Total and methyl mercury patterns in Arctic snow during springtime at Resolute,Nunavut, Canada

Patterns of gaseous elemental mercury (GEM) were monitored at 20 and 150 cm above the snowpack near Resolute Bay, Cornwallis Island, Nunavut, Canada near the Upper Air Station of Environment Canada (74°42′N, 94°58′W) from 7 May (day 127) to 12 June (day 163) 2003. At this time of year there was 24 h daylight but still a strong diel change in solar radiation. Daily patterns of GEM-tracked solar radiation with a lag of about 2 h and the GEM gradient between these two heights showed the direction of flux. In addition to the previously established autocatalytic reactions involving halogens where reactive gaseous mercury and fine particulate mercury result in direct deposition to the snow, both diffusion to and volatilization from the snow occurred on a regular basis. Total mercury (THg) in the snowpack increased to near 30 ng L⁻¹ following 8 d of atmospheric mercury depletion then decreased to values near 1 ng L⁻¹. Losses from the snow could not be accounted for in melt water as stream runoff values were also low. In other words, most of the mercury associated with increased levels in snow was volatilized back to the atmosphere either directly from the snow or from the water surfaces. However, using accepted mass transport coefficients, the flux appeared low and other mechanisms are suggested. In contrast to THg, methyl mercury (MeHg) in the snow reached values near 140 pg L⁻¹ but also declined to less than detection limit (10 pg L⁻¹) with the onset of warmer temperatures. MeHg in stream runoff water was similar to maximal values seen in the snow. This observation is consistent with the view that MeHg came in the snowfall or was deposited to the snow pack rather than produced in the snow. In contrast, much of the THg associated with mercury depletion events was volatilized back to the atmosphere.     

Soot in the arctic snowpack: a cause for perturbations in radiative transfer

Recent data collected in the Arctic have demonstrated the transport of atmospheric aerosol of anthropogenic origin into that region. Concern over the radiative effect of the highly-absorbing soot component of this aerosol has resulted in a variety of atmospheric sampling efforts aimed at assessing the climatic impact of this component. However, little attention has been given to the measurement of soot deposited on the Arctic snowpack and the resulting perturbation of snow albedo, snowmelt rates and radiative transfer. Here we report measurements of light-absorbing material in the Arctic snowpack for longitudes from 25 E to 160 W. The contributions to light absorption due to natural crustal and soot aerosol are identified by their wavelength dependence. Reductions in Arctic snow albedo of one to several percent appear probable for the soot/ice mass fractions obtained to date. Estimates of the impact of this reduced albedo on the Arctic radiation budget over a season are shown to approximately equal that of the Arctic haze itself. The absorption of shortwave radiation by the springtime snowpack is estimated to be 5–10% higher than that of soot-free snow for this data.     

Shouldn’t snowpacks be sources of monocarboxylic acids?

We report the first measurements of the mixing ratios of acetic (CH₃COOH) and formic (HCOOH) acids in the air filling the pore spaces of the snowpacks (firn air) at Summit, Greenland and South Pole. Both monocarboxylic acids were present at levels well above 1 ppbv throughout the upper 35 cm of the snowpack at Summit. Maximum mixing ratios in Summit firn air reached nearly 8 ppbv CH₃COOH and 6 ppbv HCOOH. At South Pole the mixing ratios of these acids in the top 35 cm of firn air were also generally >1 ppbv, though their maximums barely exceeded 2.5 ppbv of CH₃COOH and 2.0 ppbv of HCOOH. Mixing ratios of the monocarboxylic acids in firn air did not consistently respond to diel and experimental (fast) variations in light intensity, unlike the case for N oxides in the same experiments. Air-to-snow fluxes of CH₃COOH and HCOOH apparently support high mixing ratios (means of (CH₃COOH/HCOOH) 445/460 and 310/159 pptv at Summit and South Pole, respectively) in air just above the snow during the summer sampling seasons at these sites. We hypothesize that oxidation of carbonyls and alkenes (that are produced by photo- and OH-oxidation of ubiquitous organic compounds) within the snowpack is the source of the monocarboxylic acids.     

