Concentration Ohio River Valley

A variety of models have been developed to study acid deposition. Sulfuric acid is formed relatively slowly in the atmosphere, so its concentrations are beUeved to be more uniform than o2one, especially in and around cities. Also, the impacts are viewed as more regional in nature. This allows an even coarser hori2ontal resolution, on the order of 80 to 100 km, to be used in acid deposition models. Atmospheric models of acid deposition have been used to determine where reductions in sulfur dioxide emissions would be most effective. Many of the ecosystems that are most sensitive to damage from acid deposition are located in the northeastern United States and southeastern Canada. Early acid deposition models helped to estabUsh that sulfuric acid and its precursors are transported over long distances, eg, from the Ohio River Valley to New England (86—88). Models have also been used to show that sulfuric acid deposition is nearly linear in response to changing levels of emissions of sulfur dioxide (89). 

Current reviews of surface water monitoring data in the peer reviewed literature are lacking. The highest concentrations observed in surface waters of the United States sampled before 1984 were 394 and 120 ppb. These concentrations were observed in rivers in highly industrialized cities (Ewing et al. 1977 Pellizzari et al. 1979). Typical concentrations for most sites that are not heavily industrialized appear to range from trace levels to 22 ppb (Ohio River Valley Sanitation Commission 1980, 1982). Data from EPA s STORET database indicate that chloroform was detected in 64% of 11,928 surface water sample data points at a median concentration of 0.30 ppb (Staples et al. 1985). 

The ratio of elemental (EC) to organic carbon (OC) has been measured in many studies and is commonly found to be less than one. For example, Shah et al. (1986) measured EC and OC in particles from both urban and rural areas across the United States and found the urban average concentrations to be 6.6 /xg m 3 for OC and 3.8 gg m 3 for EC, i.e., a ratio of EC OC of 0.6. Similarly, in the Los Angeles area, EC typically represents about a third of the carbonaceous component of particles (Rogge et al., 1993d). For rural areas, the concentrations were about a third of those in the urban areas, but the ratio was about the same, at 0.5, consistent with ratios of 0.4-0.5 measured in the Ohio River Valley by Huntzicker et al. (1986). Novakov et al. (1997) measured carbonaceous aerosol off the east coast of the United States at altitudes from 0.2 to 3.0 km and report that the ratio of EC OC is 0.1. 

Trace Element Concentrations on Fine Particles in the Ohio River Valley... 

Figure. 2. Hybrid receptor model predictions of concentrations of SO2, SO4, particulate Se and the S/Se ratio from Texas up through the Ohio River Valley. Experimental data from XRF studies of Shaw and Paur (1) for southwest back-trajectories are connected by dashed lines.

Considerable progress is being made in the development of regional scale receptor modeling. There is surprisingly little variation of relative elemental concentration patterns of fine particles associated with various back-trajectory groups in the Ohio River Valley. 

Using both a hybrid receptor model, developed by Lewis and Stevens ( 2) and modified by Gordon and Olmez (3), and a simple model of emission from the Ohio River Valley, we compare the results of the College Park (CP) samples as well as those of another continuous set of samples taken from July 3-29, 1983 at Wallops Island, VA (WI), to predicted results. Single-source differential equations (2) are used to describe the time-varying concentrations of SO2, SO and a particulate element characteristic of coal-fired power plant emissions (chosen here as Se). An additional equation (3) can be added to describe the concentration variation of B(0H)3 The following rate constants apply to the concentrations of the four species in question ... 

Europe with S02 levels peaking in the industrialized regions. High concentrations also occur along the Ohio River valley where numerous power plants are located (Benkovitz, 1982). 

Our interest in the issue initially arose from examination of the US Geological Survey national soil geochemical data set (Gustavsson et al, 2001). The Ohio River Valley is the site of a concentration of coal-fired power plants (Fig. 1) and the US Geological Survey... 

---