Fugitive dust from agricultural land affecting air quality within the Columbia Plateau, USA

摘要

Windblown dust originating from agricultural land has contributed to poor air quality within the Columbia Plateau region of the Pacific Northwest United States. In fact, the United States Environmental Protection Agency (US EPA) national ambient air quality standard for PM10 (particulates ≤10 μm in diameter) is exceeded each year in the Columbia Plateau due to fugitive dust emitted from agricultural land. Winter wheat - summer fallow is the conventional crop rotation employed on >1.5 million ha within the region. During the 13-month summer fallow period, multiple tillage operations are performed to conserve soil water and control weeds; these tillage operations also create erosive soil conditions due to burial of crop residue and degradation of soil aggregates. Instrumentation was installed to measure sediment flux and PM10 concentration at the windward and leeward positions in fields maintained in summer fallow. Soil loss resulting from singular high wind events ranged from 0 to 2317 kg/ha over a four-year observation period. The corresponding loss of PM10 during these high wind events ranged from 0 to 212 kg/ha. For those events with measurable soil loss, PM10 comprised 5 to 12% of the total soil loss. Although loss of PM10 during high wind events is relatively small compared to total soil loss, such quantities are sufficient to degrade air quality. In fact, under atmospheric conditions, which accompany high wind events within the Columbia Plateau, a loss of only 5 kg/ha of PM10 from all agricultural land in summer fallow is sufficient to raise ambient PM10 concentration above the US EPA standard. Therefore, alternative tillage or cropping practices are sought for reducing the loss of topsoil and PM10 from fields managed in summer fallow during high wind events.