Megan R. Balks

Polycyclic aromatic hydrocarbons in fuel-oil contaminated soils, Antarctica

Where fuel oil spills have occurred on Antarctic soils polycyclic aromatic hydrocarbons (PAH) may accumulate. Surface and subsurface soil samples were collected from fuel spill sites up to 30 years old, and from nearby control sites, and analysed for the 16 PAHs on the USEPA priority pollutants list, as well as for two methyl substituted naphthalenes, 1-methylnaphthalene and 2-methylnaphthalene. PAH levels ranged from 41-8105 ng g-1 of dried soil in the samples from contaminated sites and were below detection limits in control site samples. PAH were detected in surface soils and had migrated to lower depths in the contaminated soil. The predominant PAH detected were naphthalene and its methyl derivatives.

Effects of hydrocarbon spills on the temperature and moisture regimes of Cryosols in the Ross Sea region

Hydrocarbon spills have occurred on Antarctic soils where fuel oils are utilized, moved or stored. We investigated the effects of hydrocarbon spills on soil temperature and moisture regimes by comparing the properties of existing oil contaminated sites with those of nearby, uncontaminated, control sites at Scott Base, the old Marble Point camp, and Bull Pass in the Wright Valley. Hydrocarbon levels were elevated in fuel-contaminated samples. Climate stations were installed at all three locations in both contaminated and control sites. In summer at Scott Base and Marble Point the mean weekly maximum near surface (2 cm and 5 cm depth) soil temperatures were warmer (P<0.05), sometimes by more than 10°C, at the contaminated site than the control sites. At Bull Pass there were no statistically significant differences in near-surface soil temperatures between contaminated and control soils. At the Scott Base and Marble Point sites soil albedo was lower, and hydrophobicity was higher, in the contaminated soils than the controls. The higher temperatures at the Scott Base and Marble Point hydrocarbon contaminated sites are attributed to the decreased surface albedo due to soil surface darkening by hydrocarbons. There were no noteworthy differences in moisture retention between contaminated and control sites.

Heavy metal contamination in some soils of the McMurdo Sound region, Antarctica

Soil samples from eight sites at Marble Point and Pram Point, McMurdo Sound region, contaminated by human activities were examined for heavy metal content, using sequential extraction methods. The redistribution of lead, zinc and copper arising from point sources of these metals was demonstrated. The levels found are not considered to represent serious pollution but do indicate that human activities can change the chemistry of the Antarctic environment in localized areas.

The effect of human activities on moisture content of soils and underlying permafrost from the McMurdo Sound region, Antarctica

Soils and the underlying permafrost from undisturbed sites and sites that had been disturbed by construction activities at Marble Point and Pram Point in the McMurdo Sound regionwere sampled from excavated pits and drill cores. Gravimetric moisture (ice) contents and particle size distribution were determined. Volumetric moisture contents were calculated from these results. At undisturbed sites soil moisture contents within the active layer (to c. 60 cm depth) were low and ranged from 0.5% by weight at the soil surface to 10% above the permafrost. The permafrostwas generally completely saturated with ice, but sometimes contained considerable excess ice, with ice contents rising as high as 80% by volume. At disturbed sites, soil moisture contents within the active layer were similar to those of the undisturbed sites, rarely exceeding 20% by weight

Soils of Seabee Hook, Cape Hallett, northern Victoria Land, Antarctica

The soils of the Seabee Hook area of Cape Hallett in northern Victoria Land, Antarctica, were mapped and characterized. Seabee Hook is a low-lying gravel spit of beach deposits built up by coastal currents carrying basalt material from nearby cliffs. Seabee Hook is the location of an Adélie penguin (Pygoscelis adeliae) colony which influences the soils with additions of guano, dead birds, eggshells and feathers. A soil-landscape model was developed and a soil association was identified between the soils formed on mounds (relict beach ridges) favoured by penguins for nests (Typic Haplorthel) and the soils in the areas between the mounds (Typic Haplorthel/Typic Aquorthel). Soils formed on the mounds inhabited by penguins contained guano in the upper 50 cm, overlying sub-rounded beach-deposited gravel and sand. Soils between mounds had a thin veneer (< 5 cm) of guano overlying basaltic gravelly sand similar to that in the lower parts of the mound soils. The soils had high concentrations of nitrogen, organic carbon, phosphorus, cadmium, zinc, copper, and increased electrical conductivity, within horizons influenced by penguin guano. Five buried penguin bones were collected from the base of soil profiles and radiocarbon dated. The dates indicate that Seabee Hook has been colonized by penguins for at least 1000 years.

