Mercury contamination was found to be widespread in soils at a property in Upstate New York. Historical site use suggested that the mercury did not result from prior industrial use of the property. Soil contamination may have resulted from atmospheric deposition of mercury released from properties in close proximity to the contaminated property. The purpose of this forensics investigation was to examine to what extent atmospheric deposition of elemental mercury may have influenced mercury levels found in surficial soils on the contaminated property and further to identify the source(s) of the mercury. Work efforts included an examination of historical records available for a chlor-alkali plant (CAP) upwind of the contaminated property to establish historical use and disposal practices for elemental mercury. Mercury emissions test data from the Upstate New York chlor-alkali facility were modeled (USEPA ISC3) as a means of estimating impacts on ambient air and soils vicinal to the facility. Mercury emissions from the facility were modeled as both a point source and volume source. For example, at a location 305 meters to the east and 30 meters to the north of the modeled source centerline elemental mercury concentrations in ambient air were estimated at 270 ng/m<sup>3</sup> (average results based upon 5 years of meteorological data). This value is contrasted to a background concentration of 1.6 ng/m<sup>3</sup> (USEPA Report to Congress 1997). As a result of the modeling data in combination with findings related to mercury use and disposal practices at the NY CAP documented from the records review, it was concluded that emissions from the CAP facility during the period of operation (1897-1991) most likely accounted for the concentrations of elemental mercury found in surficial soils at properties situated downwind of the CAP. These findings were further corroborated by information available in the open literature for CAPs world-wide.
The chlor-alkali industry represents the largest historical consumer of elemental mercury in the United States. (chlor-alkali production takes place using an electrochemical process in which elemental mercury is used as a liquid cathode in the electrolytic production of chlorine gas and alkali (NaOH) from brine salts. Refer to
Mercury contamination in soils at an industrial site in Niagara Falls, New York was widespread [
The property is located at 3163 Buffalo Avenue in Niagara Falls, New York within a highly industrialized region of the city in close proximity to the Niagara River. The property is comprised of 5.7 acres and historically housed a variety of chemical operations dating from the 1940’s. Based upon review of available records none of these prior operations used or handled mercury [
The study approach consisted of the following key elements:
1) An examination of all available records for the NYCAP related to mercury handling and disposal practices during the period 1897-1991 was conducted.
2) Identification of historical sources of mercury emissions (point and fugitive).
3) Development of emissions rates for identified sources using actual air emissions data (if available) for a representative period of operation for the NYCAP.
4) Performance of atmospheric dispersion modeling of emissions to estimate ambient air concentrations of mercury in the vicinity of the NYCAP.
5) Comparison of estimated ambient air concentrations to ambient background for mercury, as well as, mercury concentrations (both measured and estimated) in the vicinity of other CAPs worldwide.
6) Comparison of mercury concentrations present in soils at the 3163 Buffalo Avenue property to the following data sets:
a) Mercury in soils upwind of the NYCAP.
b) Background concentrations measured in soils characteristic of other US locations.
c) Mercury concentrations measured in soils in the vicinity of other CAPs worldwide.
7) Researching of the environmental impacts attributable to other CAPs worldwide. Summarize ambient air and soil mercury concentrations in the vicinity of these facilities and determine the relevance of these data to defining the environmental impacts of the NYCAP.
In summary, to what extent could the results from each of these elements collectively be used to attribute mercury concentrations found in soils at 3163 Buffalo Avenue to mercury emissions from the NYCAP.
The primary objective of this study was to identify the most likely source(s) of elevated mercury concentrations found in soils on an industrial site in Niagara Falls, New York. A three phase approach was employed as stated previously. One phase included an examination of mercury use at CAPs worldwide and their associated environmental impacts by means of a review of the open literature. The results of this review are summarized here.
