Acidity and conductivity of precipitation on central Long Island,New York in relation to meteorological variables

Three years of hourly sequential precipitation samples from central Long Island, New York were analyzed to determine the relationships between acidity and conductivity and concentrations of sulfate, nitrate plus nitrite, nitrogen in ammonium, sodium, and chloride ions. Relationships between precipitation acidity and meteorological conditions were also studied. Hydrogen ion concentrations are similar to those elsewhere in the northeastern United States. They are best correlated with sulfate concentrations but also correlate with concentrations of nitrogen in nitrate plus nitrite and nitrogen in ammonium ion. Concentrations are highest in the summer, with cold front and squall line precipitation and with rain showers and thundershowers. All ions measured contributed to sample conductivity but hydrogen ion contributed the most with sulfate ion second. Conductivity calculated from concentrations of the separate ions agreed well with measured conductivity. Conductivity showed relationships to meteorological conditions similar to those of hydrogen ion concentration except when sodium and chloride ions predominated in the sample.     

Effects of varying air trajectories on spatial and temporal precipitation chemistry patterns

This study was designed to determine if judicious use of synoptic data and an operational trajectory model could identify probable source regions of anthropogenic pollutants in northeastern United States precipitation and thus relate receptor measurements to emissions data without consideration of the complex intervening meteorological and chemical processes. The storm event of April 8 to 10, 1979, was selected for intensive study. Precipitation chemistry data were obtained from event samples at six MAP3S sampling sites and from hourly samples at Brookhaven National Laboratory. Concentrations of hydrogen, sulfate, nitrate and ammonium ions were used as receptor data. Some emissions data for SO_x and NO_x were obtained from the MAP3S emissions inventory. Surface and upper air meteorological data were analyzed. Backward trajectories ending at each of the sampling sites during the precipitation period were computed with the Heffter Interactive-Terminal Transport Model using selected transport layers. Results show that concentrations of pollutant species in event precipitation samples were much higher at stations at end points of trajectories passing through the Ohio River valley than at stations with other trajectories. Likewise, concentrations at Brookhaven were much higher during the end period of a trajectory through the same region than with more northerly and more southerly tracks. The model produced back trajectories consistent with synoptic flows. Concentrations of air pollutants in precipitation were roughly proportional to the number of major pollutant sources along the trajectory. These results suggest that a larger number of studies might identify more restricted source areas or even establish a quantitative relationship between source emissions along a trajectory and concentrations in precipitation at receptor sites.     

Evolution of the Concentration of Inorganic Ions during the Initial Stages of Precipitation Events

Ion concentrations in relatively low-intensity precipitation were measured in southern Indiana, USA and are presented as a function of their temporal evolution during individual precipitation events with a specific focus on the first 30 min of those events. These data indicate that during individual rain events potassium concentrations in precipitation may decline by up to 70%–80% in the first 30 min of the event. The other ions exhibited less rapid concentration declines during this event which are in rank order (highest to lowest); sodium, chloride, magnesium, nitrate, calcium, sulfate and ammonium. There is some evidence that the initial declines for precipitation accumulations up to 2 mm in the concentrationof chloride, calcium and sulfate in precipitation more closely approximate a power-law dependency on precipitation depth than the commonly applied exponential form which, if confirmed, may have implications for efforts to correct flux networks for under-sampling due to delay in sample collection. Scavenging coefficients (b) derived using an exponential relationship over entire events for sodium, chloride, nitrate, calcium, sulfate and ammonium indicate highest values for sodium and lowest for ammonium, but the uncertainty bounds on ion-specific values of b are sufficiently large that they are statistically indistinguishable.     

Chemistry of bulk precipitation throughfall,soil water and stream water in a small catchment in Devon,England

Monthly mean concentrations of potassium, calcium, sodium, magnesium chloride and nitrate-nitrogen were determined from samples of bulk precipitation, throughfall, soil water and streamflow collected weekly between April 1975 and September 1977 in a small catchment in Devon, England. Soil water concentrations are compared with the analysis of exchange capacity in composite soil samples. Rain contributed much sodium and chloride to total catchment output, and potassium was selectively enriched in throughfall. Calcium and magnesium concentrations were high in soil water samples and on the soil exchange complex.     

