Daniel M. White

Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export

Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were chara ...

Natural organic matter and DBP formation potential in Alaskan water supplies

Disinfection by-products (DBP) are formed when natural organic matter (NOM) in water reacts with a disinfectant, usually chlorine. DBPs are a health risk element and regulated under the Safe Drinking Water Act. A study was conducted to evaluate the characteristics of NOM that contribute to DBPs in 17 different drinking water systems in Alaska. In order to determine the nature of the organic matter contributing to DBPs, DBP formation potential was compared with standard water quality parameters such as UV-254, color and dissolved organic carbon (DOC), as well as pyrolysis-gas chromatography/mass spectrometry (GC/MS). Results showed strong correlations between UV-254 and DBP formation potential for all waters studied. DOC, on the other hand, was less strongly correlated to DBP formation potential. Unlike previous studies, the total trihalomethane and haloacetic acid formation potentials were equal on a mass concentration basis for the waters studied. Pyrolysis-GC/MS indicated that NOM contributing to DBPs were primarily phenolic compounds. This finding was consistent with previous studies; however, unlike other studies, no correlation was found between aliphatic compounds in the raw waters and DBP formation potential.

A comparison of hydraulic conductivities, permeabilities and infiltration rates in frozen and unfrozen soils

Abstract In order to protect water resources, fuel-storage facilities in Alaska are required to provide secondary containment for fuel spills. Secondary containment generally consists of a lined catchment basin. The lining must have a hydraulic conductivity of less than 1e−6 cm/s [ADEC, 1996. Alaska Department of Environmental Conservation Division of Spill Prevention and Response Industry Preparedness and Pipeline Program. “Sufficiently Impermeable Secondary Containment Systems.” March 11: 19 pages.]. A series of studies were conducted to evaluate the potential for frozen soil to serve as a secondary containment lining for fuel storage facilities in Alaska. Laboratory tests quantified hydraulic conductivities, permeabilities and fuel infiltration rates for three soil types collected at a fuel storage facility in Bethel, Alaska. Two of the soils, organic-rich silty sand and sandy silt, represented indigenous soil at the site. The third type, silty sand, was fill material imported to the facility from a nearby materials source. Unfrozen and frozen soil samples were placed in cast acrylic permeameter columns. Tests performed on unfrozen samples were conducted at room temperature (19.8 to 24.0 °C). In unfrozen soils, fuel-infiltration rates were similar at the three volumetric moisture contents tested, 15%, 30% and saturation. Tests for frozen samples were conducted in a cold room at −4 °C. Fuel-infiltration rates in the frozen soils decreased as ice-saturation increased. Hydraulic conductivity, permeability and infiltration rates for ice-rich soils were approximately 1e−9 cm/s, 1e−13 cm2 and 1e−8 cm/s, respectively.

Heterogeneity of natural organic matter from the Chena River, Alaska.

Water samples were collected in July 2001 from the Chena River in central Alaska. The natural organic matter (NOM) was size fractionated into particulate (POM,>0.45 microm), colloidal (COM,1kDa-0.45 microm) and dissolved (DOM,<1k Da) organic matter fractions, using filtration and ultrafiltration. The size-fractionated organic matter was then analyzed for organic carbon (OC) and nitrogen (N), isotopic (delta13C and delta15N) and molecular composition, using continuous flow isotope ratio mass spectrometry and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results of phase partitioning showed that, on average, about 6% of OC and 16% of N occurred in the form of POM while 66% of OC and 57% of N occurred in the form of COM, and 28% of the OC and 27% of the N were in the DOM form. Organic matter in the river water was found to be highly heterogeneous in terms of chemical composition and isotopic signatures. The C/N ratio was as low as 16+/-1 in the POM (n=2) to as high as 48+/-1 in the COM (n=3) and 38+/-4 in the DOM (n=3), suggesting a diagenetically younger POM. Values of delta13C increased with decreasing size, varying from -29.59+/-0.45% in the POM to -27.47+/-0.06% in the COM to -16.93+/-0.08% in the DOM. In contrast, values of delta15N decreased with decreasing size, from 2.64% in POM to 1.64% in COM to 1.33% in DOM. These results, together with radiocarbon measurements, suggest a preferential decomposition of lighter C isotope (12C) and heavier N isotopic (15N) from POM to COM to DOM. Results of py-GC/MS showed that the percentage of polysaccharides decreased with decreasing size, further supporting a degradation pathway of NOM from POM to COM and DOM in Chena River waters. More studies are needed to examine the seasonal and spatial variations of size-fractionated organic matter.

Food and water security in a changing arctic climate

In the Arctic, permafrost extends up to 500 m below the ground surface, and it is generally just the top metre that thaws in summer. Lakes, rivers, and wetlands on the arctic landscape are normally not connected with groundwater in the same way that they are in temperate regions. When the surface is frozen in winter, only lakes deeper than 2 m and rivers with significant flow retain liquid water. Surface water is largely abundant in summer, when it serves as a breeding ground for fish, birds, and mammals. In winter, many mammals and birds are forced to migrate out of the Arctic. Fish must seek out lakes or rivers deep enough to provide good overwintering habitat. Humans in the Arctic rely on surface water in many ways. Surface water meets domestic needs such as drinking, cooking, and cleaning as well as subsistence and industrial demands. Indigenous communities depend on sea ice and waterways for transportation across the landscape and access to traditional country foods. The minerals, mining, and oil and gas industries also use large quantities of surface water during winter to build ice roads and maintain infrastructure. As demand for this limited, but heavily-relied-upon resource continues to increase, it is now more critical than ever to understand the impacts of climate change on food and water security in the Arctic.

