Air pollution, precipitation chemistry and forest health in the Retezat Mountains, Southern Carpathians, Romania

In the Retezat Mountains concentrations of O3, NO2 and SO2 in summer season 2000-2002 were low and below toxicity levels for forest trees. While NH3 concentrations were low in 2000, the 2001 and 2002 concentrations were elevated indicating possibility for increased N deposition to forest stands. More than 90% of the rain events were acidic with pH values <5.5, contributing to increased acidity of soils. Crown condition of Norway spruce (Picea abies) and European beech (Fagus sylvatica) was good, however, defoliation described as >25% of foliage injured increased from 9.1% in 2000 to 16.1% in 2002. Drought that occurred in the southern Carpathians between fall 2000 and summer 2002 and frequent acidic rainfalls could cause the observed decline of forest condition. Both Norway spruce and European beech with higher defoliation had lower annual radial increments compared to the trees with low defoliation. Ambient O3 levels found in the Retezat did not affect crown condition of Norway spruce or European beech.     

Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Samples were collected every 2-4 weeks from a set of 37 monitoring wells over a period of 2-3 years in Araihazar, Bangladesh, to evaluate the temporal variability of groundwater composition for As and other constituents. The monitoring wells are grouped in 6 nests and span the 5-91 m depth range. Concentrations of As, Ca, Fe, K, Mg, Mn, Na, P, and S were measured by high-resolution ICPMS with a precision of 5% or better; concentrations of Cl were measured by ion chromatography. In shallow wells <30 m deep, As and P concentrations generally varied by <30%, whereas concentrations of the major ions (Na, K, Mg, Ca and Cl) and the redox-sensitive elements (Fe, Mn, and S) varied over time by up to +/-90%. In wells tapping the deeper aquifers >30 m often below clay layers concentrations of groundwater As were much lower and varied by <10%. The concentrations of major cations also varied by <10% in these deep aquifers. In contrast, the concentration of redox-sensitive constituents Fe, S, and Mn in deep aquifers varied by up to 97% over time. Thus, strong decoupling between variations in As and Fe concentrations is evident in groundwaters from shallow and deep aquifers. Comparison of the time series data with groundwater ages determined by (3)H/(3)He and (14)C dating shows that large seasonal or inter-annual variations in major cation and chloride concentrations are restricted to shallow aquifers and groundwater recharged <5 years ago. There is no corresponding change in As concentrations despite having significant variations of redox sensitive constituents in these very young waters. This is attributed to chemical buffering due to rapid equilibrium between solute and solid As. At two sites where the As content of groundwater in existing shallow wells averages 102 microg/L (range: <5 to 648 microg/L; n=118) and 272 microg/L (range: 10 to 485 microg/L; n=65), respectively, a systematic long-term decline in As concentrations lends support to the notion that flushing may slowly deplete an aquifer of As. Shallow aquifer water with >5 years (3)H/(3)He age show a constant As:P molar ratio of 9.6 over time, suggesting common mechanisms of mobilization.     

Seasonal variation of PCDD/Fs in the metropolis of Istanbul,Turkey

Atmospheric concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) compounds were investigated at three different regions of Istanbul which reflect urban, urban/industrial, and sub-urban characteristics. Air samples were collected simultaneously for both gaseous and particulate phases using high volume samplers on monthly time intervals from May 2011 to October 2012. The highest concentrations (3,056 fg/m³ and 156 fg I-TEQ/m³) were observed at the sampling site that reflects traffic, residential, and industrial emission source characteristics, while the lowest concentrations (829 fg/m³ and 38 fg I-TEQ/m³) were observed at the sampling point which is far away from centrum and reflects sub-urban characteristics. Concentrations of PCDD congeners were, in general, found to be higher than PCDF congeners, and OCDD, 1,2,3,4,6,7,8-HpCDD/F, and OCDF congeners were recorded to be the most abundant congeners. Winter season concentrations were also found to be higher especially in particulate phase. As a result, combustion processes such as motor vehicles and residential heating equipment were thought to be the principal sources of emissions of PCDD/F compounds when both congener profiles and seasonal variations are considered. Basic statistical evaluation of the data resembled high degree of inverse correlations between PCDD/F concentrations and UV and solar radiation.     

