Dissolved organic carbon average concentrations

Fig. 2 Longitudinal changes in nutrient concentrations below the effluent input of a WWTP without tertiary treatment in La Tordera Stream. Values are the average ( SEM) of monthly measurements done over a year (see more details in [47]). In the left panel, note the net decline of ammonium concentration with concomitant net increases in nitrate concentration, suggesting a potential hot spot for nitriflcation. However, in the latest meters downstream, dissolved inorganic nitrogen (DIN) tends to decrease, which indicates net lost of DIN possibly due to denitrification. The right panel shows net changes in phosphate and dissolved organic carbon (DOC) concentrations. While phosphate does not exhibit any clear trend on an annual basis, DOC seems to decline similarly to DIN, which supports the relative dominance of denitrification...

Fig. 9. Comparison of depth-averaged profiles of dissolved organic carbon (DOC) concentrations of samples from the Nova Scotian shelf measured with various oxidation methods. Data from Gershey et al. (1979). = persulfate oxidation (Menzel and Vaccaro, 1964) o = dry oxidation (MacKinnon, 1978) = photo-oxidation (Collins and Williams, 1977).

Hercules Chemical produced an acidic organic waste derived from the manufacture of dimethyl terphthalate, which is used in the production of synthetic liber. The average dissolved organic carbon concentration was about 7100 mg/L and included acetic acid, formic acid, p-toluic acid, formaldehyde, methanol, terphthalic acid, and benzoic acid. The pH ranged from 3.5 to 4.0. The waste also contained traces (less than 0.5 mg/L) of 11 other organic compounds, including dimethyl phthalate, a listed hazardous waste. 

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... 

Carbon is transported into the Amazon River/ocean mixing zone in numerous forms including dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC). The average DIC, DOC, and POC concentrations in Amazon River water are 460, 275, and 180 pmol L-1 (Richey et al. 1991), which indicates that DOC supply exceeds POC supply and that DIC is the most abundant form of carbon in the river. Sholkovitz et al. (1978) noted that most riverine dissolved... 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

The organic carbon (and thus the organic matter) in seawater is predominantly in dissolved form (DOC) with an average for the whole ocean being 97%. In general, surface ocean concentrations are about 80/ M and decrease to about 40 /iM below 500 m (Peltzer and Hayward, 1996 Hansell and Peltzer, 1998). 

On average about 20% of the BSi arriving at the sediment-water interfece dissolves prior to burial. Thus, only 3 to 5% of the surface production survives to become buried in the sediments. At some locations, where the BSi rain rate is high, a larger percentage (around 30%) is preserved. In comparison, 90% of the POC that rains onto the sediments is remineralized by the benthos, leaving sediment concentrations on the order of 1% w/w organic carbon. 

Babiarz et al. (2001) examined total mercury (Hg) and methyhnercury (Me-Hg) concentrations in the colloidal phase of 15 freshwaters from the upper Midwest and Southern United States. On average, Hg and Me-Hg forms were distributed evenly between the particulate (0.4 jm), colloidal, and dissolved (lOkDa) phases. The amount of Hg in the colloidal phase decreased with increasing specific electric conductance. Furthermore, experiments on freshwater with artificially elevated electric conductance suggest that Hg and Me-Hg may partition to different subfractions of colloidal material. The two colloidal Hg phases act differently with the same type of adsorbent. For example, the colloidal phase Hg correlates poorly with organic carbon (OC) but a strong correlation between Me-Hg and OC was observed. 

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