Reply on RC1

Karin Ardon-Dryer

doi:10.5194/amt-2021-270-ac1

Abstract

Abstract. Information on atmospheric particles' concentration and sizes is important for environmental and human health reasons. Air quality monitoring stations (AQMSs) for measuring particulate matter (PM) concentrations are found across the United States, but only three AQMSs measure PM2.5 concentrations (mass of particles with an aerodynamic diameter of <â2.5âÂµm) in the Southern High Plains of West Texas (area â¥â1.8âÃâ105âkm2). This area is prone to many dust events (â¼â21âyrâ1), yet no information is available on other PM sizes, total particle number concentration, or size distribution during these events. The Aerosol Research Observation Station (AEROS) was designed to continuously measure these particles' mass concentrations (PM1, PM2.5, PM4, and PM10) and number concentrations (0.25â35.15âÂµm) using three optical particle sensors (Grimm 11-D, OPS, and DustTrak) to better understand the impact of dust events on local air quality. The AEROS aerosol measurement unit features a temperature-controlled shed with a dedicated inlet and custom-built dryer for each of the three aerosol instruments used. This article provides a description of AEROS as well as an intercomparison of the different instruments using laboratory and atmospheric particles. Instruments used in AEROS measured a similar number concentration with an average difference of 2âÂ±â3âcmâ1 (OPS and Grimm 11-D using similar particle size ranges) and a similar mass concentration, with an average difference of 8âÂ±â3.6âÂµgâmâ3 for different PM sizes between the three instruments. Grimm 11-D and OPS had a similar number concentration and size distribution, using a similar particle size range and similar PM10 concentrations (mass of particles with an aerodynamic diameter of <â10âÂµm). Overall, Grimm 11-D and DustTrak had good agreement in mass concentration, and comparison using laboratory particles was better than that with atmospheric particles. Overall, DustTrak measured lower mass concentrations compared to Grimm 11-D for larger particle sizes and higher mass concentrations for lower PM sizes. Measurement with AEROS can distinguish between various pollution events (natural vs. anthropogenic) based on their mass concentration and size distribution, which will help to improve knowledge of the air quality in this region.

Highlights

Particulate matter (PM) comprises microscopic solid and liquid particles suspended in the atmosphere, which can be generated 20 by anthropogenic or natural sources
Air quality monitor stations (AQMSs) for measuring Particulate Matter (PM) concentrations are found across the United States, but only three AQMSs measure PM2.5 concentrations in the Southern High Plains of West Texas
This area is prone to many dust events (~21 per year), yet no information is available on other PM sizes, total particle concentration, or size distribution during these events

Summary

Introduction

Particulate matter (PM) comprises microscopic solid and liquid particles suspended in the atmosphere, which can be generated 20 by anthropogenic or natural sources. Similar PM sizes are measured by the DustTrak and Grimm 11-D, and total number concentration and size distribution (at least for the size range of 0.3-10.0) are measured by both the OPS and Grimm 11-D The usage of these three different distinct instruments as part of the AEROS aerosol measurements unit was planned to overcome times of common instrument problems, e.g., connection issues, broken units, or the need for repair. When no particles were detected, the freshly baked dryer was connected to each instrument with a clean filter at the 180 inlet, and measurements of particles were performed to verify the dryer background particle level (PM, size distribution, and total concentration). These background values were subsequently subtracted from the instruments’ atmospheric measurements. Observations of meteorological conditions (e.g., thunderstorms, rain, haze, and dust) were retrieved for that period using the “Present Weather Code”, which is provided in the METAR

Laboratory intercomparison of aerosol instrumentation using ATD particles

Intercomparison of aerosol instruments using atmospheric particles

Comparison of aerosol concentration based on different locations

AEROS limitations 410