Snowpack processing of acetaldehyde and acetone in the Arctic atmospheric boundary layer

Acetaldehyde (CH₃CHO) and acetone (CH₃C(O)CH₃) concentrations in ambient air, in snowpack air, and bulk snow were determined at Alert, Nunavut, Canada, as a part of the Polar Sunrise Experiment (PSE): ALERT 2000. During the period of continuous sunlight, vertical profiles of ambient and snowpack air exhibited large concentration gradients through the top ∼10 cm of the snowpack, implying a flux of carbonyl compounds from the surface to the atmosphere. From vertical profile and eddy diffusivity measurements made simultaneously on 22 April, acetaldehyde and acetone fluxes of 4.2(±2.1)×10⁸ and 6.2(±4.2)×10⁸ molecules cm⁻² s⁻¹ were derived, respectively. For this day, the sources and sinks of CH₃CHO from gas phase chemistry were estimated. The result showed that the snowpack flux of CH₃CHO to the atmosphere was as large as the calculated CH₃CHO loss rate from known atmospheric gas phase reactions, and at least 40 times larger (in the surface layer) than the volumetric rate of acetaldehyde produced from the assumed main atmospheric gas phase reaction, i.e. reaction of ethane with hydroxyl radicals. In addition, acetaldehyde bulk snow phase measurements showed that acetaldehyde was produced in or on the snow phase, likely from a photochemical origin. The time series for the observed CH₃C(O)CH₃, ozone (O₃), and propane during PSE 1995, PSE 1998, and ALERT 2000 showed a consistent anti-correlation between acetone and O₃ and between acetone and propane. However, our data and model simulations showed that the acetone increase during ozone depletion events cannot be explained by gas phase chemistry involving propane oxidation. These results suggest that the snowpack is a significant source of acetaldehyde and acetone to the Arctic boundary layer.     

Some results of snow chemical surveys in the Kunnes River valley,East Tienshan mountains,China

Chemical surveys of snow were carried out in the upper reaches of the Kunnes River, a tributary of the Yili River in East Tienshan Mountains, China. Some surprisingly high values of sodium and potassium (K⁺+Na⁺) ranging from 4.44 to 8.99 mg/l compared with other data from neighboring areas are detected. Moreover, some relative high values of SO₄²⁻ with mean concentration 15.8 mg/l for new snow and 14.40 mg/l for deposited snow, ranging from 10.43 to 23.71 mg/l are also found. Therefore, it is inferred that the sodium and potassium (K⁺+Na⁺) are in the forms of sulfate and that the sources of the sulfate are deserts and some dried lakes in Central Asia. It is also found that there is obviously spatial variation of ions such as K⁺+Na⁺, Ca²⁺, SO₄²⁻ and HCO₃⁻. The concentrations of K⁺+Na⁺ and SO₄²⁻, and that of Ca²⁺ and HCO₃⁻ have similar spatial pattern. The temporal pattern of ion concentration of new snow is considered to be mainly controlled by the depth and area of snow cover in the study area and in the areas to the west.     

Heavy metals in ancient tropical ice: initial results

Although a wealth of fascinating data have been obtained through the investigation of heavy metals in Greenland, Antarctic and Alpine snow and ice cores, heavy metals have until now never been measured in tropical snow and ice cores despite the great interest of such low latitude cores. We present here preliminary data on the occurrence of Al, Na, Ti, V, Cr, Mn, Co, Cu, Zn, Mo, Pd, Ag, Cd, Sb, Ba, Pt, Au, Pb, Bi and U in a dated ice core drilled at an altitude of 6542 m on the top of Sajama in Bolivia. These data were obtained by analysing four core sections dated 22,000 BP (Last Glacial Maximum, LGM), 8000 BP (early Holocene, EH), AD1650 and AD 1897, using ultrasensitive ICP-SF-MS. Concentrations observed in LGM ice are similar to those measured in EH ice. Al, Na, Ti, V, Cr, Mn, Co, Ba and U are found to derive mainly from rock and soil dust. For the other metals, additional contributions from other sources are needed to explain the observed concentrations.     

