Hybrid Receptor Model Research Articles

Atmospheric mercury deposition to Lake Michigan during the Lake Michigan Mass Balance Study.

Wet and dry mercury (Hg) deposition were calculated to Lake Michigan using a hybrid receptor modeling framework. The model utilized mercury monitoring data collected during the Lake Michigan Mass Balance Study and the Atmospheric Exchange Over Lakes and Oceans Studytogether with high-resolution over-water meteorological date provided by the National Oceanic and Atmospheric Administration (July, 1994-October, 1995). Atmospheric deposition was determined to be the primary pathway for mercury inputto Lake Michigan, contributing approximately 84% of the estimated 1403 kg total annual input (atmospheric deposition + tributary input). Wet (10.6 microg m(-2)) and dry deposition (9.7 microg m(-2)) contributed almost equally to the annual atmospheric Hg deposition of 20.3 microg m(-2) (1173 kg). Re-emission of dissolved gaseous Hg from the lake was also significant (7.8 microg m(-2)), reducing the net atmospheric deposition to 12.5 microg m(-2) (720 kg). A strong urban influence was observed in the over-water mercury deposition estimates in the southern portion of the lake. The Chicago/Gary urban area was estimated to contribute approximately 20% (127 kg) of the annual atmospheric mercury deposition to Lake Michigan. The magnitude of local anthropogenic mercury sources in the Chicago/Gary urban area suggests that emission reductions could significantly reduce atmospheric mercury deposition into Lake Michigan.

Qualitative determination of source regions of aerosol in Canadian high Arctic

A hybrid receptor model that combines both chemical and meteorological information was employed to identify the potential regions of source emission for aerosol measured at Alert, Northwest Territories (82.3[degrees] N, 62.5[degrees] W) in the Canadian Arctic. This model explores the use of 5-day air parcel backward trajectories to describe the long-range transport of atmospheric heavy metals and sulfate species through the potential source contribution function (PSCF) receptor model. The modeling results presented are for the observations made between November 1 and March 20 from 1982 to 1987, i.e., the Arctic winter, since concentrations of trace elements are generally higher in the winter. A number of geographical locations in the former USSR and Europe are found to be of high potential to be the emission source areas. The usefulness of using elemental ratios in the PSCF analysis for identifying source regions contributing to the pollution in the Arctic was explored. 49 refs., 19 figs.

The relationship between empirical orthogonal functions and sources of air pollution

Empirical Orthogonal Functions (EOFs) of airborne pollutant concentrations are shown to be closely related to the underlying advection differential equation. The averge balance of sources and sinks of a pollutant is equal to the sum of the dot product of the gradient of the EOFs with specially weighted transport winds, plus some corrections for initial and final conditions. This relationship is the basis for the Source identification Through Empirical Orthogonal Functions (SITEOF) model, a hybrid receptor model. This model is tested by applying it to simulated data from a simple dispersion model and 2 years of airborne fine sulfur concentrations from 24 western sites in the National Park Service monitoring network. In both cases, the predicted net source and sink areas derived form the SITEOF model are in good agreement with known major sulfur dioxide source areas. The effect of source location, turbulent diffusion, and averaging time of the observations on the model are discussed. Possible application include estimating emission from fugitive or nontraditional sources, estimating production rates of secondary pollutants, and deposition rates.

Estimating Emissions from Air Concentration Measurements

A one-year-long experiment in which two different tracers were simultaneously released from two different locations was used to test various hybrid receptor modeling techniques to estimate the tracer emissions using the measured air concentrations and a meteorological model. Air concentrations were measured over an 8-hour averaging time at three sites 14 to 40 km downwind. When the model was used to estimate emissions at only one tracer source, 6 percent of the short-term (8-h) emission estimates were within a factor of 2 of the actual emissions. Temporal averaging of the 8-h data enhanced the precision of the estimate such that after 10 days 42 percent of the estimates were within a factor of 2 and after six months all of them (each source-receptor pair) were within a factor of 2. To test the ability of the model to separate two sources, both tracer sources were combined, and a multiple linear regression technique was used to determine the emissions from each source from a time series of air concentratio...

Hybrid receptor model for secondary sulfate from an SO 2 point source

A formalism is presented for calculating the ambient concentration of secondary sulfate downwind (100–200 km maximum) from an SO 2 point source. The SO 2 is assumed to be affected by dispersion, dry deposition and homogeneous gas phase oxidation processes having arbitrary time dependences. A receptor model estimate of the primary particle contribution at the downwind site is used to account for all of the dispersion and part of the deposition. It is shown that the secondary sulfate is sensitive only to the average values of the deposition and oxidation rates, and not to their detailed time dependences.

Receptor-modeling approach to the apportionment of genotoxic air pollutants

The classical source-apportionment method, i.e., source-emissions inventories coupled with dispersion modeling, is inappropriate for identifying the sources of airborne mutagenic species. Receptor modeling, based on the observation of particle-borne elements, compounds, and other characteristics that form signatures unique to certain types of sources, should be useful for this purpose. Since elements do not provide good markers for some sources of carbonaceous material (which will usually be the major sources of mutagens), it will be necessary to develop markers based on organic compounds and other characteristics such as isotopic abundances of carbon isotopes. Before organic compounds can be used, their destruction by atmospheric reactions between the source and receptor must be better understood. If conservative tracers of the sources are available, they can be used in hybrid receptor models to observe destruction of reactive species. To obtain the most definitive information from receptor models, the sampling of atmospheric species should be accompanied by meteorological measurements, especially detailed information on wind speed and direction.