The chlor-alkali industry represents the largest historical consumer of elemental mercury in the United States. USEPA estimates that 28 facilities were in operation in 1973 [
Environmental contamination attributable to mercury emissions from five Swedish chlor-alkali plants was investigated in 1971 [
Facility | Location | Capacity 103 Mg/yr | Capacity 103 tons/yr | 1994 emissions Mg/yr |
---|---|---|---|---|
Georgia-Pacific Corp., Chemical Division | Bellingham, WA | 82 | 90 | 0.585 |
BF Goodrich, Chemical Group | Calvert City, KY | 109 | 120 | 0.382 |
Hanlin Group, Inc., LCP Chemicals Division | Reigelwood, NC Orrington ME | 48 76 | 53 80 | 0.497 0.264 |
ASHTA Chemicals, Inc. | Ashtabula, OH | 36 | 40 | 0.753 |
Occidental Petroleum Corp., Electrochemicals | Deer Park, TX Delaware City, DE Muscle Shoals, AL | 347 126 132 | 383 139 146 | 0.472 0.231 0.106 |
Olin Corporation, Olin Chemicals | Augusta, GA Charleston, TN | 102 230 | 112 254 | 0,597 0.684 |
Pioneer Chlor-Alkali Company Inc. | St. Gabriel, LA | 160 | 176 | N/A |
PPG Industries, Inc., Chemicals Group | Lake Charles, LA New Martinsville, WV | 233 70 | 256 77 | 0.558 0.513 |
Vulcan Materials Company, Vulcan Chemicals Division | Port Edwards, WI | 65 | 72 | N/A |
linked to CAP source emissions and in particular the hydrogen stack. Mercury deposition in the vicinity of a Finnish chlor-alkali plant was examined. Dry and wet deposition rates were measured employing the moss-bag sampling technique [
The EPA Mercury Study Report to Congress states that atmospheric concentrations of elemental mercury in the vicinity of chlor-alkali facilities are significantly higher than background concentrations [
the highest mercury concentrations in ambient air at sampling locations near the electrolytic cell rooms. Concentrations reported at these locations and along downwind vectors were 3 - 4 times higher than background levels measured at coastal sites in central Italy. Swedish researchers, reporting on mercury levels in the vicinity of two chlor-alkali plants in that country [
An emissions estimate of 787 g/day was selected to represent actual mercury emissions from the NYCAP. This estimate based upon actual emissions data [
Location/site | Concentrations (ng/m3) | Reference |
---|---|---|
Bohus/Sweden: | ||
0.25 Km from chlor-alkali plant | 43.82 | [ |
0.50 Km from chlor-alkali plant | 26.55 | [ |
1.5 Km from chlor-alkali plant | 20.93 | [ |
5.0 Km from chlor-alkali plant | 19.46 | [ |
Huelva (Spain) | 96.00 (mean) (N = 5538) | [ |
Torrela Vega (Spain) | 41.00 (N = 4401) | [ |
Monzon (Spain) | 362.3 (N = 3901) | [ |
The selected emission rate of 787 g/day is the lowest of all the rates estimated (see
Concurrent five-year records (1985-1989) of hourly meteorological data were obtained from Buffalo Airport and Niagara Falls Airport and then processed into composite wind roses. The wind rose for Niagara Falls showed a greater westerly component than did the wind rose for the same time period at Buffalo. Given the much closer proximity of the Niagara Falls Airport to the site and the differing orientations of major bodies of water near the two airports, the meteorological data from Niagara Falls were selected as most representative for the site and were used in subsequent modeling analyses to estimate the transport and dispersion of mercury emissions from the NYCAP. The wind rose for Niagara Falls Airport showed winds from the west-southwest were most frequent (approximately 11% on average). West winds were nearly as frequent (about 10%), while south, south- southeast, and southeast winds each occurred about 8% of the time on average. Concurrent upper air data from Buffalo Airport were used to determine mixing heights and were incorporated in the modeling analyses. Buffalo Airport was the closest site for which upper air data needed to estimate mixing height were available.
