The large surface area of Lake Victoria (about 68,800 km2) makes it vulnerable to high atmospheric deposition of chemical pollutants. We present measurements of polychlorinated biphenyls (PCBs) from ...the lake's atmospheric environment. High volume air (24 h) samples were collected within the northern Lake Victoria watershed in Uganda over two periods; 1999–2004 at Kakira (KAK) and Entebbe (EBB) and 2008–2010 (at EBB only). Precipitation samples were also collected monthly during the 2008–2010 period at EBB. Analysis for PCBs was done using GC-μECD in a dual column approach. The ranges of ΣPCB concentrations in the KAK air samples were 154–462 pg m−3 (KAK 1999–2000), 26.7–226 pg m−3 (KAK 2003–2004), 27.0–186 pg m−3 (EBB 2003), 46.8–174 pg m−3 (EBB 2004), 19.2–128 pg m−3 (EBB 2008), 45.8–237 pg m−3 (EBB 2009) and 65.6–244 pg m−3 (EBB 2010). The di-, tri-, tetra- and penta-PCBs were predominant in air sample sets while the tetra- and penta-PCBs were predominant in precipitation samples. The mean flux of ΣPCBs in the precipitation samples was 26.9 ng m−2 (range of 14.8–41.5 and median of 27.5). Concentrations at EBB were lower than those reported elsewhere for urban sites in the East and Central African region. Multivariate analysis and analysis of air mass movements suggested influence of combustion sources on the PCB profiles from the region, especially, from the major East African urbanized regions.
Display omitted
•Samples collected at Entebbe showed a general increase in airborne ΣPCBs from 2003 to 2010.•Combustion sources influenced the PCB profiles in Entebbe 2008–2010 samples.•Densely populated areas in the region were likely major sources PCBs.•Tetra- and penta-PCBs were predominant in precipitation samples.•Generally, the same congeners were abundant in air and precipitation samples.
High volume air and precipitation samples were collected close to the shore of Lake Victoria at Entebbe, Uganda, between October 2008 and July 2010 inclusive. Polybrominated diphenyl ethers (PBDEs) ...and alternative flame retardants (AFRs) were analyzed by GC-MS. BDEs 47, 99, and 209 were the predominant PBDEs with mean concentrations (in air) of 9.84, 4.38, 8.27 pg m(-3) and mean fluxes in precipitation of 3.40, 6.23, and 7.82 ng m(-2) sample(-1), respectively. 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), and hexabromocyclododecane (HBCDD), anti- and syn-Dechlorane plus were detected at levels comparable with those of PBDEs. Both PBDEs and AFRs in air generally increased from 2008 to 2010. Elevated PBDE concentrations in air were associated with slow moving low altitude air masses from the region immediately adjacent to the lake, while low concentrations were mostly associated with fast moving westerly and southwesterly air masses. Analysis of the octa- and nona-BDE profiles suggested photolysis and pyrolytic debromination of BDE-209 in the air samples. The highly halogenated and most abundant PBDEs and AFRs in air also predominated in precipitation samples. This is the first study to report flame retardants in high volume air samples and precipitation in Equatorial Africa.
Weekly high-volume air samples have been collected in the Canadian High Arctic (Alert, Nunavut) since 1992. Fifteen polybrominated diphenyl ethers (PBDEs) are quantified in 104 samples over the time ...period of 2002–2004. To our knowledge, this study reports the first continuous multi-year measurements of PBDEs in Arctic air. Average air concentrations (in pg
m
−3) were 7.7 (0.40–47) and 1.6 (0.091–9.8) for 14 PBDEs (excluding BDE-209) and BDE-209, respectively, over the entire sampling period. BDE-28/33, 47, 99, 100, 153, 154, and 209 accounted for 90% (72–97%,
n=104) of the 15 PBDEs. Occurrence of BDE-47, 99, and 209 suggests that PBDEs in Alert air were likely associated with the usage of “penta-BDE” and “deca-BDE” technical mixtures worldwide. Natural logarithm of concentrations for less brominated PBDEs correlated significantly with ambient temperatures in the summertime, suggesting importance of volatilization emissions in a local and/or regional scale. On the other hand, episodically elevated concentrations of the less brominated PBDEs in the wintertime and lack of seasonality for the non-volatile BDE-209 indicate potential inputs of particle-bound PBDEs through long-range transport (LRT), especially during the Arctic haze season. Inter-annual trend data further show that concentrations of the eight PBDEs increased inter-annually in 2002–2004 with doubling times of 2–6 years, which were similar to growth rates found in Arctic biotic samples. The results of this study and previous measurements suggest that potential sources of PBDEs in Arctic air include both volatilization emissions and LRT inputs.
