2005 Progress Report: Transport of Hazardous Substances Between Brownfields and the Surrounding Urban AtmosphereEPA 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: Baker, Joel E. , Mason, Robert P. , Ondov, John M.
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, 2004 through September 30, 2005
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 mercury (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.
Experimental Approach and Methods. Ambient aerosol was collected during three intensive sampling campaigns in the spring, summer, and winter of 2002-2003 at the Baltimore PM2.5 Supersite. Located in the northeast section of Baltimore, Maryland, this site is close (100 m) to a major interstate (I-895) and a bus depot (Maryland Transit Authority), providing a vehicle-emission impacted urban site to assess seasonal variability in organic aerosol composition. Gas and particle phase organics were collected at 6, 12, or 24 hour intervals on consecutive days using a modified Anderson high volume sampler (hi-vol, 0.5 m3/min). The collection media consisted of a glass fiber filter (GFF) and polyurethane foam (PUF) for particle and gas phase organics, respectively. Size resolved aerosol also was collected using a Berner low pressure impactor segregating the aerosol into five size classes (0.04 - 0.14 µm, 0.14 - 0.49 µm, 0.49 - 1.7 µm, 1.7 – 6 µm, and 6 – 21 µm). The bulk (hi-vol) samples were analyzed for alkanes, selected hopanes, polycyclic aromatic hydrocarbons (PAHs), and nitro-substituted polycyclic aromatic hydrocarbons (NPAHs) using gas chromatography/mass spectrometry (GC/MS) using authentic standards.
Brief Results and Discussion. During the first intensive (April 2002), 24-hour and a subset of 12-hour samples were collected to test new analytical methods for the determination of NPAHs on bulk and size resolved aerosol. Using large volume injection GC/MS, we were able to determine the first reported diurnal size-resolved NPAH concentrations. The increased sensitivity (>10-fold) of this method demonstrated with the impactor samples from the first intensive provides the enhanced temporal resolution required to determine sources of non-polar organics (source markers) using conventional sampling methods (Crimmins and Baker, submitted 2005).
The greatest PAH concentrations (bulk, gas, and particle, sum 53 PAHs) were found during the winter (80 ng/m3 + 40), followed by similar mean concentrations during the spring (April, 41 + 50 ng/m3) and summer (July, 38 + 22 ng/m3). Unlike PAHs, NPAHs have direct emission (primary) and photochemical (secondary) sources (Arey, 1998). In addition, several NPAH congeners are source-specific. For example, 1-nitropyrene is produced by combustion whereas 2-nitropyrene is formed via OH-mediated gas phase reactions. 1-Nitropyrene and 2-nitrofluoranthene (secondary) usually are present in the highest concentration in ambient air. The ratio of 2-nitrofluoranthene to 1-nitropyrene has been used to assess the sources of NPAHs in ambient aerosol (Cicclioli, et al., 1996). A concentration ratio greater than 5 suggests that the NPAHs are predominantly from secondary sources. A ratio below 5 indicates primary NPAH emission sources. During the intensives, this ratio was usually below 5, indicating particulate phase NPAHs are predominantly from primary sources in this area. Diesel emissions are known to have significant quantities of 1-nitropyrene (Arey, 1998), and the low 2-nitrofluoranthene/1-nitropyrene ratio during the winter intensive (0.42) suggests, in addition to increased concentrations of 1-nitropyrene, vehicular emissions appear to have dominated the area during this period.
Hopanes are emitted via lubricating oils in vehicular exhaust (Rogge, et al.,1993). In our study, the concentrations of hopanes during the winter sampling period were correlated with the PAH and NPAH concentrations, with a greater abundance during the winter period compared to spring and summer. Alkanes can be used to distinguish between anthropogenic and biogenic sources. The ratio of the odd to even n-alkane concentrations (CPI) provides insight into the biogenic versus anthropogenic origin of organic aerosol. A value of 1 indicates fossil fuel origin, whereas values greater than 1 suggest a biogenic contribution to the alkane distribution (Standley and Simoneit, 1987). During the winter sampling, this value was consistently 1 (0.8 - 1.2). During the summer period, it was as high as 5, indicating that in addition to anthropogenic emissions at this location, a biogenic influence was observed during selected summer days.
The size distributions of NPAHs (primary and secondary) and PAHs were very similar for samples collected in April 2002. After formation in the gas phase, secondary NPAHs such as 2-nitropyrene associate with particles with the greatest sorption affinity for that specific compound. Similar size distributions imply that the greatest sorption affinity of secondary NPAHs is for those particles with sizes similar to those of the primary organics (PAHs). Therefore, the size distribution data suggest that local emissions are the dominant sources of organic particulate matter during the sampling campaigns at the Baltimore Supersite. This illustrates the importance of primary emissions at this site, as these aerosol particles not only contain primary toxics but also provide the sorption surface for secondary atmospheric toxics.
