A novel analytical method to quantify Cr(VI) concentrations in atmospheric particulate matter using new highly functionalized nanodots-field measurements (Astana & Aktobe) and modeling

Faculty Development Competitive Research Grant Program 2018-2020

Atmospheric particulate matter (PM) is a global pollutant with adverse effects on human health, visibility, and climate. While atmospheric particles (chemical and biological aerosols) can produce adverse health effects including asthma, lung cancer, and cardiovascular problems, the reasons for their toxicity are not well understood. Possible source of the effects is that particles can contain metals that can have toxic forms.
In the United States, the National Air Toxics Trends Station (NATTS) Network was developed to provide long-term hazardous air pollutant (HAP) monitoring data. There are typically over 100 pollutants monitored at each NATTS including hexavalent chromium in PM. Cr(III) and Cr(VI) are the two common oxidation
states of chromium in the environment (Guertin et al., 2005). The major sources of anthropogenic Cr(VI) include metal processing, coal burning, fossil fuel emission and cement process (ATSDR, 2008; Barceloux, 1999; Kotas and Stasicka, 2000). In urban areas with heavy diesel traffics, vehicular emissions can
significantly contribute to the increase of airborne Cr in ambient air (Wang et al., 2003).
Cr(VI) is toxic and inhalation exposure to Cr (VI) may lead to cancer, nasal damage, asthma and bronchitis. In contrast, Cr(III) is a trace element essential for the proper function of living organisms (Barceloux,1999). Solubility of Cr(VI) also designates its toxicity. Animal studies illustrated that slightly soluble and highly insoluble Cr(VI) particles such as the chromates of zinc, lead, strontium, barium, and sintered calcium consistently induced a tumor response, albeit with variable efficacy (IARC, 1990). Thus, it is critical to investigate the amount of insoluble Cr(VI) in ambient PM. People residing near industrial facilities that use Cr(VI) compounds or near chromium waste disposal sites and workers of the chromium industries have the greatest potential for exposure to Cr(VI) (ATSDR, 2000).
The conversion between Cr(VI) and Cr(III) can be achieved by oxidation/reduction reactions that occur in solutions. Schroeder and Lee (1975) reported that manganese can oxidize Cr(III) to Cr(VI). Iron (II) was also an effective reducer of Cr(VI) to Cr(III) (Pettine et al., 1998). Reduced sulfur (in the form of S, S2-, H2S, and S2O3) can reduce Cr(VI) to Cr(III). Other reactions is the reduction of Cr(VI) with As and V (Guertin et al.,2005).