The EPA Industrial Source Complex Model (ISC3) was selected for use in this modeling study. ISC3 is recommended for use in EPA’s “Guideline on Air Quality Models” (EPA, 2003 [
1) Volume Source Approach
In the volume source approach, it was assumed that all the mercury emissions were released from a series of passive vents located on the walls and roof of the cell building (see
2) Point Source Approach
In the point source approach, it was assumed that all mercury vapor was emitted to the atmosphere via a single stack located adjacent to the cell building. The stack height was assumed to equal the building height, and horizontal dimensions for the cell building were used with the EPA Building Profile Input Program Preprocessor (BPIP) to determine the projected building parameters needed by ISC3 to incorporate the effects of building downwash. The point source was modeled using a stack exit diameter of 6 inches, a negligible exit velocity (0.1 meters per second), and a near ambient stack temperature to minimize any plume rise.
3) Receptor Data
The modeling analysis was conducted using a Cartesian (rectangular) receptor grid centered on the NYCAP. Receptors are locations at which the model predicts concentrations. The grid measured 4 km by 4 km and used a fine receptor spacing of 50 meters. Additional receptors were placed along the northwest corner of the downwind property (approximately 305 meters to the east) and along the edge of a nearby residential area (approximately 300 meters to the east-northeast). Flat terrain was assumed in the modeling, since there were no significant terrain variations in the inner part of the grid that covered the area of primary interest for the study.
Volume III of the Report to Congress [
For deposition modeling of the NYCAP, a representative annual average dry deposition velocity for divalent mercury was calculated through a review and analysis of the values presented in
Total dry deposition of mercury was estimated as follows. The total predicted gaseous mercury concentrations at ground level (χT) were be apportioned into elemental (χ0) and divalent (χ2) components based on the 70/30 apportionment of the gaseous mercury emissions [
The dry deposition (D) of each component was then calculated as the product of the predicted ambient air concentration at ground level (χ) and the applicable deposition velocity (v) as shown here: (The subscripts 0 and 2 refer hereafter to the elemental and divalent forms of mercury).
Substituting values of 0.06 cm/s for v0 and 3.87 cm/s for v2 yields:
If the total predicted concentration is presented in units of ng/m3, then the total dry deposition of gaseous mercury in units of milligrams per square meter per year (mg∙m−2∙yr−1) can be represented by:
The Report to Congress [
A literature survey was performed to establish mercury concentrations in ambient air representative of background and not influenced by contributions from CAPS or other mercury emitting sources. These data were used for comparison to concentrations in ambient air predicted by dispersion modeling (see Sections 3.6 and 3.7 Results and Discussion) and directly attributable to air emissions from the NYCAP.
The Expert Panel on Mercury Atmospheric Processes cited in the EPA Report [
Background concentrations for mercury in surface soils were needed for comparison to levels present in soils at the 3163 Buffalo Avenue site directly downwind of the NYCAP. Some background and reference concentrations used in the comparison are summarized in
Additionally, a comprehensive data-base of mercury levels in surficial soils of the continental United States was generated by the US Geological Survey [
Location/area type | ng/m3 mean (range) | Reference |
---|---|---|
Chicago, IL | 8.7 (1.8 - 62.7) | [ |
Lake Michigan | 2.3 (1.3 - 4.9) | [ |
South Haven, MI | 2.0 (1.8 - 4.3) | [ |
Ann Arbor, MI | 2.0 (max. 4.4) | [ |
Detroit, MI Site B | 3.7 (max 8.5) | [ |
Underhill Center, VT | 2.0 (1.2 - 4.2) | [ |
Broward County, FLBackground Site nearAtlantic Ocean (Site 1) | 1.8 | [ |
Broward County, FLInland (Site 2) | 3.3 | [ |
Broward County, FLInland (Site 3) | 2.8 | [ |
