site in southern Indiana was analyzed for effect of seasons and synoptic storm types. The storms were classified as frontal, cyclonic, convective and other. Statistically significant (5 percent level) higher concentrations of sulfate, ammonium and hydrogen ion and lower sodium occurred in the warm seasons (April-September) than in the cold (October-March); nitrate, chloride and calcium concentrations were similar in both seasons. In general, convective and frontal storms contained the highest concentrations of ions, and cyclonic and other the lowest. Frontal storms showed significant higher sulfate, nitrate, ammonium and hydrogen ion and lower sodium in warm seasons than in cold, while cyclonic storms yielded significant (1 percent level) higher nitrate in the cold seasons. These results are generally consistent with the well-known behavior of the meteorological weather system categories.     

Observation based analysis for the determination of equilibrium time constant between ammonia, acid gases, and fine particles

Experimental measurements of ammonia, acid gases, and the inorganic components of atmospheric aerosols were made at a commercial hog farm in eastern North Carolina from May 1998 to June 1999 by an annular denuder system (ADS). The ADS consisted of a cyclone separator, one diffusion denuder coated with sodium carbonate, another diffusion denuder with citric acid, and a filter pack containing Teflon and nylon filters in series. The equilibrium time constant for transfer between ammonia, acid gases, and aerosol phase of ammonium nitrate and ammonium chloride was determined based on kinetic rate constants (k_N as the rate constant of ammonium nitrate aerosol: 2.04 × 10^-4 m³/µmole/sec; k_Cl as the rate constant of ammonium chloride aerosol: 3.44 × 10^-4 m³/µmole/sec) and the observed inorganic components of atmospheric aerosols. The equilibrium time constant was determined based on kinetic rate constants and the observed inorganic components of atmospheric aerosols. The equilibrium time constant has a wide range of values, with an average value of 15.26 (±10.94) minutes for ambient equilibrium time between ammonia, nitric acid gas and ammonium nitrate aerosol; and 8.22 (±6.81) minutes for ammonia, hydrochloric acid, and ammonium chloride. Significant correlations were determined between comparisons of equilibrium time constant estimates with meteorological parameters, such as ambient temperature and relative humidity. The predicted chemical compositions in the particle by EQUISOLV II Model are in good agreement with the observed chemical composition at the experimental site.     

Modeling Inorganic Aerosols and Their Response to Changes in Precursor Concentration in Mexico City

Abstract

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM_2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM_2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.     

Modeling inorganic aerosols and their response to changes in precursor concentration in Mexico City

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.     

Observational and modeling studies of chemical species concentrations as a function of raindrop size

The Guttalgor method has been used to determine the chemical species concentrations in size-selected raindrops in nine rain events at Hong Kong from 1999 to 2001. The curve (concentration against raindrop radius) patterns for all the species are similar but depend on the starting time of sampling within a rain event. In these plots, the maximum concentration occurs at the same range of droplet radius, irrespective of the species, and this indicates the importance of coalescence and breakup processes. The maximum is located at a smaller droplet radius than was found in previous studies in Germany. All results show almost constant concentrations with size for large raindrops, and these indicate the in-cloud contributions. The pH of raindrops of similar size is linearly correlated with a function of the sulfate, nitrate, acetate, formate, calcium and ammonium ion species concentrations. Within a single raindrop, chloride depletion is not significant, and sulfate, ammonium and hydrogen ions are found in ratios compatible with the precursor solid-phase mixture of ammonium sulfate and ammonium bisulphate. When simulated by a below-cloud model, good agreement between the modeled and measured sodium and sulfate concentrations has been found. Below-cloud sulfur dioxide scavenging contributes at most 60% of the sulfate concentration in a single raindrop.     