In-stack emissions of heavy metals estimated by moss biomonitoring method and snow-pack analysis

Data from the chemical analysis of moss growing close to a thermal power station and snowpack have been used for the estimation of heavy metal deposition close to the point pollution sources. A semi-empirical model was proposed to describe atmospheric trace metal deposition close to the point pollution source. Model parameters were derived from experimental data, and nickel and vanadium quantities, washed out with snow and rain, were calculated. Using long-term meteorological observation data of rain and snow duration and metal uptake efficiencies in moss, the average emission rates of vanadium and nickel from the stack were calculated. The coincidence between data from emission inventory and model results was within 25%. It was estimated that in the vicinity of pollution source (within 30 km) about 15% out of total emitted metals were washed out by rain and snow events. Metal concentrations in the environment become indistinguishable from the background at a distance of about 20 km from the stack.     

Snow-to-air exchanges of mercury in an Arctic seasonal snow pack in Ny-Ålesund,Svalbard

The study of mercury (Hg) cycle in Arctic regions is a major subject of concern due to the dramatic increases of Hg concentrations in ecosystem in the last few decades. The causes of such increases are still in debate, and an important way to improve our knowledge on the subject is to study the exchanges of Hg between atmosphere and snow during springtime. We organized an international study from 10 April to 10 May 2003 in Ny-Ålesund, Svalbard, in order to assess these fluxes through measurements and derived calculations.Snow-to-air emission fluxes of Hg were measured using the flux chamber technique between ∼0 and 50 ng m⁻² h⁻¹. A peak in Gaseous Elemental Mercury (GEM) emission flux from the snow to the atmosphere has been measured just few hours after an Atmospheric Mercury Depletion Event (AMDE) recorded on 22 April 2004. Surprisingly, this peak in GEM emitted after this AMDE did not correspond to any increase in Hg concentration in snow surface. A peak in GEM flux after an AMDE was observed only for this single event but not for the four other AMDEs recorded during this spring period.In the snow pack which is seasonal and about 40 cm depth above permafrost, Hg is involved in both production and incorporation processes. The incorporation was evaluated to ∼5–40 pg m² h. Outside of AMDE periods, Hg flux from the snow surface to the atmosphere was the consequence of GEM production in the air of snow and was about ∼15–50 ng m⁻² h⁻¹, with a contribution of deeper snow layers evaluated to ∼0.3–6.5 ng m⁻² h⁻¹. The major part of GEM production is then mainly a surface phenomenon. The internal production of GEM was largely increasing when snow temperatures were close to melting, indicating a chemical process occurring in the quasi-liquid layer at the surface of snow grains.     

Measurements of JNO3− in snow by nitrate-based actinometry

Chemical actinometry was used to measure nitrate photolysis rate coefficients, J_NO3⁻, on and in snowpack at Summit, Greenland. Sealed glass tubes containing nitrate and a hydroxyl radical trapping system were buried in snow and exposed for between 2 and 24 h. Average J_NO3⁻ values for 2-h midday exposures in early June on surface snow were 10–14×10⁻⁷ s⁻¹. Averages over 24 h were 3.5–4.5×10⁻⁷ s⁻¹. These values reflect the integrated photon flux and also any variation of the nitrate photolysis rate with temperature. Attenuation of J_NO3⁻ within the firn was 0.03–0.04 cm⁻¹ for 24-h exposures and 0.08 cm⁻¹ for a 2-h exposure. Different attenuation coefficients may relate to differential light penetration due to changes in sun angle over the course of 24 h.     