New Particle Concentrator. We have completed design of a high-speed (20,000 RPM) 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 (mmad), could deliver an 80-fold increase in aerosol particle concentration in a 30-minute sampling interval at an inlet flow rate of 210 L/minute. A schematic drawing is shown in Figure 1.
Concentrator Design. The fundamental design equation gives the smallest (aerodynamic diameter, dp) particle that can be concentrated as a function of the major flow (Qmajor), rotational speed (RPS), diameter of the rotating cylinder (r), rotating cylinder length (L), and fraction of cylinder area available for exit flow (α ), as follows.
where Cc, ρp, and η are the particle slip correction, particle density, and absolute viscosity of the gas.
Particles larger than dp will not escape the concentrator through the major flow stream. Because the minor flow is smaller than the total (i.e., inlet) flow rate, and starting with an empty (particle free) concentrator volume, more particles will be aspirated initially into the chamber than will be leaving through the minor flow. Therefore, the particle concentration in the concentrator volume will increase. This condition continues until the concentration of particles inside the concentrator volume is so large that the rate at which particles are removed in the minor flow will begin to exceed the rate at which particles will be aspirated into the volume in the sampled air.
For a concentrator, two parameters are of interest: (1) the mass delivered through the aerosol outlet; and (2) the average effective concentration factor; both of which are functions of sampling time. The mass delivered (Mdelivered) is shown to be given by the following equation:
Outlet Port Flow
Figure 1. Skematic Drawing of the Virtual Concentrator
Where Vconc, Qminor, Qinlet, and Camb are the concentrator volume, minor flow rate, inlet flow rate, and ambient particle mass concentration.
For our purposes, we define the effective concentration factor (CFe) simply as the amount of mass delivered by the concentrator to the instrument during the sampling time divided by the amount of mass that the instrument would have sampled at its normal sampling rate. For a given instrument, the virtual centripetal concentrator would be designed such that the minor flow rate would be equal to the normal sampling flow rate for the instrument. The amount of mass delivered to the instrument at its Qminor then is simply the product of Qminor and Camb. Thus,
We have designed a prototype concentrator with the following parameters, chosen to provide a cutoff diameter of approximately 38 nm.
A plot of predicted mass collected and CFe versus sampling time, for a convenient ambient particle concentration of 1 µg/m3, suggests that the expected effective concentration factor is greater than 80 after only 30 minutes. This means that a sample normally requiring 24 hours to collect will be collected in slightly less than 30 minutes. The low volumetric delivery rate (1 LPM) makes the device suitable for many instruments, e.g., single particle mass spectrometers.
Construction. Torque loads on the rapidly rotating inner cylinder have been evaluated by our mechanical engineering group. Construction materials have been identified and we have been soliciting bids from contractors to build and balance the inner rotating cylinder. Appropriate bearings have been located. The outer-most cylinder will be constructed of clear polycarbonate to allow inspection and visualization of air flows in the concentrator annulus. We anticipate receipt of the prototype concentrator in approximately 60 days. Testing to verify the cut point, determine losses, and more optimum design is to be completed by the end of this calendar year.
No future activities were identified by the investigators.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
|Other subproject views:||All 20 publications||8 publications in selected types||All 6 journal articles|
|Other center views:||All 108 publications||22 publications in selected types||All 20 journal articles|
||Crimmins BS, Baker JE. Measurement of aerosol PAH and Nitro-PAH concentrations in ambient urban air with hourly resolution. Atmospheric Environment.||
||Pancras JP, Ondov JM, Zeisler R. Multi-element electrothermal AAS determination of 11 marker elements in fine ambient aerosol slurry samples collected with SEAS-II. Analytica Chimica Acta 2005;538(1-2):303-312.||
||Park SS, Pancras JP, Ondov J, Poor N. A new pseudodeterministic multivariate receptor model for individual source apportionment using highly time-resolved ambient concentration measurements. Journal of Geophysical Research: Atmospheres 2005;110(D7):D07S15, doi:10.1029/2004JD004664.||
Supplemental Keywords:aerosol particle collection, concentrator, fine particles,, 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, brownfield sites, environmental hazards, ambient aerosol, ambient air quality, urban air, contaminant transport, air toxics, contaminant dynamics, human health effects, risk assessment , air quality models, airborne particulate matter, contaminant cycling, bioavailability, air pollution, air sampling, environmental health effects, human exposure, aerosol composition, airborne aerosols, respiratory impact, PM, aersol particles, technology transfer, urban environment, airborne urban contaminants, human health risk, aerosols, technical outreach
Progress and Final Reports:Original Abstract
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