Central Mineral and Environmental Resources Science Center
The California transect pilot study was designed with two overall objectives. The first was to evaluate alternative sampling and analytical procedures in support of the national survey. The second was to undertake soil science studies that will further Bureau science goals (as well as adding to the Project's overall soil science expertise). To support project goals, this sub task focusd on assessing the ability of random versus stratified sampling designs (e.g. soil type, geologic map unit, and/or land use) to reproduce soil geochemical trends at various map scales. We also determined the variability of pesticide and polyaromatic hydrocarbon (PAH) contents in soils as a function of spatial scale and soil depth. This organic geochemical study helped us to choose appropriate pesticide and PAH compounds to measure as well as providing background for the interpretation of the national-scale organic data. The topical studies generally focused on geologic, climatic, and anthropogenic controls on soil composition. We documenedt soil composition for the same rock type in multiple climate zones. We also focused on the behavior of chromium (Cr) during weathering from mafic rocks. This last study was motivated by potential carcinogenic behavior of Cr and the existence of several bands of Cr-rich rocks that cross the study area. The organic geochemical portion of the research was expanded to research processes of pesticide and PAH alteration in soil profiles.