Annual deposition

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About one third of the total deposition is from Kazakhstan and 10% is from other Asian sources. In both cases about 20% is contributed by natural sources. The total annual deposition of mercury to Kazakhstan amounts to 28 t/yr and to Kyrgyzstan—2.9 t/yr. 

The observation that nodules grow at widely varying rates provides further support for the existence of multiple formation mechanisms. The nodules that accrete most slowly (1 mm per million years) appear to have formed primarily by the process of hydrogenous precipitation. This accretion rate is equivalent to the annual deposition of a layer that is only one atom deep. These slow rates cause a significant amount of metal-rich seawater to become occluded between the Fe-Mn oxide layers. 

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Carbon and Phosphorus Burial Efficiencies. The estimate of diatom carbon demand (12-15 g/m2 per year) is consistent with the flux of carbon to the sediment surface. With sediment-trap fluxes corrected for resuspension, we measured a total annual deposition flux of 12.5 g of C/m2. In comparison, Eadie et al. (24) obtained 23 g of C/m2 for a 100-m station, based on three midsummer metalimnion deployments. Of our total, 83% of the carbon was associated with diatoms, and the primary diatom carbon flux was 10.3 g of C/m2. Thus, about 15-30% of the diatom carbon was regenerated in the water column during sedimentation. Approximately 10% of the diatom flux reached the sediment surface encapsulated in copepod fecal pellets the remaining 90% was unpackaged. 

The overall objective of the precipitation study was to (1) determine the occurrence and temporal distribution of herbicides and their degradation products in precipitation, (2) estimate the amounts of atrazine deposited by precipitation annually in individual states and over a large part of the United States, (3) relate annual deposition of atrazine to amounts applied annually, and (4) compare annual herbicide deposition by precipitation within the Mississippi River Basin to the estimated annual amount transported out of the basin in streamflow. 

Sr calculated by dividing the annual deposit gauge collection by the average air concentration. The contribution of dry deposition to the deposit gauge is in fact usually ignored in calculating the washout ratio. Hence the velocity of deposition by washout is... 

Little Rock Lake sediment trap measurement period was 7/85-12/86. Since two summer periods but only one winter were included, deposition rates are seasonally weighted to represent the best estimate of annual deposition. 2Reference (19). Data are for 15.5 m (deepest) trap. 

Wet removal processes are further controlled by precipitation types and rates. Dry deposition processes on surfaces are affected by atmospheric transport rates that mix fresh pollutant into the surface boundary layers and by the physical properties of particles. For the Eastern U.S., the approximate annual deposition rates of sulfate can be compared as follows (Table III), considering that deposition flux is the product of a concentration and a velocity of deposition (Vd) (20) ... 

Studies comparing emissions from known sources of PCDD/Fs to aerial deposition rates in Sweden56 and the United Kingdom57,58 found that annual depositions were 8-20 times higher than annual emissions, suggesting that the bulk of dioxin present in the atmosphere is due to unidentified sources. Estimates of atmospheric deposition rates for PCDD/Fs vary from 1-2 ng TEQ m 2 yr 1 for limited US data to 2-30 ng TEQnU2 yU1 for more extensive European data. Based on an assumed combined wet and dry particulate and gaseous deposition... 

Table 2 Annual deposition of chemical components at 11 stations in Japan...

The deposition amount of nitrate ion is shown in Fig. 4a. The amount was high at Tokyo and Osaka, which are the highly populated and industrialized areas with heavy traffic. The values of nitrate in the summer season, however, should be treated with much care, because some microbiological change of nitrate to ammonium ions may have occurred during the sampling period of one month (5). It is of interest to mention, however, that the annual deposition amounts of nitrate at the stations on the Japan Sea side were fairly constant around the value of 1.3 g/nry which is comparable to the amount reported by EML for the polluted area of the east coast of the United States (6). 

The Japanese Society of Soil Science and Plant Nutrition provided the soil map for assessing the susceptibility of Japanese soils to acid precipitation (7). Fig. 6 shows a summary of the map together with the annual deposition of sulfate (excess) at eleven stations in Japan. The most susceptible and most tolerant areas are distinguished on the map. The soils in unmarked regions of the map have intermediate susceptability. 

Williams et al. also measured DOC (Dissolved Organic Carbon) at average values of 138 and 238 pM for the dry and wet seasons, respectively. The annual volume weighted mean of 159 pM implies an annual deposition of about 0.4 moles C m. The acidity was basically determined by the concentrations of organic acids. The concentration of acetate was 9 3 peq and formate was 2.9 peq hk The average conductivity was... 

The average concentration of phosphorus was found to be 3000 ppm. Given the calculated yearly material deposition rate, approximately 11 kg phosphorus would have been contributed each year. Cook and Heizer arrived at an annual deposition rate of 124 kg phosphorus to a site area by a standard population of 100 individuals (28). By utilizing this rate, a population of only nine individuals would have been required to account for the amounts of phosphorus found to be present. Because phosphorus as phosphate is the least mobile of the elements tested, this figure can be considered to represent an absolute minimum permanent population estimate for the site during the period of occupation under consideration. It should be remembered, however, that soil phosphate is also found in occluded forms and in organic combination and that these fractions were not totally measured by the procedure utilized (29). Consequently, the minimum population estimate should be increased, perhaps by as much as 50-60%, to about 15 individuals. 

The annual continental river discharge of Ca ions to the ocean is 0.48 x tons. The similar value is discharged in suspended form, 0.47 x 10 tons/yr. In addition, 0.048 X 10 tons/yr. is windblown off the land into the ocean. The average calcium content in the precipitation over the ocean is 0.36 mg/L (Savenko, 1976). Therefore, the total annual deposition flux of Ca over the global ocean isO. I6x lO tons, including about 20% of dry deposition, 0.03 x 10 tons/yr. (Dobrovolsky, 1994). The total amount of Ca entering the atmosphere from the global ocean is about 0.20 x lO tons annually. About 0.02 x lO" tons/yr. is transported to terrestrial ecosystems, and the rest is returned to the ocean (Table 31). 

Fig. 7.3 Cross-section through a speleothem showing annual deposits of varying size...

Cementum annuli Annual deposits of cementum around the base of teeth. 

The day to day situation is very different from this average picture. With southerly winds, concentrations of 20-30 pg/m of sulphur dioxide and sulphate particles are frequently observed in southern Scandinavia. For this area, more than 90% of the annually deposited sulphate comes from other countries. Half of the deposition may be due to 10 or so episodes with highly polluted precipitation. A similar situation is observed in other remote areas. 

Quarterly and Annual Deposition of 90Sr in Selected U.S. Cites for the Year 1990... 

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