Meteorological Processes Affecting the Transport of Emissions from the Navajo Generating Station to Grand Canyon National Park

Lindsey, C.G.; Dye, Timothy S.; Richards, L.W.; Blumenthal, D.L.

doi:10.1175/1520-0450(1999)038<1031:mpatto>2.0.co;2

Cited by 11 publications

(4 citation statements)

References 9 publications

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“…If operators did not believe the WHITEX source attribution, they could conduct their own study, and they did with the Navajo Generating Station Visibility Study (NGSVS). [114][115][116][117][118][119][120][121][122][123] This study also found SO 4 2contributions from NGS in the Grand Canyon. Although not as large as those of Malm et al, 84 the SO 4 2contributions were still large enough to cause perceptible changes in haze.…”

Section: -supporting

confidence: 58%

Visibility: Science and Regulation

Watson

2002

Journal of the Air & Waste Management Association

933

548

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The 1999 Regional Haze Rule provides a context for this review of visibility, the science that describes it, and the use of that science in regulatory guidance. The scientific basis for the 1999 regulation is adequate. The deciview metric that tracks progress is an imperfect but objective measure of what people see near the prevailing visual range. The definition of natural visibility conditions is adequate for current planning, but it will need to be refined as visibility improves. Emissions from other countries will set achievable levels above those produced by natural sources. Some natural events, notably dust storms and wildfires, are episodic and cannot be represented by annual average background values or emission estimates. Sulfur dioxide (SO2) emission reductions correspond with lower sulfate (SO4(2-)) concentrations and visibility improvements in the regions where these have occurred. Non-road emissions have been growing more rapidly than emissions from other sources, which have remained stable or decreased since 1970. Simpler models representing transport, limiting precursor pollutants, and gas-to-particle equilibrium should be used to understand where and when emission reductions will be effective, rather than large complex models that have insufficient input and validation measurements. Examples of model-based source attribution show large differences among estimates from various modeling systems and with ambient measurements.

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Section: -supporting

confidence: 58%

Visibility: Science and Regulation

Watson

2002

Journal of the Air & Waste Management Association

933

548

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“…Damming of river systems has the potential to increase Hg and Se accumulation in stream food webs by linking lotic ecosystems to lentic habitats that often serve as sources of bioavailable forms of these elements . This is particularly true in the Colorado River Basin, where large reservoirs proliferate and sources of contaminants are abundant (e.g., Se) or proximate to reservoirs (e.g., Hg) . In the present study we found no significant differences in Hg and Se accumulation among sites throughout the Grand Canyon.…”

Section: Discussioncontrasting

confidence: 59%

“…Our research adds to a growing body of evidence showing that remote ecosystems are vulnerable to long‐range transport and subsequent bioaccumulation of contaminants . Airborne transport and deposition is most commonly identified as the mechanism for contaminant introduction to remote ecosystems , and this is a potential pathway for Hg entering the Grand Canyon food web . In addition, long‐range downstream transport from upstream sources can play a significant role in delivering contaminants to lotic ecosystems, particularly in the case of Se transport within the Colorado River Basin .…”

Section: Discussionmentioning

confidence: 88%

“…Atmospheric deposition is a common vehicle for Hg introduction to aquatic ecosystems in remote areas of the world including western US national parks . Potential sources of atmospheric Hg deposition to the Grand Canyon ecosystem include a large regional atmospheric pool, and nearby point sources such as a coal burning power plant located near Page, Arizona, northeast of Grand Canyon . Reactive forms of inorganic Hg in aquatic systems can be converted to methylmercury (MeHg) via microbial processes in sediment, algal mats, or periphyton biofilms , and MeHg efficiently biomagnifies through aquatic food webs .…”

Section: Introductionmentioning

confidence: 99%

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Mercury and selenium accumulation in the Colorado River food web, Grand Canyon, USA

Walters

Kennedy

Cross

et al. 2015

Enviro Toxic and Chemistry

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Mercury (Hg) and selenium (Se) biomagnify in aquatic food webs and are toxic to fish and wildlife. The authors measured Hg and Se in organic matter, invertebrates, and fishes in the Colorado River food web at sites spanning 387 river km downstream of Glen Canyon Dam (AZ, USA). Concentrations were relatively high among sites compared with other large rivers (mean wet wt for 6 fishes was 0.17-1.59 μg g(-1) Hg and 1.35-2.65 μg g(-1) Se), but consistent longitudinal patterns in Hg or Se concentrations relative to the dam were lacking. Mercury increased (slope = 0.147) with δ(15) N, a metric of trophic position, indicating biomagnification similar to that observed in other freshwater systems. Organisms regularly exceeded exposure risk thresholds for wildlife and humans (6-100% and 56-100% of samples for Hg and Se, respectfully, among risk thresholds). In the Colorado River, Grand Canyon, Hg and Se concentrations pose exposure risks for fish, wildlife, and humans, and the findings of the present study add to a growing body of evidence showing that remote ecosystems are vulnerable to long-range transport and subsequent bioaccumulation of contaminants. Management of exposure risks in Grand Canyon will remain a challenge, as sources and transport mechanisms of Hg and Se extend far beyond park boundaries.

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