Mark B. David

Analysis of organic and inorganic sulfur constituents in sediments, soils and water

Abstract A suite of analytical methods for determining the amount of organic sulfur (carbon-bonded sulfur and ester sulfate) and inorganic sulfur (sulfate and sulfide) is described. Organic sulfur fractions, which have often been ignored, are major constituents of oxic substrates and have a major role in sulfur dynamics. Methods of sample preparation and a modification of the Johnson-Nishita digestion-distillation apparatus are given. HCl digestion, Zn-HCl reduction, hydriodic acid reduction, sulfate extraction, wet oxidation and dry oxidation are utilized for determining sulfur constituents. With only minor modifications these analyses were adapted for examining 35S transformation rates. Results from these analyses on sewage sludge, lake sediment, soil, and water demonstrate the usefulness of these methods.

Characterization of solid and dissolved carbon in a spruce-fir Spodosol

Organic substances are an integral part of the biogeochemistry of many elements in forest ecosystems. However, our understanding of the composition, chemistry, and reactions of these materials are incomplete and sometimes inconsistent. Therefore, we examined in detail dissolved organic carbon (DOC) in forest floor leachates over a two-year period (1992–1993), soil C, and DOC adsorption by a mineral soil to determine the relationship between soil solid and solution C characteristics in a spruce-fir ecosystem. The structural composition of DOC, DOC fractions (hydrophobic and hydrophilic acids, hydrophilic neutrals), and soil samples from the organic and mineral horizons were also analyzed using13C nuclear magnetic resonance (NMR) spectroscopy.Total DOC in forest floor leachates ranged from 7.8 to 13.8 mmol L−1 with an average of 8.6 mmol L−1. Concentrations were highest in September of both 1992 and 1993. Fractionation of the forest floor DOC indicated these solutions contained high organic acid contents that averaged 92% of the total DOC. Hydrophobic acids were also preferentially adsorbed by the B horizon. The13C NMR data suggested alkyl, carbohydrate, aromatic, and carboxylic C were the primary constituents for organic and mineral soils, DOC, and DOC fractions. Compositional changes of C were observed as aromatic and carbohydrate decreased, whereas alkyl, methoxy, and carbonyl moieties increased with depth. However, C composition changed little among the three organic layers based on the similarity of alkyl/carbohydrates ratios as determined from NMR area integration, suggesting that in this acid soil, decomposition proceeds rather slowly. Hydrophobic acids contained high contents of aromatic C, whereas hydrophilic acids were comprised primarily of carboxylic C. Hydrophilic neutrals were rich in carbohydrate C. Results indicated that these DOC fractions were unaltered during the isolation process. Carboxylic C groups appeared to dissolve easily and were probably the primary contributor to organic acidity in our organic dominate leachates. Results also suggested that DOC materials adsorbed on the B horizon underwent further biodegradation. Several seasonal patterns of C composition were observed in the forest floor leachates and DOC fractions collected between 1992 and 1993.Overall, the evidence from this study suggested that (i) DOC levels were mainly controlled by biological activity, (ii) forest floor DOC was comprised primarily of organic acids, (iii) contact of soil leachates with B horizon material affected DOC quantitatively and qualitatively, (iv) phenolic, carboxylic, and carbonyl C appeared to dissolve readily in the forest Oa horizon, (v) DOC materials adsorbed on the B horizon selectively underwent further decomposition, and (vi) C composition is a function of the extent of decomposition and DOC fractions.

Importance of biological processes in the sulfur budget of a northern hardwood ecosystem

SummaryTotal S, organic S and sulfate were measured in foliage, litter, roots, soil and solutions at a hardwood site within the Adirondack Mountains of New York. Sulfate as a percentage of total S was similar in foliage and litter (10%), but was greater in roots (30%). Sulfur constituents in the hardwood forest ecosystem were dominated by C-bonded S (60 g m−2) and ester sulfate (16 g m−2) which are formed by biological processes. Because sulfur mineralization (1.42 g m−2 yr−1) was greater than wet precipitation inputs (0.82 g m−2 yr−1), those factors that influence mineralization-immobilization processes are important in evaluating S cycling and sulfate fluxes in this ecosystem. Ester sulfate was formed within the forest floor by the soil biota and was leached to mineral horizons. Annual turnover of this pool was high (25%) within the mineral forest floor. Forest-floor C-bonded S was derived from root and above-ground litter, and substantial amounts were leached to mineral horizons. Calculated storage + outputs (1.64 g m−2 yr−1) was much greater than wet inputs (0.82 g m−2 yr−1).

