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M.L. Olson

Publications and source records attributed to M.L. Olson.

12 recordsLinked to original sources
USGS2012

Evaluation of an offline method for the analysis of atmospheric reactive gaseous mercury and particulate mercury

Reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected in Milwaukee, WI, between April 2004 and May 2005, and in Riverside, CA, between July 25 and August 7, 2005 using sorbent and filter substrates. The substrates were analyzed for mercury by thermal desorption analysis (TDA) using a purpose-built instrument. Results from this offline-TDA method were compared with measurements using a real-time atmospheric mercury analyzer. RGM measurements made with the offline-TDA agreed well with a commercial real-time method. However, the offline TDA reported PHg concentrations 2.7 times higher than the real-time method, indicating evaporative losses might be occurring from the real-time instrument during sample collection. TDA combined with reactive mercury collection on filter and absorbent substrates was cheap, relatively easy to use, did not introduce biases due to a semicontinuous sample collection strategy, and had a dynamic range appropriate for use in rural and urban locations. The results of this study demonstrate that offline-TDA is a feasible method for collecting reactive mercury concentrations in a large network of filter-based samplers. Copyright 2008 Air & Waste Management Association.

Journal of the Air and Waste Management Associatio↗
USGS2010

Patterns of mercury dispersion from local and regional emission sources, rural Central Wisconsin, USA

Simultaneous real-time changes in mercury (Hg) speciation-reactive gaseous Hg (RGM), elemental Hg (Hg??), and fine particulate Hg (Hg-PM 2.5 ), were determined from June to November 2007, in ambient air at three locations in rural Central Wisconsin. Known Hg emission sources within the airshed of the monitoring sites include: 1) a 1114 megawatt (MW) coal-fired electric utility generating station; 2) a Hg-bed chlor-alkali plant; and 3) a smaller (465 MW) coal-burning electric utility. Monitoring sites, showing sporadic elevation of RGM, Hg o and Hg-PM 2.5 , were positioned at distances of 25, 50 and 100 km northward of the larger electric utility. A series of RGM events were recorded at each site. The largest, on 23 September, occurred under prevailing southerly winds, with a maximum RGM value (56.8 pg m -3 ) measured at the 100 km site, and corresponding elevated SO 2 (10.41 ppbv; measured at 50 km site). The finding that RGM, Hg o , and Hg-PM 2.5 are not always highest at the 25 km site, closest to the large generating station, contradicts the idea that RGM decreases with distance from a large point source. This may be explained if: 1) the 100 km site was influenced by emissions from the chlor-alkali facility or by RGM from regional urban sources; 2) the emission stack height of the larger power plant promoted plume transport at an elevation where the Hg is carried over the closest site; or 3) RGM was being generated in the plume through oxidation of Hg o . Operational changes at each emitter since 2007 should reduce their Hg output, potentially allowing quantification of the environmental benefit in future studies.

Atmospheric Chemistry and Physics Discussions↗
USGS2008

Mercury, trace elements and organic constituents in atmospheric fine particulate matter, Shenandoah National Park, Virginia, USA: A combined approach to sampling and analysis

