Sedimentation periodical

The concentration profiles of all elements analysed exhibited similar trends, but on different concentration levels. Lead, copper and zinc occurred in significantly higher concentrations as compared to cadmium, nickel and chromium with values ranging from 95 to 400 pg/g for Pb, from 56 to 430 pg/g for Cu and from 517 to 2373 pg/g for Zn. These data correspond to values measured for other study areas on the Lippe river, which are highly influenced by industrial emissions (Poppe et al., 1991). Lower concentrations were determined for Cd (2.7 to 15.7 pg/g), Ni (28 to 62 pg/g) and Cr (34 to 199 pg/g). With respect to the concentration trends, two significant maxima at a depth of approx. 25 cm and between 88 and 115 cm were observed for most of the metals analysed as indicated by the hatched areas in Fig. 4. These horizons are correspond to sedimentation periods from 1975 to 1980 and from 1945 to 1955, respectively. 

Two 40 cm cores were taken by means of a tube coring system in May 1999 from a zodiac at location TKS (see Figure 1). The fresh sediment material was characterised as a black fine mud, without sand, with a high water content and an anoxic sediment-water interface. Considering former results of nearby located cores, the 40 cm of these cores represent an sedimentation period of approx. 40 to 50 years. 

Preliminary organic geochemical investigations were performed on layers of a formerly dated sediment core taken from a riparian wetland of the Lippe river (Germany). The samples were collected from two distinct depth intervals representing sedimentation periods of 1944-1952 and 1972-1984, respectively. The quantitative distribution of selected persistent lipophilic organic substances characteres municipal as well as... 

Figure 3.4.21 Velocity of sand particles in water for two different particle diameters d during the initial sedimentation period Pp= 1500 kg m , ...

The terminal velocity in the case of fine particles is approached so quickly that in practical engineering calculations the settling is taken as a constant velocity motion and the acceleration period is neglected. Equation 7 can also be appHed to nonspherical particles if the particle size x is the equivalent Stokes diameter as deterrnined by sedimentation or elutriation methods of particle-size measurement. 

It appears that pesticides with solubiHties greater than 10 mg/L are mainly transported in the aqueous phase (48) as a result of the interaction of solution/sediment ratio in the mnoff and the pesticide sorption coefficient. For instance, on a silt loam soil with a steep slope (>12%), >80% of atra2ine transport occurs in the aqueous phase (49). In contrast, it has been found that total metolachlor losses in mnoff from plots with medium ground slopes (2—9%) were <1% of appHed chemical (50). Of the metolachlor in the mnoff, sediment carried 20 to 46% of the total transported pesticide over the monitoring period. 

Constmction of new power plants in the coal region of the western United States presents serious problems in states whose laws dictate zero effluent. In these plants, cooling-tower water withdrawn from rivers cannot be returned to them. In these situations, cooling-tower effluent is purified by distillation (vapor-compression plants have predominated) and by a combination of distillation and membrane technology. The converted water then is used as boiler feedwater the plant blowdown (effluent) is evaporated from open-air lined pools, and pool sediment is periodically buried back in the coal mine with the flue ashes. 

Most commercial marine diatomite deposits exploit accumulations resulting from large blooms of diatoms that occurred ia the oceans during the Miocene geological epoch. Diatomite sediments older than the Jurassic period are rare in the fossil record. Commercial deposits of diatomite are accumulations of the fossil skeletons, which can occur in beds as thick as 900 m in some locations (5). Marine deposits must have been formed on the bottom of protected basins or other bodies of quiet water, undisturbed by strong currents, in an environment similar to the existing Santa Barbara Channel or Gulf of California (3,6). 

Except for fine particulate matter (0.2 /xm or less), which may remain airborne for long periods of time, and gases such as carbon monoxide, which do not react readily, most airborne pollutants are eventually removed from the atmosphere by sedimentation, reaction, or dry or wet deposition. 

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