Mark S. Shuman

Copper binding by dissolved organic matter: I. Suwannee River fulvic acid equilibria

Abstract A cupric ion-selective electrode measured free Cu in solutions of Suwannee River fulvic acid (FA) in a series of 30 titrations carried out both at variable and at constant (5.14, 7.00, 8.44) pH. Total Cu varied 0.1–100 μM, dissolved organic carbon (DOC) 1–10 mg C/l, Ca and Mg 0–10 mM, and ionic strength 0.005–0.1. Copper complexation by FA is first order in DOC for 1–10 mg C/liter, and variable-order in pH. Increasing Ca++ or Mg++ from 0 to 10 mM slightly increases Cu++ activity, while increasing ionic strength from 0.005 to 0.1 significantly increases Cu++ activity. An empirical N- site model was calibrated using a pooled set of six titrations with varying pH and DOC. Five binding components of varying proton dependence predict Cu binding by FA over a range of pH, DOC and total Cu in two verification tests of the model parameters. Parameters in this and other models tested are only empirical constructs.

Copper binding by dissolved organic matter: II. Variation in type and source of organic matter

Copper binding properties of several fulvic acid (FA) and whole water samples are compared by means of an empirical model that was calibrated using Suwannee River FA. Within the calibration limits of the model (pH 5.0–8.5, total Cu concentration 0.1–100 μM, ionic strength 0.1, and dissolved organic carbon, DOC, 1–10 mg C/1), ρCu in solutions of a variety of FA samples are predicted with < 0.2 ρCu units root mean square error (RMSE). Within the calibration limits, many whole water sample ρCus are predicted with <0.3 ρCu units RMSE if only one-half of the dissolved organic carbon is assumed to bind Cu. Agreement between prediction and experiment at lower ionic strength is not as good. Variations in Cu binding among different sources of dissolved organic matter appear to be much smaller than those due to chemical factors such as pH and ionic strength.

Copper dissociation from estuarine humic materials

Dissolved humic material from three locations on the Ogeechee River Estuary near Savannah, GA, was ultrafiltered into three size fractions and used for kinetic experiments with Cu(II). A Cu(II)-humic mixture was reacted with a colorimetric reagent for Cu(II) and absorbance observed from 50 msec to at least 1835 sec corresponding to rate constants from 0.001–40 sec−1. The apparent dissociation rate constants were distributed over a wide range, with most bound Cu(II) having k > 1 sec−1 (t12 < 0.7 sec). Nearly all the variation seen in the kinetic distribution was among size fractions; as size fraction decreased, the distribution of bound Cu(II) shifted to larger rate constants. Location of sampling stations on the estuary had little effect on results.

Liver cadmium levels in North Carolina residents who died of heart disease

SummaryUsing data from an autopsy series, we found a strong positive correlation between liver concentration of cadmium and death from heart disease. In view of recent experiments reported in the literature, the possibility that a low level of cadmium has a toxic effect on the cardiac conduction system is supported.

Contribution of cigarette smoking to cadmium accumulation in man.

SummaryA North Carolina autopsy population was examined for cadmium level in lung, liver and kidney. A questionnaire on the smoking habits and occupational exposure of each decedent was sent to the nearest relative. Analysis of these data indicates a positive association between cigarette smoking and body burden of cadmium as indexed by the organs, thus confirming the work by LEWIS and colleagues, who concluded that tobacco smoke constitutes a major source for cadmium accumulation in man.

Determination of Mercury in Surface Waters Using an Optimized Cold Vapor Spectrophotometric Technique

Abstract An analytical method to measure mercury in environmental samples was optimized based upon amalgamation of mercury on gold-coated sand and subsequent ultraviolet absorption measurement of the mercury vapor driven off the sand upon heating. Sample handling and storage methods were employed that were virtually free from mercury loss or contamination. Analytical procedures were tested on standard reference materials obtained from the USEPA and USGS and at concentration levels in the range anticipated for the environmental samples. Stream samples, collected over a seven-month period, were filtered (0.45 μm) in the field, and the mercury in dissolved and particulate fractions was determined. Dissolved mercury concentrations ranged from 24.1 ng/1 to 116.9ng/1 (N = 120) while particulate mercury concentrations ranged from 0.2 μg/g to 33.4 μg/g (N = 120). The method has been found useful for analyzing environmental samples and has been shown to be very sensitive and free of interferences.

Fractionation and trace metal content of a commercial humic acid

Abstract Aldrich humic acid was separated into humin, humic acid, and fulvic acid. These fractions and the unfractionated humic material were wet digested and analyzed for Cu, Cd, Cr, Fe, Mn, Ni, Pb and Zn by atomic absorption. Solid samples and digests were also analyzed for manganese by neutron activation.

Photo-oxidation of dissolved organic matter for trace metal analysis

AbstractPhoto-oxidation of dissolved organic matter in saline and non- saline samples is monitored by measurement of residual fluorescence intensity. For fulvic acids, the method has a detection limit of 0.005 mg C L−1, and maximum photo-oxidation is achieved with H2O2 oxidant and a low-intensity UV source.

Distribution and Transport of Mercury into Jordan Lake, North Carolina

ABSTRACT Jordan Lake, located in central North Carolina, is currently under consideration as a source of drinking water for communities in the surrounding area. A number of streams that discharge into the lake receive considerable industrial and municipal wastewater effluent, of which the toxic metal mercury is of particular concern. Stream samples, coinciding with low and high flow events, were collected and analyzed for dissolved and particulate total mercury. Mercury loading was estimated from flow-weighted mean concentrations and mean stream flow data. Results indicated that total dissolved mercury concentrations decreased with increasing flow, dilution effects, and that total particulate mercury concentrations decreased sharply with increasing suspended loads. This decrease was attributed to changes in particle size distribution. In addition, variability in particulate mercury concentration decreased dramatically with increased flow. Total mercury concentrations ranged from 54 ng/L to 195 ng/L (mean ...