EMISSION INVENTORY SOURCE CATEGORY

METHOD SUMMARY

Wind blowing across exposed agricultural land results in particulate matter (PM) emissions. This revision of the windblown dust methodology (last revised in 1989) has been applied to nearly all of the crops in the California Department of Food and Agriculture 1993 crop data base that might be expected to produce windblown emissions. Orchard and vineyard acreages have been excluded, because the methodologies for determining the emissions have not been developed. Pasture lands have been included for the first time with this revision. The standard methodology for estimating agricultural windblown dust, referred to as the wind erosion equation, tends to produce inflated California emission estimates, because it was developed in the Midwestern United States, and it does not take into account many of the environmental conditions and farm practices specific to California.

In this revised methodology, Air Resources Board staff has added adjustments to the wind erosion equation to improve its ability to estimate windblown emissions from California agricultural lands. The annual climatic factors are now generated using the California Irrigation Management Information System data and surface contour / grid count methods. This revision includes adjustments for the long-term effects of irrigation (cloddiness), as well as the short-term effects of irrigation on erodibility (surface wetness). The annual vegetative cover factor has been replaced with "crop canopy coverage," "postharvest soil cover," and "postharvest replanting to another crop" factors, calculated on a temporal (monthly) basis. Bare and border field regions were also accounted for in this revision. The monthly emissions profile no longer relies strictly on temporal variations in wind, but now takes into account variations in temperature, precipitation, irrigation, canopy coverage, postharvest soil cover, postharvest replanting to another crop, as well as wind. This revised methodology has been applied to 26 counties which represent the bulk of the agricultural acreage in California. In addition to the emissions from these counties, the emissions summary below includes the emissions from the remaining counties. The emissions from these remaining counties are based on (1) district calculations, (2) ARB's 1989 methodology, or (3) some combination of ARB's methodology and the revised methodology.

STATEWIDE EMISSIONS SUMMARY (1993 - ANNUAL AVERAGE TONS / DAY)

CES No.	TOG	CO	NOX	SOX	PM
83337	0.00	0.00	0.00	0.00	522.00
84863	0.00	0.00	0.00	0.00	28.00

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This page last revised on November 12, 1997.

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