Orographic enhancement of wet deposition in the United Kingdom: Continuous monitoring

Continuous monitoring of cloud and rain samples at three mountain sites in the UK has allowed consideration of the long term impact of the enhancement of the wet deposition of pollutants by orographie effects, specifically the scavenging of cap cloud droplets by rain falling from above (the seeder-feeder effects). The concentration of the major pollutant ions in the cloud water is related to the relative proximity of each site to marine and anthropogenic sources of aerosol. In general, the concentrations of major ions in precipitation at summit sites exceed those in precipitation to low ground nearby by 20% to 50%. Concentrations in orographie cloud exceed those in upwind rain by between a factor of five and ten. The results are consistent with seeder-feeder scavenging of hill cloud by falling precipitation in which the average concentration of ions in scavenged hill cloud exceed those in precipitation upwind by a factor of 1.7 to 2.3 for sulphate and nitrate respectively at Dunslair Heights and 1.5 to 1.8 for sulphate and nitrate at Holme Moss. The results suggest that the parameterisation of this relationship with scavenged feeder cloud water concentrations assumed to exceed those in seeder rain by a factor of two for the production of predictive maps of wet deposition in mountainous regions of the U.K. is satisfactory.     

Chemical Characteristics of Precipitation at an Atlantic Station

Weekly or half-monthly bulk rainwater samples were collected over 3 yr (1993–1995) at Porspoder, an Atlantic station near Brest, France. They were analyzed for 0.08 M HNO3-leachable trace metals Cd, Cu, Fe, Mn, Ni, Pb and Zn by direct electrothermal atomic absorption spectrometry. Major ions and nitrogen species (NO3- and NH4+) in precipitation were determined by ion chromatography. In coastal precitation, a high correlation was observed for major ions having a seawater origin (Na+, CL- and Mg2+. Zn, Cd, Cu, Ni and Pb were well correlated indicating their anthropogenic origin. In the case of nitrogen species and nssSO42- a high correlation with Zn was observed, taken as an anthropogenic pollution tracer. Major ions and nitrogen species were determined according to wind sector direction showing clearly the impact of the pollution at this station attributed to continental air masses. A relative constancy of pH values in all wind directions was observed. Due to an important oceanic influence, trace metal concentrations and annual deposition densities were significantly lower at Porspoder than at North Sea coastal stations. In the case of nitrogen species, the relatively higher concentration levels probably indicated a significant local agricultural contribution.     

The influence of storm characteristics on sulfate in precipitation

The effects of storm dynamics on precipitation chemistry were examined using an atmospheric budget for SO₄ ^? . One hundred storms occurring between 1975 and 1978 at Hubbard Brook Experimental Forest in New Hampshire were used as test data. Concentrations of major ions were usually greater in convective storms than in continuous or layer storms. For example the geometric mean concentrations of SO₄ ^? in convective and continuous storms were 4.1 and 1.1 mg L^?1, respectively. Higher SO₄ ^? concentrations also occurred when surface wind directions were south or southwest. The summer maximum in convective activity along with the seasonal dependence of surface wind directions and the seasonal atmospheric chemistry cycle can account for the summer maximum in SO₄ ^? concentrations observed in the northeastern United States.     

Study of the Relationship between Elevated Concentrations of Photochemical Oxidants and Prevailing Meteorological Conditions in the North Kanto Area, Japan

Ambient concentrations of photochemical oxidants (Ox) averaged throughout all ambient monitoring stations in Japan have increased slightly during the past two decades despite decreasing emissions of oxidant precursors such as NOx and hydrocarbons. In the Kanto area of Japan, which is heavily populated and industrialized, Ox concentrations are often high, especially in late spring and summer, and a photochemical smog warning is frequently issued. Although the north Kanto area is about 150 km from the southern metropolitan area, and, moreover, local emissions of precursors are limited because of its agricultural and forested character, high Ox concentration levels (>120 ppbv (1-h average)) are often observed there. We analyzed the relationship between the occurrence of high Ox concentrations in the north Kanto and meteorological conditions. By combining the regional wind pattern and the presence of the inversion layer in the atmospheric boundary layer, we identified five distinct meteorological patterns. High Ox concentrations in the north Kanto area were associated with a southerly extended sea breeze accompanied by a subsidence inversion layer. We inferred that the transport of Ox from the southern urban area by southerly winds and restricted dispersion below the inversion layer can lead to high Ox concentrations in the north Kanto area. This meteorological condition is associated with the presence of a high pressure system centered in the southeastern or eastern sector offshore of the Kanto area. Thus, Ox concentrations in the north Kanto area, where emissions of precursors are relatively low, can easily increase to very high levels under favorable meteorological conditions.     

