Seasonal Observations of Atmospheric Volatile Organic and Sulfide
Compounds near a Pulp Paper Mill in North-Central Idaho
Abstract
Air composition of the Lewis-Clark Valley (LCV) was studied over a
two-year period to investigate the effects of a local pulp paper mill on
ambient air and to assess potential health risk to the community.
Lewiston, Idaho and Clarkston, Washington are twin cities in the Snake
River Valley bordering North-Central Idaho and Southeastern Washington,
with a population of over 50,000 including the surrounding areas. The
paper mill is located in North Lewiston and releases malodorous sulfur
air pollutants in the LCV. The neighboring Nez Perce Tribe has conducted
a couple of air studies, in 2006-2007 and the summer of 2016-17, but to
date no longer term study has taken place. Our current study utilized
active air sampling via sorbent tubes followed by thermal desorption gas
chromatography-mass spectrometry (TD-GC-MS) analysis to measure over 50
volatile organic compounds, hazardous air pollutants, and sulfides in
ambient air (adapted from EPA Method TO-17). Seasonal, diurnal, and
spatial variations in air composition were explored. In addition,
monthly averaged passive air samples were collected for comparison at
nearby urban areas – Boise, ID, Coeur d’Alene, ID, and Spokane, WA in
2018. In the LCV, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS)
were the primary sulfur compounds detected, with concentrations highest
adjacent to the paper mill. However, concentrations varied considerably
depending on time of day, season, location and meteorology. Seasonal
observations include DMS, benzene and chloroform peaking in the summer
months, while DMDS peaks in the winter. Diurnal trends show DMS and
chloroform with higher values during the morning hours than later in the
day. The long-term monthly samples show benzene decreasing from winter
to spring, with LCV levels comparable to Coeur d’Alene and Spokane, and
Boise slightly higher. In most cases, benzene levels exceed those
recommended for ambient air in the state of Idaho. Sources and potential
health implications will be discussed.