Chemical coupling between ammonia, acid gases, and fine particles

The concentrations of inorganic aerosol components in the fine particulate matter (PM(fine)< or =2.5 microm) consisted of primarily ammonium, sodium, sulfate, nitrate, and chloride are related to the transfer time scale between gas to particle phase, which is a function of the ambient temperature, relative humidity, and their gas phase constituent concentrations in the atmosphere. This study involved understanding the magnitude of major ammonia sources; and an up-wind and down-wind (receptor) ammonia, acid gases, and fine particulate measurements; with a view to accretion gas-to-particle conversion (GTPS) process in an agricultural/rural environment. The observational based analysis of ammonia, acid gases, and fine particles by annular denuder system (ADS) coupled with a Gaussian dispersion model provided the mean pseudo-first-order k(S-1) between NH(3) and H(2)SO(4) aerosol approximately 5.00 (+/-3.77)x10(-3) s(-1). The rate constant was found to increase as ambient temperature, wind speed, and solar radiation increases, and decreases with increasing relative humidity. The observed [NH(3)][HNO(3)] products exceeded values predicted by theoretical equilibrium constants, due to a local excess of ammonia concentration.     

Vapour pressure of ammonium chloride aerosol: Effect of temperature and humidity

The effect of relative humidity (RH) on the constant for dissociation of ammonium chloride into gaseous HCl and NH₃ has been estimated for different temperatures, using thermodynamic data. At RH over 75–85% the ammonium chloride aerosol exists in the liquid phase, with the dissociation constant two orders of magnitude lower at 98% RH than for solid aerosol at the same temperature. It is predicted that ammonium chloride aqueous aerosol forms predominantly in fogwater and cloud droplets, and in regions where local emissions of NH₃ are important.     

Ammonium Nitrate,Nitric Acid,and Ammonia Equilibrium in Wintertime Phoenix,Arizona

A secondary aerosol equilibrium model, SEQUILIB, is applied to evaluate the effects of emissions reductions from precursor species on ambient concentrations during the winter in Phoenix, Arizona. The model partitions total nitrate and total ammonia to gas-phase nitric acid and ammonia and to particle-phase ammonium nitrate. Agreement between these partitions and ambient measures of these species was found to be satisfactory. Equilibrium isopleths were generated for various ammonium nitrate concentrations corresponding to high and low humidity periods which occurred during sampling. These diagrams show that ammonia is so abundant in Phoenix that massive reductions in its ambient concentrations would be needed before significant reductions in particulate ammonium nitrate would be observed. When total nitrate is reduced by reductions in its nitrogen oxides precursor, proportional reductions in particulate nitrate are expected. Many of the complex reactions in SEQUILIB do not apply to Phoenix, and its ability to reproduce ambient data in this study does not guarantee that it will be as effective in areas with more complex chemistry. Nevertheless, the nitrate chemistry in SEQUILIB appears to be sound, and it is a useful model for addressing the difficult apportionment of secondary aerosol to its precursors.     

Control of ammonia toxicity to Hyalella azteca by sodium, potassium and pH

The toxicity of ammonia to Hyalella azteca at constant pH in artificial media was controlled by sodium and potassium, and not by calcium, magnesium, or anions. Small increases in the LC50 for total ammonia (from 0.15 to 0.5 mM) occurred as sodium was increased from 0.1 to 1 mM and above, but major increases in the LC50 (to over 10 mM total ammonia) required the addition of potassium. Potassium was, however, more effective at reducing ammonia toxicity at high (1 mM) sodium than at low (0.1 mM) sodium. Ammonia toxicity was independent of pH at low sodium and potassium concentrations, when ammonia toxicity appeared to be associated primarily with aqueous ammonium ion concentrations. At high sodium and potassium concentrations, the toxicity of ammonia was reduced to the point where un-ionized ammonia concentrations also affected toxicity, and the LC50 became pH dependent. A mathematical model was produced for predicting ammonia toxicity from sodium and potassium concentrations and pH.     

Ammonia flux from open-lot dairies: development of measurement methodology and emission factors

Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 microg m(-3) and from 2 to 43% of total PM2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head(-1) day(-1), showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.     