Air concentrations of organochlorine pesticides (OCPs) were measured on a weekly basis in 2000–2003 at six Arctic stations, which include Alert, Kinngait, and Little Fox Lake in Canada; Point Barrow ...in the USA; Valkarkai in Russia; and Zeppelin in Norway. These stations cover a large region in the Arctic, providing a comprehensive perspective on OCPs in the circumpolar atmosphere. Currently used pesticide endosulfan I had similar concentrations across the stations in November–May, whereas large spatial divergence was found in June–October. This implies the extensive usage of endosulfan during summertime followed by long-range transport to the Arctic. The median air concentration of endosulfan I was 3.2
pg
m
−3 (
n=245). Seasonally and spatially uniform concentrations of legacy chlordane-related compounds indicated that the influence of primary emissions on Arctic air has become less important than volatilization emissions. Median air concentrations (pg
m
−3) of
trans-chlordane,
cis-chlordane,
trans-nonachlor, oxychlordane, and heptachlor
exo-epoxide were 0.20 (
n=413), 0.58 (
n=413), 0.44 (
n=413), 0.30 (
n=245), and 0.54 (
n=244), respectively. Although extensive usage was banned in the 1970s, large spatial variations reflected that DDT-related compounds were not well mixed in Arctic air. Concentrations of DDT-related compounds were low in general, and median concentrations of
p,
p′-DDT,
o,
p′-DDT,
p,
p′-DDE,
o,
p′-DDE, and ∑
4DDT were 0.10, 0.18, 0.37, 0.10, and 0.79
pg
m
−3 (
n=418), respectively. Air concentrations of pentachloroanisole and dieldrin showed strong seasonal/spatial variations with median values of 3.8 and 0.48
pg
m
−3 (
n=245). Uniform concentrations were observed for octachlorostyrene with a median of 0.32
pg
m
−3 (
n=245). Arctic air concentrations of other measured OCPs, such as endrin, heptachlor, methoxychlor, mirex, photomirex, tetrachloroveratrole, trichloroveratrol, and trifluralin, were generally low and mostly below method detection limits.
A flow-through sampler (FTS) was codeployed with a super high volume active sampler (SHV) between October 2007 and November 2008 to evaluate its ability to determine the ambient concentrations of ...pesticides and brominated flame retardants in the Canadian High Arctic atmosphere. Nine pesticides and eight flame retardants, including three polybrominated diphenyl ether (PBDE) replacement chemicals, were frequently detected. Atmospheric concentrations determined by the two systems showed good agreement when compared on monthly and annually integrated time scales. Pesticide concentrations were normally within a factor of 3 of each other. The FTS tended to generate higher PBDE concentrations than the SHV presumably because of the entrainment of blowing snow/ice crystals or large particles. Taking into account uncertainties in analytical bias, sample volume, and breakthrough estimations, the FTS is shown to be a reliable and cost-effective method, which derives seasonally variable concentrations of semivolatile organic trace compounds at extremely remote locations that are comparable to those obtained by conventional high volume air sampling. Moreover, the large sampling volumes captured by the FTS make it suitable for the screening of new and emerging chemicals in the remote atmosphere where concentrations are usually low.
Weekly high-volume air samples were collected between 2000 and 2003 at six Arctic sites, i.e., Alert, Kinngait, and Little Fox Lake (LFL) in Canada, Point Barrow in Alaska, Valkarkai in Russia, and ...Zeppelin in Norway. Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were quantified in all samples. Comparison showed that alpha-HCH and HCB were homogeneously distributed in the circumpolar atmosphere and uniform throughout the seasons. However, significantly higher atmospheric concentrations of alpha-HCH and HCB and strongertemperature dependence of alpha-HCH and gamma-HCH were found at LFL in Yukon (YK), which is unique among the sites by virtue of its high altitude and low latitude, resulting in higher precipitation rates and summer temperatures. Strong temperature dependence of alpha- and gamma-HCH at this location suggests that secondary emissions, i.e., re-evaporation from surfaces, were more important at this site than others. It is hypothesized that a higher precipitation rate at LFL facilitated the transfer of alpha-HCH from the atmosphere to surface media when technical HCH was still in use worldwide. On the other hand, higher temperature at LFL enhanced reevaporation to the atmosphere after the global ban of technical HCH. In contrast to alpha-HCH and HCB, larger spatial and seasonal differences were seen for gamma-HCH (a currently used pesticide), which likely reflect the influence of different primary contaminant sources on different Arctic locations. Fugacity ratios suggest a net deposition potential of HCB from air to seawater, whereas seawater/air exchange direction of alpha-HCH varies in the circumpolar environment.