Little Rock Lake, WI | 1.6 (1.0 - 2.5) | [ |
Crab Lake, WI | 1.7 | [ |
French Guiana, Dorlin Camp Hill/Rural | 5.4 ± 1.6 | [ |
French Guiana, Petie Saut Lake/Rural | 2.8 ± 1.4 | [ |
French Guiana, Background Levels/Pristine | (1.0 - 4.0) | [ |
Bondville, IL/(background) | 2.0 ± 0.5 (1.3 - 3.8) | [ |
Chicago, IL/Urban | 3.6 ± 2.9 (1.6 - 22.1) | [ |
Kenosha, WI/Rural | 2.2 ± 0.7 (1.1 - 5.7) | [ |
Sleeping Bears Dunes, MI/Rural | 2.1 ± 0.7 (1.4 - 5.0) | [ |
South Haven, MI/Rural | 2.2 ± 0.7 (1.4 - 6.1) | [ |
France, Champ Sur Drac/Suburban | 3.4 ± 3.6 (1.9 - 4.8) | [ |
Antarctica, Neumayer Station/Pristine | 1.08 ± 0.29 (0.27 - 2.34) | [ |
Soil type/location | Description/source | mg/kg | Reference |
---|---|---|---|
NY CAP Site | Upwind CAP (South and West) Composite Samples | 0.003 | [ |
Niagara Falls | Surface Soils―Niagara Falls Board of Health―Clean-up Target―Site Remediation | 0.50 | [ |
NY State | Surface Soils (Control) | 0.12 | [ |
US | Typical Soils―NJDEP 1993; US EPA Report | 0.008 - 0.117 | [ |
East St, Louis, MO | Surface Soils (63 Sample Set) | 0.17 | [ |
Europe | Surface Soils―Upwind CAP | 0.150 | [ |
Europe | Surface Soils―Upwind CAP | 0.075 | [ |
of 0.17 mg/kg for the 63 sample set is well below the maximum surface soil concentration of 0.382 mg/kg found in the USGS survey.
Large quantities of elemental mercury were used on a routine basis during the long operating history (1897-1991) of the NYCAP. Mercury containing process wastes were routinely disposed of on the CAP property and at a landfill off site [
A series of soil composite samples were collected at the 3163 Buffalo Avenue property during remedial investigations performed at the site [
1) Volume Source Scenario
2) Point Source Scenario
The maximum overall impact from the NYCAP is predicted to occur to the east of the source at the nearest modeled receptor (50 meters). It is again common to have maximum concentrations predicted immediately downwind of a point source subject to significant building downwash effects (i.e., sources with very short stacks on or adjacent to buildings). The pattern and nature of impacts obtained from the point source release configuration are similar in many respects to those obtained from the volume source release configuration. The magnitude of the overall maximum impact is approximately 10% lower using the point source configuration than was observed using the volume source configuration. The results can also be used to characterize ambient mercury impacts over parcels downwind of the CAP. The maximum concentrations over the 3163 Buffalo Avenue property again predicted to occur in the northwest corner of the site. The predicted impacts at this location vary from year to year with a maximum value of 273 ng/m3 and an average value of approximately 240 ng/m3. Concentrations decrease with distance to the southeast corner of the site where annual average concentrations of approximately 100 ng/m3 are predicted. An average value for the entire site would be approximately 175 ng/m3. The impacts
predicted over the site using the point source release configuration are again slightly lower (10%) than those obtained using the volume source release configuration. The mercury impacts predicted from the NYCAP at a distance of 2.5 km are roughly comparable to but somewhat larger than those predicted by EPA [
The maximum and mean ambient concentrations (
1) Dry Deposition―Volume Source Release Configuration
Average dry deposition of mercury due to emissions from the NYCAP was estimated to range between about 102 mg/m2 per year at the northwest corner of the 3163 Buffalo Avenue property and 42 mg/m2 per year at the southeast corner of the property. An average dry deposition value over the property would be approximately 72 mg/m2 per year.
2) Dry Deposition―Point Source Release Configuration
Average dry deposition of mercury due to emissions from the NYCAP was estimated to range between about 91 mg/m2 per year at the northwest corner of the 3163 Buffalo Avenue property and 38 mg/m2 per year at the southeast corner of the property. An average dry deposition value over the entire property would be approximately 66 mg/m2 per pear.