High sodium/calcium ratios in alkaline Wimmera soils: The role of magnesium and a hypothesis for their development

Sodium calcium ratios are often sufficiently high to limit root growth and result from lower calcium rather than high sodium, and was the focus of this study. A simple model of complex ion formation by magnesium and carbonate was derived, which adequately explained the relationship between pH, calcium, and magnesium, particularly the typical supersaturation of calcium with respect to calcium carbonate. Concentrations of magnesium and calcium declined when excess bicarbonate was applied, and the frequency of adverse sodium/calcium ratios increased. Calcium and magnesium declined proportionately until low concentrations when the proportion of calcium increased. Increased carbonate concentrations could depress calcium and magnesium concentrations to low levels with magnesium being buried in calcium carbonate and unable to redissolve once carbonate levels return to normal. Magnesium soil amendment may be the key to addressing adverse sodium calcium ratios. Plant selection for tolerance to adverse sodium calcium ratios is warranted.     

The Chemical Composition of Precipitation in Madrid

The present study examines the chemical characteristics of first-fraction precipitation samples collected over a period of one year in Madrid, and patterns of temporal and spatial variation observed in their composition. One hundred and sixty-four samples of wet precipitation collected on an event basis were analysed for anions, cations, pH and electrical conductivity. Precipitation in Madrid was neutral, with only 3% of samples showing pH < 5.6. Dominant ions were calcium andsulphates. Calcium was the principal neutralizing agent, explaining 64% of all nitrates and sulphates. The marine influence did not appear to be relevant, while the soil seemed to play an important role in the composition of precipitation. Precipitation chemistry displayed seasonal differences, with higher concentrations of sulphates and chloride in autumn and winter and of calcium and sodium in the summer. There was an inverse relationship between concentrations and sample volumes; while the correlation between concentrations and the time elapsedsince the last rain event was positive, though poor for normalized concentrations. Four variables (sample volume, days elapsed since the last rain event, maximum wind gust direction and season) explained to a large extent (more than 90% for some sampling stations) the variability of certain chemical variables.     

Trace inorganic species in precipitation and their potential use in source apportionment studies

Trace species in atmospheric particles have frequently been used to apportion pollutants in acid rain to their sources by comparing the relative concentrations of trace species at the source and receptor sites. Another approach is to use the trace species in precipitation directly in a source apportionment. This has rarely been done due to the paucity of data on trace species in precipitation and the unknown fractionation of the species during the scavenging process. A study was undertaken to analyze precipitation for a large number of trace species and to compare the concentrations with those in atmospheric particles. Precipitation was collected in Lenox, MA during the summer of 1984. Extreme measures were taken to avoid contamination during collection and analysis. Using five analytical methods, including the novel method of freeze-drying the precipitation followed by neutron-activation analysis, 31 species were analyzed in the rain. The trace concentrations measured in this study were lower than those found in earlier studies, where contamination was believed to be a problem. Concentrations of trace species in the precipitation were compared with those in atmospheric particles. A few species were enriched in precipitation relative to particles, including some large-particle species (Ca, Ti, Fe) and species with gaseous precursors (SO₄, NO₃, Br). Due to this enrichment, these species should be carefully considered before using them in source apportionment calculations. However, most species showed similar enrichments in precipitation and in atmospheric particles, suggesting that negligible fractionation had taken place during the scavenging process. These species could be used effectively in the future to apportion the pollutants in precipitation to their various sources.     

Characterizinig Precipitation Chemistry in Changhua, Central Taiwan Using Weather Conditions And Multivariate Analysis

Few studies of atmospheric deposition come from the fast growing region of Southeast Asia. Precipitation in Changhua City in central Taiwan was collected to examine its chemical composition and relationship with meteorological patterns. Fifty percent of the precipitation measurements had pH<5.0. Deposition fluxes of most ions were comparable to that reported for heavily industrialized temperate regions. Storms associated with air masses which originated in China had higher ion concentrations than other storms, suggesting substantial contribution of long-range transport. Two factors, a sea salt factor and an anthropogenic factor, explained more than 70% of the variation in precipitation chemistry. A third factor had a high loading only on H⁺, suggesting that pH of precipitation in Changhua City was not dominated only by acidic or basic ions alone. Instead it is determined by all components. The influences of soil and dust, as indicated by high loading on Ca²⁺ and K⁺, cannot be recognized without sea salt correction.     

