Carl J. Miles

Oxygen consumption in humic-colored waters by a photochemical ferrous-ferric catalytic cycle.

A reaction cycle involving humic substances and iron as a catalyst acts as an oxygen sink in humic-colored waters. The cycle consists of photoreduction of Fe(II1) to Fe(I1) by humic matter and subsequent oxidation of Fe(I1) back to Fe(II1) by dissolved oxygen. Laboratory experiments to parameterize the reaction cycle indicate that rates of oxygen consumption are linear functions of iron and humic color concentration and a nonlinear function of light energy and pH. Esterification of carboxylic groups in dissolved humic material decreased oxygen consumption rates by 50%, suggesting that oxidation of humic matter results from a ligand-to-metal charge transfer through iron chelated by these functional groups. In situ consumption rates of 0.12 mg of 0 2 L-l h-l caused by this reaction sequence were measured in the surface water of Lake Mize, a highly colored lake in Florida. Such rates could account for the frequently observed low oxygen concentrations (ca. 3-4 mg L-I) in the surface waters of colored lakes.

A rapid gas chromatographie procedure for the analysis of oxalate ion in urine

A specific, precise, rapid and sensitive method for the analysis of oxalic acid in urine is described. This microanalytical procedure can detect concentrations of urinary oxalic acid as low as 4 mg/l with a relative standard deviation of replicates of less than 5% (24-h urine collections). 10% BCl3:2-chloroethanol is used to derivatize 0.1 ml of urine after evaporation to dryness or lyophilization. The bis-2-chloroethyl ester of oxalic acid formed is extracted into ethyl acetate/isopropyl ether (1:3, v/v) and is detected by electron capture gas chromatography at the 50 pg level. The total analysis time for 35 samples in 8 h per GC column. A series of determinations of urinary oxalic acid in 21 kidney stone-forming patients resulted in values ranging from 10.6 to 42.0 mg/24 h with a mean recovery of added oxalic acid of 98.2% (range 84.0-111.3%).

Efficiency of isolating humus from natural waters using DEAE cellulose

Humic material has a weak acidic character that enables the use of anion-exchange materials such as diethylaminoethyl (DEAE) cellulose to concentrate and isolate aquatic humus (Miles et al. , 1983: Sirotkina et al. , 1974). Ion-exchange celluloses are easy to pretreat and the hydrophilic support material (cellulose) does not irreversibly adsorb organics. This paper discusses the mechanism responsible for sorption of organics to DEAE cellulose, and describes how to maximize recovery of aquatic humus.