Mobile and Fixed-Site Characterization of Valley Winter Wood Smoke Concentrations in Northern NY Using Highly Time-Resolved Measurements

GEORGE ALLEN (1) Paul Miller (1) Lisa Rector (1)

(1) NESCAUM

     Abstract Number: 394
     Last modified: November 9, 2009

Abstract
Woodsmoke from space heating may be thought of as natural, but there is ample evidence that wood burning emits significant quantities of known health damaging pollutants, with PM2.5 being the largest health threat from woodsmoke. The increasing popularity of wood-fired heating appliances in cold winter climates, both in rural areas as well as increasingly in more suburban and urban areas, has focused attention on increasing woodsmoke exposures. Woodsmoke is a major concern in northern climates with valley topography, where night-time inversions can limit dispersion of ground-level pollutant sources. An intensive characterization of ambient woodsmoke was performed in the Adirondacks in northeastern NY state during the winter of 2008-2009. Highly time-resolved measurements of woodsmoke PM were made for four months at eight fixed sites and two mobile routes using Aethalometers (TM) and nephelometers to provide data with both high spatial and temporal resolution. The “Delta-C” optical absorption method using the two-wavelength Aethalometer (black carbon or BC at 880 nm and a similar measurement at 370 nm) was used as a specific semi-quantitative measurement of local woodsmoke PM at all eight fixed sites. A nephelometer was used at two of the fixed sites to provide an estimate of PM2.5 from all sources. The mobile measurements used both methods.

A total of 14 mobile runs were made during the study - ten in the northern domain and four further south where valley topography was less of a factor. Mobile runs were done overnight, from 9 pm to 3am to catch the peak woodsmoke hours. Fixed site measurements ran for the entire study duration. Woodsmoke was the only significant contributor to elevated valley PM concentrations overnight. Short-term PM concentrations (minutes to an hour) frequently exceeded 100 micrograms/cubic meter. Concentrations in individual plumes exceeded several hundred micrograms/cubic meter. Woodsmoke was consistently found at valley bottoms where the majority of the population lives, and approached zero at high elevations. Mixing heights on calm wind inversion nights were estimated to often be less than 150 meters based on data from one fixed site that was partially out of the valley. Analysis of diurnal profiles showed woodsmoke levels peaking near midnight; a secondary peak was observed around 7 AM. These peaks are consistent with wood heating use patterns. A distinct woodsmoke minimum was observed during mid-day when sources were minimal and dispersion was improved. The diurnal analysis of BC and DC also allow a relative assessment of the contribution of local mobile sources to PM2.5 for the towns in this study.