Mineralization carbon role

Collectors ndFrothers. Collectors play a critical role ia flotation (41). These are heteropolar organic molecules characterized by a polar functional group that has a high affinity for the desired mineral, and a hydrocarbon group, usually a simple 2—18 carbon atom hydrocarbon chain, that imparts hydrophobicity to the minerals surface after the molecule has adsorbed. Most collectors are weak acids or bases or their salts, and are either ionic or neutral. The mode of iateraction between the functional group and the mineral surface may iavolve a chemical reaction, for example, chemisorption, or a physical iateraction such as electrostatic attraction. 

Oxygen is by far the most abundant element in cmstal rocks, composing 46.6% of the Hthosphere (4). In rock mineral stmctures, the predominant anion is, and water (H2O) itself is almost 90% oxygen by weight. The nonmetaUic elements fluorine, sulfur, carbon, nitrogen, chlorine, and phosphoms are present in lesser amounts in the Hthosphere. These elements aU play essential roles in life processes of plants and animals, and except for phosphoms and fluorine, they commonly occur in earth surface environments in gaseous form or as dissolved anions. 

Their contribution to the total dissolved load in rivers can be estimated by considering the mean composition of river water and the relative importance of various rocks to weathering. Estimates (18) indicate that evaporites and carbonates contribute approximately 17% and 38%, respectively, of the total dissolved load in the wodd s rivers. The remaining 45% is the result of the weathering of siUcates, underlining the significant role of these minerals in the overall chemical denudation of the earth s surface. 

Other than a nutritional role linked to mineralization processes, humic compounds have been hypothesized to directly affect plant nutrition, since it has been suggested that roots may take up low-molecular-weight humic molecules (21). Interestingly, plants have been ob.served to express carriers for amino acids (22) and small peptides (23) at the root level. Certain components of the humic fraction have been found inside root cells and were, moreover, translocated to the shoots (24,25). Recent experiments performed on rice cells in suspension culture seem to suggest that they may use carbon skeletons from humic molecules to synthesize proteins and DNA (26). 

Hemond C, Hofmann AW, Heusser G, Condomines M, Rhodes JM, Garcia MO (1994) U-Th-Ra systematics in Kilauea and Manna Loa basalts. Contrib Mineral Petrol 116 163-180 Hirose K (1997) Partial melt compositions of carbonated peridohte at 3 GPa and role of CO2 in alkali basalt magma generation. Geophys Res Lett 24 2837-2840... 

Carbonates, organic matter, Fe and Mn oxides, and clay minerals play important roles in controlling overall reactivity of trace elements in soils and sediments. This chapter addresses the interaction of trace elements with carbonates, organic matter, Fe and Mn oxides and clay minerals. Analytical techniques for trace element speciation in solid-phase and their distribution among various solid-phase components in arid and semi-arid soils are reviewed. Solubilities of trace elements in solid phases and their mineralogical characteristics in arid and semi-arid soils also are discussed. 

Walter and Morse (1984) were able to document the relative importance of microstructure for the dissolution of biogenic carbonates. Biogenic magnesian calcites are structurally disordered and chemically heterogeneous. Both these factors play a role in the reactivity of these minerals in natural systems. 

Liu Z, Dreybrodt W. Dissolution kinetics of calcium carbonate minerals in H20-C02 solutions in turbulent flow—the role of the diffusion boundary layer and the slow reaction H20 + CO2 <-> H+ + HC03. Geochim Cosmochim Acta 1997 61(14) 2879-2889. 

Environmental releases of PCBs often accompany releases of carriers from utility equipment. An example would be mineral oil released from oil filled transformers. When PCBs are present in a mineral oil-PCB mixture the aqueous solubility of the PCBs is reduced significantly. Two factors play a role in this reduction partitioning of the lipophilic (oil-loving) PCBs into the oil phase, and the reduced interaction of the PCBs with precipitation or groundwater caused by the hydrophobic nature of the oil matrix. Interpretation of aqueous PCB concentrations in the field must consider the presence of dissolved organic carbon (DOC) [382,386,397,403]. 

---