Initiated in 1984, the Committee Earth Observing Satellites' Working Group on Calibration and Validation (CEOS WGCV) pursues activities to coordinate, standardize and advance calibration and validation of civilian satellites and their data. One subgroup of CEOS WGCV, Land Product Validation (LPV), was established in 2000 to define standard validation guidelines and protocols and to foster data and information exchange relevant to the validation of land products. Since then, a number of leaf area index (LAI) products have become available to the science com-
Concerns over data quality have raised many questions related to sampling soils for volatile organic compounds (VOCs). This paper was prepared in response to some of these questions and concerns expressed by Remedial Project Managers (RPMs) and On-Scene Coordinators (OSCs). The following questions are frequently asked: 1. Is there a specific device suggested for sampling soils for VOCs? 2. Are there significant losses of VOCs when transferring a soil sample from a sampling device (e.g., split spoon) into the sample container? 3. What is the best method for getting the sample from the split spoon (or other device) into the sample container? 4. Are there smaller devices such as subcore samplers available for collecting aliquots from the larger core and efficiently transferring the sample into the sample container? 5. Are certain containers better than others for shipping and storing soil samples for VOC analysis? 6. Are there any reliable preservation procedures for reducing VOC losses from soil samples and for extending holding times? Guidance is provided for selecting the most effective sampling device for collecting samples from soil matrices. The techniques for sample collection, sample handling, containerizing, shipment, and storage described in this paper reduce VOC losses and generally provide more representative samples for volatile organic analyses (VOA) than techniques in current use. For a discussion on the proper use of sampling equipment the reader should refer to other sources (Acker, 1974; U.S. EPA, 1983; U.S. EPA, 1986a).Soil, as referred to in this report, encompasses the mass (surface and subsurface) of unconsolidated mantle of weathered rock and loose material lying above solid rock. Further, a distinction must be made as to what fraction of the unconsolidated material is soil and what fraction is not. The soil component here is defined as all mineral and naturally occurring organic material that is 2 mm or less in size. This is the size normally used to differentiate between soils (consisting of sands, silts, and clays) and gravels.Although numerous sampling situations may be encountered, this paper focuses on three broad categories of sites that might be sampled for VOCs: 1. Open test pit or trench. 2. Surface soils (<5 ft in depth). 3. Subsurface soils (>5 ft in depth).
Leaf surface area has been quantified in the ratio of leaf area to ground surface area, a ratio termed the leaf area index (LAI). LAI has been defined here as one-half the total green leaf area per unit ground surface area (Chen and Black, 1992a). LAI has been estimated from remote sensing satellites using empirical relationships between ground-estimated LAI and vegetation indices derived from primary spectral bands, especially the red and the near-infrared (NIR) wavelengths, taking advantage of the red-edge phenomenon existent within photosynthetically active vegetation (Chen et al., 2002; Lee et al., 2004; Schlerf et al., 2005). The contrast between the visible and the NIR wavelengths forms a strong step in the electromagnetic spectrum of green vegetation between 680 and 750 nm that is often referred to as "the red edge." Many vegetation indices are predicated on this vegetative feature determined by leaf reflectance and transmittance properties, both which are affected by leaf pigments, internal scattering, and leaf water content (
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