New LA-ICP-MS cryocell and calibration technique for sub-millimeter analysis of ice cores

Ice cores provide a robust reconstruction of past climate. However, development of timescales by annual-layer counting, essential to detailed climate reconstruction and interpretation, on ice cores collected at low-accumulation sites or in regions of compressed ice, is problematic due to closely spaced layers. Ice-core analysis by laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) provides sub-millimeter-scale sampling resolution (on the order of 100μm in this study) and the low detection limits (ng L–1) necessary to measure the chemical constituents preserved in ice cores. We present a newly developed cryocell that can hold a 1m long section of ice core, and an alternative strategy for calibration. Using ice-core samples from central Greenland, we demonstrate the repeatability of multiple ablation passes, highlight the improved sampling resolution, verify the calibration technique and identify annual layers in the chemical profile in a deep section of an ice core where annual layers have not previously been identified using chemistry. In addition, using sections of cores from the Swiss/Italian Alps we illustrate the relationship between Ca, Na and Fe and particle concentration and conductivity, and validate the LA-ICP-MS Ca profile through a direct comparison with continuous flow analysis results.

Bench-scale evaluation of the activated sludge process for treatment of a high -strength chemical plant wastewater

A bench-scale treatability study was conducted on a high-strength wastewater from a chemical plant to develop an alternative for the existing waste stabilization pond treatment system. The objective of this study was to determine the treatability of the wastewater by the activated sludge process and, if treatable, to determine appropriate operating conditions, and to evaluate the degradability of bis(2-chloroethyl)ether (Chlorex) and benzene in the activated sludge system. Four 4-L Plexi-glass, complete mixing, continuous flow activated sludge reactors were operated in parallel under different operating conditions over a 6-month period. The operating conditions examined were hydraulic retention time (HRT), sludge retention time (SRT), nutrient supplement, and Chlorex/benzene spikes. Generally the activated sludge system treating high-strength wastewater was stable under large variations of organic loading and operating conditions. At an HRT of 2 days, more than 90% removal efficiency with good sludge settleability was achieved when the organic loading was less than 0.4 g BOD$\sb5$/g MLVSS/d or 0.8 g COD/g MLVSS/d. At least 20 days of SRT was required to maintain steady operation. Phosphorus addition enhanced the performance of the system especially during stressed operation. On the average, removals of benzene and Chlorex were 73-86% and 37-65%, respectively. In addition, the low-strength wastewater was treatable by activated sludge process, showing more than 90% BOD removal at a HRT of 0.5 days. In general, the sludge had poor settling characteristics. The aerated lagoon process treating high-strength wastewater also provided significant organic reduction, but did not produce an acceptable effluent concentration. ^

Molar gas ratios and stable oxygen and nitrogen isotopes of air entrapped in ice, North America

The molar ratios of atmospheric gases change during dissolution in water due to differences in their relative solubilities. We exploited this characteristic to develop a tool to clarify the origin of ice formations in permafrost regions. Extracted from ice, molar gas ratios can distinguish buried glacier ice from intrasedimental ground ice formed by freezing groundwaters. An extraction line was built to isolate gases from ice by melting and trapping with liquid He, followed by analysis of N2, O2, Ar, 18O-O2 and 15N-N2, by continuous flow mass spectrometry. The method was tested using glacier ice, aufeis ice (river icing) and intrasedimental ground ice from sites in the Canadian Arctic. O2/Ar and N2/Ar ratios clearly distinguish between atmospheric gas in glacial ice and gases from intrasedimental ground ice, which are exsolved from freezing water. 615NN2 and 618OO2 in glacier ice, aufeis ice and intrasedimental ground ice do not show clear distinguishing trends as they are affected by various physical processes during formation such as gravitational settling, excess air addition, mixing with snow pack, and respiration.

Aeolian dust and chemistry records from the EDML and EDC ice cores

To improve quantitative interpretation of ice core aeolian dust records a systematic methodical comparison has been made involving methods of water-insoluble particle counting (Coulter Counter and laser-sensing particle detector), soluble ions (ion chromatography, IC, and continuous flow analysis, CFA), elemental analysis (inductively coupled plasma mass spectroscopy, ICP-MS, at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission, PIXE). Ice core samples covering the last deglaciation have been used from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land (EDML) ice cores. All methods correlate very well amongst each other. The ratios of glacial age concentrations to Holocene concentrations, which are typically a factor ~100, differ significantly between the methods, but differences are limited to a factor < 2 for most methods with insoluble particles showing the largest change. The recovery of ICP-MS measurements depends on the digestion method and is different for different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analysed samples further reveal a change of dust composition during the last deglaciation.

Chemistry record of icecore BER11C95_25

A 181 m deep ice core drilled in 1994/95 on the south dome of Berkner Island, Antarctica, was analyzed for stable isotopes, major ions and microparticle concentrations. Samples for ion chromatography were prepared by using a novel technique of filling decontaminated sample from a device for continuous ice-core melting directly into the sample vials. The core was dated through identification of volcanic horizons and interpolative layer counting. The core, together with a similar core from the north dome, reveals a 1000 year history of relatively stable climate. Temporal variations in the two cores deviate from each other owing to changing patterns of regional-scale circulation; the best correspondence between them is found for MSA-. delta18O, accumulation rate and a sea-salt proxy show only negligible correlation, which suggests a complex meteorological setting. Increasing annual accumulation is observed for the last 100 years. A period of increased sea-salt concentrations started around AD 1405, as has also been observed in other cores. Microparticle concentrations are on average 1220 particles (>=1.0 ?m diameter)/mL; they are enhanced from AD 1200 to 1350, possibly because of a higher atmospheric mineral dust load or because local volcanic activity was stronger than previously thought. Microparticles and NH4+show marked but multiple and very irregular sub-annual peaks; long-term stacking of 1 year data intervals yields seasonal maxima in austral spring or mid-summer, respectively. Post-depositional redistribution was observed for MSA, NO3- and F- at volcanic horizons.

