2004 Progress Report: Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere

EPA Grant Number: R828771C015
Subproject: this is subproject number 015 , established and managed by the Center Director under grant R828771
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: HSRC (2001) - Center for Hazardous Substances in Urban Environments
Center Director: Bouwer, Edward J.
Title: Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere
Investigators: Mason, Robert P. , Baker, Joel E. , Crimmins, Bernard , Laurier, Fabien , Ondov, John M. , Pancras, Patrick
Current Investigators: Mason, Robert P. , Baker, Joel E. , Ondov, John M.
Institution: University of Maryland
EPA Project Officer: Lasat, Mitch
Project Period: October 1, 2001 through September 30, 2007
Project Period Covered by this Report: October 1, 2003 through September 30, 2004
RFA: Hazardous Substance Research Centers - HSRC (2001) RFA Text |  Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management


This research project is being conducted in two parts. The first part involves the research group at the Chesapeake Biological Laboratory (CBL) of the University of Maryland. The overall objective of the first part is to estimate the fate and bioavailability of atmospherically transported chemical contaminants in the urban environment. The second part involves the research group in the Department of Chemistry and Biochemistry at the University of Maryland at College Park. The objectives of the second part of the project encompass three areas of interest: (1) availability of metals in coarse urban particles; (2) concentrations and sources of metals and Hg in the urban atmosphere; and (3) methods to concentrate fine and coarse urban aerosol particles to permit improved measurements of concentrations for investigating their atmospheric burdens and fate.

Progress Summary:

Part 1

This project is part of a larger study encompassed within the Center for Hazardous Substances in Urban Environments to quantify the sources and cycling of hazardous materials in the urban environment, specifically the exchange of contaminants between the land and the atmosphere. This project quantifies the sources and cycling of airborne contaminants to better characterize the sources, pathways, and bioavailability of these contaminants. Parallel field and laboratory studies of trace metal, mercury, and organic contaminant speciation are underway.

Experimental Approach and Methods. A long-term study was conducted at a coastal site at the CBL to further assess the impact of regional and urban-derived air masses on mercury inputs to coastal ecosystems. This study involved the measurement of mercury speciation, both elemental mercury (Hg0) and gaseous ionic Hg (reactive gaseous Hg [RGHg]), using the Tekran analytical system (Tekran, Inc., Toronto, Canada; Landis, et al., 2002). Hg0 is determined using the Model 2537A analyzer every 5 minutes, whereas the Model 1130 denuder unit is used for the RGHg measurements (2-hour integration). Rain and snow samples also were collected to assess the scavenging of Hg species during precipitation. From these studies, refined estimates of the wet and dry deposition of Hg can be made. In addition, we took part in a multi-investigator, largescale study of the impact of urban air masses on the cycling of contaminants during their interaction with marine air during July and August 2004 off the coast of Maine (http://www.csmonitor.com/2004/0805/p14s01-sten.html?s=ent Exit ). Samples were collected at Star Island, Isles of Shoals, in New Hampshire, in conjunction with other simultaneous atmospheric collections. Although no further studies were conducted in Baltimore, the data collected in 2003 were analyzed further. Given these activities and the difficulty in determining a suitable site for the proposed Brownfields study, this study will be completed in the upcoming year.