Recent atmospheric Pb deposition at a rural site in southern Germany assessed using a peat core and snowpack,and comparison with other archives

In a peat bog from Black Forest, Southern Germany, the rate of atmospheric Pb accumulation was quantified using a peat core dated by ²¹⁰Pb and ¹⁴C. The most recent Pb accumulation rate (2.5 mg m⁻² y⁻¹) is similar to that obtained from a snowpack on the bog surface, which was sampled during the winter 2002 (1 to 4 mg m⁻² y⁻¹). The Pb accumulation rates recorded by the peat during the last 25 yr are also in agreement with published values of direct atmospheric fluxes in Black Forest. These values are 50 to 200 times greater than the “natural” average background rate of atmospheric Pb accumulation (20 μg m⁻² y⁻¹) obtained using peat samples from the same bog dating from 3300 to 1300 cal. yr B.C. The isotopic composition of Pb was measured in both the modern and ancient peat samples as well as in the snow samples, and clearly shows that recent inputs are dominated by anthropogenic Pb. The chronology and isotopic composition of atmospheric Pb accumulation recorded by the peat from the Black Forest is similar to the chronologies reported earlier using peat cores from various peat bogs as well as herbarium samples of Sphagnum and point to a common Pb source to the region for the past 150 years. In contrast, Pb contamination occurring before 1850 in southwestern Germany, differs from the record published for Switzerland mainly due to the mining activity in Black Forest. Taken together, the results show that peat cores from ombrotrophic bogs can yield accurate records of atmospheric Pb deposition, provided that the cores are carefully collected, handled, prepared, and analysed using appropriate methods.     

Spatial and seasonal variations of elemental composition in Mt. Everest (Qomolangma) snow/firn

In May 2005, a total of 14 surface snow (0–10 cm) samples were collected along the climbing route from the advanced base camp to the summit (6500–8844 m a.s.l.) on the northern slope of Mt. Everest (Qomolangma). A 108 m firn/ice core was retrieved from the col of the East Rongbuk Glacier (28.03°N, 86.96°E, 6518 m a.s.l.) on the north eastern saddle of Mt. Everest in September 2002. Surface snow and the upper 3.5 m firn samples from the core were analyzed for major and trace elements by inductively coupled plasma mass spectroscopy (ICP-MS). Measurements show that crustal elements dominated both surface snow and the firn core, suggesting that Everest snow chemistry is mainly influenced by crustal aerosols from local rock or prevalent spring dust storms over southern/central Asia.There are no clear trends for element variations with elevation due to local crustal aerosol inputs or redistribution of surface snow by strong winds during the spring. Seasonal variability in snow/firn elements show that high elemental concentrations occur during the non-monsoon season and low values during the monsoon season. Ca, Cr, Cs, and Sr display the most distinct seasonal variations. Elemental concentrations (especially for heavy metals) at Mt. Everest are comparable with polar sites, generally lower than in suburban areas, and far lower than in large cities. This indicates that anthropogenic activities and heavy metal pollution have little effect on the Mt. Everest atmospheric environment. Everest firn core REE concentrations are the first reported in the region and seem to be comparable with those measured in modern and Last Glacial Maximum snow/ice samples from Greenland and Antarctica, and with precipitation samples from Japan and the East China Sea. This suggests that REE concentrations measured at Everest are representative of the background atmospheric environment.     

Black carbon concentrations in precipitation and near surface air in and near Halifax,Nova Scotia

Black carbon (soot) concentrations have been measured in rain water, snow samples and near surface air at several locations in Nova Scotia, Canada. The average black carbon concentration in near surface air in summer was found to be 0.54 μg m^-3 compared to 1.74 μg m^-3 in the winter season. These values are comparable to black carbon concentrations found in other mid-size urban areas. The black carbon concentration in rain water and snow samples varied between an undetectable amount to about 20 μg kg^-1 of rain (or melt) water. The relatively low concentrations of black carbon in precipitation are attributed to extratropical cyclones that often develop off-shore to the east and south of Nova Scotia in relatively clean conditions of the marine boundary layer.     