Sublethal ammonia exposure of Nile tilapia (Oreochromis niloticus L.): effects on gill, liver and kidney histology

The effects of exposures to sublethal ammonia concentrations on Nile tilapia (Oreochromis niloticus L.) were determined with respect to histology. The experiments were conducted for six weeks and with four different ammonia concentrations (control, 1, 2, 5, 10 mg l(-1) TA-N). Fish exposed to different ammonia concentrations displayed histopathologic alterations in the gills, liver and kidney. Gill tissues displayed hyperemia, chloride cell proliferation, fusion in secondary lamella, telangiectasis. Liver tissue revealed cloudy swelling and hydropic degeneration, whereas in kidney tissues hyperemia and glomerulonephritis were observed.     

Chronic toxicity of ammonia to the amphipod Hyalella azteca; Importance of ammonium ion and water hardness

Ammonia toxicity resulted in the continuous mortality of Hyalella azteca for up to 10 weeks with similar mortality rates for adults and young. Growth was not reduced at concentrations below those causing chronic mortality (1 mM total ammonia in Lake Ontario water), but reproduction was reduced at concentrations as low as 0.32 mM. Chronic mortality was a function of total ammonia (or ammonium ion), and not un-ionized ammonia, when the pH was adjusted by addition of acid. However, a 1 in 10 dilution of Lake Ontario water in distilled water resulted in a 10-fold reduction in the 4 week LC50. In contrast to common practice, ammonia toxicity to Hyalella is best defined on a total ammonia basis, but variations in hardness and other ions must be taken into account.     

Indoor-outdoor relationship of suspended particulate matter and its chemical composition at different sizes

The indoor-outdoor concentration relationship of particulate matter PM_9.0 (aerodynamic diameter 9 μm or smaller) and its chemical composition (sulfate, nitrate, chloride and ammonium) has been studied. Samples were collected using four identical Anderson impactors, each one collecting nine size ranges by eight impactor stages (9, 5.8, 4.7, 3.3, 2.1, 1.1, 0.65 and 0.43 μm) plus a back-up filter representing particles finer than 0.45 μm. Concentrations of sulfate, nitrate and chloride were determined by ion chromatography, and an ammonium-selective ion electrode plus a Corning pH ion meter were used to determine ammonium ion. The results revealed that sulfate was the predominant component and chloride the least abundant. The size distribution of sulfate, nitrate and ammonium very strongly peaked near 0.65 μm and with very little at the larger sizes. The chloride concentration was depleted in the fine particles and enhanced in the relatively coarser particles, with the peak at 3.3 μm. All these concentrations had a significant linear relationship with mass concentrations in outdoor samples. In indoor samples, the same relation was observed only for sulfate and ammonium, which were also significantly correlated with each other. Furthermore, indoor sulfate, chloride and ammonium concentrations were higher towards the finest particle sizes, indicating a higher potential inhalation health hazard. The study also confirmed that indoor air quality depends on outdoor atmospheric pollution level, indoor activities and virtually on the particle size. Finally, the study would assist in selecting the type of collector required to reduce the level of particulates to an acceptable level for indoor ambient air.     

城市污水处理厂除臭生物滤池运行效果及影响因素研究

对山东某城市污水处理厂散发的恶臭气体进行除臭研究,考察了除臭生物滤池的运行效果、工艺影响因素和除臭生物滤池内微生物相特点。结果表明:(1)在进气量为828 m3/h、气体停留时间为30 s、硫化氢和氨进气质量浓度分别为0.5~28.4、0.9~34.3 mg/m3的条件下,稳定运行时,大部分时间硫化氢和氨去除率分别达98%和80%以上,而且除臭生物滤池对于进气负荷具有较强的抗冲击能力。(2)当填料含湿量为43.6%~63.4%时,硫化氢去除率在90%以上;氨去除受填料含湿量的影响较大,填料含湿量越高越利于氨的去除。(3)在处理低浓度含硫化氢和氨的恶臭气体时,生物除臭工程可以在低填料pH(3.0左右)下长期运行,并保持较高的恶臭气体去除率。(4)运行第60天后,当温度为10℃以上时,硫化氢和氨去除率几乎不受影响;第169天后,当温度降至10℃以下时,硫化氢和氨去除率均有一定程度的下降,最低分别为94.6%和79.8%。(5)除臭生物滤池稳定运行时,优势硫氧化菌主要为嗜酸性硫细菌。     

