Categorized | Sci-Tech

Volcano Watch: Kilauea’s emissions, effects all about location

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

A common saying in the real estate business is that three things matter regarding property: “location, location, location.” The same might be said about the effects of Kilauea’s irritating sulfur dioxide (SO2) emissions and resulting vog. It’s all about location.

Since 1983, SO2 has been emitted from two main source locations on Kilauea: in and around Halemaumau Crater at the volcano’s summit, and at the Puu Oo vent on its East Rift Zone.

Beginning in late 2007, however, summit emissions began to climb steadily and by early January 2008, they had reached their highest level in 20 years. The location of the summit emission source relative to popular visitor areas, along with an associated increase in respiratory emergency calls, resulted in the National Park Service closing roughly half of Crater Rim Drive in mid-February 2008.

Gas emissions from the summit source increased further in mid-March 2008 with the opening of a new volcanic vent just below the Halemaumau Overlook. Since the grand opening of this vent, summit SO2 emissions have varied widely, but, on average, have been about 850 tonnes/day.

This amount of gas release is substantial, well above its previous average of 140 tonnes/day, yet the increased summit emissions represent only a modest change, about 30 percent of the total amount of SO2 emitted by Kilauea.

By comparison, in 2005, the volcano’s East Rift Zone emissions increased by a whopping 200 percent, but that increase didn’t generate air quality standard exceedences like those produced by the recent summit activity.

The reason for this seeming disparity between changes in emission rates and corresponding changes in air quality links back to the real estate catchphrase, “location, location, location.” The summit vent is closer to locations where people live and work than is the east rift vent.

Tradewinds blow roughly 90 percent of the year, and when they do, communities including Pahala, Naalehu, and Hawaiian Ocean View Estates are directly downwind of and relatively close to the summit emission source. This proximity to Halemaumau was a primary factor driving the 42 exceedences of the 24-hour SO2 air quality standard—as measured in Pahala by the Hawaii Department of Health—since the new summit vent opened.

East Rift Zone emissions, swept along the southerly Ka`u coastline by tradewinds, are frequently brought back on shore in the lee of Kilauea’s landmass by daytime onshore breezes and further impact air quality, especially in Pahala.

With a longer travel time to Pahala from Puu Oo than from the summit vent, east rift SO2 emissions are more likely to be converted to particles, a factor which reasonably contributed to the 19 exceedences of Federal particle standards in Pahala since April 2008.

When the northeasterly tradewinds are absent or when Kona (southerly) winds blow, folks in the National Park, Volcano Golf Course subdivision and Volcano Village, all located immediately adjacent to the summit vent, are subjected to brief, but episodically spectacular SO2 and particle levels.

There has been, however, some improvement in air quality. While summit emissions continue at variable but elevated, levels, East Rift Zone SO2 emissions decreased in late 2008 and remain at about 60 percent of their previous four year average. This decrease appears to have produced some relief for downwind communities.

The number of monthly air quality standard exceedences recorded by Department of Health monitors declined by about half in 2009 for both Pahala and South Kona. It is reasonable to expect that populated areas from Keaau to Volcano Village, which are sometimes impacted by Puu Oo emissions during variable or southerly winds might also experience some relief.

Despite the decrease at Puu Oo, the combined SO2 emissions from Kilauea’s summit and East Rift Zone vents still remain high. Seasonal tradewind lapses have begun, and high gas and particle concentrations returned to Hawaii Volcanoes National Park and adjacent communities for several days this past week.

These bad air days remind us that on Kilauea “location, location, location” (summit, rift, and your location relative to these vent areas) are three things that matter greatly regarding the effects of SO2 emissions on Hawaii Island residents and visitors.

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