Atmospheric Trace Metal Concentrations Research Articles

Atmospheric trace metals measured at a regional background site (Welgegund) in South Africa

Abstract. Atmospheric trace metals can cause a variety of health-related and environmental problems. Only a few studies on atmospheric trace metal concentrations have been conducted in South Africa. Therefore the aim of this study was to determine trace metal concentrations in aerosols collected at a regional background site, i.e. Welgegund, South Africa. PM1, PM1–2. 5 and PM2. 5–10 samples were collected for 13 months, and 31 atmospheric trace metal species were detected. Atmospheric iron (Fe) had the highest concentrations in all three size fractions, while calcium (Ca) was the second-most-abundant species. Chromium (Cr) and sodium (Na) concentrations were the third- and fourth-most-abundant species, respectively. The concentrations of the trace metal species in all three size ranges were similar, with the exception of Fe, which had higher concentrations in the PM1 size fraction. With the exception of titanium (Ti), aluminium (Al) and manganese (Mg), 70 % or more of the trace metal species detected were in the smaller size fractions, which indicated the influence of industrial activities. However, the large influence of wind-blown dust was reflected by 30 % or more of trace metals being present in the PM2. 5–10 size fraction. Comparison of trace metals determined at Welgegund to those in the western Bushveld Igneous Complex indicated that at both locations similar species were observed, with Fe being the most abundant. However, concentrations of these trace metal species were significantly higher in the western Bushveld Igneous Complex. Fe concentrations at the Vaal Triangle were similar to levels thereof at Welgegund, while concentrations of species associated with pyrometallurgical smelting were lower. Annual average Ni was 4 times higher, and annual average As was marginally higher than their respective European standard values, which could be attributed to regional influence of pyrometallurgical industries in the western Bushveld Igneous Complex. All three size fractions indicated elevated trace metal concentrations coinciding with the end of the dry season, which could partially be attributed to decreased wet removal and increases in wind generation of particulates. Principal component factor analysis (PCFA) revealed four meaningful factors in the PM1 size fraction, i.e. crustal, pyrometallurgical-related and Au slimes dams. No meaningful factors were determined for the PM1–2. 5 and PM2. 5–10 size fractions, which was attributed to the large influence of wind-blown dust on atmospheric trace metals determined at Welgegund. Pollution roses confirmed the influence of wind-blown dust on trace metal concentrations measured at Welgegund, while the impact of industrial activities was also substantiated.

Atmospheric trace metal concentrations, solubility and deposition fluxes in remote marine air over the south-east Atlantic

Total and soluble trace metal concentrations were determined in atmospheric aerosol and rainwater samples collected during seven cruises in the south-east Atlantic. Back trajectories indicated that the samples all represented remote marine air masses, consistent with climatological expectations. Aerosol trace metal loadings were similar to previous measurements in clean, marine air masses. Median total Fe, Al, Mn, V, Co and Zn concentrations were 206, 346, 5, 3, 0.7 and 11pmolm−3 respectively. Solubility was operationally defined as the fraction extractable using a pH4.7 ammonium acetate leach. Median soluble Fe, Al, Mn, V, Co, Zn, Cu, Ni, Cd and Pb concentrations were 6, 55, 1, 0.7, 0.06, 24, 2, 1, 0.05 and 0.3pmolm−3 respectively. Large ranges in fractional solubility were observed for all elements except Co; median solubility values for Fe, Al and Mn were below 20% while the median for Zn was 74%. Volume weighted mean rainwater concentrations were 704, 792, 32, 10, 3, 686, 25, 0.02, 0.3 and 10nmolL−1 for Fe, Al, Mn, V, Co, Zn, Cu, Ni, Cd and Pb respectively (n=6). Wet deposition fluxes calculated from these values suggest that rain makes a significant contribution to total deposition in the study area for all elements except perhaps Ni.

