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Determination of Mercury and other Trace Elements in Home Heating Oil Used in New York State Mahdi Ahmadi, John Graham, Laura Shields, and Paul J. Miller Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b02404 • Publication Date (Web): 04 Dec 2017 Downloaded from http://pubs.acs.org on December 4, 2017
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Determination of Mercury and other Trace Elements
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in Home Heating Oil Used in New York State
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Mahdi Ahmadi*†, John Graham‡, Laura Shields±, Paul J. Miller†
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† Northeast States for Coordinated Air Use Management, 89 South Street, Suite 602, Boston,
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Massachusetts 02111-2604, U.S.A.
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‡ Clean Air Task Force, Columbus, Ohio
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± San Diego Air Pollution Control District, San Diego, California
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KEYWORDS: Mercury, fuel oil, elemental analysis, sulfur, No. 2 home heating oil
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ABSTRACT: A 2002 mercury emissions inventory developed by the Northeast States for
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Coordinated Air Use Management using standard fuel oil mercury (Hg) emission factors from
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the U.S. Environmental Protection Agency (known as US EPA “AP-42” factors) identified
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residential fuel oil combustion as an important contributor to Hg air emissions in the northeastern
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United States. Published literature values, however, suggest much lower mercury content in
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heating oil than inferred from the US EPA factors. To better characterize mercury (along with
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other trace element) content in heating oil sold in the Northeast, we conducted a two-phase
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sampling and analysis study of commercially available fuel oil sold in the northeastern U.S., with
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a focus on New York State. Changes between the two study periods and relationships between
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trace element and sulfur levels were evaluated. The study found that concentrations of mercury
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and other trace elements sampled during both study phases were within typical ranges reported in
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the literature. Although the average sulfur level in the samples dropped by two orders of
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magnitude between the two phases because of new government regulations limiting sulfur
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content in fuel oil after the first sampling phase, we observed no significant relationship between
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sulfur content and the other trace elements. In addition, derived emission factors for almost all
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trace elements showed lower values than the tabulated US EPA AP-42 factors. The lower
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mercury content measured in the samples indicate that heating oil combustion is a much lower
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source of mercury emitted to the air in the northeastern U.S. than would be inferred from an
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emission inventory developed using US EPA emission factors.
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INTRODUCTION
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Approximately 6 million households in the northeastern U.S. rely on home heating oil for
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heating needs, representing approximately 84% of the total households in the U.S. that are
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dependent upon home heating oil as their primary heating fuel.1 The top consuming state for
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home heating oil is New York State (NYS), followed by Pennsylvania, Massachusetts,
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Connecticut, and Maine. In 2015, NYS consumers bought a little over 890 million gallons of
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home heating oil, or over 22% of all heating oil sold in the entire U.S.2 In addition, some
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institutional and commercial buildings use heating oil for space and water heating. According to
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the EIA, 92% of all residential and 40% of all industrial and residential distillate fuel oil sales in
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2015 occurred on the East Coast, comprising approximately 3.7 and 1.9 billion gallons of heating
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oil sold to residential and commercial consumers, respectively.2
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With the relatively large preponderance of heating oil consumption in the northeastern United
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State, we conducted a two-phase sampling and analysis study to better characterize the trace
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element content in heating oil (commonly referred to as No. 2 fuel oil or distillate). This study,
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which focuses on New York State, improves the understanding of the relative importance of
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heating oil combustion in regional emissions inventories for the analyzed elements. The elements
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included are mercury (Hg), vanadium (V), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn),
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arsenic (As), antimony (Sb), selenium (Se), and lead (Pb).
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Our study placed special emphasis on Hg, a toxic metal found in residential heating oil (and
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other fuel oils) that is emitted to the air when the oil is burned. Once in the atmosphere, Hg can
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be deposited locally or transported over long distances before falling back to the surface. When
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released into the environment and deposited or carried into water bodies, Hg can be converted to
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methylmercury (MeHg), a particularly toxic form of Hg. Methylated Hg in the aquatic food
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chain can bioaccumulate in fish tissue to concentrations markedly higher than in the surrounding
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water.
