Copyright (c) 2009 All rights reserved. http://works.bepress.com/edward_burton Recent documents in Edward D Burton en-us Thu, 22 Oct 2009 15:33:49 PDT 3600 http://works.bepress.com/edward_burton/46 http://works.bepress.com/edward_burton/46 Sun, 12 Jul 2009 16:40:00 PDT Received for publication May 11, 2004. The geochemical partitioning of copper (Cu), lead (Pb), and zinc (Zn) was examined in benthic sediment profiles (0- to 20-cm depth interval) composed of relatively coarse (65-90% sand-sized particles), noncohesive, suboxic material (Eh +120 to +260 mV). Total Cu, Pb, and Zn concentrations ranged from 8.3 to 194, 16.3 to 74.8, and 30.1 to 220 mg/kg, respectively, and were related to vertical trends in sediment texture. The observed distribution coefficients describing solid-solution partitioning were in the range of 100 to 1000 L/kg. The geochemical partitioning of solid-phase Cu, Pb, and Zn between six operationally defined fractions was examined with a sequential extraction scheme. The association of Cu, Pb, and Zn with amorphous oxides, crystalline oxides, and organic matter was linearly dependent on the abundance of each respective phase. For retention by amorphous oxide minerals, the observed stoichiometry ranged from 5.2 to 23.7 mg/g for Cu, 12.8 to 21.5 mg/g for Pb, and 23.1 to 85.7 mg/g for Zn. Corresponding values for association with crystalline oxides were an order of magnitude less than those for amorphous oxides, indicating a lesser affinity of trace metals for crystalline oxides. The stoichiometric relationships describing association with organic matter ranged from 17.6 to 54.0 mg/g for Cu, 6.1 to 9.6 mg/g for Pb, and 6.4 to 16.4 mg/g for Zn. The results from this study provide an insight into processes controlling trace metal partitioning in coarse-textured, suboxic, estuarine sediments. Edward D. Burton http://works.bepress.com/edward_burton/45 http://works.bepress.com/edward_burton/45 Sun, 12 Jul 2009 16:39:59 PDT This paper reports the abundance of elemental S in drain sediments associated with acid sulfate soils. The sediments exhibited near-neutral pH (5.97-7.27), high concentrations of pore-water Fe2+ (1.37-15.9 mM) and abundant oxalate-extractable Fe (up to 4300 μmol g−1). Maximum acid-volatile sulfide (AVS) concentrations in each sediment profile were high (118-1019 μmol g−1), with AVS often exceeding pyrite-S. Elemental S occurred at concentrations of 13-396 μmol g−1, with the higher concentrations exceeding previous concentrations reported for other sedimentary systems. Up to 62% of reduced inorganic S near the sediment/water interface was present as elemental S, due to reaction between AVS and oxidants such as O2 and Fe(III). Significant correlation (r = 0.74; P < 0.05) between elemental S and oxalate-extractable Fe(III) is indicative of elemental S formation by in situ oxidation of AVS. The results indicate that AVS oxidation in near-surface sediments is dynamic in acidified coastal floodplain drains, causing elemental S to be a quantitatively important intermediate S fraction. Transformations of elemental S may therefore strongly influence water quality in ASS landscapes. Edward D. Burton http://works.bepress.com/edward_burton/44 http://works.bepress.com/edward_burton/44 Sun, 12 Jul 2009 16:39:58 PDT Edward D. Burton http://works.bepress.com/edward_burton/43 http://works.bepress.com/edward_burton/43 Sun, 12 Jul 2009 16:39:56 PDT We examined processes regulating reduced inorganic sulfur (RIS) speciation in drain sediments from coastal acid sulfate soil (ASS) landscapes. Pore water sulfide was undetectable or present at low levels (0.6-18.8 M), consistent with FeS(s) precipitation in the presence of high concentra tions of Fe2+ (generally >2 mM). Acid-volatile sulfide (AVS), with concentrations up to 1019 mol g-1, comprised a major proportion of RIS. The AVS to pyrite-S ratios were up to 2.6 in sediment profiles containing abundant reactive Fe (up to ~4000 mol g-1). Such high AVS:pyrite-S ratios are indicative of inefficient conversion of