Compliance with U.S. air quality regulatory standards for atmospheric fine particulate matter (PM 2.5 ) is based on meeting average 24 hour (35 μ m −3 ) and yearly (15 μg m −3 ) mass‐per‐unit‐volume limits, regardless of PM 2.5 composition. Whereas this presents a workable regulatory framework, information on particle composition is needed to assess the fate and transport of PM 2.5 and determine potential environmental/human health impacts. To address these important non‐regulatory issues an integrated approach is generally used that includes (1) field sampling of atmospheric particulate matter on filter media, using a size‐limiting cyclone, or with no particle‐size limitation; and (2) chemical extraction of exposed filters and analysis of separate particulate‐bound fractions for total mercury, trace elements and organic constituents, utilising different USGS laboratories optimised for quantitative analysis of these substances. This combination of sampling and analysis allowed for a more detailed interpretation of PM 2.5 sources and potential effects, compared to measurements of PM 2.5 abundance alone. Results obtained using this combined approach are presented for a 2006 air sampling campaign in Shenandoah National Park (Virginia, USA) to assess sources of atmospheric contaminants and their potential impact on air quality in the Park. PM 2.5 was collected at two sampling sites (Big Meadows and Pinnacles) separated by 13.6 km. At both sites, element concentrations in PM 25 were low, consistent with remote or rural locations. However, element/Zr crustal abundance enrichment factors greater than 10, indicating anthropogenic input, were found for Hg, Se, S, Sb, Cd, Pb, Mo, Zn and Cu, listed in decreasing order of enrichment. Principal component analysis showed that four element associations accounted for 84% of the PM 2.5 trace element variation; these associations are interpreted to represent: (1) crustal sources (Al, REE); (2) coal combustion (Se, Sb), (3) metal production and/or mobile sources (Mo, Cd, Pb, Cu, Zn) and (4) a transient marine source (Sr, Mg). Concentrations of Hg in PM 2.5 at background levels in the single pg m −3 were shown by collection and analysis of PM 2.5 on filters and by an automated speciation analyser set up at the Big Meadows air quality site. The speciation unit revealed periodic elevation of reactive gaseous mercury (RGM) that co‐occurred with peaks in SO 2 , indicating an anthropogenic source. GC/MS total ion current chromatograms for the two sites were quite similar indicating that organic signatures were regional in extent and/or that the same compounds were present locally at each site. Calculated carbon preference index values for n ‐alkanes indicated that plant waxes rather than anthropogenic sources, were the dominant alkane source. Polycyclic aromatic hydrocarbons (PAHs) were detected, with a predominance of non‐alkylated, and higher molecular weight PAHs in this fraction, suggestive of a combustion source (fossil fuel or forest fires).

Virginia↗
USGS2008

Characterization and cycling of atmospheric mercury along the central US Gulf Coast

Concentrations of atmospheric Hg species, elemental Hg (Hg ∘ ), reactive gaseous Hg (RGM), and fine particulate Hg (Hg-PM 2.5 ) were measured at a coastal site near Weeks Bay, Alabama from April to August, 2005 and January to May, 2006. Mean concentrations of the species were 1.6 ± 0.3 ng m −3 , 4.0 ± 7.5 pg m −3 and 2.7 ± 3.4 pg m −3 , respectively. A strong diel pattern was observed for RGM (midday maximum concentrations were up to 92.7 pg m −3 ), but not for Hg ∘ or Hg-PM 2.5 . Elevated RGM concentrations (>25 pg m −3 ) in April and May of 2005 correlated with elevated average daytime O 3 concentrations (>55 ppbv) and high light intensity (>500 W m −2 ). These conditions generally corresponded with mixed continental-Gulf and exclusively continental air mass trajectories. Generally lower, but still elevated, RGM peaks observed in August, 2005 and January–March, 2006 correlated significantly ( p < 0.05) with peaks in SO 2 concentration and corresponded to periods of high light intensity and lower average daytime O 3 concentrations. During these times air masses were dominated by trajectories that originated over the continent. Elevated RGM concentrations likely resulted from photochemical oxidation of Hg ∘ by atmospheric oxidants. This process may have been enhanced in and by the near-shore environment relative to inland sites. The marine boundary layer itself was not found to be a significant source of RGM. Size segregation determination, using a limited dataset from two different methods, suggested that a significant fraction of particulate Hg was bound to coarse particles (>2.5 μm). A potential source of the large fraction of coarse particulate Hg in the study area is sequestration of RGM within sea salt aerosols. The presence of rapidly depositing RGM and coarse particulate Hg may be important sources of Hg input along the Gulf Coast. However, the impact of these species on deposition rates is yet to be determined.

Applied Geochemistry↗
USGS2008

A comparison of speciated atmospheric mercury at an urban center and an upwind rural location

