The use of tracers to assess leakage from the sequestration of CO2 in a depleted oil reservoir,New Mexico,USA

Geological sequestration of CO₂ in depleted oil reservoirs is a potentially useful strategy for greenhouse gas management and can be combined with enhanced oil recovery. Development of methods to estimate CO₂ leakage rates is essential to assure that storage objectives are being met at sequestration facilities. Perfluorocarbon tracers (PFTs) were added as three 12 h slugs at about one week intervals during the injection of 2090 tons of CO₂ into the West Pearl Queen (WPQ) depleted oil formation, sequestration pilot study site located in SE New Mexico. The CO₂ was injected into the Permian Queen Formation. Leakage was monitored in soil–gas using a matrix of 40 capillary adsorbent tubes (CATs) left in the soil for periods ranging from days to months. The tracers, perfluoro-1,2-dimethylcyclohexane (PDCH), perfluorotrimethylcyclohexane (PTCH) and perfluorodimethylcyclobutane (PDCB), were analyzed using thermal desorption, and gas chromatography with electron capture detection. Monitoring was designed to look for immediate leakage, such as at the injection well bore and at nearby wells, and to develop the technology to estimate overall CO₂ leak rates based on the use of PFTs. Tracers were detected in soil–gas at the monitoring sites 50 m from the injection well within days of injection. Tracers continued to escape over the following years. Leakage appears to have emanated from the vicinity of the injection well in a radial pattern to about 100 m and in directional patterns to 300 m. Leakage rates were estimated for the 3 tracers from each of the 4 sets of CATs in place following the start of CO₂ injection. Leakage was fairly uniform during this period. As a first approximation, the CO₂ leak rate was estimated at about 0.0085% of the total CO₂ sequestered per annum.     

Effects of Flow Regulation in Flow Regime on the Murrumbidgee River,South Eastern Australia: an assessment using a daily estimation hydrological model

In this paper, modelled hydrological data are used to quantify the effects of regulation on the flow regime of the lower Murrumbidgee River in the period 1970–1998. Although other studies report historical changes in flood frequency and duration, this study uses modelled natural daily flow data rather than pre-regulation records or aggregated modelled monthly data. The comparison of modelled natural and regulated daily flows shows the magnitude of changes to mean and seasonal flows, flood peaks and flow duration. At gauges upstream of major irrigation off-takes, mean flows have been increased by approximately 10 per cent, flood peaks have been reduced by 21–46 per cent, and there has been a seasonal redistribution such that flows in summer and autumn have been increased at the expense of those in winter and spring. At gauges downstream of the major irrigation off-takes, mean flows have been reduced by 8–46 per cent, flood peaks have been reduced by 16–61 per cent, and flows have been decreased in all seasons.     

Unprecedented last-glacial mass accumulation rates determined by luminescence dating of loess from western Nebraska

A high-resolution chronology for Peoria (last glacial period) Loess from three sites in Nebraska, midcontinental North America, is determined by applying optically stimulated luminescence (OSL) dating to 35–50 μm quartz. At Bignell Hill, Nebraska, an OSL age of 25,000 yr near the contact of Peoria Loess with the underlying Gilman Canyon Formation shows that dust accumulation occurred early during the last glacial maximum (LGM), whereas at Devil’s Den and Eustis, Nebraska, basal OSL ages are significantly younger (18,000 and 21,000 yr, respectively). At all three localities, dust accumulation ended at some time after 14,000 yr ago. Mass accumulation rates (MARs) for western Nebraska, calculated using the OSL ages, are extremely high from 18,000 to 14,000 yr—much higher than those calculated for any other pre-Holocene location worldwide. These unprecedented MARs coincide with the timing of a mismatch between paleoenvironmental evidence from central North America, and the paleoclimate simulations from atmospheric global circulation models (AGCMs). We infer that the high atmospheric dust loading implied by these MARs may have played an important role, through radiative forcing, in maintaining a colder-than-present climate over central North America for several thousand years after summer insolation exceeded present-day values.     