Instrument development and application in studies and monitoring of ambient ammonia

During recent years, it has become clear that ammonia is an important gas in relation to different environmental issues, such as acidification, eutrophication, human health and climate change (through particle formation). Therefore, there is a growing need to develop and apply instrumentation suitable for research into emission, dispersion, conversion and deposition of ammonia and ammonium. Recently, several instruments were developed suitable for measuring concentrations in ambient conditions even at very low levels, such as ammonia sensors suitable for monitoring and research, deposition measuring systems and aerosol samplers for on-line measurement of aerosol composition. These instruments have been tested and applied in a number of field studies. These studies include dry deposition measurements, ammonium nitrate studies in relation to the (in)direct aerosol effect, emission studies and policy evaluation with concentration and deposition monitoring data. The policy evaluation study showed that the measures to reduce ammonia emissions were not as successful as projected beforehand by statistical studies.     

天然沸石吸附氨氮的影响因素

对比研究了沸石对生活污水和人工配制氯化铵溶液中氨氮的吸附特性,考察了沸石投加量、反应时间、悬浮物、阳离子和阴离子对沸石吸附氨氮的影响。结果表明,沸石对生活污水中氨氮的吸附能力明显低于人工配制氯化铵溶液,氨氮去除率随着沸石投加量的增加而增加,但单位质量沸石的氨氮吸附量却随之减小,吸附过程呈现快速吸附,缓慢平衡的特点。生活污水中悬浮物的存在,会削减沸石对氨氮的吸附能力。不同类型的阳离子和阴离子的加入都能导致人工配制氯化铵溶液中氨氮在沸石上的吸附量存在差异。阳离子的影响趋势主要为价态的影响,即价态越高,对氨氮吸附阻碍作用越显著,当阳离子当量浓度〉2meq／L时,影响吸附强弱的顺序为Ca2＋〉Mg2＋ 〉Na＋;阴离子影响沸石吸附强弱的顺序受初始氨氮的浓度影响较大。Langmuir等温方程式较Freundich、DubininRadushkevich、KobleCorrigan和Temkin等温方程式更好地描述沸石吸附氨氮的行为。     

Ammonia Flux from Open-Lot Dairies: Development of Measurement Methodology and Emission Factors

Abstract

Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 μg m^?3 and from 2 to 43% of total PM_2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head^?1 day^?1, showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.     

Modelling the formation and atmospheric transport of secondary inorganic aerosols with special attention to regions with high ammonia emissions

Regional simulations of sulfate, nitrate and ammonium aerosols were performed by a nested application of the online-coupled three-dimensional Eulerian model system COSMO-MUSCAT. This was done in a domain covering the northern part of Germany and surrounding regions for the full month of May and a 6-week period in August/September 2006 with the primary focus on secondary inorganic aerosol levels caused by ammonia emissions from domesticated animals and agricultural operations.The results show that in situations with westerly winds ammonium nitrate dominates with concentrations of about 5–10 μg m^?3 whereas the ammonium sulfate concentrations are about 5 μg m^?3. In situations with winds mainly from the East characterized by warmer and dryer air the ammonium sulfate concentrations have their maximum at about 10 μg m^?3 whereas at the same time no ammonium nitrate is present.A reduction of agricultural NH₃ emissions by 50% in a regional scale reduces the ammonium nitrate concentrations to a maximum of 30%, while the ammonium sulfate concentrations are unchanged. The reduction of NH₃ emissions in a more limited area (here in the Federal state of Germany Niedersachsen) does have no noticeable effect neither on ammonium sulfate nor on ammonium nitrate.     

Continued development of a general equilibrium model for inorganic multicomponent atmospheric aerosols

A model is presented that predicts the total quantities of ammonium, chloride, nitrate and water contained in atmospheric aerosols, their physical state and their distribution among aerosol particles of different sizes. The model is based on the thermodynamic equilibrium calculation of the ammonium/chloride/nitrate/sodium/sulfate/water system. The existence of water in the aerosol phase at low relative humidities is shown to be explained. Observed aerosol concentrations at Long Beach, California during 30–31 August 1982 are successfully predicted.