Brief Results and Discussion. Overall, RGHg concentrations were not as elevated during the summer study as has been found on occasion at the CBL; however, it is clear that there is an apparent diurnal trend for the data, with daily maximum values and then zero values at night. In addition, the highest concentrations of RGHg occur during times of low ozone, not of elevated ozone and other pollutants. Lower peaks, and a shift in the timing of the peak maxima, appear to correlate with the high ozone and/or SO2 events. Additionally, the peaks in RGHg and Hg0 do not occur at the same time, and the Hg0 peaks are more correlated with peaks in ozone and other pollutants. At this preliminary stage in data analysis, we interpret these results to suggest that the processes that are more important in contributing to elevated RGHg are those associated with halogen chemistry and ozone destruction in marine air. In polluted air masses, ozone oxidation of Hg0 is possible, but the rate is slower than that in the presence of halogen radicals. Modeling studies confirm these results (Hedgecock, et al., 2004) as our open-ocean studies have found similar results (Laurier, et al., 2003). These results reinforce the results obtained at the Baltimore site; whereas RGHg is associated with the presence of plumes, the overall elevated concentrations of oxidants in urban air does not necessarily result in more RGHg. Overall, however, concentrations are more elevated in Baltimore, as we have found previously (Sheu, et al., 2002). Finally, although there is some association between air mass direction and high RGHg at the CBL, these air masses also are associated with no or low concentrations. Again, it is evident that local reactions are the major source of the higher RGHg peaks found during the day. Finally, there is evidence of rapid scavenging of RGHg by precipitation in the Baltimore and CBL data. During extended rainfall events, RGHg concentrations fall to zero. The estimated amount of RGHg in the air mass is sufficient to account for a large fraction of Hg in rainfall, suggesting that scavenging of RGHg is an important source of Hg to coastal rain. More detailed estimates of Hg deposition will be made based on the data shown here, plus the long-term 7-month record of collections at the CBL, upon further analysis. Clearly, there is a complex interaction between coastal air and polluted air masses, and this can have an important impact on Hg cycling between the atmosphere and the coastal environment.

Part 2

Work conducted at the University of Maryland–College Park, has involved the sources and fate of contaminants in urban airborne particles and their potential bioavailability in precipitation and in nearby surface waters, such as the Chesapeake Bay.

Availability of Metals in Coarse Urban Particles. An important finding of the U.S. Environmental Protection Agency’s Air Exchange Over Lakes and Oceans (AEOLOS) study was that large particles (i.e., those with aerodynamic diameters larger than 1 μm) carry most of the dry deposition fluxes of many particulate constituents, even for species whose mass is associated predominantly with small urban aerosol particles. Despite this observation, there appeared to be little effect of these large particles on dissolved concentrations of various metals in surface waters in AEOLOS studies conducted over southern Lake Michigan. We proposed that the metals associated with these large particles might not be leachable into the water column. The purpose of the study described herein was to test this hypothesis.

As described previously, bulk sample collections using the University of Maryland Ultra-High Volume Aerosol Sampler provided material for leaching studies to determine the true contribution of metals to the water column of the Chesapeake Bay and similar bodies around which numerous eastern seaports have been built. The system consists of an air inlet, a 1-m cyclone separator (with > 2.5 μm cut point), filter cassettes, and a positive displacement regenerative blower). The system is installed in a trailer at Clifton Park, about 2 km northeast of downtown Baltimore, to collect fine particulate matter (PM2.5) for use as a standard reference material. Several grams of coarse PM were harvested from the cyclone on August 7, 2003. This material was mixed thoroughly and dried in an oven at 110°C for 4 hours to remove moisture. Aliquots of the material were analyzed for Be, Mg, Al, K, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Ag, Cd, Sn, Sb, Ba, and Pb using inductively coupled plasma-mass spectrometry (ICP-MS) after total dissolution using a microwave digestion procedure.

Established leaching methods were consulted as a basis for the method used in this experiment; most used acidic conditions as one environment in which to measure the amount of metal that leached from the sample. For the purposes of the present experiment, a pH 4.2 phosphate buffer was used to simulate conditions of acidic rain such as that which would fall on urban areas of the eastern United States. In addition to the acidic conditions, deionized (DI) water and water collected from the Baltimore Inner Harbor were used as solvents. Various extraction volumes were used to determine if a point of saturation exists for the metals measured. Fourteen samples were prepared for use in the leaching experiments. These were leached with 5 mL of either: (1) ultra-pure DI water at pH 6.5; (2) 1 mL of pH 4.2 phosphate buffer (purity of 99.99%) mixed with 4 mL of ultra-pure DI water; or (3) water collected from the Baltimore Inner Harbor after shaking twice for 1 hour in an orbit shaker and filtered using 0.45 µm sterile filters and then analyzed using ICP-MS for the elements listed above. The harbor water (pH 6.5) was collected on December 7, 2003, and also was filtered prior to use. In addition to the samples, three blanks were prepared: 5 mL of DI water, 1 mL of pH 4.2 phosphate buffer with 4 mL of DI water, and 5 mL of water from the Inner Harbor.