Improving the level of seismic hazard parameters in Saudi Arabia using earthquake location

Saudi Arabia is characterized as largely aseismic; however, the tectonic plate boundaries that surround it are very active. To improve characterization of seismicity and ground motion hazard, the Saudi Arabian Digital Seismic Network (SANDSN) was installed in 1998 and continues to be operated by the Saudi Geological Survey (SGS) and King Abdulaziz City for Science and Technology (KACST). This article describes research performed to improve seismic hazard parameters using earthquake location and magnitude calibration of the high-quality SANDSN data. The SANDSN consists of 38 seismic stations, 27 broadband, and 11 short period. All data are telemetered in real time to a central facility at KACST in Riyadh. The SANDSN stations show low background noise levels and have good signal detection capabilities; however, some stations show cultural noise at frequencies above 1.0 Hz. We assessed the SANDSN event location capabilities by comparing KACST locations with well-determined locations derived from ground truth or global observations. While a clear location bias exists when using the global average iasp91 earth model, the locations can be improved by using regional models optimized for different tectonic source regions. The article presents detailed analysis of some events and Dead Sea explosions where we found gross errors in estimated locations. New velocity models we calculated that should improve estimated locations of regional events in three specific regions include (1) Gulf of Aqabah—Dead Sea region, (2) Arabian Shield, and (3) Arabian Platform. Recently, these models were applied to the SANDSN to improve local and teleseismic event locations and to develop an accurate magnitude scale for Saudi Arabia. The Zagros Thrust presents the most seismic hazard to eastern Saudi Arabia because of the frequent occurrence of earthquakes. Although these events are 200 km or further from the Arabian coast, wave propagation through sedimentary structure of the Gulf causes long-duration ground motions for periods between 3 and 10 s. Such ground motions could excite response in large engineered structures (e.g., tall buildings and long bridges) such as was experienced after the November 22, 2005 Qeshm Island earthquake off the southern coast of Iran.     

Book reviews

BURNING BUSH: a fire history of Australia by S.J. Pyne. 15 × 23 cm, xix + 520 pp. Allen & Unwin, Sydney 1992. (ISBN 1–86373–194–6) $19–95 (soft).

ADVANCES IN RESOURCE MANAGEMENT: tributes to W.R. Derrick Sewell edited by H.D. Foster. 15 × 23 cm, viii + 366 pp. Belhaven Press, London 1992 (ISBN 1–85293–292‐ 9) £39.50 (hard).

FEMINISM AND GEOGRAPHY: the limits to geographical knowledge by G. Rose. 15 × 23 cm, 205 pp. Polity Press, Cambridge 1993. (ISBN 0–7456–1156–7) $34.95 (soft).

EVERYDAY LIFE: women's adaptive strategies in time and space (Lund Studies in Geography, Ser.B Human Geography 55) by T. Friberg (translated by M. Gray). 16 × 24 cm, 217 pp. Lund University Press, Lund, and Chartwell‐Bratt, Bromley 1993. (ISBN 0‐ 86238–345–5)

NATURAL DISASTERS by D. Alexander. 16 × 23 cm, xix + 632 pp. University College London Press, London 1993 (ISBN 1–85728–094–6) $55.00 (soft).     

Periods and stability of solar g-modes

We consider the rotation independent (m = 0) frequencies of Hill and Gu (1988) and Henning and Scherrer (1988). Comparison with Cox, Guzik, and Kidman (CGK) frequencies shows that CGK are systematically 5.7 ± 0.7% larger. This effect may be due to the larger central density in this model (162 g cm^–3) compared to the real Sun. A known systematic error of about one percent in the pressure calculated by the Iben (1965) procedure can account for the higher CGK central helium and density. A check of this increase of g-mode frequency with central density is made by calculating g-mode frequencies for a WIMP model with a central density of 210 g cm^–3. This 30% density increase gives a 17% frequency increase, and implies a law with frequency increasing with the 17/30 power of the central density. Thus the 5.7% decrease of frequencies from the model to the real Sun indicates a central density decrease of about 9.7% to about 147 g cm^–3. Comparison with the recent van der Raay g-mode frequencies shows that the CGK model frequencies are about 14% larger, as one would expect for these observed frequencies with a large P ₀ of 41.2 min.Destabilizing mechanisms of the normal -effect at the top of the convection zone and convection blocking at the bottom of the convection zone for low order and low-l g-modes produces pulsation driving that does not seem to be damped by radiation and convection effects at the surface. Since the surface motions are very small, photospheric damping does not stabilize these modes at it does for the 5-min p-modes. For higher-order and degree modes, deep damping by radiation flow across nodes overwhelms the destabilization and any small effect.     

