Monitoring of Fogwater Chemistry in the Gulf Coast Urban Industrial Corridor: Baton Rouge (Louisiana)

Abstract

Seventeen fog events were sampled in Baton Rouge, Louisiana during 2002-2004 as part of characterizing wet deposition by fogwater in the heavily industrialized corridor along the Louisiana Gulf Coast in the United States. These samples were analyzed for chemical characteristics such as pH, conductivity, total organic and inorganic carbon, total metals and the principal ion concentrations. The dominant ionic species in all samples were NH4+, NO3-, Cl- and SO4(2-). The pH of the fogwater sampled had a mean value of 6.7 with two cases of acidic pH of 4.7. Rainwater and fogwater pH were similar in this region. The acidity of fogwater was a result of NO3- but partly offset by high NH4+. The measured gaseous SO2 accounted for a small percentage of the observed sulfate concentration, indicating additional gas-to-particle conversion of SO2 to sulfate in fogwater. The gaseous NOx accounted for most of the dissolved nitrate and nitrite concentration in fogwater. The high chloride concentration was attributable to the degradation of chlorinated organics in the atmosphere. The metal composition was traced directly to soil-derived aerosol precursors in the air. The major metals observed in fogwater were Na, K, Ca, Fe, Al, Mg and Zn. Of these Na, K, Ca and Mg were predominant with mean concentrations > 100 microM. Al, Fe and Zn were present in the samples, at mean concentrations < 100 microM. Small concentrations of Mn (7.8 microM), Cu (2 microM), Pb (0.07 microM) and As (0.32 microM) were also observed in the fogwaters, and these were shown to result from particulates (PM2.5) in the atmosphere. The contribution to both ions and metals from the marine sources in the Louisiana Gulf Coast was minimal. The concentrations of all principal ionic species and metals in fogwater were 1-2 orders of magnitude larger than in rainwater. Several linear alkane organic compounds were observed in the fogwater, representing the contributions from petroleum products at concentrations far exceeding their aqueous solubility. A pesticide (atrazine) was also observed in fogwater, representing the contribution from the agricultural activities nearby.

Determination of aldehydes and acetone in fog water samples via online concentration and HPLC

“…The fog event collected on 12/01/2012 exhibited a high amount of DOC content with 262.2 mgC·L −1 ; however, this value was consistent with previous values of DOC observed from the same sampling site (Raja et al 2005). This high concentration was not only specific to Baton Rouge fog events, but there also was a similar maximum concentration reported for a fog sample collected in Bakersfield, CA (276.2 mgC·L −1 ) (Jacob et al 1984).…”

“…Duration of sampling averaged 4.5 h for all events. Temperature of the events ranged from 6.8°C to 20.2°C (average value: 15.2°C), which is also typical of fog events in Baton Rouge (Raja et al 2005). Mass of sample collected varied considerably from 19.2 to 614.9 g (average value: 247.5).…”

“…The majority of the fog events in this study occurred in the fall months, with two events each taking place in the winter and spring. Although fog can occur in Baton Rouge year round, events most commonly occur from October-December and March-April (Raja et al 2005), which is representative of this study. The fog events generally began in the early morning hours (around 4:00 a.m.) and dissipated by 9:00 a.m. Only two events began closer to the midnight hours.…”

“…The solvent used for this further dilution and derivatization test was artificial fog water adjusted to pH 6 in order to simulate the behavior of aldehydes in the natural samples. The components of the artificial fog water are the five major ions found in natural samples (Raja et al 2005): Cl − (3 mM), NO 3 − (3 mM), SO 4 2− (2 mM), Na + (3.325 mM), and NH 4 + (6 mM). Blank samples, in this case the artificial fog water without the addition of the aldehydes, were also derivatized with DNPH.…”

Characterization of mineral particles in winter fog of Beijing analyzed by TEM and SEM

“…Once mineral particles are coated by hygroscopic materials, they can act as cloud/fog condensation nuclei (CCN). Water chemistry of fog and cloud plays an important role in interaction between mineral particles and gases as they may strongly influence atmospheric chemistry and air quality (Raja et al 2005;Collett et al 1999;Del Monte and Rossi 1997;Hoag et al 1999). Fog droplets can serve as microreactors converting some of primary pollutants into secondary pollutants, such as SO 2 to secondary sulfates (Seinfeld 1986).…”