William D. Ellenson

An environmental scoping study in the Lower Rio Grande Valley of Texas — III. Residential microenvironmental monitoring for air, house dust, and soil

A principal aspect of the 1993 Lower Rio Grande Valley Environmental Scoping Study was the analysis and interpretation of residential air, household dust, and soil pollutant concentration data for exposure assessments. Measurements included respirable particulate matter (PM2.5), volatile organic compounds (VOCs), pesticides, and polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air. Household dust, road dust, and yard soil were analyzed for elements, pesticides, and PAHs. Nine residences were monitored for three weeks in the spring of 1993. Additional monitoring was conducted at six of the nine residences for ten days the following summer. Generally good agreement was found between outdoor residential air and same-species measurements collected concurrently at a non-residential central site in Brownsville, TX (Ellenson et al. 1997) for fine particulate matter, elements, and VOCs indicating the dominance of regional influences. PM2.5 mass and element concentrations in residential indoor and outdoor air were generally higher in the summer than in the spring. Indoor air concentrations of many species were higher than outdoor air concentrations and were attributed to household activities, ventilation of residences, and track-in of dislodged soils. Evidence of agricultural activities was noted in the occurrence of crop-related pesticides (e.g., malathion and chlorpyrifos) in indoor and outdoor air. Concentrations of common household pesticides (e.g., chlordane, chlorpyrifos, diazinon, heptachlor, and propoxur) were generally higher indoors than outdoors and were also present in house dust. Seasonal comparisons of pesticides and PAHs were also presented using matched residences in spring and summer; VOCs also may have indicated seasonal effects. VOCs (notably propane and butane isomers) and PAHs were higher indoors, presumably due to cooking-related activities.

An environmental scoping study in the lower Rio Grande Valley of Texas : I. Comparative assessment of air sampling methods

Abstract The atmospheric monitoring component of the 1993 Lower Rio Grande Valley Environmental Scoping Study measured a wide range of pollutant species from different sampling and analysis methods. Extensive QA/QC activities were also conducted on the sampling and analysis techniques. This enabled a unique comparison of these methods to provide insights into air sampling for larger, long-term exposure monitoring studies. Pollutants monitored were particulate mass and elements, acidic gases, volatile organic compounds, pesticides, and polycyclic aromatic hydrocarbons. This included collocated monitoring devices which monitored same-species pollutants. Sample collection efficiencies of certain atmospheric pollutants are discussed. Finally, data from two sites located in the Lower Rio Grande Valley are also presented and compared.

Development and evaluation of an acid-precipitation monitor for fractional event sampling with capability for real-time pH and conductivity measurement

An acid precipitation monitor has been developed that collects fractions of rain events, measures the pH and conductivity in real-time, and stores the remaining samples under refrigerated conditions. A Z-80 microprocessor controls all operations of the monitor including sample collection, sample analysis, quality control analysis, and data recording. Quality control analysis consists of analysis upon demand of a low-ionic-strength solution. The monitor was evaluated in the field and about 40 rain events were monitored. Excellent stability of the pH electrode was found under field conditions.

Monitoring and Source Apportionment of Particulate Matter near a Large Phosphorus Production Facility

ABSTRACT A source apportionment study was conducted to identify sources within a large elemental phosphorus plant that contribute to exceedances of the National Ambient Air Quality Standards (NAAQS) for 24-hr PM10. Ambient data were collected at three monitoring sites from October 1996 through July 1999, and included the following: 24-hr PM10 mass, 24-hr PM2.5 and PM10–2.5 mass and chemistry, continuous PM10and PM2.5 mass, continuous meteorological data, and wind-direction-resolved PM2.5 and PM10 mass and chemistry. Ambient-based receptor modeling and wind-directional analysis were employed to help identify major sources or source locations and source contributions. Fine-fraction phosphate was the dominant species observed during PM10 exceedances, though in general, re-suspended coarse dusts from raw and processed materials at the plant were also needed to create an exceedance. Major sources that were identified included the calciners, the CO flares, process-related dust, and electric-arc furnace operations.