Progress 10/01/98 to 09/30/04
Outputs
This research aimed to characterize how contaminants bind in soils and related systems; and to utilize this knowledge toward mitigating impacts of a variety of environmental contaminants. Major accomplishments: 1. We determined quantities and forms of trace elements (Cu, Zn, As, Cr, Pb etc.) in soils from two military sites in the NC Coastal Plain. Our research showed that movement of the modest quantities of heavy metals at these sites can be minimized by maintaining soil pH > 5. 2. We published the first use of XANES (x-ray absorption near edge structure) spectroscopy for quantitative analysis of different forms of phosphorus in soils. In sets of soils that contained the same quantities of total P, but varied in pH, specific P forms associated with Fe- and Al-oxide minerals were identified in addition to various Ca-phosphate minerals. No Fe- or Al-phosphate minerals were identified, as hypothesized in soil chemistry textbooks. Other studies on phosphate binding
evaluated the effectiveness of various minerals for preventing P discharge from horticultural systems (greenhouses) into the environment, and we collaborated on research on inducing struvite formation in swine waste to remove phosphorus and nitrogen. 3. The important role of organic and inorganic sulfides on metal binding in the environment was evaluated. Organic sulfides in soil organic matter have a very high affinity for ionic mercury [Hg(II)]. Direct (spectroscopic) analyses showed that as mercuric ions are added to purified organic matter, they first bind to the reduced organic sulfur. To translate these results to unaltered soil organic matter, we found that sulfur oxidation states do not change during purification of organic matter if pH < 12.5 is maintained. In wetland soils at a lead-contaminated in Idaho, a significant fraction of the lead was identified as Pb-sulfide using EXAFS (extended x-ray absorption fine structure) spectroscopy. Sulfide minerals tend to render certain
heavy metals less soluble and less bioavailable in the environment. We also found a prevalence of cupric sulfide in contaminated soils at a military base in eastern NC. Furthermore, these techniques showed that zinc taken up by trout from metal-contaminated waters is detoxified in the fish liver by binding to sulfur in metallothionein proteins. 4. In other studies, we provided spectroscopic and chemical insights on immobilizing soil contaminants by chemical fixation. These approaches included lead immobilization by phosphates, and radioactive waste scavenging (at high level waste repositories) by various minerals. 5. Fundamental surface chemistry research showed that when divalent copper ions react with an Fe-oxide mineral (goethite) surface containing bound soil organic matter, the Cu(II) serves as a mineral-organic bridge at low levels of adsorbed organic matter (Type A ternary complex). At near-maximum levels of organic matter, the Cu(II) is bound to the organic matter, which
itself is bound to the Fe-oxide mineral (Type B ternary complex).
Impacts
Soil contaminants accumulated during decades or even centuries of industrial development worldwide are now a focus of costly cleanup efforts to protect the health of humans and natural ecosystems. It is recognized that solving this immense cleanup problem with cost-effective technologies will require a very precise understanding of contaminant binding in soils. In fact, the most cost-effective way to decrease impacts of environmental contaminants is alter native soils properties or apply harmless chemicals to fix (immobilize) the contaminants in place at their source. However, a very thorough understanding of the mechanism of fixation is essential for relying on such technologies into the indefinite future. If we do not understand these mechanisms, changes in soils that induce mobilization of contaminants can have catastrophic effects. The alternative is to dig up contaminated soils (at a very high cost) and dispose of the contaminated material in regulated landfills.
Our research demonstrated in a variety of contaminated soils that chemical fixation to diminish the hazards of potential pollutants is a viable option. Furthermore, ongoing research on specific interactions between contaminants and soil particles provides the basis for developing novel approaches to contaminant fixation in soils.
Publications
- Bang, J. and Hesterberg, D. 2004. Dissolution of trace element contaminants from two Coastal Plain soils as affected by pH. Journal of Environmental Quality 33:891-901.
- Beauchemin, S., Hesterberg, D., Nadeau, J., and McGeer, J. C. 2004. Speciation of hepatic Zn in trout exposed to elevated waterborne Zn using X-ray absorption spectroscopy. Environmental Science and Technology 38:1288-1295.
- McKinney, D. S., Yim, M.S., and Hesterberg, D. 2004. Examination of Backfill Materials for High-Level Waste Repository. Technology 9:187-194.