Atmospheric PBDEs were measured on a monthly basis in 2002–2004 at Point Petre, a rural site in the Great Lakes. Average air concentrations were 7.0 ± 13 pg m
−3 for Σ
14BDE (excluding BDE-209), and ...1.8 ± 1.5 pg m
−3 for BDE-209. Concentrations of 3 dominant congeners (i.e., BDE-47, 99, and 209) were comparable to previous measurements at remote/rural sites around the Great Lakes, but much lower than those at urban areas. Weak temperature dependence and strong linear correlations between relatively volatile congeners suggest importance of advective inputs of gaseous species. The significant correlation between BDE-209 and 183 implies their transport inputs associated with particles. Particle-bound percentages were found greater for highly brominated congeners than less brominated ones. These percentages increase with decreasing ambient temperatures. The observed gas/particle partitioning is consistent with laboratory measurements and fits well to the Junge–Pankow model. Using air mass back-trajectories, atmospheric transport to Point Petre was estimated as 76% for BDE-47, 67% for BDE-99, and 70% for BDE-209 from west–northwest and southwest directions. During the same time period, similar congener profiles and concentration levels were found at Alert in the Canadian High Arctic. Different inter-annual variations between Point Petre and Alert indicate that emissions from other regions than North America could also contribute PBDEs in the Arctic. In contrast to weak temperature effect at Point Petre, significant temperature dependence in the summertime implies volatilization emissions of PBDEs at Alert. Meanwhile, episodic observations in the wintertime were likely associated with enhanced inputs through long-range transport during the Arctic Haze period.
Polycyclic aromatic hydrocarbon (PAH) air concentrations measured over the period 1992-2000 at the Canadian High Arctic station of Alert were subject to time-series analysis using dynamic harmonic ...regression (DHR). For most of the PAHs, the DHR model fit to the observed data was good, with DHR capable of interpolating over missing data points during periods when air concentrations were below detection limits. As expected, DHR identified seasonal increases in PAH air concentrations. However, it has also identified additional, subtler "seasonal" patterns as a series of harmonics with varying periodicity. For example, a regular summer high in air concentrations was apparent for many PAHs, particularly the lower molecular weight (two- to three-ringed) compounds, which may be attributed to summertime regional combustion events such as forestfires and/or revolatilization from surfaces (e.g., soil and oceans, as well as arctic surfaces). Comparison of wintertime PAH concentrations (where sigmaPAH ranged from 260 to 516 pg m(-3)) with an earlier arctic study did not reveal a reduction in PAH levels. However, removal of the seasonal components by DHR revealed a declining trend in PAH concentrations over the 1992-2000 period. For many lighter PAHs, this was typified by a linear decrease over the whole time series, although, for the higher molecular weight PAHs, a marked reduction was apparent in the first few years of sampling followed by a leveling off in concentrations by the mid/late-1990s. This behavior is similar to reported trends of other air pollutants in the Arctic, may be attributed to the decline in Soviet industry during the early 1990s, and has implications regarding the major PAH sources affecting the Arctic.
Multi-year measurements of polybrominated diphenyl ethers (PBDEs) in the Arctic atmosphere were conducted. Volatilization appeared to be the most important in the summertime for less brominated ...congeners in a local and/or regional scale because of significant correlations between In C and ambient temperatures. Samples were analyzed by a gas chromatograph equipped with an auto-sampler and a mass spectrometric detector. It was indicated that potential sources of PBDEs in air at Alert could include both volatilization emissions and long-range transport (LRT) inputs. Doubling times of PBDEs derived from inter-annual air trend data were similar to the growth rates reported previously in biotic samples. The results indicated that the PBDE concentrations decreased with increasing latitude, which suggested that PBDEs were emitted at mid-latitudes and then subjected to LRT to higher latitudes.