Risks from sediments contaminated with organochlorine pesticides in Hangzhou,China

In September 2009, we investigated the residues, enantiomer fractions (EFs) and biological risks of organochlorine pesticides (OCPs), including dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs), in three different depth ranges (0–5 cm, 5–10 cm and 10–15 cm) of sediments from 15 sites in Hangzhou, China. The concentration (ng g^?1 dry weight) ranges of HCHs and DDTs in surface sediments were 0.74–5.8 and 0.76–17, respectively. The vertical distribution of mean OCP concentrations was in the order of 10–15 cm > 5–10 cm > 0–5 cm and implied that the residues of HCHs and DDTs gradually decreased after they were banned. The residues of OCPs in the study area mainly originated from the historical OCP use. The isomer ratios of <alpha>-HCH (α-HCH)/<gamma>-HCH (γ-HCH) (0.10–7.6) implied that HCH residues were derived not only from historical technical HCH use but also from additional use of lindane in this area. The isomer ratios of o,p′-DDT/p,p′-DDT (51% of samples were in the range of 0.3–1.3) suggested that both dicofol-type DDT and technical DDT applications may be present in most study areas. The (+)-enantiomers of α-HCH and o,p′-DDT were more prevalent than (?)-enantiomer in most samples with the fractions contain different enantiomers greater than 0.5. DDTs, especially p,p′-DDE, are the main OCP species of more ecotoxicological concern in Hangzhou.     

Analysis of particulate polycyclic aromatic hydrocarbons by on-line coupled supercritical fluid extraction–liquid chromatography–gas chromatography–mass spectrometry

An on-line supercritical fluid extraction–liquid chromatography–gas chromatography–mass spectrometry (SFE–LC–GC–MS) method was developed for the analysis of the particulate polycyclic aromatic hydrocarbons (PAHs). The limits of detection of the system for the quantification standards were in the range of 0.25–0.57 ng, while the limits of determinations for filter samples varied from 0.02 to 0.04 ng m⁻³ (24 h sampling). The linearity was excellent from 5 to 300 ng (R²>0.967). The analysis could be carried out in a closed system without tedious manual sample pretreatment and with no risk of errors by contamination or loss of the analytes. The results of the SFE–LC–GC–MS method were comparable with those for Soxhlet and shake-flask extractions with GC–MS. The new method was applied to the analysis of PAHs collected by high-volume filter in the Helsinki area to study the seasonal trend of the concentrations. The individual PAH concentrations varied from 0.015 to more than 1 ng m⁻³, while total PAH concentrations varied from 0.81 to 5.68 ng m⁻³. The concentrations were generally higher in winter than in summer. The mass percentage of the total PAHs in total suspended particulates ranged from 2.85×10⁻³% in July to 15.0×10⁻³% in December. Increased emissions in winter, meteorological conditions, and more serious artefacts during the sampling in summer season may explain the concentration profiles.     

Heavy metals in fresh snow collected at different altitudes in the Chamonix and Maurienne valleys,French Alps: initial results

The Chamonix and Maurienne valleys, French Alps, are major pathways for international truck and automobile traffic in Western Europe since they give access to the transalpine Mont Blanc and Frejus road tunnels. Moreover, the seasonal snow pack, which accumulates from autumn to spring in these two valleys, is a major contributor to fresh water resources for a large number of people, especially in large cities such as Geneva, Lyon and Grenoble. During winter 1998, we have collected a series of snow samples from two well-identified snowfall events at various altitudes ranging from 1150 to 3532 m on the sides of these two deep valleys. They were analysed for Li, B, Ti, V, Mn, Fe, Co, Cu, Zn, Mo, Pd, Ag, Cd, Sn, Sb, Ba, Pt, Au, Pb, Bi and U by double focusing inductively coupled plasma mass spectrometry with micro concentric nebulization (DF-ICP-MS-MCN). Ultraclean procedures were used for field sampling and laboratory analysis. The results show surprisingly low concentration values. With the exception of Li, B, Pd, Sn, Pt and Au, concentrations are found to decrease with increasing altitude. Crustal enrichment factors larger than ±10 times the mean crustal abundance are observed for Cu, Zn, Li, Mo, Pb, Ag, Bi, B, Sb, Sn, Cd, Au, Pt and Pd, strongly suggesting contributions from non-crustal sources for these metals, especially local and/or regional anthropogenic sources. Significant contributions are likely to originate from truck and automobile traffic, electrometallurgical and electrochemical industries and municipal incinerators. These data provide with a unique snapshot of the situation which prevailed in the two valleys before the disaster which occurred on 24 March 1999 in the tunnel of Mont Blanc, which resulted into a massive fall of the traffic in the Chamonix valley and a parallel rise in the traffic in the Maurienne valley.     