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Progress 10/01/02 to 09/30/03
Outputs
Research under this project was focused mainly on heavy metal (zinc, copper, and lead) binding in different environmental systems. Research on modestly contaminated soil from around abandoned incinerator sites associated with the Marine Corps Air Station at Cherry Point, NC addressed dissolution of heavy metals during long-term acidification of soils. Acidifying samples in laboratory soil column studies showed that dissolved Cu and Zn concentrations increased with decreasing pH below a threshold of pH 4.2 for Cu and pH 5 for Zn. Copper concentrations at pH 4 increased linearly with increasing soil Cu concentrations, but no relationship was found between soil Zn and dissolved Zn concentrations. Synchrotron x-ray absorption near-edge structure (XANES) spectroscopy analysis of Cu and Zn in selected samples indicated an association of Cu(II) with soil organic matter and Zn(II) with Al- and Fe-oxides or franklinite (an Fe-Zn-oxide). Because of the limited data, we could
not make a direct link between the XANES speciation data and the non-linear trends in Zn dissolution. As part of our aim to link molecular-scale chemical speciation of metals to environmental impacts, we completed synchrotron extended x-ray absorption fine structure (EXAFS) spectroscopy analysis of solid-phase Pb species in wetland mine tailings from a site in Idaho. To develop a treatment to restore the tailings area to a functioning wetland, the tailings were treated with various amendments in the greenhouse. Results showed that the original tailings contained a proportion of Pb as lead sulfide, possibly residual mineral that was originally present. Lead sulfide tends to be insoluble under reducing conditions. After incubating tailings for 99 d in the greenhouse under wet conditions with amendments containing sulfate, the proportion of Pb as Pb-sulfide increased. Sulfate reduction to sulfide apparently enhanced Pb-sulfide formation, and in some cases also decreased Pb
bioavailability according to chemical indicators. Addressing environmental impacts of zinc from a more holistic standpoint, EXAFS spectroscopy was used to determine directly the molecular nature of Zn binding in the liver of trout exposed to Zn-enriched waters. This research was done in collaboration with environmental scientists and biologists from Natural Resources Canada (CANMET). Results showed that hepatic Zn was mainly coordinated with sulfur atoms, indicating Zn binding by metallothionein proteins in the liver. This mechanism is consistent with data from indirect experiments published in the literature. Our results also suggested that the mechanisms of these fish dealing with an extra load of bioaccumulated Zn in high exposure conditions were the same as in the control group exposed to water containing greater than 20-fold lower Zn concentrations.
Impacts
This research aims to improve our ability to predict negative environmental impacts of toxic heavy metals in soils and waste materials. Highly specialized methods for analyzing how heavy metals are bound in various soils and wastes allowed us to understand qualitatively why these metals become more mobile as soil conditions change. Research also provided a better understanding of how fish can improve their survival by detoxifying heavy metals that are taken up from contaminated water.
Publications
- Beauchemin, S., D. Hesterberg, J. Chou, M. Beauchemin, R. R. Simard, and D. E. Sayers. 2003. Speciation of phosphorus in P-enriched agricultural soils using XANES spectroscopy and chemical fractionation. Journal of Environmental Quality 32:1809-1819.
- DeVolder, P. S., S. L. Brown, D. Hesterberg, and K. Pandya. 2003. Metal bioavailability in tailings-contaminated sediment amended with biosolids compost, ash, and sulfate. Journal of Environmental Quality 32: 851-864.
- Nelson, N.O., R.L. Mikkelsen, and D.L. Hesterberg. 2003. Struvite precipitation in anaerobic swine lagoon liquid: Effect of pH, Mg:P ratio, and determination of rate constant. Bioresource Technology 89:229-236.
