Organically bound copper

Amendment with soluble copper in arid Israeli soils, particularly at high loading levels, resulted in initial perturbation and increased the amounts of copper in the exchangeable and the carbonate fractions in the loessial soil. This also occurred with the carbonate and the organic bound fractions (Fig. 6.10, Fig. 6.1). Even so, the soils converged quite rapidly... 

Copper in sludge was predominately found in the organically bound fraction. The Cu in sludge from Israel prevailed in the organically bound portion (80%) (Banin et al., 1990). Sposito et al. (1983) and Emmerich et al. (1982) also reported that Cu mainly occurred in the organic fraction, followed by the carbonate and residual fractions. 

Copper and copper-containing alloys are susceptible to attack by elemental sulfur and hydrogen sulfide as well as organically bound sulfur. Active or elemental sulfur and hydrogen sulfide gas can attack copper to form copper sulfide, a dark-brown to black compound. This can be seen through ASTM D-130 copper corrosion testing. 

As shown in Figs. 3-6, at low concentration levels of both metals, namely for /o(Cu2+) = 1.5 mg/L and for p(Zn2+) = 9 mg/L, the rankings of metal forms remained unchanged as the HRT increased. On the other hand, at the high concentration levels of these metals, namely for p(Cu2+) = 4.5 mg/L and for p(Zn2+) = 27 mg/L, the rankings of the different forms of these metals changed with the HRT the least represented forms for both are the sulfides, and the dominant metal forms are the organically bound forms for both zinc and copper. 

In soil research, the term speciation is often applied to operationally defined fractionation of heavy metals into five or more components.25 Typically, water soluble, exchangeable, organically bound (which includes what is in biomass), amorphous oxide bound, crystalline oxide bound, and residual fractions are measured.26 Sometimes residual fractions are further subdivided according to particle size distributions to give amounts in sand, silt, and clay fractions. Similar fractionation procedures are often applied to aquatic sediments.27 In arid regions, often the calcium carbonate bound fractions of heavy metals are also measured.28 Because of the constraints of detection limits, generally only cadmium, copper, iron, manganese, and zinc are usually monitored by flame spectrometry in such heavy metal speciation studies.28... 

Copper was selected as the first metal for which to attempt to optimize the shipboard analyses because considerable information is available about the marine chemistry of copper, and because this new analytical capability would greatly enhance our ability to study copper in the ocean. The concentration of copper in the ocean varies from 0.5 to 5 nmol/kg in response to biological and geochemical processes (Table I). The chemical speciation of copper has received considerable attention because the biological effects of copper depend on its chemical form (i-3). The principal forms of copper include inorganic complexes such as CUCO3, CuHCO , CuOH, and organically bound copper (4, 5). 

In designing a preconcentration scheme to operate in real time, consideration must be given to kinetic factors involved in the preconcentration step. In general, any preconcentration step will alter the trace metal s chemical equilibrium and will involve a time-dependent reaction or mass-transfer step. Of those species likely to be affected during preconcentration, the most thermodynamically and kinetically stable are typically the organically bound forms. Organically bound copper has been carefully studied and provides the best example. 

The chromatographic procedure intially investigated was reverse-phase liquid chromatography (RPLC) using Cig-bonded silica gel. This technique has been used previously for the preconcentration of trace metals from seawater prior to analysis by atomic absorption spectrophotometry (23, 24) and for the isolation of organically bound copper from seawater (4). These methods were modified and adapted for automation. 

Isolation of organically bound copper was accomplished by using the method of Mills et al. (4). The same preconcentrator configuration employed for total metals was used, and the Cjg-SEP-PAK cartridges were cleaned in the manner just described. Untreated seawater was passed through the column, a Milli-Q water wash followed, and elution was by a 50 50 water-methanol mixture. The column was then prepared for another run by cleaning with water-methanol and Milli-Q water. 

Column-loading rates, elution volumes, and other operating parameters were similar to those used for total-metal determination, except that the volume of seawater used was 287 mL. Because a percent recovery cannot be determined for organically bound copper, only what is measured can be reported. The blank was about 0.1 nmol/kg. 

The results obtained in this field test demonstrated the feasibility of shipboard atomic absorption measurements for low-level metal measurements. The reproducibility of the duplicate measurements of total and organically bound copper were encouraging at the less than 1-nmol/L level. The vertical profiles show structure that is related to oceanographic factors... 

There is a good deal of information on the inorganic forms of several elements in many rocks, soils and coals, but much remains to be done on the organic associations of trace elements. For example copper, lead and zinc are associated with humic acids, probably through carboxyl or phenolic groups (Saxby, 1969 Nissenbaum and Swaine, 1976). Vanadium porphyrins occur in petroleum (Davis, 1967), but the form of vanadium in coal has not been established. In most shales and coals, trace elements probably occur partly inorganically and partly organically bound. 

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