Cadmium concentration ocean

However, it is clear from many tracers that there was continued ventilation of deep waters in the North Atlantic as well. Boyle and Keigwin (1982) argued that the fact that reconstructed cadmium concentrations in the deep North Atlantic were still lower than average ocean values suggests that there was not a... 

The vertical distribution of dissolved cadmium concentration in the oceans follows a profile typical of phytoplankton nutrients from a few picomolar at the... 

Two major patterns of horizontal distribution can be discerned for Cd in the oceans (i) a much smaller concentration in the deep Atlantic compared to the deep Pacific and Indian Oceans, as is characteristic of all algal nutrients (ii) a decrease in surface concentrations from the coasts of continents to the open oceans, which is observed for many elements. Cadmium concentrations in the deep Atlantic 0.3 nM) are roughly three times lower than in the deep Pacific or Indian Oceans (0.9 nM Fig. 4) about the same factor as observed for phosphate [20-22]. This higher accumulation in the deep waters of the Pacific than in those of the Atlantic results from the simultaneous downward transport of the elements that are incorporated in settling biomass and the horizontal transport by major oceanic currents, which run toward the Atlantic at the surface and toward the Pacific in deep waters [23]. 

Sodium-dibenzyldithiocarbamate (Na-DBDTC) tends to precipitate as carbamic acid at pH levels less than 4.8. Introduced into the column it accumulates at the column on its top and later redissolves in the CHCls CHsOH mixture, resulting in poor sample spots on the carrier. This leads to a large background signal and deterioration of the detection limits. Low lead and cadmium concentrations in open ocean water can be difficult or impossible to detect under such conditions. Thus, precipitation of carbamic acid must be avoided. 

Ammonium pyrrolidine dithiocarbamate (APDC) chelate coprecipitation coupled with flameless atomic absorption provides a simple and precise method for the determination of nanomol kg 1 levels of copper, nickel, and cadmium in seawater. With practice, the method is not overly time-consuming. It is reasonable to expect to complete sample concentration in less than 20 min, digestion in about 4 h, and sample preparation in another hour. Atomic absorption time should average about 5 min per element. Excellent results have been obtained on the distribution of nickel and cadmium in the ocean by this technique. 

Unlike halogenated solvents, it does not produce noxious substances in the inductively coupled plasma, has a very low aqueous solubility, and yields hundredfold concentration in one step. Detection limits ranged from 0.02 jtg/l (cadmium) to 0.6 pg/1 (lead). The results indicate that the proposed procedure should be useful for the precise determination of metals in oceanic water, although a higher sensitivity would be necessary for lead and cadmium. 

A comparison was carried out on the results obtained using ICP-AES and AAS for eight elements in coastal Pacific Ocean water. The results for cadmium, lead, copper, iron, zinc, and nickel are in good agreement. For iron, the data obtained by the solvent extraction ICP method are also in good agreement with those determined directly by ICP-AES. In most of the results the relative standard deviations were 4% for all elements except cadmium and lead, which had relative standard deviations of about 20% owing to the low concentrations determined. 

Rainbow, P.S. 1989. Copper, cadmium and zinc concentrations in oceanic amphipod and euphausiid crustaceans, as a source of heavy metals to pelagic seabirds. Mar. Biol. 103 513-518. 

Correlation plots for the North Pacific Ocean concentration data from Figure 11.14 (a) zinc versus nitrate, phosphate, and silica, (b) cadmium versus nitrate, phosphate, and silica, (c) copper versus nitrate, phosphate, and silica, and (d) nickel versus nitrate, phosphate, and silica. 

On a worldwide basis, toxic concentrations of the heavy metals have thus far been limited to industrialized harbors. The only metals that appear to have accumulated to toxic levels on a regional scale are mercury, cadmium, and lead in the Arctic Ocean. This concentration of mercury and lead has been fecilitated by a natural process, called the grasshopper effect, which acts to transport volatile compoimds poleward. This transport plays a major role in redistributing the volatile organic pollutants, such as the PCBs, and, hence, is discussed at further length in Chapter 26.7. The process responsible for the cadmium enrichment in the Arctic appears to involve low-altitude transport of the fine particles that compose Arctic haze. 

For the nuclides studied (rubidium, cesium, strontium, bariun silver, cadmium, cerium, promethium, europium, and gadolinium) the distribution coefficients generally vary from about 10 ml/gm at solution-phase concentrations on the order of 10 mg-atom/ml to 10 and greater at concentrations on the order of 10 and less. These results are encouraging with regard to the sediment being able to provide a barrier to migration of nuclides away from a waste form and also appear to be reasonably consistent with related data for similar oceanic sediments and related clay minerals found within the continental United States. 

Spencer, M.3., Piotrowicz, S.R. and Betzer, P.R., 1982. Concentrations of cadmium, copper, lead and zinc in surface waters of the northwest Atlantic Ocean - a comparison of Go-Flo and teflon water samplers. Mar. Chem., 11 403-410. 

Cadmium is taken up by phytoplankton slightly preferentially to PO4 (Loscher et al, 1998 Elderfield and Rickaby, 2000). Waters with low PO4 concentrations thus have lower Cd PO ratios (0.1 nmolCd per p,mol PO4) than waters with higher PO4 concentrations where Cd POJ may approach 0.4 nmol Cd per p,mol PO (Elderfield and Rickaby, 2000). Additionally, surface water Cd PO4 ratios drop over the development of the spring bloom in the Southern Ocean (Loscher et al, 1998). 

In order to estimate paleoceanographic nutrient levels, and thereby explore links between nutrient variability, atmospheric CO2 and climate change, a range of nutrient proxies have been developed. The ratio of cadmium (Cd) to calcium (Ca) in benthic foraminifera has been used as a proxy for dissolved phosphate, based on the observation that dissolved cadmium and phosphate concentrations are linearly correlated in modern oceanic waters (Boyle, 1988). While the basis of the Cd PO4 relationship is not understood, from either a biochemical or geochemical standpoint (e.g., Cullen et al., 2003),... 

Selenium profiles in sediments from the northeast Atlantic Ocean indicate concentrations of —0.2-0.3 mg kg in the oxic zone, and typically 0.3-0.5 mg kg below the redox boundary reflecting immobilization under reduced conditions (Thomson et al., 2001). Similar increases for cadmium, uranium, and rhenium have also been observed in the suboxic zone. 

Data obtained on Legs 1 and 2 are presented in Table II. Concentrations were calculated by comparison with an added standard which increased the concentrations of the samples by 2.0 X 10" M cadmium and 2.0 X 10" M lead. Results for measurements which were not followed by standard additions were estimated by interpolating between bracketing standard additions. The concentration levels are those generally expected for open-ocean water (13). Lead values are somewhat higher than those of Southern Cahfomia surface waters recently measured by isotope dilution (10), but it must be noted that these data were not corrected for an analysis T)lank, which in our system may include... 

J. E. Harris, G. J. Fabris, Concentrations of suspended matter and particulate cadmium, copper, lead and zinc in the Indian Sector of the Antarctic Ocean, Mar. Chem., 8 (1979), 163-179. 

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