Investigation of the behavior and metabolism of pharmaceutical residues during purification of contaminated ground water used for drinking water supply

Residues of phenazone-type pharmaceuticals originating from spills of a former pharmaceutical production plant have recently been detected in ground water in Berlin, Germany. The degradation pathways of phenazone, propyphenazone, and dimethylaminophenazone (DMAA) during water purification were enlightened in batch experiments with groundwater and filter material obtained from operating waterworks. For phenazone and propyphenazone a complete biological transformation into their respective metabolites 1,5-dimethyl-1,2-dehydro-3-pyrazolone (DP) and 4-(2-methylethyl)-1,5-dimethyl-1,2-dehydro-3-pyrazolone (PDP) was observed. Generally, removal of phenazone-type pharmaceutical residues during rapid sand filtration was almost exclusively caused by microorganisms only present in polluted raw water. DMAA applied to fresh filter materials was rapidly degraded into its metabolites 1-acetyl-1-methyl-2-phenylhydrazide (AMPH), acetoaminoantipyrine (AAA), formylaminoantipyrine (FAA), and 1-acetyl-1-methyl-2-dimethyloxamoyl-2-phenylhydrazide (AMDOPH). DMAA, AAA, and FAA were, however, only detected at low levels in a few samples of purified water from an operating water works. Whereas, the metabolites AMDOPH and DP were detected up to 1 μg l⁻¹. Propyphenazone was rapidly removed and AMPH, phenazone, and PDP were only measured with concentrations in the low ng l⁻¹ range. The concentrations of the metabolites DP and PDP are even higher in the purified water than in the raw water caused by their formation during degradation of phenazone and propyphenazone. Reduction of filtration velocity on an experimental filter from 5 m h⁻¹ down to 2 m h⁻¹ resulted in improved removal of phenazone, propyphenazone and their metabolites DP and PDP, respectively. AMDOPH, however, was highly persistent in all experiments independent from filtration velocities and contact times.     

Seasonal patterns of heavy metal deposition to the snow on Lambert Glacier basin,East Antarctica

Al, V, Mn, Fe, Cu, As, Cd, Ba, Pb, Bi and U were determined in a continuous series of 46 snow samples from a 2.3-m snow pit, covering the time period from austral spring 1998 to summer 2002, at a site on the east side of the Lambert Glacier basin in East Antarctica. Concentrations are very low for all metals and differ by orders of magnitude from one metal to another, with the mean concentrations ranging from 0.028 pg g⁻¹ for Bi to 165 pg g⁻¹ for Al. It is estimated that anthropogenic contributions are dominant for Cu, Pb and probably As, in the snow in our study area while the natural contributions from rock and soil dust, sea-salt spray and volcanic emissions account for most of the measured concentrations of the other metals. Our snow profiles show pronounced seasonal variations for Mn, As, Ba, Pb and Bi throughout the year, but a very different situation is observed between different metals. These observations suggest that heavy metals determined in our samples are controlled by different transport and deposition mechanisms related to physical and chemical alterations in the properties and sources of aerosol.     

