Streams soil horizons

A total of 80 soil samples and 30 stream sediment samples were collected in the vicinity of known mineralization and analyzed for 36 elements in four size fractions. Orientation results indicate that soil samples should be collected from the near-surface soil horizon on a 100 by 200 m grid pattern, and sieved to the coarse, -8+35 mesh fraction prior to analysis. Stream sediment samples should be collected at a sample density of approximately 1 sample per 1 km and sieved to the fine, -150 mesh fraction. As expected, copper and molybdenum show the strongest response to copper-molybdenum mineralization at both Pico Prieto and Venado in addition, the following elements are also associated with mineralization at Tameapa Au, Ag, Pb, Zn, V, W, Ni, As, Sb, Bi, Se, Sr, and Ba. 

There have been a number of regional analyses showing that stream and river DOC concentrations appear to be highly influenced by the flowpath of water across the landscape. Streams draining landscapes dominated by water flowpaths at the land surface in contact with organic-rich soil horizons... 

Interflow fraction of rainfall that infiltrates into soils and moves laterally through the upper soil horizons until intercepted by a stream channel, or until it returns to the surface at some point downslope from its point of infiltration. 

Understanding sulfate transport and retention dynamics in forest soils is a prerequisite in predicting S04 concentration in the soil solution and in lake and stream waters. In this study, forest soil samples from the Gardsjon catchments, Sweden, were used to study S04 transport in soil columns from the upper three soil horizons (E, Bs, and BC). The columns were leached using a sequential leaching technique. The input solutions were CaS04 equilibrated with forest floor material. Leaching behavior of S04 and concentration in the effluent were measured from columns from individual horizons. S04 was always retained in the Bs and BC horizons, while... 

For comparison, with the Pb concentrations of the topmost layers, the solutions collected from the deeper soil horizons all had <1 pg/L and were below the LOD provided by Q-ICP-MS. Hirao and Patterson [125] reported 0.015 pg/L in stream runoff in the Sierra Nevada Mountains, but were only able to accomplish this because of the extreme cautions taken to avoid contaminating their samples with industrial lead, and because they used ID-MS to measure the Pb concentrations. The Sierra Nevada watershed is characterized by granitic rocks, and most of the Pb in uncontaminated streamwater is probably derived from the chemical weathering of biotite and potassium feldspar [126]. Therefore, their measured Pb concentration (15 parts per trillion) is probably not an unreasonable estimate of the natural Pb concentration in uncontaminated waters from crystalline terrains. Thus, any study of soil solution Pb has to be capable of reliably measuring Pb in this concentration range. 

HBEF, much of the lead entering the ecosystem from the atmosphere appears to be retained in the forest floor. Concentrations and fluxes of lead in bulk deposition are much greater than in Oa horizon leachate. Solution concentrations and fluxes of Pb decrease through the soil profile and losses in stream water are low. There was a strong correlation between concentrations of Pb and dissolved organic carbon (DOC) in soil solution and stream water at Hubbard Brook Driscoll et al., 1994, 1998). 

Stream sediment (mineral sediment, <0.150 mm) Residual soil, upper horizon (topsoil) 0 - 25 cm with out the top organic layer (<2 mm)... 

Stream water Stream sediment (mineral sediment) Residual soil, upper horizon (topsoil) 0 - 25 cm without organic layer Residual soil, lower (C) horizon (subsoil) a 25 cm layer within a depth range of 50 cm - 200 cm Soil samples should represent the dominant soil type of the small catchment. W s T C... 

FIGURE I Molecular weight distribution (thousands of daltons) of dissolved organic carbon in wet precipitation, throughfall, A and B horizon soil solution, and stream water at Hubbard Brook, New Hampshire. Source Adapted from McDowell (1982) and Cole et al. (1984). 

In general, the DOC of streams in forested catchments is formed in soil organic horizons, while minimal amounts of stream DOC are accounted for by through fall or atmospheric deposition (Schiff et al., 1990). Riparian flow paths can account for the greatest proportion of DOC exported to headwater streams (Hinton et al., 1998). The 6 C of stream DOC can also serve to distinguish between terrigenous-derived DOC and that derived in situ in streams in cases where decomposition of phytoplankton is a major DOC source (Wang et al., 1998). 

The final two samples Investigated consisted of a marine fulvlc acid Isolated by XAD-2 resin absorption (14) of a bulk sample of near surface seawater collected from a site in the Gulf of Mexico (15) and also a soil fulvlc acid extracted from an horizon B podsol (16). These samples were dissolved In filtered Gulf Stream seawater and deionized (MllllQ) water respectively, with the addition of sufficient O.IM NaOH to effect dissolution of the solid soil fulvlc acid. 

Soil was collected from two horizons (surface and O.S m depfli) in an uncontaminated area near the Tim s Branch stream system at the DOE SRS site, and stored at 4 °C in the dark until use. Our interest in working with this type of soil stems from the fact that Tim s Branch, a second order stream system flowing into a tributary of the Savannah River, experienced large influxes of depleted and natural uranium (U), nickel (Ni), and aluminum (Al) as well as other metals. Tim s Branch soils and vegetation have had a strong inq>act on flie deposition of metals and metal-laden sediments (28). 

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