Fluorometric field instrument for continuous measurement of atmospheric hydrogen sulfide.

A sensitive (limit of detection approximately <100 pptv at S/N = 3), fully automated, portable (32 x 25 x 38 cm, 4.5 kg) instrument has been designed for continuous field measurement of atmospheric hydrogen sulfide. Air is sampled by a PTFE membrane-based diffusion scrubber and collected into an aLkaline fluorescein mercuric acetate (FMA) solution flowing under a controlled and constant pneumatic pressure. The collected sulfide quenches the fluorescence that is measured with a miniature blue LED photodiode-based fluorescence detector. Acquisition and interpretation of signal and all flow control are carried out via a mininotebook personal computer (PC) using custom software written in HP-VEE. The instrument provides for self-calibration and zero functions using an on-board permeation tube enclosed in a thermostated block, at any preprogrammed desired interval. During sampling, the computed H2S concentration is stored every 2 min. The complete system, including the PC, is operated in the field by a 12-V marine battery. The system was field tested near oil field operations in West Texas and showed good correlations with a concurrently operated lead acetate tape-based commercial sampler, with a response speed and time resolution much better than that of the latter instrument.

Using GIS to study the health impact of air emissions.

Geographical Information Systems (GIS) is a fast-developing technology with an ever-increasing number of applications. Air dispersion modeling is a well-established discipline that can produce results in a spatial context. The marriage of these two applications is optimal because it leverages the predictive capacity of modeling with the data management, analysis, and display capabilities of GIS. In the public health arena, exposure estimation techniques are invaluable. The utilization of air emission data, such as U.S. EPA Toxic Release Inventory (TRI) data, and air dispersion modeling with GIS enable public health professionals to identify and define the potentially exposed population, estimate the health risk burden of that population, and determine correlations between point-based health outcome results with estimated health risk.