Dioxins,furans and polycyclic aromatic hydrocarbons emissions from a hospital and cemetery waste incinerator

An experimental campaign was carried out on a hospital and cemetery waste incineration plant in order to assess the emissions of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polycyclic aromatic hydrocarbons (PAHs). Raw gases were sampled in the afterburning chamber, using a specifically designed device, after the heat recovery section and at the stack. Samples of slags from the combustion chamber and fly ashes from the bag filter were also collected and analyzed. PCDD/Fs and PAHs concentrations in exhaust gas after the heat exchanger (200–350 °C) decreased in comparison with the values detected in the afterburning chamber. Pollutant mass balance regarding the heat exchanger did not confirm literature findings about the de novo synthesis of PCDD/Fs in the heat exchange process. In spite of a consistent reduction of PCDD/Fs in the flue gas treatment system (from 77% up to 98%), the limit of 0.1 ng ITEQ Nm⁻³ at the stack was not accomplished. PCDD/Fs emission factors for air spanned from 2.3 up to 44 μg ITEQ t⁻¹ of burned waste, whereas those through solid residues (mainly fly ashes) were in the range 41–3700 μg ITEQ t⁻¹. Tests run with cemetery wastes generally showed lower PCDD/F emission factors than those with hospital wastes. PAH total emission factors (91–414 μg kg⁻¹ of burned waste) were in the range of values reported for incineration of municipal and industrial wastes. In spite of the observed release from the scrubber, carcinogenic PAHs concentrations at the stack (0.018–0.5 μg Nm⁻³) were below the Italian limit of 10 μg Nm⁻³.     

Atmospheric trace element concentrations in total suspended particles near Paris,France

To evaluate today’s trace element atmospheric concentrations in large urban areas, an atmospheric survey was carried out for 18 months, from March 2002 to September 2003, in Saclay, nearby Paris. The total suspended particulate matter (TSP) was collected continuously on quartz fibre filters. The TSP contents were determined for 36 elements (including Ag, Bi, Mo and Sb) using two analytical methods: Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The measured concentrations were in agreement within the uncertainties with the certified values for the polycarbonate reference material filter SRM-2783 (National Institute for Standard Technology NIST, USA). The measured concentrations were significantly lower than the recommended atmospheric concentrations. In 2003, the Pb atmospheric level at Saclay was 15 ng/m³, compared to the 500 ng/m³ guideline level and to the 200 ng/m³ observed value in 1994. The typical urban background TSP values of 1–2, 0.2–1, 4–6, 10–30 and 3–5 ng/m³ for As, Co, Cr, Cu and Sb, respectively, were inferred from this study and were compared with the literature data. The typical urban background TSP concentrations could not be realised for Cd, Pb and Zn, since these air concentrations are highly influenced by local features. The Zn concentrations and Zn/Pb ratio observed in Saclay represented a characteristic fingerprint of the exceptionally large extent of zinc-made roofs in Paris and its suburbs. The traffic-related origin of Ba, Cr, Cu, Pb and Sb was demonstrated, while the atmospheric source(s) of Ag was not identified.     

Boundary-layer dynamics and its influence on atmospheric chemistry at Summit,Greenland

Sonic anemometer turbulence measurements were made at Summit, Greenland during summer 2004 and spring 2005. These measurements allow for the characterization of the variability of the atmospheric boundary layer at this site by describing seasonal and diurnal changes in sensible heat flux and boundary layer stability as well as providing estimates of mixing layer height. Diurnal sensible heat fluxes at Summit ranged from −18 to −2 W m⁻² in the spring and from −7 to +10 W m⁻² in the summer. Sustained stable surface layer conditions and low wind speeds occured during the spring but not during the summer months. Unstable conditions were not observed at Summit until late April. Diurnal cycles of convective conditions during the daytime (0700–1700 h local time) were observed throughout July and August. Boundary layer heights, which were estimated for neutral to stable conditions, averaged 156 m for the spring 2005 observations. Comparisons of the boundary layer characteristics of Summit with those from South Pole, Antarctica, provide possible explanations for the significant differences in snowpack and surface-layer chemistry between the two sites.