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Progress 10/01/01 to 09/30/02
Outputs
The objective of our studies on phosphorus was to determine how microbial reduction affected phosphorus dissolution in a P-enriched Ultisol soil from the Coastal Plain of North Carolina, and to understand mechanisms of P release in reduced soils. Silt + clay fractions of a Cape Fear soil sample (clayey, mixed, thermic Typic Umbraquult) were exposed to anoxic conditions in a continuously-stirred reactor for 40 days. Duplicate reactor suspensions were amended with a single addition of 0.2% dextrose (on a dry weight basis of silt+clay) at time 0 day, or with spiked additions of 0.067% dextrose at 0, 13 and 26 days, or no dextrose addition (control). Regardless of the dextrose treatment, redox potential (Eh) decreased over time due to microbial activity, although the rate Eh decline was initially most rapid in the reactors receiving a single addition of dextrose as a microbial carbon source. pH increased to near neutrality as expected for reduced soil. Dissolved reactive
phosphorus (phosphate) increased nearly 7-fold (from an average of 1.5 to 10 mg P/L for all reactors) as Eh decreased during the 40-day incubations. Similarly, dissolved organic carbon (DOC) increased 5-fold with decreasing Eh for all treatments, and we found a significant linear relationship between dissolved phosphate and DOC (coefficient of determination = 0.91). Dissolved aluminum (and ferrous and ferric Fe) also increased during reduction to concentrations that were greater than would be predicted by thermodynamics. Contrary to the conventional notion that reductive dissolution of Fe(III)-oxides and Fe(III)-phosphate minerals caused dissolution of phosphate in reduced soils, our results suggested that aqueous complexation of phosphate complexes with dissolved Fe/Al-DOC associations may be an important mechanism for increasing dissolved P during reduction. In research on heavy metals in soils, we applied synchrotron EXAFS and XANES spectroscopies to more accurately quantify the
proportion of nickel occuring as the potential carcinogen nickel oxide in samples of contaminated soils from Ontario, Canada. Using least-squares, linear combination fitting of soil XANES and EXAFS (chi) data, and with various mineral and adsorbed or co-precipitated Ni standards, we found within 5% that 80% of Ni in a sample containing 5540 mg Ni/kg occurred as NiO. The proportion of total Ni occurring as NiO in a sample containing 1630 mg Ni/kg was 68%. EXAFS spectral features indicated that NiO in the soil samples was crystallographically pure, but of smaller particle size than that of the NiO standard used. In other research, synchrotron XANES analysis of modestly contaminated soil samples from a US Marine Corps base on the Coastal Plain of North Carolina showed that arsenic occurred in the less-mobile As(V) oxidation state, consistent with column flow experiments showing no detectable aresenic dissolution during acidification of soil samples over 10 days.
Impacts
Dissolved phosphate often increases as soils undergo reduction under wet conditions, or perhaps during application of easily metabolized organic compounds as are found in animal waste. Our research on the fundamental mechanisms of phosphate release from reduced soils will assist in developing more quantitative models of predicting P discharge from agricultural fields to surface or ground waters. Our results for an Ultisol from the NC Coastal Plain suggest that the mechanisms of P release (and potential mobilization) in reduced soils is more complicated than a simultaneous dissolution of ferric iron and associated phosphate. Research on heavy metal contaminants in soils showed that spectroscopic analyses can be refined to the point where some chemical species of metals, nickel oxide in this case, could be accurately quantified. Such results could not be achieved with more conventional analytical methods, particularly x-ray diffraction analysis, because of the low soil
concentrations of metals. Quantification of soil nickel oxide as a potential carcinogen is important to determine the possible adverse health effects of airborne soil particles containing nickel. Results of chemical speciation of arsenic helped explain the low mobility of this potentially toxic contaminant in samples of a Coastal Plain soil.
Publications
- Appelboom, T. W., G. M. Chescheir, R. W. Skaggs. and D. L. Hesterberg. 2002. Management practices for sediment reduction from forest roads in the coastal plains. Transactions of the ASAE. 45:337-344.
- Beauchemin, S., D. Hesterberg, and M. Beauchemin. 2002. Principal component analysis approach for the modeling of sulfur K-XANES spectra of humic acid. Soil Science Society of America Journal 66:83-91.
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Progress 10/01/00 to 09/30/01
Outputs
We determined mobilities of various EPA priority contaminants (chromium, arsenic, lead, copper, zinc, cadmium, and selenium) occurring at concentrations typically < 50 mg/kg soil as affected by pH in contaminated soils associated with a military base. The mobility of some metal cations (Pb, Zn, and Cu) increased substantially at pH < 4, but maximum dissolved concentrations of most metals usually did not exceed groundwater standards. XANES (x-ray absorption near edge structure) spectroscopy showed no evidence for chromium oxidation during acidification, so the less hazardous, less mobile trivalent chromium [Cr(III)] persisted. Synchrotron XANES and EXAFS (extended x-ray absorption fine structure) analyses were used to quantify nickel oxide (an inhalation carcinogen) at >90% of total nickel in a smelter-impacted soil. We also designed samples to obtain Ni(II) associated with ferrihydrite (poorly-crystalline iron oxide). In collaborative studies related to the mobility
of metals in neutralization (limed) sludges from mine wastes, our XANES and EXAFS results indicated that zinc(II) present during precipitation of ferrihydrite became incorporated into the Fe-oxide structure at levels <9% of total Fe in the mineral.