Importance of organic and inorganic sulfur to mineralization processes in a forest soil

Abstract Sulfur mineralization rates, changes in organic and inorganic S constituents and arylsulfatase activity were determined in four soil horizons (O2, B21h, B22hir and B23) which represent the major portion of a forest Spodosol (Becket). Biweekly, for 20 weeks, soil subsamples were leached with deionized water and analyzed for S constituents. Rates of water-soluble sulfate release were 123, 39, 34 and 18 nmol S g−1 dry mass week−1 for O2, B22hir, B23 and B21h horizons, respectively. Only in the organic O2 horizon did non-sulfate inorganic S (Zn-HCl-S) increase (15 nmol S g−1) while phosphate extractable S decreased in all the mineral horizons (13, 19 and 28 nmol S g−1 week−1, B21h, B22hir and B23, respectively) due to desorption. Ester sulfate was mineralized in the B22hir and B23 horizons (−66 and −22 nmol S g−1 week−1) and increased in the O2 (174 nmol S g−1 week−1). Arylsulfatase activity varied among horizons and decreased with time. Carbon-bonded S decreased in all horizons, especially those with high respiration rates (i.e. O2 and B21h), but changes were not significant. Only the B22hir horizon exhibited a significant loss of total S (128 nmol S g−1 week−1). The interrelationships among inorganic and organic S dynamics were outlined.

Analysis of sulfur in soil, plant and sediment materials: Sample handling and use of an automated analyzer

Abstract Methods for analyzing soil, vegetation and sediment samples for total S and handling soil samples for analysis of S constituents were examined. A LECO automated total S analyzer (SC-132) was used for the analysis of vegetation, sediments and soil samples. Results from the LECO analyzer compared favorably with other currently used total S techniques such as alkaline oxidation. Calibrating the instrument on soil or vegetation standards using two combusion accelerators improved accuracy and recovery. The upper 99% confidence interval RSD values for duplicate samples using the LECO analyzer were

Organic and inorganic sulfur constituents of the Sediments in three New York lakes: Effect of site, sediment depth and season

Water and sediment parameters, with emphasis on S constituents, were compared among lakes (Oneida, South, Deer), seasons, sites and sediment depths. The three lakes differed in size, morphometry, productivity and acid neutralizing capacity and none of the lakes had anoxia in the water column. Redox potentials (Eh) were higher for oligotrophic South and mesotrophic Deer than cutrophic Oneida within the sediment. In the water column, the only S constituent measured was sulfate which was higher in nutrient rich Onieda (110 to 490 μmol I−1) than South (30 to 70 μmol I−1) or Deer (10 to 60 μmol −1)Total S in sediment was higher for South than for either Deer or Oneida. For Deer and South sediment, total S was greatest in the 5 to 15 cm layer, and this was likely due to historical changes in anthropogenic inputs through atmospheric deposition. The high S concentration in South sediment can be accounted for by particulate deposition of S through the water column. Organic S constituents constituted major forms of S in the sediments of the three lakes. Non-HI reducible S, of which carbon-bonded S was a dominant constituent, comprised a major portion of total S in Oneida, South and Deer. Ester sulfate was the next largest S constituent in South and Deer. As a percent of total S, sulfide (HCL digestion) and sulfate was higher in Oneida than South or Deer. There was an inverse relationship between sediment Eh and sulfide. Pyritic S was measured on bulk samples and constituted 37, 12, and 6% of total S in Oneida, South and Deer. Both inorganic and organic S forms showed seasonal variation and the transformation and translocation of these forms play an important role in the S dynamics of lakes.

Transformations of Organic and Inorganic Sulfur: Importance to Sulfate Flux in an Adirondack Forest Soil

Sulfate flux from forest soils as a result of inputs from acidic deposition is thought to be a critical process in regulating acidification of surface waters. The purpose of this study was to evaluate biotic transformations of sulfur in an Adirondack Mountain forest soil by adding 35S-sulfate to the forest floor. In September 1983 to each of two 0.5 m2 plots, 2.22 × 1010 dpm of 35S-sulfate was added in 4 liters of solution. Analysis of soil horizons from the plot at the end of the six week incubation indicated that 70 and 99 percent of the added 35S was retained in the soil at plots 1 and 2, respectively. More than 70 percent of the 35S was found in Oa, Bh, and Bs1 horizons. In O horizons greater than 80 percent of the 3sS was found as organic sulfur, whereas in mineral horizons most was found as adsorbed sulfate. These findings indicated that a portion of the sulfate moving through the soil is both rapidly immobilized in the forest floor and adsorbed in the mineral horizons. On a net basis, however, the ...