The trace metal signature of atmospheric aerosols sampled at a European regional background site (puy de Dôme, France)

Trace metal composition of atmospheric aerosols provides clues as to emission sources and history of air masses. Atmospheric trace metal concentrations measured between 2011 and 2013 at puy de Dome (1,465 m elevation, central France) are, on average, intermediate between low-altitude urban sites and Atlantic remote environment (115 ng/m3 Al, 0.55 ng/m3 Sr, 0.136 ng/m3 Ce, 1.34 ng/m3 Pb). Three main factors control trace metal variability: (1) the concentrations markedly decrease at night while the site is generally located in the free troposphere/nocturnal residual layer (average of 43 ng/m3 Al, 0.27 ng/m3 Sr, 0.052 ng/m3 Ce, 0.25 ng/m3 Pb during 2012 summer nights). The nocturnal depletion is greater for refractory crustal elements (Al, Fe, Ti and rare earth elements) than for B, Na and chalcophile/siderophile elements (e.g., Tl, In, Sb, Zn, Cd, Cu, Bi, Mo, Re, Pt and Pd), which probably partition into the gas phase and/or a fine mode fraction. (2) Cr, Ni, Mo, Ag, Pb and Pt record a greater influence of anthropogenic sources (combustion, iron/steel industry, and automobile exhaust catalysts) in winter, and/or in the continental air mass that most frequently influences the site during the cold season. (3) Air masses reaching the site have distinct trace element fingerprints depending on their origin. The African air has crustal like signatures (Al/Ti, La/Sm). The Atlantic air is enriched in B, Cu, Bi, Co, W, Re and Ag and depleted in Tl, Sb and Se relatively to Al. Continental air is enriched in Cr and Ni and depleted in Na. Local air (France) is enriched in chalcophile elements (Zn, Pb, Se, As, Sb, Tl) and to a lesser extent in alkalis and rare earth elements, likely due to limited activation and scavenging of primary particles during a short-history of transport.

Assessment of atmospheric trace metals in the western Bushveld Igneous Complex, South Africa

Trace metal species emitted into the atmosphere from natural and anthropogenic sources can cause various
 health-related and environmental problems. Limited data exist for atmospheric trace metal concentrations in
 South Africa, which has the largest industrialised economy in Africa, with significant mining and metallurgical
 activities. A large fraction of these mineral assets is concentrated in the Bushveld Igneous Complex, with the
 western limb being the most exploited. To partially address this knowledge gap, atmospheric trace metals
 were collected in the western Bushveld Igneous Complex at Marikana in the North West Province. Diurnal
 PM
 2.5
 and PM
 10
 samples were collected for 1 year. A total of 27 trace metal species were determined.
 With the exception of Ni, none of the trace metals measured during the sampling period exceeded local or
 international air quality standard limit values. Total trace metal concentrations in the PM
 10
 fraction peaked
 during the dry months and were regularly washed out during the wet season. A less significant seasonal
 trend was observed for the trace metal concentrations in the PM
 2.5
 fraction; a finding attributed to a faster
 replenishment of smaller particles into the atmosphere after rain events. About 80% of the PM
 10
 trace metal
 levels measured occurred in the PM
 2.5
 fraction, while 40% or more of all metals emanated from the PM
 2.5
 fraction. This finding indicated a strong influence of anthropogenic sources. Four meaningful emission
 sources were determined from explorative principal component factor analysis: crustal, vanadium related,
 base metal related and ferrochromium related, which correlated well with the anticipated atmospheric trace
 metal sources in the region.

Atmospheric trace metal concentrations at Norwegian background sites during 25 years and its relation to European emissions

A comprehensive time trend analysis for a 25-years data set on trace metal concentrations from Norwegian monitoring stations have been carried out. At the Birkenes station, one of the stations with longest data record and located at a region in Southern Norway which is mostly affected by atmospheric long-range transport, the reductions have been 97%, 95% and 70% for, respectively, Pb, Cd and Zn in precipitation in the period 1980–2005. Changes in pollution levels are mainly due to changes in emission data and transboundary pollution. A comparison of the changes in monitoring data with changes in the anthropogenic emissions for Europe and Norway have therefore been carried out especially for Pb and Cd.

