Sandy horizon

Wide-spaced sampling was carried out in an area of approximately 150 000 km at density of one sample per 100 km (Wang et al. 2007). Soil samples were collected from the weakly cemented sandy horizon at a depth of 20-30cm. The soil samples were subjected to total analysis and selective leaching of mobile metals. Elements were determined by ICP-MS. 

Early work by the Public Health Engineering Department, Government of West Bengal (PHED, 1991) reported that arsenic is present as adsorbed ions on clay particles/quartz particles and also as primary arsenic mineral(s) . X-ray diffraction of the arseniferous horizons was reported to have shown traces of arsenopyrite. The reported As contents of sediments from Kochua, West Bengal were extremely low, <0.2 mg kg" in all cases, and below the detection limit (probably about O.I mg kg ) in the sandy horizons. 

The typical Clarendon profile consists of a dark grayish-brown, sandy horizon underlain by a yellowish-brown, sandy clay loam horizon, which is underlain by a mottled yellowish-brown, red, and gray, sandy clay loam horizon that contains 5 to 30 percent plinthite. Clarendon soils originate from unconsolidated sediments of medium texture. They are typically found on uplands and have a slope gradient of less than 2 percent. The soils are moderately well drained and have slow runoff. The upper part of the soil profile is more permeable than the lower part. 

Depression where there is a south-facing wedge of productive sandy horizons in certain parts of the Triassic and Permo-Triassic (Fig. 2.4). Along this wedge zone of reservoir rocks we may observe lithological traps in the basal rocks of the Mesozoic complex. It is even possible to locate stratigraphic traps resulting from the closure of reservoir rocks by internal unconformities. 

Layers 3-9 are presented by disperse plastic soils (clayey, organic and organo-mineral). They deposited on territory flood plain under a layer of artificial soils. Below these sediments the sandy horizon begins. 

Sandy horizon (layers 10-14) distributed throughout the study area. The size of sand increases with depth. The total thickness of sand varies from 1.0 to 16.0 m, average—8.0-10.0 m. 

The alluvial greatly-clastic soils (layer 15) and eluvial loamy and greatly-clastic deposits with clay filler (layers 16, 17) are developed under deposits of the sandy horizon. It is products of destruction of basement rock. Their development has sporadic character in the profile. 

Samples were collected from the weakly cemented sandy clay-rich horizon of soils at a depth of 15-30cm and sieved to -120 mesh in the field. 

Fig. 7. Seasonal variations in concentrations and exoenzymatic decomposition rates of organic material in the O to 1 cm horizon of a sandy-mud sediment (water depth 18 m) of the Kiel Bight (Baltic Sea, FRG). Illustrated are concentrations of protein and carbohydrate, and activity ofO(-amylase (mg of amylopectin azure decomposed per g of dry weight sediment per hour). The headline on top characterizes specific ecological situations and events affecting the sediments.

When tested with KSCN as described above, the rootless horizons showed high concentrations of free Fe " despite the poor sandy soil. (Table 6). 

A detailed look at the evolution of soil-moisture chemistry was reported by Sears (1976). In his study Sears assumed the average composition of precipitation shown in Table 8.7. Table 8.7 also lists analyses of the soil moisture he collected from suction lysimeters at 1- and 3-m depths in respective B- and C-horizon soils formed by the weathering of underlying sandy dolomite. The 1-m sample is chiefly a Na -NOj water, with the nitrate probably from fertilizer. The TDS is about 70 mg/L at 1 m and has increased to 500 mg/L at the 3-m depth. In order to explain changes occurring between the 1- and 3-m depth, it is useful to select a solute we can assume to be practically un-reactive in the soil. The best common species for this purpose is probably Cl, with which we can then compare other species concentrations. Relative increases from 1- to 3-m depth are shown in the third column. Increases compared to chloride are given in the fourth column. 

The minimum contents are in sandy soils of river floodplains. The maximum values (70-290 ppm) monitor in the Pre-Caucasian Chernozem. The zones of elevated concentrations are locally distributed and afforded to both natural and anthropogenic factors. The first factor is related to the biogeochemical barrier in the upper soil humus horizon, with increasing content of organic matter, and the second one is related to the pollution due to application ofCu-containing fungicides in orchards and vineyards. 

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