Temporal variability of airborne bacterial community structure in an urban area

Temporal airborne bacterial genetic community structure and meteorological factors were analysed above an urban area in the northwest of France from December 2003 to April 2004 with a sampling strategy considering different time intervals (from an hour to a month). Principal component analysis (PCA) of B-ARISA (Bacterial-Automated Ribosomal Intergenic Spacer Analysis) profiles revealed a hierarchy in the temporal variability of bacterial community: daily<weekly<seasonal. Co-inertia analysis between B-ARISA data and meteorological factors demonstrated the correlation between the seasonal variability in the bacterial community and climatic conditions such as temperature and relative humidity, whereas daily and weekly variability seemed likely to be managed by other factors such as anthropogenic activities.     

Factors influencing the variability of SO2 concentrations in Istanbul

The correlation between sulfur dioxide (SO2) concentrations measured at the European and Asian sides of Istanbul and meteorological parameters is investigated using principal component analysis (PCA) and multiple regression analysis techniques. Several meteorological parameters are selected to represent the atmospheric conditions during two winter periods: 1993-1994 and 1994-1995. Six principal components are found to explain the majority of the observed meteorological variability. Surface pressure, 850-mb temperature, and surface zonal (east-west) and meridional (north-south) winds show high loadings on separate factors identified by PCA. We seek dominant meteorological parameters that control the SO2 levels at each monitoring station. Several multiple regression analysis models are fitted to the data from each monitoring station using six principal components and previous-day SO2 concentrations as independent variables. Results suggest that the most important parameters, highly correlated with SO2 concentrations in the Istanbul metropolitan area, are atmospheric pressure and surface zonal and meridional winds. These components have more influence on the determination of the air pollution levels at the Asian side than at the European side.     

Size distribution and seasonal variation of airborne particulate matter in five areas in Istanbul,Turkey

Goal, scope, and background  

Many studies have focused on measuring fine and course particulate matter (PM) in urban and rural sites around the world. The aim of this research is to gain information on the size distribution of particles. The physical characteristics of PM in the urban air of Istanbul were determined.     

An assessment of spatial and temporal variation of sulfur dioxide levels over Istanbul, Turkey

Sulfur dioxide concentration levels are investigated in Istanbul to assess air pollution during the heating seasons in which the concentration of air pollutants reach high levels due to the consumption of low-quality fossil fuels. Results reveal that in the 1985-91 period there is an increasing trend in the concentrations of air pollutants. One reason for this increase is found to be the switching to use of low-quality fossil fuels instead of cleaner ones; the consumption ratio of coal/fuel-oil increased drastically in the 1980s from the ratio of 0.62 during 1980 to 3.09 by 1990. Linear regression analysis also indicated the similar variability of sulfur dioxide and particulate matter curves with a correlation coefficient R2=0.87. An optimum interpolation technique, kriging, is used to obtain the spatial distribution of sulfur dioxide over the area. Results indicated that the maximum concentration regions over the European side, exceeding 300 microg/m(3) monthly averages, are found to be the Fatih-Gaziosmanpa?a-Bayrampa?a, Beyo?lu-Si?li, and Emin?nü areas. On the Asian side, the G?ztepe-Kadik?y area received a major threat from sulfur dioxide pollution. Results also indicated that there was a considerable decrease in air pollution levels over Istanbul in the 1995-96 season compared with the previous two seasons. This can be explained by (1) the increase in ventilation, (2) switching to natural gas as a home and business heating fuel, and (3) treatment of coal before its entrance to the city. The variability in weather conditions is explained by the adoption of a ventilation index, which is the product of wind speed and inversion height.     

Long-term trends in precipitation chemistry at Hubbard Brook,New Hampshire

A continuous, 19-year record (1963–1982) of weekly, bulk precipitation chemistry at the Hubbard Brook Experimental Forest in West Thornton, New Hampshire shows no statistically significant trend in annual volume-weighted concentrations of hydrogen ion and nitrate, but a 34% decrease in sulfate, a 34% decrease in ammonium, a 63% decrease in chloride, a 79% decrease in magnesium and an 86% decrease in calcium during the period. Nitrate concentrations increased from 1964 to 1971 and H-ion concentrations decreased after 1970. Frequency distributions of the concentrations of the chemical components of precipitation are skewed. The range of H-ion concentrations in weekly samples has narrowed, and the frequency distribution has shifted toward higher concentrations (lower pH) during the last 19 years. Highest concentrations generally occur with lowest amounts of precipitation for most ions, but low concentrations can occur with either low or high amounts of precipitation. Time trends in deposition generally parallel trends in concentration over the 19-year period. Chemical deposition generally increases with increasing amount of precipitation in weekly samples.     