Trend analysis of the published concentrations of heavy metals in aerosols above the North Sea and the English Channel for the period 1971-1994

A literature review is given of atmospheric trace metal concentrations in aerosols above the North Sea and the English Channel over the period 1971-1994. Literature data have been gathered and intercompared to look for possible trends in the reported concentrations. Six trace metals are considered: Cd, Cu, Pb, Zn, Ni, and Cr. A distinction is made between measurements in different regions of the North Sea, and between coastal and marine areas. The majority of the data deals with the Southern Bight, providing the most reliable trends. Strong decreasing trends are observed for the Pb and Zn concentrations above the North Sea during the years 1971-1994. For Cd, Cu, Ni, and Cr, much less data are available in the literature. Despite this, also for Cd and Cu a decreasing trend is present. Cr and Ni concentrations are fluctuating, mostly without a certain pattern. The trends in the concentrations are also compared to changes in the European emission profiles. Key words: heavy metals, aerosols, North Sea, trend analysis, literature.

Determination of atmospheric trace metal concentrations by isotope dilution inductively coupled plasma mass spectrometry after separation from interfering elements by solvent extraction

An isotope dilution ICP-MS method for the determination of six elements (Ni, Cu, Zn, Cd, Tl and Pb) in atmospheric particulate samples is described. The method involves a complexation/solvent extraction step to separate these elements from potentially interfering elements prior to ICP-MS analysis. Accuracy of the method was demonstrated by analysis of a Vehicle Exhaust Particulates CRM. The method was successfully applied to the analysis of atmospheric particulates collected in a remote mountainous area of Hokkaido Island, Japan.

Atmospheric input of trace metals to the western Mediterranean Sea: 1. Factors controlling the variability of atmospheric concentrations

The factors controlling the variability of atmospheric trace metal concentrations over the western Mediterranean Sea have been investigated using a combination of geochemical and meteorological approaches. Al, Br, Cd, Na, Pb and 210Po concentrations from bulk filters and cascade impactor samples collected during five cruises (1980–1983) have been used to characterize the aerosol sources: the marine source (Na), the aeolian soil mobilization (Al), the anthropic sources (Cd, Pb), and the volcanic source (210Po). It has been confirmed that Cd and Pb directly derive from anthropic sources. As shown by three‐dimensional air mass trajectory analyses, the variability of daily atmospheric concentrations reflects both changes in continental source strengths and in airflow patterns. Atmospheric concentrations appear to be higher during episodes of short‐range transport of continental material from riparian countries. It is suggested that such source regions can be precisely identified by a careful examination of both geochemical data and three‐dimensional trajectories. From our data set, southwestern Europe would be responsible for the largest Pb and Cd inputs to the western Mediterranean atmosphere (30–40%), but the inputs from North Africa are also likely to be significant (20–25%). However, it cannot be ascertained whether this conclusion is valid on a yearly time scale. Indeed, whereas our sample set is representative of the yearly airflow climatology, it has not been possible to assess the effect of seasonal (for Pb) or sporadic (for Al) changes in source strengths. This points out that over such a marine environment, continuous sampling programs are needed to assess the respective contributions of individual source regions to the atmospheric burden of particulate trace elements.

Trace metals in Bermuda rainwater

The concentrations of Cd, Cu, Fe, Mn, Ni, Pb, and Zn have been measured in Bermuda rainwater. Factor analysis indicates that Fe, Mn, and Pb have similar origins to acidic components derived from North America. The other metals all behave similarly but differently to the acids. Sea salt, even after allowances for fractionation, apparently contributes minor amounts of Cu, Pb, and Zn and uncertain amounts of Fe, Mn, and Cd to Atlantic Ocean precipitation. Wash‐out ratios, calculated from this data along with earlier measurements of atmospheric trace metal concentrations on Bermuda, are of the same order as those reported from other remote ocean areas. The wet depositional fluxes of Cu, Ni, Pb, and Zn to the western Atlantic Ocean are significant compared to measured oceanic flux rates. However, the wet depositional fluxes of Fe and Mn to this area are relatively small, suggesting additional inputs, while an excess wet depositional flux of Cd suggests large‐scale atmospheric recycling of this element.