Gaseous elemental mercury (GEM), particulate mercury (PHg) and reactive gaseous mercury (RGM) were measured every other hour at a rural location in south central Wisconsin (Devil's Lake State Park, WI, USA) between April 2003 and March 2004, and at a predominantly downwind urban site in southeastern Wisconsin (Milwaukee, WI, USA) between June 2004 and May 2005. Annual averages of GEM, PHg, and RGM at the urban site were statistically higher than those measured at the rural site. Pollution roses of GEM and reactive mercury (RM; sum of PHg and RGM) at the rural and urban sites revealed the influences of point source emissions in surrounding counties that were consistent with the US EPA 1999 National Emission Inventory and the 2003-2005 US EPA Toxics Release Inventory. Source-receptor relationships at both sites were studied by quantifying the impacts of point sources on mercury concentrations. Time series of GEM, PHg, and RGM concentrations were sorted into two categories; time periods dominated by impacts from point sources, and time periods dominated by mercury from non-point sources. The analysis revealed average point source contributions to GEM, PHg, and RGM concentration measurements to be significant over the year long studies. At the rural site, contributions to annual average concentrations were: GEM (2%; 0.04 ng m-3); and, RM (48%; 5.7 pg m-3). At the urban site, contributions to annual average concentrations were: GEM (33%; 0.81 ng m-3); and, RM (64%; 13.8 pg m-3). ?? The Royal Society of Chemistry.

Journal of Environmental Monitoring↗
USGS2006

Atmospheric mercury speciation in Yellowstone National Park

Atmospheric concentrations of elemental mercury (Hg 0 ), reactive gaseous Hg (RGM), and particulate Hg (pHg) concentrations were measured in Yellowstone National Park (YNP), U.S.A. using high resolution, real time atmospheric mercury analyzers (Tekran 2537A, 1130, and 1135). A survey of Hg 0 concentrations at various locations within YNP showed that concentrations generally reflect global background concentrations of 1.5–2.0 ng m − 3 , but a few specific locations associated with concentrated geothermal activity showed distinctly elevated Hg 0 concentrations (about 9.0 ng m − 3 ). At the site of intensive study located centrally in YNP (Canyon Village), Hg 0 concentrations did not exceed 2.5 ng m − 3 ; concentrations of RGM were generally below detection limits of 0.88 pg m − 3 and never exceeded 5 pg m − 3 . Concentrations of pHg ranged from below detection limits to close to 30 pg m −3 . RGM and pHg concentrations were not correlated with any criteria gases (SO 2 , NO x , O 3 ); however pHg was weakly correlated with the concentration of atmospheric particles. We investigated three likely sources of Hg at the intensive monitoring site: numerous geothermal features scattered throughout YNP, re-suspended soils, and wildfires near or in YNP. We examined relationships between the chemical properties of aerosols (as measured using real time, single particle mass spectrometry; aerosol time-of-flight mass spectrometer; ATOFMS) and concentrations of atmospheric pHg. Based on the presence of particles with distinct chemical signatures of the wildfires, and the absence of signatures associated with the other sources, we concluded that wildfires in the park were the main source of aerosols and associated pHg to our sampling site.

Science of the Total Environment↗
USGS2002

Methylmercury in flood-control impoundments and natural waters of northwestern Minnesota, 1997-99

We studied methylmercury (MeHg) and total mercury (HgT) in impounded and natural surface waters in northwestern Minnesota, in settings ranging from agricultural to undeveloped. In a recently constructed (1995) permanent-pool impoundment, MeHg levels typically increased from inflow to outflow during 1997; this trend broke down from late 1998 to early 1999. MeHg levels in the outflow reached seasonal maxima in mid-summer (maximum of 1.0 ng L &minus;1 in July 1997) and late-winter (maximum of 6.6 ng L &minus;1 in February 1999), and are comparable to high levels observed in new hydroelectric reservoirs in Canada. Spring and autumn MeHg levels were typically about 0.1&ndash;0.2 ng L &minus;1 . Overall, MeHg levels in both the inflow (a ditch that drains peatlands) and outflow were significantly higher than in three nearby reference natural lakes. Eleven older permanent-pool impoundments and six natural lakes in northwestern Minnesota were sampled five times. The impoundments typically had higher MeHg levels (0.071&ndash;8.36 ng L &minus;1 ) than natural lakes. Five of six lakes MeHg levels typical of uncontaminated lakes (0.014&ndash;1.04 ng L &minus;1 ) with highest levels in late winter, whereas a hypereutrophic lake had high levels (0.37&ndash;3.67 ng L &minus;1 ) with highest levels in mid-summer. Seven temporary-pool impoundments were sampled during summer high-flow events. Temporary-pool impoundments that retained water for about 10&ndash;15 days after innundation yielded pronounced increases in MeHg from inflow to outflow, in one case reaching 4.6 ng L &minus;1 , which was about 2 ng L &minus;1 greater than the mean inflow concentration during the runoff event.