Excepting K and Mg, concentrations achieved when PMcoarse was leached with unbuffered DI and harbor water were nearly identical. Except for Al, Mn, Zn, Sr, Ba, and Pb, concentrations induced in pH 4.2 buffered DI water were similar to those for unbuffered DI water. For these reasons, DI water was used to determine extraction efficiency as a function of solvent-to-PMcoarse mass ratio. Herein, extraction efficiency is defined operationally as the mass of an element contained in the filtered extracts (i.e., , which clearly contain particles with diameters less than the filter pore size) divided by the amount of the element contained in the PMcoarse before extraction. In Baltimore Harbor surface water, water-to-dissolved solids (operationally defined as the concentration in filtered water) ratios range from 100 to 500 mL/g. Results suggest that extraction efficiencies increase as water:PM mass increases, but for all metals studied, efficiencies are at most 15 percent at 500 mL/g (the largest ratio expected for Baltimore Harbor). Clearly, more material can be extracted at much larger ratios. These results, however, suggest that only minor amounts of the metals studied actually are available to the water column.

Highly Time-Resolved Atmospheric Metals Measurements. Between January 26 and February 12, 2003, more than 700 30-minute samples were collected with the University of Maryland’s Semicontinuous Elements in Aerosol Sampler (SEAS) to permit analyses of metals (including Al, As, Se, Cu, Cr, Cd, Mn, Fe, Se, Pb, and Zn), useful as markers of high-temperature combustion sources and urban dust, to reveal their atmospheric burdens and sources and to complement Hg and organic measurements made by our colleagues. On February 4 and 8, days for which discrete Hg-containing plumes were observed, concentrations of Cd, Zn, Sb, and Pb (markers of municipal incinerator particle emissions) were elevated between 10:30 and 11:30 am. Se and V peaks also are evident. The relative abundances of these elements and wind directions suggest that these samples were influenced by the Baltimore municipal incinerator (station angle of 250º) and Gould Street power plant. A plume containing elevated levels of Zn and Ca, a composition probably related to the calcium carbide coke dryer located at 243º, was more evident on the 8th, when winds were more between 240º and 280o. Large RG Hg concentrations were observed on February 10 during a period when the site was influenced by several sources including a paint pigment plant, a cement plant (140º), steel mill (141º), gypsum plant (144º), yeast plant (151º), and possibly an inorganic chemicals plant (164º).

New Particle Concentrator. We are designing a new virtual centripetal aerosol concentrator for use in urban aerosol studies. The concentrator design is based on that of cyclones but uses a rotating central outlet pipe and porous wall. In the concentrator, the sample air is caused to rotate at high speeds by virtue of viscous coupling with the surface of the rotating central outlet pipe. Particles accelerate towards the porous outer wall where they are carried into the annulus between cylinders through a secondary outlet port with a small flow of air (minor flow). A computer model was constructed and used to perform preliminary design calculations. These suggest that a concentrator with a lower cutoff size of 0.035 µm (mass medium aerodynamic diameter) could deliver an 80-fold increase in aerosol particle concentration in a 30-minute sampling interval at an inlet flow rate of 210 L/min.


Hedgecock IM, Trunfio GA, Sprovieri F, Pirrone N, Laurier FJG, Mason RP. Modelling RGM concentrations from Hg0 Measurements in the Pacific Ocean and Mediterranean Sea: comparison with measured values. In: Proceedings of the 7th International Conference on Mercury as a Global Pollutant, Slovenia, 27 June-2 July 2004.

Landis MS, Stevens RK, Schaedlich F, et al. Development and characterization of an annular denuder methodology for the measurement of divalent inorganic reactive gaseous mercury in ambient air. Environmental Science & Technology 2002;36(13):3000-3009.