Standard error calculations for non-seasalt constituents in marine precipitation

Pollutant transport studies and investigations of geochemical cycling often involve calculation of excess (non-seasalt) concentrations for various ions found in precipitation. Excess concentrations are calculated from measurements of the concentrations of a reference species and the species of interest. Formulas for determining the accuracy of calculated excess concentrations are necessary because this accuracy can vary significantly from sample to sample within the same data set, as well as from one study to another. The formulas derived in this paper demonstrate that the standard error of calculated excess concentrations is dependent on the nature and magnitude of the analytical errors made in measuring total concentrations. Application to a real data set indicates that this standard error is often greater than the calculated excess concentration, and that the standard error may vary by orders of magnitude for various samples in the same data set. The magnitude of the potential errors has important implications for the reliability of conclusions based on calculated excess concentrations, while the sample-to-sample variation of these errors complicates the process of determining the accuracy of summary statistics such as the volume-weighted mean concentration. In addition, these variations in accuracy can obscure the relationships between excess concentrations and other variables, both chemical and meteorological. This complicates investigations of source-receptor relationships and geochemical cycling, and may lead to faulty conclusions.     

Atmospheric deposition in maritime environments and its impact on terrestrial ecosystems

Seasalts are the dominant chemical constituents of precipitation in maritime regions. Dry deposition of these salts is also an important process and consequently, canopy interception by forest ecosystems greatly augments wet deposition. The separation of seasalt from non-seasalt sulphur is usually accomplished by reference to the concentration ratio of other major component ions of seawater, such as sodium-, chloride-, or magnesium-to sulphate. Biogenic sulphur, from the oceans or from terrestrial ecosystems is sometimes of importance in maritime regions. Seasalts, which dominate atmospheric deposition in maritime regions can induce short-term acidification in surface waters as a result of ion-exchange reactions following storm events. The results of one large storm in western Ireland in 1991 and the recovery process in a peat soil were clearly discernible in soil water analysis. The seasalt impact on acid mineral soils can be seen in the exchangeable sodium levels and the degree of base saturation of these soils.     

A classification of CO2 concentrations based on a binary meteorological six variable system

CO₂ is one of the most important gases linked to climate change. However, its ambient concentrations in a clean atmosphere have scarcely been investigated. In this paper a close relationship between CO₂ concentrations and meteorological variables was proposed to establish atmospheric conditions linked to high CO₂ values. A detailed 3-year campaign was carried out in a rural area with a CO₂ continuous analyser and a RASS sodar for meteorological variables. Daily and yearly CO₂ cycles were obtained. In addition, semi-hourly medians and quartiles were fitted to straight lines during the night time and daily maxima and minima were parameterised by means of a second order cylindrical model. Six meteorological variables were considered: wind speed, wind direction and temperature at one level and differences between them at two levels. Intervals were proposed from the highest CO₂ concentrations during the night to build up a binary system of 64 meteorological classes. Analysis of both CO₂ medians and meteorological classes enabled simplification of the system to four groups. The first group, characterised by high temperatures and drainage flow, was associated with detrended median concentrations above 15 ppm. Two groups of moderate concentrations were linked to thermal inversions and no prevailing wind directions. The final group corresponded to low concentrations associated with less than three meteorological variables with values linked to high concentrations. Only high directional shear and low wind speed were relevant in this group. This 4-group system was successfully used with the whole dataset.     

The Effect of Precipitation Amount and Atmospheric Concentrations on Wet Deposition Fluxes of Oxidized and Reduced Nitrogen Species in Connecticut

The effects of precipitation amount and atmospheric concentrations of inorganic nitrogen species on precipitationconcentrations and wet fluxes of oxidized and reduced nitrogen inConnecticut were studied for a period of 152 weeks (7 February,1997 through 31 December, 1999). The annual volume weighted mean(VWM) concentration in precipitation of oxidized and reducednitrogen varied with precipitation amount between sites andyears. To investigate the effect of varying precipitation amountand mean monthly temperatures on concentrations of inorganicnitrogen species in precipitation, the precipitation events wereclassified into seven groups and each year was divided into twowarm and cold sampling periods. Increasing precipitation amounthad a substantial decreasing effect on the VWM concentration ofnitrate and ammonium ions in precipitation. The highest VWMconcentrations of oxidized and reduced nitrogen in precipitationwere found in the lower weekly precipitation range of 0 to 0.5 cm. The results of this study indicated that precipitationamount was one of the main factors affecting volume weighted meanconcentrations and fluxes of oxidized and reduced nitrogen. Chemical composition of inorganic nitrogen species in theatmosphere showed that during warm and cold sampling periodsreduced nitrogen was the predominant atmospheric specie, andoxidized nitrogen was the predominant wet specie in precipitationat all sampling sites.     