Water chemistry, and biological traits and mercury content of Salvelinus alpinus and S. namaycush in Laflamme and Pingualuit lake

Pingualuk Lake fills a deep crater in the Parc National des Pingualuit on the Ungava Peninsula (Nunavik, Canada) and is isolated from nearby surface waters. The main objectives of this study were to determine and compare the concentrations of two atmospherically derived contaminants, mercury and perfluorinated chemicals (PFCs), in the lake water column and fish of Pingualuk Lake and to assess the physical and biological factors influencing contaminant concentrations. Mercury concentrations in arctic char muscle tissue were comparable to those of char in other Arctic lakes, while the total amount of PFCs was below reported levels for remote lakes in the Arctic and elsewhere. Stable isotope and stomach content analyses were made to investigate the feeding ecology of the Pingualuk Lake arctic char population and indicated the possibility of multiple feeding groups. Genetics characteristics (MH and mtDNA) of fish from Pingualuk Lake revealed that this population is likely distinct from that of nearby Laflamme Lake. However, both arctic char populations exhibit differential variation of their allele families. Physical characteristics determined for Lake Pingualuk revealed that the water column was inversely stratified beneath the ice and extremely transparent to visible and ultraviolet radiation. The highest mercury concentrations (3- 6 pg/mL THg) occurred just beneath the ice surface in each lake. Pingualuk Lake, given its near pristine state and exceptional limnological features, may serve as a most valuable reference ecosystem for monitoring environmental stressors, such as contaminants, in the Arctic.

Physical properties and accumulation rates in Dronning Maud Land, Antarctica

The European Programme for Ice Coring in Antarctica includes a comprehensive pre-site survey on the inland ice plateau of Dronning Maud Land, Antarctica. The German glaciological programme during the 1997/98 field season was carried out along a 1200 km traverse on Amundsenisen and involved sampling the snow cover in pits and by shallow firn cores. This paper focuses on the accumulation studies. The cores were dated by dielectric-profiling and continuous-flow analysis. Distinct volcanogenic peaks and seasonal signals in the profiles served to establish a depth time-scale. The eruptions of Krakatoa, Tambora, an unknown volcano, Kuwae and El Chichon are well-documented in the ice. Variations of the accumulation rates over different times were inferred from the depth time-scales. A composite record of accumulation rates for the last 200 years was produced by stacking 12 annually resolved records. According to this, accumulation rates decreased in the 19th century and increased in the 20th century. The recent values are by no means extraordinary, as they do not exceed the values at the beginning of the 19th century. Variations in accumulation rates are most probably linked to temperature variations indicated in d18O records from Amundsenisen.

Seasonally resolved chemical records of six ice cores from the Dronning Maud Land, Antarctica

The ammonium, calcium, and sodium concentrations from three intermediate depth ice cores drilled in the area of Dronning Maud Land, East Antarctica, have been investigated. Since all measurements were performed by a high-resolution Continuous Flow Analysis system, for the first time seasonal signals of chemical trace species could be obtained from the interior of central Antarctica over a period of approximately 2 millennia. Although the elevation as well as the accumulation rate differ between the drilling sites, similar values were obtained by comparing mean concentrations spanning the last 900 years. However, a distinct lack of intersite correlation was found on decadal timescales. Despite a noticeable accumulation change, apparent in one core, no significant concentration change of all three species has occurred. All the measured ions show clear seasonal signals over the whole records. While the sea-salt-related component sodium peaks simultaneously with calcium, the maximum ammonium concentration occurs in the snow with a time lag of 2 months after the sea-salt peak. More than 60% of the calcium concentration can be attributed to an ocean source. Elevated sodium concentrations were found within this millennium compared to mean values of the whole records, but the spatially varying shape of the increase suggests that a possible climatic signal is biased by local deposition effects.

Stable-isotope records from Dronning Maud Land, Antarctica

The European Project for Ice Coring in Antarctica (EPICA) includes a comprehensive pre-site survey on the inland ice plateau of Dronning Maud Land. This paper focuses on the investigation of the 18O content of shallow firn and ice cores. These cores were dated by profiles derived from dielectric-profiling and continuous flow analysis measurements. The individual records were stacked in order to obtain composite chronologies of 18O contents and accumulation rates with enhanced signal-to-noise variance ratios.These chronologies document variations in the last 200 and 1000 years.The 18O contents and accumulation rates decreased in the 19th century and increased during the 20th century.Using the empirical relationships between stable isotopes, accumulation rates and the 10m firn temperature, the variation of both parameters can be explained by the same temperature history.But other causes for these variations, such as the build-up of the snow cover, cannot be excluded. A marked feature of the 1000 year chronology occurs during the period AD 1180-1530 when the 18O contents remains below the long-term mean. Cross-correlation analyses between five cores from the Weddell Sea region and Dronning Maud Land show that 18O records can in some periods be positively correlated and in others negatively correlated, indicating a complex climatic history in time and space.