Impacts
The results from metal mobility studies at the military base suggested that the heavy metal contaminants could be managed in place at these sites by maintaining circumneutral pH through periodic liming. In the Zn ferrihydrite studies, the mobility of Zn and other heavy metals in neutralized mine sludges disposed on land should be related to the chemical species of the metals. Determinations of the maximum amount of Zn(II) that is co-precipitated with poorly crystalline Fe-oxide during neutralization of a Fe/Zn solution in a pure system should represent the maximum amount of Zn(II) that can be incorporated into freshly precipitated Fe-oxides in a mine waste sludge. We can hypothesize that Zn(II) co-precipitated with Fe-oxide would be immobile under conditions where the Fe-oxide is stable (e.g., oxidizing conditions).
Publications
- Hesterberg, D., Chou, J.W., Hutchison, K. J., and Sayers, D. E.. 2001. Bonding of Hg(II) to reduced organic sulfur in humic acid as affected by S/Hg ratio. Environ. Sci. Technol. 35:2741-2745.
- Alcacio, T. E., Hesterberg, D., Chou, J., Martin, J. D., Beauchemin, S. and Sayers, D. E.. 2001. Molecular scale characteristics of Cu(II) bonding in goethite-humate complexes. Geochim. Cosmochim. Acta 65:1355-1366.
- Hutchison, K. J., Hesterberg, D. and Chou, J. W.. 2001. Stability of reduced organic sulfur in humic acid as affected by aeration and pH. Soil Sci. Soc. Am. J. 65:704-709. Zhang, P., Brady, P. V., Arthur, S. E., Zhou, W., Sayers, D. E., and Hesterberg, D.. 2001. Adsorption of barium(II) on montmorillonite surfaces. Colloids Surf.: A. Physicochem. Engin. Aspects 190:239-249.
- Ryan J. A., Zhang, P.C., Hesterberg, D., Chou, J. and Sayers, D. E.. 2001. Formation of chloropyro-morphite in a lead-contaminated soil amended with hydroxyapatite Environ. Sci. and Techn. 35: 3798-3803.
- Fichtner, E. J., Hesterberg, D., and Shew, H. D.. 2001. Nonphytotoxic aluminum-peat complexes suppress Phytophthora parasitica. Phytopathology. 91:1092-1097.
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Progress 10/01/99 to 09/30/00
Outputs
Research addressed the environmental chemistry of heavy metals and phosphorus in soils and in minerals of importance in soils. Measurements on soil samples collected around two abandoned incinerator sites at outlying airfields associated with the Marine Corps Air Station in Cherry Point, NC showed modestly elevated levels of various priority heavy metal contaminants (chromium, arsenic, lead, copper, and zinc). Total concentrations were typically less than 50 mg/kg. Using an advanced analytical technique, synchrotron X-ray absorption near edge structure (XANES) spectroscopy, we determined that chromium in soil samples analyzed was mainly trivalent chromium, and arsenic was primarily in oxidation state +5. These are the less mobile oxidation states of these metals, and trivalent chromium is less hazardous than hexavalent chromium. In research on phosphorous, we completed XANES studies to determine the molecular-scale nature of phosphate bound to iron and aluminum oxide
minerals. These are considered the most important minerals affecting the phosphate binding capacity of soils. The molecular configuration of phosphate on the mineral surfaces would affect both the capacity and strength of phosphate binding. For phosphate adsorbed on goethite (iron oxide), changes in features of the XANES spectra indicated that the surface bound phosphate species changed with level of adsorbed phosphate at pH 6. A wider range of adsorbed phosphate concentrations (10 to 480 mmol/kg) were used in our studies compared with ranges used in previous infrared spectroscopic studies of adsorbed phosphate species. Furthermore, XANES results on aqueous samples containing a mixture of iron- and aluminum oxide minerals indicated that the level of adsorbed phosphate on each mineral was proportional to the surface area of the mineral in the suspension. These measurements were conducted at concentrations of phosphate that were so low that no dissolved phosphate could be detected using
a sensitive analytical method.