Laurier FJG, Mason RP, Whalin L, Kato S. Reactive gaseous mercury formation in the north Pacific Ocean’s marine boundary layer: a potential role of halogen chemistry. Journal of Geophysical Research–Atmospheres 2003;108(D17):4529.

Park SS, Pancras PJ, Ondov JM, Poor N. A new pseudo-deterministic multivariate receptor model for accurate individual source apportionment using highly time-resolved ambient concentrations measurements. Journal of Geophysical Research (in press, 2005).

Sheu GR, Mason RP, Lawson NM. In: Lipnick, et al., eds. Chemicals in the Environment: Fate, Impacts and Remediation, ACS Symposium Series 806. Washington, DC: American Chemical Society, 2002, pp. 223-242.

Future Activities:

We will try to code sources in the Baltimore area into our new pseudo-deterministic receptor model and model the Hg and SEAS elemental data to determine their emission rates. A prototype centripetal concentrator is being built and will be tested in our laboratory.

Journal Articles:

No journal articles submitted with this report: View all 20 publications for this subproject

Supplemental Keywords:

ultra-high-volume particle collection, elemental composition, urban particle solubility, toxics, exposure, hazardous substances, assessment, cleanup, risk communication,, RFA, Health, Scientific Discipline, Air, INTERNATIONAL COOPERATION, Waste, particulate matter, Air Quality, Health Risk Assessment, Air Pollutants, Risk Assessments, Brownfields, Hazardous Waste, Biochemistry, Ecology and Ecosystems, Hazardous, ambient aerosol, ambient air quality, urban air, brownfield sites, environmental hazards, air toxics, contaminant transport, human health effects, contaminant dynamics, air quality models, bioavailability, risk assessment , airborne particulate matter, contaminant cycling, air pollution, air sampling, environmental health effects, human exposure, airborne aerosols, aerosol composition, respiratory impact, PM, technology transfer, urban environment, aersol particles, aerosols, human health risk, technical outreach, hazardous substance contamination

Relevant Websites:

http://www.chem.umd.edu/supersite Exit

http://www.jhu.edu/hsrc Exit

Progress and Final Reports:

Original Abstract
  • 2002
  • 2003
  • 2005 Progress Report
  • 2006
  • Final Report

  • Main Center Abstract and Reports:

    R828771    HSRC (2001) - Center for Hazardous Substances in Urban Environments

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R828771C001 Co-Contaminant Effects on Risk Assessment and Remediation Activities Involving Urban Sediments and Soils: Phase II
    R828771C002 The Fate and Potential Bioavailability of Airborne Urban Contaminants
    R828771C003 Geochemistry, Biochemistry, and Surface/Groundwater Interactions for As, Cr, Ni, Zn, and Cd with Applications to Contaminated Waterfronts
    R828771C004 Large Eddy Simulation of Dispersion in Urban Areas
    R828771C005 Speciation of chromium in environmental media using capillary electrophoresis with multiple wavlength UV/visible detection
    R828771C006 Zero-Valent Metal Treatment of Halogenated Vapor-Phase Contaminants in SVE Offgas
    R828771C007 The Center for Hazardous Substances in Urban Environments (CHSUE) Outreach Program
    R828771C008 New Jersey Institute of Technology Outreach Program for EPA Region II
    R828771C009 Urban Environmental Issues: Hartford Technology Transfer and Outreach
    R828771C010 University of Maryland Outreach Component
    R828771C011 Environmental Assessment and GIS System Development of Brownfield Sites in Baltimore
    R828771C012 Solubilization of Particulate-Bound Ni(II) and Zn(II)
    R828771C013 Seasonal Controls of Arsenic Transport Across the Groundwater-Surface Water Interface at a Closed Landfill Site
    R828771C014 Research Needs in the EPA Regions Covered by the Center for Hazardous Substances in Urban Environments
    R828771C015 Transport of Hazardous Substances Between Brownfields and the Surrounding Urban Atmosphere