Short- and long-term impacts of human disturbances on snow-free surfaces in Antarctica

The speed with which tracks form as a result of trampling on exposed ground surfaces in Antarctica was investigated in the McMurdo Sound and Dry Valleys regions, by a simple treading experiment. Distinct tracks formed with fewer than 20 foot passes — as measured by stone cover, surface soil exposure, and track width — and they continued to develop with increasing traffic levels. Track development was rapid and most obvious on sandy gravel soils with a pebbly desert pavement, but slower and less distinct on soils with an extensive cover of surface boulders. The persistence of human impact from ground disturbances, which occurred up to 30 years previously, when pits were dug during field science investigations, was assessed using a range of previously defined criteria. Recently disturbed sites, where some action had been taken to restore the site immediately after disturbance, showed the least overall impact. Impacts persisted longer at sites where no restoration had been undertaken, but the remaining impact varied with factors such as exposure to wind and the age of the land surface. These results demonstrate the fragility of Antarctic soil surfaces and the terrestrial environment, as well as the long time-scales for recovery of Antarctic ground-surface disturbances.

A simple visual technique for estimating the impact of fieldwork on the terrestrial environment in ice-free areas of Antarctica

A set of simple criteria for visual assessment of the effects of low-intensity fieldwork in ice-free areas of Antarctica was developed. These criteria were tested by using them to examine the impact of soil science investigations, both immediately and some time after disturbance, at Marble Point and at Cape Evans, on the shores of McMurdo Sound, Antarctica. The use of these criteria showed that for some types of impacts there had been a marked recovery of the surface with time, ranging from 22 months to 30 years. This was apparently due to repeated freeze and thaw of the soil surface and, to a lesser extent, to the influence of wind, which had partly or completely obliterated some of the earlier disturbances. More durable features remained, while deeper surface impressions, such as old soil inspection pits and vehicle tracks, showed little recovery after more than 30 years. Some biological colonisation of areas disturbed 30 years previously was occurring.

Solubilisation of soil carbon following treatment with cow urine under laboratory conditions

There have been reported losses of soil carbon (C) under intensively grazed pastures, and soil C solubilisation following cow urine deposition was identified as a possible mechanism. We measured potential soil C solubilisation in pasture and plantation pine soils following treatment of soil with cow urine. Soils from five paired pasture and pine sites were collected. Adsorption of urine-C and desorption of soil C was determined by shaking air-dried soil with cow urine for 4 h at 4°C, decanting the urine, and then extracting the soil with water. Soil C solubilisation was the difference between adsorption of urine-C and desorption of soil C. Solubilisation of soil C in the pine soils including the organic layers was 21.6 ± 2.6 mg/g (10.5 ± 1.1% of soil C concentration), in the pine soils excluding the organic layers 7.5 ± 2.2 mg/g (18.7 ± 5.8%), and in the pasture soils 12.4 ± 5.3 mg/g (27.8 ± 7.3%). There was no significant difference with respect to soil C solubilisation between the pine (with and without organic layers) and pasture soils. Soil C lower in the profile may be as susceptible to solubilisation as C in topsoils. Adsorption of urine-C was minimal. Solubilisation of soil C under urine patches may contribute to losses of soil C under intensively grazed pastures, and this hypothesis would benefit from further testing under field conditions.

Characterization of active layer water contents in the McMurdo Sound region, Antarctica

Abstract The liquid soil water contents in the seasonally thawed layer (active layer) were characterized from seven soil climate monitoring sites - four coastal sites from south to north (Minna Bluff, Scott Base, Marble Point and Granite Harbour), and inland sites from low to high altitude (Wright Valley, Victoria Valley and Mount Fleming). Mean water contents ranged from 0.013 m3 m-3 near the surface at Victoria Valley to 0.33 m3 m-3 near the ice-cemented layer at Granite Harbour. The coastal sites have greater soil water contents than the McMurdo Dry Valley and Mount Fleming sites, and moisture contents increase with depth in the active layer. The Wright Valley site receives very little infiltration from snowmelt, with none in most years. All other sites, except Mount Fleming, received between one and four wetting events per summer, and infiltrated water moved to greater depths (≈ 10–25 cm). The Scott Base and Granite Harbour sites are on sloping ground and receive a subsurface flow of water along the ice-cemented permafrost. Our findings indicate that water contents are low with very little recharge, are greatly influenced by the local microclimate and topography, and show no significant increasing or decreasing trend over 10 years of monitoring.

Regional, Annual, and Individual Variations in the Dihydroxyacetone Content of the Nectar of Ma̅nuka (Leptospermum scoparium) in New Zealand

A method was designed and validated for the analysis of dihydroxyacetone in the floral nectar of ma̅nuka (Leptospermum scoparium). The method was applied to samples collected from different regions of the North Island and the Nelson region of the upper South Island of New Zealand during the period 2009-2012 as well as to nectar samples from some Australian Leptospermum species. The ratio of dihydroxyacetone to total sugar (DHA/Tsugar) was classified as low (<0.001 mg/mg), moderate (0.001-0.002 mg/mg), or high (>0.002 mg/mg). Inter- and intraregional variation were observed as well as interannual variation with variation from low to high classification occurring within one region and from low to moderate between years. Australian species also demonstrated elevated levels of dihydroxyacetone in the nectar. Some garden cultivars were shown to produce very high nectar DHA/Tsugar, and a survey of cultivars was undertaken; cultivars with single-flowered red or pink flowers were the most common producers of very high nectar DHA/Tsugar.