Simulated Summertime Regional Ground-Level Ozone Concentrations over Greece

Ground-level ozone concentrations were estimated for Greece during a summer period of the year 2000 using the regional air quality model UAM-V off-line coupled with the mesoscale meteorological model MM5. An anthropogenic NOx, NMVOCs and CO emission inventory and biogenic NMVOCs emission data were used to support model simulations. The evaluation analysis indicates a quite satisfactory model performance in reproducing ozone levels. The simulated mean ozone concentrations are above the 32-ppb EU phytotoxicity limit over almost all continental and maritime areas of Greece. Over the greater part of the country, the background mean ozone levels range from 40 to 55 ppb. Ozone values higher than the 55-ppb EU human health protection limit reaching 60 ppb dominate part of the southern Aegean Sea that is influenced by the Athens urban plume. In the areas where anthropogenic emission densities are high, the mean ozone levels vary between 20 and 40 ppb. Over the greater part of Greece, the simulated mean daily maximum ozone concentrations range from 50 to 65 ppb. More enhanced maximum ozone concentrations up to 95 ppb mainly dominate over the greater areas of the two largest Greek urban centres (Athens and Thessaloniki) and over the continental and maritime areas south of Athens which are under the influence of the urban plume.     

Predominance of Dehalococcoides in the presence of different sulfate concentrations

Urban stormwater runoff is contaminated by nutrients that wash off of roadways, parking lots and lawns during storms. In-ground permeable filter systems that consist of carefully selected filter material have the potential to remove these nutrients from the run-off. In this paper, four filter materials, calcite, zeolite, sand and iron filings, were investigated using laboratory batch tests to evaluate their efficiency in the removal of nitrate and phosphate from the simulated stormwater at different initial concentrations under the same 24-h exposure time period. The range of removal for nitrate was from 39 % to 65 % for calcite, from 42 % to 77 % for zeolite, from 40 % to 70 % for sand, and from 74 % to 100 % for iron filings. The removal of phosphate ranged from 35 % to 41 % for calcite, 59 % to 100 % for zeolite, 49 % to 100 % for sand, and 73 % to 100 % for iron filings. The removal of nitrate is mainly attributed to electrostatic adsorption, except when iron filings were used as a filter material where additional processes such as electrochemical reduction, ligand complexation and precipitation may have contributed to the higher nitrate removal. Phosphate removal is also attributed to electrostatic adsorption in all filter materials; however, at higher phosphate concentrations, the precipitation process may be the dominant process for all of the filter materials except calcite. The Langmuir and Freundlich isotherms fitted the observed nonlinear adsorption results, but the mechanism of removal of phosphate changed from adsorption to precipitation at concentrations higher than 1 mg/l in zeolite, sand, and iron filings; therefore, the adsorption models are valid below this concentration limit. A typical application of these batch adsorption test results is presented in the design of a field in-ground permeable filter system.