A winter study of air,cloud and precipitation chemistry in Ontario,Canada

During January and February 1984, a field project was conducted near North Bay, Ontario, Canada. The principal objective was to characterize the chemical and microphysical properties of the air masses, clouds and precipitation in this region of NE North America during the winter season. Two extensively instrumented aircraft with some newly designed cloudwater and snow collectors were used, as well as a surface station continuously monitoring pollutant concentrations and a precipitation event sampling network. Pollutant concentrations at the surface were found to vary with the airmass back trajectory with the highest concentrations observed for trajectories from the S and SW and the lowest from the N. Vertical profiles of aerosol particle (0.2−2 μm diameter) and NOx concentrations show similar trends with maxima of 1200 cm⁻³ and 7 ppb, respectively near ground level with air mass trajectories from the S, in comparison to values of 250 cm⁻³ and 1 ppb obtained with trajectories from the N. Cloudwater, aircraft precipitation and ground precipitation samples had a daily median pH of 3.6,4.6 and 4.2, respectively with the cloudwater having the highest sulphate and nitrate concentrations. The nitrate/sulphate equivalent concentration ratios in the cloudwater, aircraft precipitation and ground precipitation samples were 0.7,0.6 and 1.4, respectively. The data suggest that precipitation scavenging of nitric acid below cloud base is an important process during the winter season.     

Analysis of cloud and precipitation chemistry at Whiteface Mountain,NY

Federal and state programs over the past two decades have resulted in the reduction of emissions of precursors of acid rain. Concomitant with these changes, measured concentrations of acidity in precipitation and in watersheds have shown a downward trend or improvement. However, another pathway for these precursors is through cloud and fog events that often tend to occur at high-elevation regions affecting the fauna and flora as well. In this study we report on long-term measurements of cloud water and precipitation chemistry made from 1994 onwards at a high-elevation location, Whiteface Mountain NY, in the northeastern United States. Trends and inter-relationship between the ions were examined along with ambient SO₂ measurements and Adirondack lakes chemistry data.     

Spatial and temporal trends of precipitation chemistry in the United States, 1985-2002

A Seasonal Kendall Trend (SKT) test was applied to precipitation-weighted concentration data from 164 National Atmospheric Deposition Program National Trends Network (NADP/NTN) sites operational from 1985 to 2002. Analyses were performed on concentrations of ammonium, sulfate, nitrate, dissolved inorganic nitrogen (DIN, sum of nitrogen from nitrate and ammonium), and earth crustal cations (ECC, sum of calcium, magnesium, and potassium). Over the 18-year period, statistically significant (p< or =0.10) increases in ammonium concentrations occurred at 93 sites (58%), while just three sites had statistically significant ammonium decreases. Central and northern Midwestern states had the largest ammonium increases. The generally higher ammonium concentrations were accompanied by significant sulfate decreases (139 sites, 85%), and only one significant increase which occurred in Texas. In the west central United States there were significant nitrate increases (45 sites, 27%), while in the northeastern United States there were significant decreases (25 sites, 15%). Significant DIN decreases were observed in the northeastern United States (11 sites, 7%); elsewhere there were significant increases at 75 sites (46%). ECC decreased significantly at 65 sites (40%), predominantly in the central and southern United States, and increased at 11 sites (7%). The concentrations of sulfate, nitrate, and ammonium in precipitation have changed markedly over the time period studied. Such trends indicate changes in the mix of gases and particles scavenged by precipitation, possibly reflecting changes in emissions, atmospheric chemical transformations, and weather patterns.     