Impacts
Research results on the forms of chromium and arsenic in soils at contaminated military sites indicate that these potentially toxic contaminants would not be very mobile in these soils. This information along with measurements of total metal concentrations will be useful for deciding on safe, yet cost-effective remediation options for these sites. Measurements of phosphate binding mechanisms on iron- and aluminum oxide minerals are important for understanding how changes in soil wetness will impact phosphorus mobility, and hence the potential impacts of phosphorus-enriched soils on water quality. Such information is also important for designing more routine soil test methods to assess a soil's ability to bind phosphorus, and hence to develop Best Management Practices (BMPs) for optimizing land application of phosphorus-rich animal wastes.
Publications
- Nelson, N.O., R.L. Mikkelsen, and D.L. Hesterberg. 2000. Struvite formation to remove phosphorus from anaerobic swine lagoon effluent. p.18-26. In J.A. Moore (ed.) Animal, agricultural and food processing wastes. Proc. of the eighth international symposium. Des Moines, IA, October 9-11, 2000. ASAE, St. Joseph, MI.
- De Vos, J.A., D. Hesterberg, and P. A. C. Raats. Nitrate leaching in a tile-drained silt loam soil. 2000. Soil Science Society of America Journal 64:517-527.
- Williams, K. A., P. V. Nelson, and D. Hesterberg. 2000. Phosphate and potassium retention and release during chrysanthemum production from precharged materials: I. Alumina. Journal of the American Society for Horticultural Science. 125:748-756.
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Progress 10/01/98 to 09/30/99
Outputs
Research addressed the environmental chemistry of heavy metals and phosphorus in soils. Focus areas included molecular-scale nature of Cu(II) bonding on goethite mineral surfaces containing adsorbed soil organic matter (humic acid), stability of heavy metal sulfides in soil, speciation of copper and zinc in swine lagoon sludge, and redox effects on chemical speciation of soil phosphorus. X-ray absorption spectroscopy (XAS) analysis of Cu(II) bound with goethite-humate complexes in aqueous suspensions indicated that Cu(II) was typically complexed with both humic acid and goethite surface functional groups. However, at levels of adsorbed humic acid greater than 200 g/kg goethite, Cu(II) bonded primarily the adsorbed humic acid. Spatially resolved X-ray absorption analysis (micron-size scale) of reduced soils revealed that oxidation of Cu- and Zn-sulfides occurs at different rates in different regions of elevated metal concentration. Samples of sludge collected from
swine waste lagoons in North Carolina were analyzed using XAS to determine the speciation of Cu and Zn in the waste. Copper occurred primarily as Cu-sulfide and Zn occurred as a mixture of Zn-sulfide and other unidentified Zn species. Much of our work on phosphorus speciation in soils focused on a set of five soil samples that were subjected in the laboratory to three reduction and oxidation cycles. Phosphorus XAS analysis showed that changes in redox conditions induced changes in the solid-phase forms of soil phosphorus, although the specific phosphorus species involved have not been quantified.
Impacts
Research addressing the bonding of heavy metals and phosphorus in soils provides a basis for understanding and predicting the long-term impacts of soil contaminants. For example, knowing that copper in swine lagoon sludge is a copper-sulfide mineral, we can project that the mobility of copper from the sludge will be low under reducing conditions.
Publications
- Hesterberg, D., W. Zhou, K. J. Hutchison, S. Beauchemin, and D. E. Sayers. 1999. XAFS study of adsorbed and mineral forms of phosphate. Journal of Synchrotron Radiation 6:636-638.
- Zhou, W., D. Hesterberg, P. D. Hansen, K. Hutchison, and D. E. Sayers. 1999. Stability of copper sulfide in a contaminated soil. Journal of Synchrotron Radiation 6:630-632.
- Oh, Y.-M., D. Hesterberg, and P. V. Nelson. 1999. Phosphate adsorption on clay minerals as a pre-plant source of phosphorus in soilless root media. Communications in Soil Science and Plant Analysis 30:747-756.
- Colberg, M. T., A. E. Saez, C.S. Grant, K. Hutchison, and D. Hesterberg. 1999. Dynamic hydration of phospholipid films in aqueous environments. Colloids and Surfaces 151:483-495.
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