FeS(s) to pyrite. This may be due to low pore water sulfide levels causing slow rates of pyrite formation via the polysulfide and H2S oxidation pathways. Overall, RIS speciation in ASS-associated drain sediments is unique and is largely regulated by abundant reactive Fe. Edward D. Burton http://works.bepress.com/edward_burton/42 http://works.bepress.com/edward_burton/42 Sun, 12 Jul 2009 16:39:55 PDT A sequential extraction scheme was combined with sorption isotherm analysis in order to investigate sorption of sewage sludge-derived Cu and Zn to the A-horizon of a humic-gley soil as a whole, and to the operationally defined exchangeable (1 M MgCl2), carbonate (1 M NaOAc), Fe/Mn oxide (0.04 M NH2OH.HCl), and organic (0.02 M HNO3+30% H2O2) soil fractions. Sorption parameters were compared for a sample of sludge leachate (with 97.4% of Cu and 63.2% of Zn present as dissolved metal-organic matter complexes, as calculated by geochemical modelling involving MINTEQA2 and verified using an ion exchange resin method) with that of a reference solution exhibiting the same chemical characteristics as the leachate, except for the presence of dissolved organic material. Dissolved metal-organic matter complexes were found to significantly (P<0.05) depress sorption to the bulk soil and each fraction. The greatest depression of Cu and Zn sorption was observed for the exchangeable, carbonate, and Fe/Mn oxide fractions, while the organic fraction of the soil was the least affected. This reflects a greater affinity for the exchangeable, carbonate, and Fe/Mn oxide fractions by the free divalent metal (Cu2+, Zn2+), with sorption by these fractions attributed to cation exchange, chemisorption, and co-precipitation processes. The sorption characteristics of the organic fraction indicated that Cu and Zn sorption by soil organic matter mostly involved dissolved metal-organic matter complexes. This may be attributed to hydrophobic interactions between nonpolar regions of the dissolved metal-organic matter complexes and solid-phase soil organic matter. Edward D. Burton http://works.bepress.com/edward_burton/41 http://works.bepress.com/edward_burton/41 Sun, 12 Jul 2009 16:39:54 PDT Edward D. Burton http://works.bepress.com/edward_burton/40 http://works.bepress.com/edward_burton/40 Sun, 12 Jul 2009 16:39:53 PDT The geochemical partitioning of trace metals in sediments is of great importance in risk assessment and remedial investigation. Selected factors that may control the partitioning behavior of Cu, Pb and Zn in non-sulfidic, estuarine sediments were examined with the use of combined sorption curve--sequential extraction analysis. This approach, which has not been previously used to examine estuarine sediments, allowed determination of sorption parameters for Cu, Pb and Zn partitioning to individual geochemical fractions. Partitioning behavior in sulfidic sediments was also determined by sequentially extracting Cu, Pb, and Zn from synthetic sulfide minerals and from natural sediment and pure quartz sand after spiking with acid-volatile sulfide (AVS). Trace metal sorption to the "carbonate" fraction (pH 5, NaOAc extraction) increased with metal loading due to saturation of sorption sites associated with the "Fe-oxide" (NH2OH·HCl extraction) and "organic" (H2O2 extraction) fractions in non-sulfidic sediments. Freundlich parameters describing sorption to the "Fe-oxide" and "organic" fractions were controlled by the sediment Fe-oxide and organic carbon content, respectively. Sequential extraction of Cu from pure CuS, AVS-spiked sediment and AVS-spiked quartz sand showed that AVS-bound Cu was quantitatively recovered in association with the "organic" fraction. However, some AVS-bound Pb and Zn were recovered by the NH2OH·HCl step (which has been previously interpreted as "Fe-oxide" bound metals) in the sequential extraction procedure used in this study. This indicates that the sequential extraction of Pb and Zn in sulfidic sediments may lead to AVS-bound metals being mistaken as Fe-oxide bound