Water dissolved inorganic species

The 0.45 /am cutoff between dissolved and particulate fractions is arbitrary (Danielsson, 1982), and many researchers have commented on the inadequacy of this standard for removal of colloidal species. Sharp (1973) points out that colloids are of the approximate size range of 0.001-1.0 fim, and Kennedy et al. (1974) report that clay minerals of the types found in stream sediments can be much smaller than 0.45 jum. The concern of Kennedy et al. (1974) is that such material can pass the 0.45 /xm filter in sufficient quantities to seriously influence the analysis of dissolved inorganic species. These authors recommend a 0.1 xm filter pore size to remove clay colloids more effectively. The presence of these clay minerals is also of concern in the study of aquatiq humic substances however, decrease in pore size from 0.45 to 0.1 )um is accompanied by a decrease in flow rate through the filter, which is a major disadvantage when hundreds of liters of water are to be processed. Use of 0.45 /am filters represents a compromise between flow rate and rejection of clay minerals. 

We determined the shell C and O isotopic composition of the cultured foraminifera, and compared these isotopic values with the water chemistry of the culture chambers, and also with the shell chemistry of field specimens collected from sites on the North Carolina and South Carolina (USA) continental margin. The culmred foraminifera showed substantial offsets from the 8 C of system water dissolved inorganic carbon (—0.5 to —2.5%c, depending on species) and smaller offsets (0 to — 0.5%o) from the predicted 8 0 of calcite in equilibrium with the culture system water at the growth temperature. These offsets reflect at least three factors species-dependent vital effects ontogenetic variations in shell chemistry and the aqueous carbonate chemistry ([COJ] or pH) of the experimental system. 

Table 1. Dissolved inorganic species released from a sample of Monterey Shale (MR-216) into the surrounding water after heating for 72 h at 330 °C in 1-1 reactors with different surface compositions. Concentrations are given in mg/l and were determined by A A or ICP-AES... 

In aquatic systems dissolved aluminum species are toxic to fish. There exists a vast number of aluminum species, ranging from inorganic monomeric to complex colloidal. polymeric and organic complexes. A major problem, when studying aluminum species in water is that the species quickly convert one into the other (Fairman and Sanz-Medel 1995). 

Sunda and Hanson [247] have used ligand competition techniques for the analysis of free copper (II) in seawater. This work demonstrated that only 0.02 -2% of dissolved copper (II) is accounted for by inorganic species. (i.e., Cu2+, CuC03, Cu(OH)+, CuCl+, etc.) the remainder is associated with organic complexes. Clearly, the speciation of copper (II) in seawater is markedly different from that in fresh water. 

In natural waters, dissolved zinc speciates into the toxic aquo ion [Zn(H20)6]2+, other dissolved chemical species, and various inorganic and organic complexes zinc complexes are readily transported. Aquo ions and other toxic species are most harmful to aquatic life under conditions of low pH, low alkalinity, low dissolved oxygen, and elevated temperatures. Most of the zinc introduced into aquatic environments is eventually partitioned into the sediments. Zinc bioavailability from sediments is enhanced under conditions of high dissolved oxygen, low salinity, low pH, and high levels of inorganic oxides and humic substances. 

Furthermore, in aqueous solutions, the influence of dissolved organic and inorganic species (e.g., buffer solutions used in laboratory experiments, the major ions and dissolved organic matter present in natural waters, trace metals, mineral oxide surfaces) on transformation rates has to be evaluated in each case. As we will see in the following chapters, such species may act as reactants or catalysts, or they may influence the reaction rate indirectly. 

Concentration. This group consists of those processes in which water is removed and the dissolved substances are left behind. Examples are freeze concentration, lyophilization (freeze-drying), vacuum distillation, and membrane processes such as reverse osmosis and ultrafiltration. A common disadvantage of these methods is that inorganic species are concentrated along with the organic constituents. 

In other situations, such as at mines in Ron Phibun (Thailand) and Globe and Phoenix (Zimbabwe), arsenopyrite may not completely oxidize and water-soluble arsenic species may form instead of less soluble scorodite (Williams, 2001, 274). The Ron Phibun and Globe and Phoenix waters contain up to 5.114 and 7.400mgL-1 of arsenic, respectively (Williams, 2001, 270). About 40% of the total dissolved inorganic... 

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