Minnesota↗
USGS1998

Trophic transfer of methyl mercury in the northern Florida Everglades

There are spatial differences in methyl mercury (MeHg) concentrations in biota in Water Conservation Areas 2 and 3 in the Everglades, with higher concentrations generally found in the southern areas. Fish and hemipterans had the most MeHg on a wet weight basis, with levels exceeding 30 ng g-1. The magnitude of MeHg accumulation in biota varies seasonally and does not always appear to be associated with changes in water column concentration. This is exemplified by periphyton, the base of the foodweb in the Everglades, at a high nutrient sampling site. Although limited in scope, MeHg concentrations presented for biota provide insight into beginning to understand the dynamic nature of Hg transfer in the Everglades foodweb on a spatial and temporal basis.

Biogeochemistry↗
USGS1998

System controls on the aqueous distribution of mercury in the northern Florida Everglades

The forms and partitioning of aqueous mercury species in the canals and marshes of the Northern Florida Everglades exhibit strong spatial and temporal variability. In canals feeding Water Conservation Area (WCA) 2A, unfiltered total Hg (HgT(U)) is less than 3 ng L-1 and relatively constant. In contrast, methyl mercury (MeHg) exhibited a strong seasonal pattern, with highest levels entering WCA-2A marshes during July. Stagnation and reduced flows also lead to particle enrichment of MeHg. In the marshes of WCA-2A, 2B and 3A, HgT(U) is usually <5 ng L-1 with no consistent north-south patterns. However, for individual dates, aqueous unfiltered MeHg (MeHg(U)) levels increase from north to south with generally lowest levels in the eutrophied regions of northern WCA-2A. A strong relationship between filtered Hg species and dissolved organic carbon (DOC), evident for rivers draining wetlands in Wisconsin, was not apparent in the Everglades, suggesting either differences in the binding sites of DOC between the two regions, or non-organic Hg complexation in the Everglades.

Biogeochemistry↗
USGS1998

Diel variability of mercury phase and species distributions in the Florida Everglades

Preliminary studies of mercury (Hg) cycling in the Everglades revealed that dissolved gaseous mercury (DGM), total mercury (Hg(T)), and reactive mercury (Hg(R)) show reproducible, diel trends. Peak water-column DGM concentrations were observed on or about noon, with a 3 to 7 fold increase over night-time concentrations. Production of DGM appears to cease during dark periods, with nearly constant water column concentrations that were at or near saturation with respect to the overlying air. A simple mass balance shows that the flux of Hg to the atmosphere from diel DGM production and evasion represents about 10% of the annual input from atmospheric deposition. Production of DGM is likely the result of an indirect photolysis reaction that involves the production of reductive species and/or reduction by electron transfer. Diel variability in Hg(T) and Hg(R) appears to be controlled by two factors: inputs from rainfall and photolytic sorption/desorption processes. A possible mechanism involves photolysis of chromophores on the surface of a solid substrate (e.g., the periphyton mat) giving rise to destabilization of sorbed mercury and net desorption during daylight. At night, the sorption reactions predominate and the water-column Hg(T) decreases. Methylmercury (MeHg) also showed diel trends in concentration but were not clearly linked to the solar cycle or rainfall at the study site.

Biogeochemistry↗
USGS1997

Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades

Aqueous samples from the Florida Everglades present several problems for the analysis of total mercury (HgT) and methyl mercury (MeHg). Constituents such as dissolved organic carbon (DOC) and sulfide at selected sites present particular challenges due to interferences with standard analytical techniques. This is manifested by 1) the inability to discern when bromine monochloride (BrCl) addition is sufficient for sample oxidation for HgT analysis; and 2) incomplete spike recoveries using the distillation/ethylation technique for MeHg analysis. Here, we suggest ultra-violet (UV) oxidation prior to addition of BrCl to ensure total oxidation of DOC prior to HgT analysis and copper sulfate (CuSO 4 ) addition to aid in distillation in the presence of sulfide for MeHg analysis. Despite high chloride (Cl - ) levels, we observed no effects on MeHg distillation/ethylation analyses.

Fresenius' Journal of Analytical Chemistry↗