Environmental influences on respirable dust production from agricultural operations in California

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Abstract

Agricultural operations may contribute to the respirable dust (RD) that affects the air quality of California's Central Valley. In order to minimize RD production, it is necessary to understand the role of two of the more important variables that influence RD production, soil water content and air temperature. Personal cyclone samplers were mounted on agricultural implements used in farming operations over two years to capture ⩽4 μm aerodynamic-diameter RD particles. For cultivation operations under widely different environmental conditions, RD concentration decreased as a power function as soil water content increased between 2 and 14% and increased linearly as air temperature increased. Similar results were found for an experiment with a land plane when samples were collected at 126, 156, 186, 216, 246, and 276 cm above the soil surface with either soil water content or air temperature held constant. For some cultivation operations, RD increased as a power function of air temperature between 7 and 24°C. For a loam surface horizon at one sample site, RD concentration increased 2–5 times at 34°C compared to 18.6°C.

Introduction

Agricultural operations generate different amounts of dust (Clausnitzer and Singer, 1996, Clausnitzer and Singer, 1997). The highly industrialized agriculture in the Central Valley of California may contribute to the seasonal variability of this region's air quality (California Air Resources Board, 1986–1994). Airborne particulate matter from farming consists mainly of minerals (soil origin) or a combination of mineral and organic dusts (plant origin). High concentrations of this kind of dust are associated with a number of health problems. These include skin and eye irritations (International Labour Organization, 1979), respiratory disorders (Dosman and Cockcroft, 1989) and an increased risk of lung and skin cancer (McDuffie et al., 1989; Doelman et al., 1990; Schenker et al., 1993). The United States Environmental Protection Agency (EPA) officially acknowledged the potential danger of high particulate-matter (PM) concentrations in their 1996 PM standards guidelines (EPA, 1996). Of particular interest to public health is the respirable particle-size fraction (RD), which generally means particles less than about 10 μm. In 1993, Europe and the United States the American Conference of Governmental Industrial Hygienists – International Standards Organization/European Committee (ACGIH-ISO/CEN, 1993) defined a unified standard for RD which is composed of atmospheric particles with a cut size of ⩽4 μm (i.e., 50% of the particles have an aerodynamic diameter of ⩽4 μm). Long-term health effects can be caused by these small particles reaching the gas-exchange region of the lungs.

From 1986 to 1996 EPA's National Ambient Air Quality Standard was for PM-10 (particulate-matter concentration with a nominal aerodynamic diameter ⩽10 μm). The limits were either an annual average of 50 μg m−3 air or a one-time exposure of ⩾150 μg m−3 air for 24 h. The current California exposure limit for PM-10 is an annual average of 30 μg m−3 air and 50 μg m−3 air for the one-time exposure.

In a previous study, we measured dust concentrations emitted by 29 individual agricultural operations performed on furrow-irrigated organic and conventional corn and tomato and on winter wheat crops in the Central Valley, CA (Clausnitzer and Singer, 1996, Clausnitzer and Singer, 1997). The results indicated that environmental influences such as soil water content and air temperature influence the quantity of RD emitted. In this paper we report on the quantitative relationship between soil water content, air temperature and RD production from soil tillage operations.

Section snippets

Sampling sites

Data were collected at two sampling sites in the Southern Sacramento Valley near the University of California, Davis over three years (Fig. 1). For 2 yr, respirable dust was collected at the implement from 29 agricultural operations for two complete annual crop cycles on 22 4097-m2 plots 11 km west of Davis, CA. The plots are part of the UC Long-Term Research in Agricultural System (LTRAS) experiment. Plots included conventional and organic corn (Zea mays cv. NC+4616 and Pioneer 3152) and tomato (

Influence of soil moisture

Data from the 149 tillage operations at the LTRAS site were sorted and RD concentration was calculated for intervals of 1% water content (Table 1). The first interval was from 1 to 1.99%. The second was from 2.0 to 2.99% and so forth. No samples were collected between water content intervals of 10–11.99%. Many more samples were collected at water contents between 2 and 4% than at other soil water contents because these are typical soil water contents at which cultivation operations are done. RD

Conclusions

RD production from cultivation operations was well correlated with soil water content and air temperature. As soil water content increased, RD concentration decreased by a power function. An apparent soil water content threshold was a little below half of the permanent wilting point of plants between 5 and 6% volumetric moisture content, below which RD concentrations exceeded 1 mg m−3 and increased rapidly. Higher air temperature was related to higher RD concentration. For the Yolo loam on one

Acknowledgments

The Kearney Foundation of Soil Science and the University of California, Division of Agriculture and Natural Resources supported this work. We thank Mike Mata and the staff at the University of California LTRAS plots for their invaluable assistance.

References (13)

  • ACGIH-ISO/CEN, 1993. Annual reports of committees on TLVs and BEIs. Applied Occupational and Environmental Hygiene 8...
  • California Air Resources Board, 1986–1994. California air quality data. Quarterly summaries. Technical Support...
  • W.S. Chepil

    Influence of moisture on erodibility of soil by wind

    Soil Science Society of America Proceedings

    (1956)
  • H. Clausnitzer et al.

    Respirable-dust production from agricultural operations in the Sacramento Valley, California

    Journal of Environmental Quality

    (1996)
  • H. Clausnitzer et al.

    Intensive land preparation emits respirable dust

    California Agriculture

    (1997)
  • C.J.A. Doelman et al.

    Mineral dust exposure and free radical-mediated lung damage

    Experimental Lung Research

    (1990)
There are more references available in the full text version of this article.

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