Trend and seasonal variation of precipitation chemistry data in the Netherlands

A multiple regression model is introduced to describe temporal variations in precipitation chemistry data. The model considers the effects of the annual cycle, a linear trend and precipitation-quantity simultaneously. The paper discusses the application of the model to concentrations and depositions of hydronium, ammonium, nitrate and sulfate for monthly bulk samples in The Netherlands for the period 1978–1984.Statistical conclusions about the annual cycle and the trend are hardly influenced by the choice of the dependent variable (depositions, concentrations or logarithms of concentrations). With the exception of H⁺ concentrations, a large part of the temporal variations was due to precipitation-quantity effects. Significant annual cycles were found for nitrate, ammonium and sulfate. There was statistical evidence of a downward trend for sulfate and nitrate. A complex, non-linear trend was observed for H⁺ which resulted in a significant autocorrelation of the residuals from the regression equation.Much attention is paid to the detectability of trend. For ammonium, nitrate and sulfate it is possible to discriminate small systematic changes in quite short records (a mean annual change of 4–6% in a 5-year record). This is not the case for H ⁺, because temporal variations of this component are insufficiently explained by the systematic annual cycle and precipitation-quantity.     

Temporal variability of selected air toxics in the United States

Ambient measurements of hazardous air pollutants (HAPs, air toxics) collected in the United States from 1990 to 2005 were analyzed for diurnal, seasonal, and/or annual variability and trends. Visual and statistical analyses were used to identify and quantify temporal variations in air toxics at national and regional levels. Sufficient data were available to analyze diurnal variability for 14 air toxics, seasonal variability for 24 air toxics, and annual trends for 26 air toxics. Four diurnal variation patterns were identified and labeled invariant, nighttime peak, morning peak, and daytime peak. Three distinct seasonal patterns were identified and labeled invariant, cool, and warm. Multiple air toxics showed consistent decreasing trends over three trend periods, 1990–2005, 1995–2005, and 2000–2005. Trends appeared to be relatively consistent within chemically similar pollutant groups. Hydrocarbons such as benzene, 1,3-butadiene, styrene, xylene, and toluene decreased by approximately 5% or more per year at more than half of all monitoring sites. Concentrations of carbonyl compounds such as formaldehyde, acetaldehyde, and propionaldehyde were equally likely to have increased or decreased at monitoring sites. Chlorinated volatile organic compounds (VOCs) such as tetrachloroethylene, dichloromethane, and methyl chloroform decreased at more than half of all monitoring sites, but decreases among these species were much more variable than among the hydrocarbons. Lead particles decreased in concentration at most monitoring sites, but trends in other metals were not consistent over time.     

Temporal variability of mercury speciation in urban air

Semi-continuous measurements of ambient mercury (Hg) species were performed in Detroit, MI, USA for the calendar year 2003. The mean (±standard deviation) concentrations for gaseous elemental mercury (GEM), particulate mercury (HgP), and reactive gaseous mercury (RGM) were 2.2±1.3 ng m⁻³, 20.8±30.0, and 17.7±28.9 pg m⁻³, respectively. A clear seasonality in Hg speciation was observed with GEM and RGM concentrations significantly (p<0.001) greater in warm seasons, while HgP concentrations were greater in cold seasons. The three measured Hg species also exhibited clear diurnal trends which were particularly evident during the summer months. Higher RGM concentrations were observed during the day than at night. Hourly HgP and GEM concentrations exhibited a similar diurnal pattern with both being inversely correlated with RGM. Multivariate analysis coupled with conditional probability function analysis revealed the conditions associated with high Hg concentration episodes, and identified the inter-correlations between speciated Hg concentrations, three common urban air pollutants (sulfur dioxide, ozone, and nitric oxides), and meteorological parameters. This analysis suggests that both local and regional sources were major factors contributing to the observed temporal variations in Hg speciation. Boundary layer dynamics and the seasonal meteorological conditions, including temperature and moisture content, were also important factors affecting Hg variability.     

Spatial and Seasonal Variations of Disinfection Byproducts (DBPs) in Drinking Water Distribution Systems of Istanbul City,Turkey