Pyrolysis-GC/MS fingerprinting of environmental samples

Abstract This paper describes four recent applications of analytical pyrolysis in environmental science and engineering. In all applications, samples were analyzed in order to provide information about the origin of organic matter or changes to an organic matrix. In the first application, pyrolysis-gas chromatography/mass spectrometry (GC/MS) and pyrolysis-GC/flame ionization detection (FID) were used to help classify the origin of natural organic matter (NOM) buried in the Antarctic. In the second application, pyrolysis-GC/MS was used to compare the recalcitrance of NOM to biological degradation. In the third application, pyrolysis-GC/FID was used to quantitatively differentiate between lipogenic NOM and petroleum contamination in highly organic soil. In the fourth application, pyrolysis-GC/MS was used to fingerprint organic matter in water samples to help describe the relationship between surface water, groundwater and springs in a complex watershed. In all applications the benefits of analytical pyrolysis are still being discovered.

TREATMENT OF CYANIDE WASTE IN A SEQUENCING BATCH BIOFILM REACTOR

Abstract Biological treatment of a synthetic leachate containing cyanide was accomplished in a sequencing batch biofilm reactor (SBBR). A mixed culture of organisms growing on silicone tubing were provided with cyanide as a sole carbon and nitrogen source. Organisms consumed cyanide (20 mg/liter CN − WAD ) and produced ammonia in an approximate 1:1 molar yield. The SBBR was operated on a 24-h cycle. Over the course of each cycle, 20 mg/liter of cyanide was degraded to below 0.5 mg/liter. Results from four track studies are presented. It was demonstrated that, when supplied with glucose, the organisms would readily consume excess ammonia. For each mole of glucose added, 10 moles of NH 3 -N were removed from solution. The SBBR can be used as a mobile system for treatment of leachate from gold-mining operations. Large volumes of low concentration wastewater can be treated in the SBBR since it is not necessary to maintain a consortium of settling organisms.

Fingerprinting soil organic matter in the arctic to help predict CO2 flux

Abstract In the past 30 years, the arctic climate has warmed appreciably and there is evidence for a significant polar amplification of global warming in the future. A warming and drying of northern soils could result in an increase in organic matter decomposition and positive feedback to future climate warming. Northern ecosystems have accumulated 25–33% of the worlds soil carbon, much of which is preserved as poorly decomposed plant remains. The soil organic matter (SOM) decomposition rate, however, depends on many variables such as temperature, nutrient availability, pH, oxidation/reduction potential, and chemical composition of the SOM. This paper addresses the effect of SOM composition on CO2 respiration in arctic soil. In order to isolate the effect of SOM composition on respiration rate, 19 soils from the circumpolar arctic were incubated in a 25 °C, nutrient-rich, pH neutral, constantly mixed environment. The SOM composition was studied using pyrolysis-gas chromatography/mass spectrometry (py-GC/MS), an analytical technique that produces a “fingerprint” of SOM. Correlations were made between SOM composition and CO2 respiration rate for the 19 soils. From these data, a model was built to predict respiration rates in soil subjected to similar incubation conditions using py-GC/MS fingerprints. Results go on to compare model predictions of measured respiration in laboratory incubations of 15 soils from four different locations in the Northern and Western Alaska Transects. Predictions for cumulative respiration over a 70-day laboratory respiration test were within 20% of measured values.

Pyrolysis-gas chromatography/mass spectrometry and pyrolysis-gas chromatography/flame ionization detection analysis of three Antarctic soils

Abstract The research presented herein used pyrolysis-gas chromatography/mass spectrometry (GC/MS) to characterize potential parent organic materials for three Antarctic podzols and statistically compare the parent materials to soil organic matter (SOM) depth profiles. Pyrolysis-GC/flame ionization detection (FID) was used to quantify the relative percentage of a suite of biochemical compounds in the various horizons of three soils as well as potential parent organic materials consisting of mosses, algae and penguin guano. Pyrolysis-GC/FID was not used to classify and quantify all compounds in the soil pyrolysate, nor could it be used to describe the full nature of the soil organic material prior to pyrolysis. The method did, however, provide a powerful tool for correlating the various soils with parent organic materials and with each other in order to elucidate SOM transformation and translocation processes. The data suggested a general migration of polysaccharides and probably some amino carbohydrates in the Antarctic podzols and an impact of soil texture on preservation and transformation of the organic matter. Recent vegetation also appeared to affect the SOM in the topsoils to a greater extent than the organic matter derived from the parent materials of penguin guano.

The use of solid peroxides to stimulate growth of aerobic microbes in tundra

Solid peroxides and peroxyhydrates degrade into a basic salt, water, and molecular oxygen when in contact with biologically active soils. Column reactors were used to quantify the extent to which three solid peroxides would stimulate growth of aerobic, heterotrophic bacteria and fungi in contaminated tundra soil. Soils in contact with a peroxide compound were incubated in column reactors at field moisture conditions at either 12 or 25°C with no mixing. After 1200-h incubations, localized concentrations of bacteria and fungi were at least 2 orders of magnitude greater in soil amended with sodium carbonate peroxyhydrate than in soil containing either calcium peroxide or magnesium peroxide. Only in soil containing sodium carbonate peroxyhydrate did microbes grow to an appreciably higher concentration than in control soil, which contained no peroxide. Stimulation of both bacterial and fungal growth occurred primarily at distances of less than 5 cm from the peroxide, suggesting that under static moisture conditions, only localized microbial growth can be expected in acidic tundra soils.