species. Caution should therefore be exercised when interpreting sequential extraction results for Pb and Zn in anoxic sediments. Edward D. Burton http://works.bepress.com/edward_burton/39 http://works.bepress.com/edward_burton/39 Sun, 12 Jul 2009 16:39:52 PDT Tributyltin (TBT) sorption to four natural sediment samples in artificial seawater was examined under a range of modified pH and salinity conditions. Three of the sediment samples were relatively pristine with regard to TBT contamination, but the fourth was a TBT-contaminated sediment from a commercial marina. Sorption of TBT was described well by linear sorption isotherms, with distribution coefficients ranging from 6.1 to 5210 L/kg depending on the pH and salinity. The sediment organic C content and particle size distribution were important determinants of sorption behavior. The presence of resident TBT in the contaminated marina sediment caused a substantial reduction in further TBT sorption. Desorption of TBT from the marina sediment was described by relatively large observed distribution coefficients ranging from 5100 to 9400 L/kg, suggesting that aging effects may reduce sorption reversibility. Increased artificial seawater salinity generally reduced TBT sorption at pH 4 and 6, but enhanced TBT sorption at pH 8. Regardless of salinity, maximum sorption of TBT was observed at pH 6, which is attributed to an optimal balance between the abundance of cationic TBT+ species and deprotonated surface ligands. Consideration of aqueous TBT speciation along with octanol-water partitioning behavior suggests that hydrophobic partitioning of TBTCl0 to nonpolar organic matter was important for pH < 6, while partitioning of TBTOH0 was important at higher pH. Edward D. Burton http://works.bepress.com/edward_burton/38 http://works.bepress.com/edward_burton/38 Sun, 12 Jul 2009 16:39:51 PDT The effect of aging on the solid/pore-water partitioning and desorption behaviour of tributyltin (TBT) in sediments was examined. Three sediment samples with contrasting physical and chemical properties were spiked with 10 mg/kg TBT and aged under sterile conditions for periods of time ranging from 1 to 84 days. Aging had a negligible effect on partitioning and desorption behaviour in a sandy sample with very low organic carbon content (0.2% w/w). In contrast, for samples with larger amounts of organic carbon (2.6% and 4.8% w/w), aging caused substantial increases in TBT sorption. For these samples, apparent distribution coefficients (KD,app) obtained from sequential 2 h desorption experiments also exhibited a twofold increase between spiked sediments subjected to aging for 1 day and 84 days. This study demonstrates that aging effects may be an important aspect of TBT fate in contaminated sediments. Edward D. Burton http://works.bepress.com/edward_burton/37 http://works.bepress.com/edward_burton/37 Sun, 12 Jul 2009 16:39:50 PDT This study describes iron and sulfur fractionation, and the related extractability of selected trace elements (As, Cd, Cr, Cu, Ni, Pb and Zn) in estuarine sediments. The sediments were sulfidic, with moderately high concentrations of pore-water sulfide (200-600 μmol l−1) and acid-volatile sulfide (AVS; 9.9-129 μmol g−1). Pyrite-S concentrations increased with depth, with 63-251 μmol g−1 at site W1 and 312-669 μmol g−1 at site W2. The degree of sulfidisation was generally high (>80%), indicating that Fe may be limiting pyrite accumulation. The ratios of AVS to pyrite-S increased with sediment depth, as expected for the pyritisation of solid-phase AVS. Cadmium, Pb and Zn extractability in 1 M HCl indicated that these elements are not significantly sequestered during pyritisation, whereas sequestration may be important for As, Cu and possibly Ni. Extractability trends for Cr suggest that diagenesis in sulfidic sediments may enhance Cr reactivity. Overall, replacement of AVS by pyrite during diagenesis may enhance the reactivity of Cd, Cr, Pb and Zn, whereas As, Cu and possibly Ni may be rendered less reactive. Edward D. Burton