This study presents the seasonal and spatial variations of trihalomethanes (THMs) and haloacetic acids (HAAs) in 30 sampling points within three water distribution systems of Istanbul City, Turkey. The effects of surface water quality, seasonal variation, and species differences were examined. The occurrence of chlorinated THMs and HAAs levels was considerably lower in the system in which raw water is subjected to pre-ozonation versus pre-chlorination. Seasonal analysis of the data indicated that the median concentration of four THMs (THM₄) was higher than nine HAAs (HAA₉) concentrations in all three distribution systems sampling points. For all distribution systems monitored, the highest median THM₄ and HAA₉ concentrations were observed in the spring and summer season, while the lowest concentrations of these disinfection byproduct (DBP) compounds were obtained in the fall and winter period. Due to the higher level of bromide in supplying waters of these two systems, moderate levels of brominated DBP species have been observed in the Kagithane and Buyukcekmece distribution systems districts. In fact, Spearman partial correlations (Spearman rank correlation coefficients [rs]) tend to be higher among analogues in terms of number and types of substituent, especially TCAA with TCM (rs 0.91), and DBAA with DBCM (rs 0.90). In contrast, the hydraulic (residence time and flow rate) and chemical mechanisms (hydrolysis, volatilization, and adsorption) affect the fate and transport of DBPs in distribution systems. Seasonal and spatial variations of DBPs presented in this study have important implications on regulatory issues and from an epidemiological point of view.     

Ionic composition of precipitation at the Central Anatolia (Turkey)

Concentrations of major ions, SO₄²⁻, NO₃⁻, Cl⁻, H⁺, Ca²⁺, K⁺, Mg²⁺, Ca²⁺ and conductivity were measured in approximately 300 daily, wet-only rain samples collected at a permanent rural station between 1993 and 1998. Concentrations of anthropogenic ions NH₄⁺, SO₄²⁻ and NO₃⁻ were among the highest values reported in whole EMEP network, suggesting that the Anatolian plateau is under strong influence of distant emission sources. Although transport of pollutants have significant influence on the chemical composition of precipitation, average pH of the rainwater is 6.2 due to extensive neutralization of acidity. Approximately 95% of the acidity in collected samples is neutralized, particularly in summer season. The neutralizing agents are primarily CaCO₃ and NH₃. Concentrations of crustal ions are higher in summer season due to enhanced resuspension of soil particles from dry surface soil. Concentrations of anthropogenic ions SO₄²⁻ and NO₃⁻ do not change significantly between summer and winter due to higher intensity of rains in summer season. Although concentrations of ions measured in this study is among the highest reported in EMEP network, wet deposition fluxes are low compared to flux values reported for similar sites in Europe, due to low annual precipitation in the Anatolia. Wet deposition fluxes of all measured parameters are highly episodic. Source regions affecting chemical composition precipitation in the Central Anatolia is investigated using trajectory statistics.     

Sulfate in precipitation as observed by the European atmospheric chemistry network

The temporal variation in sulfur concentration/deposition involves long term fluctuations which show striking similarities within certain areas but are different between areas in different positions relative to major sulfur emission areas in Europe. As an example, the deposition has been constant or decreasing during the last ten years in most of the area covered by the network, indicating that an increasing amount of the sulfur emitted in Europe is transported and deposited elsewhere, possibly in an eastward direction.The seasonal variation in deposition resembles that for amount of precipitation and shows a maximum during the summer or autumn for most areas. The concentration shows a maximum in the spring and a minimum in the autumn at most stations.The concentration field has a maximum approximately over Belgium and Holland with decreasing concentrations towards SW to NE (over W) but with comparatively high levels extending up over Finland. (Areas to the east and south are not covered by the network.)The deposition field was, based on a brief discussion of the relation between concentration and amount of precipitation, obtained as the product of these latter fields. High deposition rates are found in the south of Norway and in the middle of Britain in addition to the areas with high concentration.Sulfur and hydrogen ion are the dominating ions in precipitation followed by ammonium and nitrate except in coastal areas and in places where the soil is bare.Sources of errors in the data base are discussed and the results from a large number of additional sampling sites around and between the regular network sampling sites are most helpful in this regard. These latter measurements also permit an estimate of the uncertainty in areal concentration averages which are due to local and mesoscale variability.Finally, past and future importance of continuous measurements (as in the EACN) is discussed briefly.     

Field studies of aldehyde chemistry in the Paris area

Measurements of carbonyl compound concentrations at different sites in the Paris area have been carried out. Interpretation of the results made use of the following data: general meteorological conditions, wind field analysis and type of primary pollutant sources. The principal phenomena observed were: a sharp formaldehyde decrease during rainfall; concentration levels of lower aldehydes in rural sites comparable to those found in the literature; an important variation in the ratio of primary aldehydes to secondary aldehydes depending on meteorological conditions; a significant increase in lower aldehyde concentrations downwind from the urban center despite vertical dispersion of the pollutants.