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A major route of exposure to Hg is through the consumption of fish. Women of child bearing
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age are of special concern as MeHg ingested by a mother can transport across the placenta into
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the brain of a developing fetus. In young children and fetuses, MeHg inhibits the normal
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development of the nervous system, an effect that may occur even at low exposure levels. Often
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this damage is not apparent until later in the developmental process, when motor and verbal
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skills are found to be delayed or abnormal. Developmental effects have been found in children
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exposed in utero, even though their mothers did not experience any symptoms of adult toxicity.3
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Women in the Northeast have the highest Hg exposure in the U.S., with 19% having blood
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organic Hg level exceeding what is considered safe for fetuses.4
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Most of the Hg present in water bodies − and the fish within them − in NYS and the Northeast
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is deposited from the atmosphere.5,6 To address Hg in the environment and its threat to human
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health, NYS and surrounding states have pursued a number of initiatives aimed at the virtual
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elimination of Hg releases into the environment. In December 2007, the U.S. Environmental
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Protection Agency (USEPA) approved a request from NYS and the six New England states to
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establish a regional Total Maximum Daily Load (TMDL) for Hg under the federal Clean Water
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Act. The regional Hg TMDL was set at a level that would decrease Hg levels in fish tissue low
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enough for states to lift their fish consumption advisories.7 Subsequently in 2009, New Jersey
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also received approval from the USEPA for a Hg TMDL for 122 impaired bodies of water within
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the state. The New Jersey TMDL was set at a comparable level to the regional Hg TMDL
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previously established by NYS and the six New England states.8
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There have been a number of relatively recent programs in the U.S. to reduce Hg air emissions,
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most notably, new state and federal rules aim to reduce or eliminate Hg emissions from
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municipal waste combustion, medical waste incineration, and coal-fired electric power plants.9,10
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Studies occurring after these Hg reduction measures took effect have documented measureable
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decreases in Hg concentrations in leaf litterfall in eastern U.S. forests11 as well as in freshwater
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fish tissue collected in the northeastern U.S.12,13 and in important commercial marine fish from
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the Atlantic Ocean off the eastern U.S. coast.14,15 As the large Hg source sectors reduce or
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eliminate their emissions, other source sectors, such as residential heating oil combustion, can
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become relatively more important for efforts to reduce the public’s exposure to Hg being
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deposited from the air onto land and into water bodies.
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An analysis by the Northeast States for Coordinated Air Use Management16 using fuel oil Hg
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emission factors taken from the USEPA AP-42 database17,18 identified residential fuel oil
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combustion as an important source sector in a 2002 regional Hg air emissions inventory of eight
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northeastern states (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New
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York, Rhode Island, Vermont). When added to estimated Hg emissions from oil used to fire
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boilers in the commercial, industrial, institutional, and electrical generating sectors, emissions
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derived from oil combustion comprised nearly one-fourth of the regional Hg inventory total.
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We note that USEPA AP-42 emission factors are developed mainly for national inventory
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purposes and may not be suitable for a particular source or location. In addition, comparing the
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results of elemental fuel analysis and USEPA AP-42 emission factors should be made with the
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consideration that the AP-42 emission factors are based on the emitted elements after
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combustion. While the amount of trace elements entering the combustion chamber only depends
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on the fuel composition, the amount emitted post-combustion depends on combustion
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temperature, fuel feed mechanism, and particulate matter (PM) treatment technology, in addition
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to the fuel composition.18 For example, lower flame temperature would result in less metal
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volatilization from the fuel and less subsequent condensation and enrichment on fine PM, thus
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lowering the amount of volatized elements in the stack exhaust gas. On the other hand, erosion of
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metal components or mercury re-entrainment from “cold spots” after combustion may add small
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amounts of metal emissions to the stack gas. Apart from these latter factors, metal emissions in
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the stack gas can not be greater than assuming all metal content of the fuel is volatilized through
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the stack after fuel combustion. This is particularly salient for our study’s focus on Hg, which is
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more volatile relative to other trace elements analyzed in this study, and is chiefly emitted in the
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gas phase during combustion.
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Since the early 1980s, several estimates of Hg in No. 2 distillate oil have been published,
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describing a wide range of concentrations. The USEPA estimated the concentration of Hg in No.
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2 distillate oil as 400 µg/kg,19 and with a later adjustment to