The status of wet deposition of nitrogen compounds in an intensive dairy farming area in central Japan

(pp. 47–52)

The wet deposition of nitrogen compounds in the intensive dairy farming area and its environs in the northern part of the Kanto region in central Japan was investigated from April 2003 to April 2005. Open-bulk samplers were used to collect open-bulk precipitation, which approximates the sum of wet and dry deposition. Furthermore, wet-only samplers were applied to collect the precipitation for every 1 mm in a rainfall, termed the wet sample. The concentrations of total nitrogen and ammonium ions in the open-bulk precipitation were high in the central part of the dairy farming area and low in the remote mountainous area more than 15 km away the concentrations were generally high during winter and spring, and low during summer and autumn. There was a large difference in the annual deposition of nitrogen between the farming area and the surrounding area. The annual deposition of nitrogen in the farming area was significantly high compared to the values of existing data in Japan and Europe. The concentrations of respective nitrogen compounds in the wet sample, which accounted for 40 of the total rainfalls events, were notably high at the beginning of precipitation and rapidly decreased by 8 mm of continuous precipitation. The nitrogen concentrations at the beginning of precipitation were high in the farming area, and relatively low in the surrounding area. It was thought that the cause of the large wet deposition in the farming area was due to ammonia emissions, mainly from cattle manure produced at dairy farms. The factors of the seasonal changes were considered to be the frequency and the amount of precipitation, and the change in ammonia emissions from manure management performed by dairy farmers.     

Elimination of interferences in the colorimetric analysis of ammonium in water and soil extracts

Abstract

The manual method for analyzing ammonium (NH₄) in water and 1 M potassium chloride soil extracts using the Berthelot reaction was studied with the goal of eliminating interferences from commonly found ions. Three complexing agents at varying concentrations were evaluated. A 12% solution of sodium citrate was found to eliminate normal interferences in soil extracts and natural waters and was chosen as being the best of the three. Using sodium citrate as one component of the method, each component or parameter of the method was studied to be sure the maximum sensitivity was achieved.     

Variabilité spatio-temporelle de l'aluminium chez l'epinette noire (Picea mariana)

Concentrations of metals in the environment have greatly increased in the past decade since large quantities of pollutants are released annually in to the atmosphere. Exposure of the population atmospheric pollutants is believed to be responsible for the development of a number of illnesses and there is an increasing need for bio-indicators which may serve as monitors of pollutants such as heavy metals. Many animal and plant species are used as bio-indicators. Certain species of trees are used as bio-indicators because they add an additional temporal dimension. By their growth rings, trees may reflect annual variations in metal concentrations in the environment. In general, conifers are preferred because of the primitive nature of their wood which decreases the lateral transfer of contaminants between rings and, thus, gives them a better potential for the evaluation of environmental contamination. The aim of this work is to evaluate black spruce (Picea mariana) as an historical indicator of Al deposition from the atmosphere. The territory studied extends to a radius of 10 km around the Alcan aluminum refinery at Jonquiere, Quebec, Canada. The sampling strategy was designed to determine the variability within an individual tree and to determine local and regional differences. Using an incremental corer, xylem samples were taken from trees at six sites at 5 and 10 km from the refinery. At each site, three samples were taken from each of five trees separated by 100 m. The wood samples, containing from 30 to 50 rings, were sliced into two-year sections which were dried and analysed for Al by neutron activation. This involved irradiation of each section in the neutron flux of a nuclear reactor followed by gamma-ray spectroscopy with a germanium detector. The Al concentrations were thus determined in over two thousand xylem sections with a precision of 5% at levels as low as 0.2 µg g^?1. The calculation of Kendall's τ for the Al concentrations in the three samples from each tree revealed correlations in 85% of the trees from the four sites situated along the line of the prevailing winds from the refinery. For the other two sites correlations were found in 40% of the trees. Higher Al levels were found in the growth rings of more recent years at all the sites. At each site the inter-tree variations in the Al concentrations in wood of a given age were about 50%. Among the six sites, the lowest concentrations were found by an SNK test, at the two which were away from the line of prevailing winds from the refinery. The highest concentrations were found at the site 10 km west of the refinery. This site is also 5 km from a paper mill. These results suggest that the trees most exposed to atmospheric contamination will contain high concentrations of Al. However, the temporal fluctuations of Al concentrations have not yet been related to fluctuations in industrial contamination. Moreover, the Al concentrations accumulated in the growth rings of black spruce could be related to the quantity of Al available in the soil, to the atmospheric release of NO_X and SO_X and to the natural pH of the soil which can induce chemical transformations, more particularly those related to the speciation and bio-availability of this metal. Although other variables must be taken into account, it appears that black spruce may be a useful historical monitor of environmental Al contamination once the relation between xylem concentration and atmospheric deposition is determined.