The total mercury deposition rates for the 3163 Buffalo Avenue Property estimated from dispersion modeling of the NYCAP emissions averaged 72 mg/m2 per year for the volume source scenario and 66 mg/m2 per year for
Ambient air (ng/m3) | Source type | Value type | Location |
---|---|---|---|
270 | Volume | Maximum | NW corner site |
240 | Point | Maximum | NW corner site |
190 | Volume | Mean | Site wide |
175 | Point | Mean | Site wide |
1.6 | - | Mean | US background |
the point source scenario. Both of these values exceed the deposition rates reported as part of the European CAP study by factors ranging from 8 - 30 [
Deposition rates for mercury ranging from 7 - 25 μg/m2 per year have been reported to represent global background deposition rates for mercury in the atmosphere [
A net mercury deposition rate of 2475 μg/m2 per year was reported for European CAP-1 [
The chlor-alkali industry represents the largest historical consumer of elemental mercury in the United States. Large quantities of mercury were typically consumed or used annually at each CAP, as well as over the CAPs period of operation. Air emissions to the atmosphere represent but a small percentage (2% - 4%) of the total quantity consumed or used. The most significant pathway for introduction of mercury to the vicinal environment was emissions of elemental mercury to the atmosphere from chlor-alkali process emissions points. These include but are not limited to cell room roof top vents, hydrogen reactors stacks, end box vents and fugitive or secondary emissions from a variety of sources including contaminated soils. Mercury air emissions from these facilities were introduced to the environment by a combination of dry and wet deposition processes as well as gaseous dispersion. The environmental impacts are most pronounced in areas 0.25 - 1.0 kilometers downwind of the facility. As a result, mercury levels in both ambient air and surficial soils in the immediate vicinity and especially locations downwind of chlor-alkali facilities are typically significantly above corresponding background levels. (>100 times background). The mercury contamination found in soils in the immediate vicinity of these CAPs is a systemic and widespread global problem. Soil contamination appears to be their legacy even after the CAPs are no longer operational and the attendant process emissions have ceased.
Predicted impacts on ambient concentrations of mercury as a result of air emissions from the NYCAP at locations downwind of the CAP were found to be significant. For example, at a location 305 meters to the east and 30 meters to the north of the modeled cell source centerline elemental mercury concentrations in ambient air were estimated at 270 ng/m3 annually (average results based upon 5 years of meteorological data). This value is contrasted to a background concentration of 1.6 ng/m3 (USEPA Report to Congress 1997). Predicted ambient concentrations were comparable (10% difference) for both the volume and point source NYCAP emissions scenarios and comparable to or higher than concentrations estimated or measured downwind of other CAPs globally at comparable distances.
Mercury in shallow soils at the 3163 Buffalo Avenue site was widespread with the majority of the samples having mercury concentrations ranging from 0.26 - 23.4 mg/kg. Such concentrations are well above what has been established as the upper limit for mercury burdens in US surface soils including urban industrialized regions of the country. The lower end of the range of concentrations are comparable to what is viewed as the upper limit for mercury contamination in the studies cited.
Predicted dry deposition rates of mercury on the 3163 Buffalo Avenue site attributable to the NYCAP emissions range between 38 and 102 mg∙m−2 per year with average values of approximately 70 mg∙m−2 per year. Predicted deposition rates (site wide average) for the volume (72 mg∙m−2 per year and point source scenarios (66 mg∙m−2 per year) were found to be comparable (10% difference). Mercury deposition rates of this magnitude over a period of years would be expected to yield significant quantities of mercury deposited to the surface soils on the property. For example a 28 year period of operation could be expected to results in surficial soil concentrations of 11.8 to 12.9 mg/kg at a location 0.25 km downwind of the NYCAP. Soil mercury concentrations at the site are consistent with concentrations found downwind of other CAPs worldwide and moreover CAPs with lower mercury deposition rates than were calculated for the Niagara Falls CAP.
The findings presented here collectively provide compelling evidence that mercury emissions from the Niagara Falls CAP over time were most likely responsible for the widespread mercury contamination found in soils on the 3163 Buffalo Avenue property.
Gary Hunt, (2016) Elevated Mercury in Ambient Air and Soils Impacts of Historical Air Emissions (1897-1991) from a Chlor-Alkali Plant (CAP). Journal of Environmental Protection,07,435-452. doi: 10.4236/jep.2016.73038