Phenolics in aquatic ecosystems: A selected review of recent literature

This review surveys the pertinent literature on phenolics in the aquatic ecosystem. Approximately 2% of the total organics manufactured in the US were phenols. Of the total phenolics produced in the US, 96% were synthetic and 4% were naturally occurring. Synthetic phenols arise from coking of coal, gas works and oil refineries, chemical plants, pesticide plants, wood preserving plants and dye manufacturing plants. Natural phenolics occur from aquatic and terrestrial vegetation and much of this is released by the pulp and paper industry.Toxicity of phenolics has been studied on selected microbes (e.g. protozoa, yeast and bacteria), algae, duckweed, and numerous invertebrates and vertebrates. Depending on the organism tested, the acute toxicity of phenol varies from 6·5 to 1840 mg/litre phenol. For other phenolics toxicity ranges from 0·084 to 555 mg/litre. The toxicity of phenolics varies with the type, position and number of substitutions on the parent molecule. Environmental factors affect the toxicity of phenolics and these include photolytic action, microbial degradation, pH, water hardness and temperature. Based on limited data, toxicity of phenolics may be less in continuous flow tests than in their sensitivity to phenolics as does the presence of oxygen. A seasonal factor may also affect the sensitivity of various fish. Starvation and lack of suitable substrate for bottom fauna increases organism sensitivity to phenol. The source of test animals may affect their sensitivity to phenolics and this effect may be due to short-term physiological acclimation and genetic selection.Studies on the biological effects of phenolics are limited and varied. Fish development and embryo survival were not affected by phenol levels less than 25 mg/litre. Amphibian embryos were sensitive to 0·5 mg/litre phenol. Pentachlorophenols inhibited fish growth at levels down to 1·74, μg/litre.Exposure of fish to phenol in concentrations as low as 4 mg/litre caused haemorrhaging at the base of the fins. Two hour exposure to 6·5 mg/litre phenol caused disruption of blood vessel walls and gill epithelium. Oedema and blood infiltration was a common effect observed in most major tissues studied from fishes exposed to phenol. Phenol, at 12·5 mg/litre, reduces the levels of neurohormones in fish exposed for 10 days. The effects of pentachlorophenol on blood glucose and blood lactate levels, and in vivo and in vitro activity levels of seven liver enzymes of eels are discussed. Pentachlorophenol, at 1·8 μg/litre, decreased assimilation conversion efficiency in underyearling salmon. Phenol also affects immunoglobin levels, blood protein levels and tissue micro-element levels. Feeding rates are affected by phenolics. Phenolics affect oxygen consumption rates and the effect may be on uncoupling of oxidative phosphorylation with a subsequent reduction of ATP formation.Many aspects of behaviour are affected by phenolics and the phases of ‘intoxication’ leading to death have been described for fish and invertebrates.Fish detoxify phenolics by forming conjugate glucuronides and sulphates. Body burdens of phenolics varied with exposure time and exposure concentration. When fish pre-exposed to phenol are transferred to clean water, body burdens drop up to 90% after three to four hours. Depuration rates for other phenolics took longer; up to 30 days for pentachlorophenol.Little research has been done on the cycling of phenol and phenolics (other than pesticides) in aquatic ecosystems. Microbial degradation will decompose phenolics rapidly if suitable bacteria are present. Other factors affecting the loss of phenolics from aquatic ecosystems include photolysis, adsorption and dilution. Phenol entering subterranean aquifers may not dilute or degrade very quickly. In one documented case well-water levels up to 200 mg/litre were measured 18 months after a spill.     

Carbonate chemistry and the anthropogenic CO2 in the South China Sea

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Anthropogenic CO2 distribution in the North Pacific Ocean

The depth of penetration of anthropogenic CO₂ in the North Pacific Ocean based on carbonate data in the literature is discussed. The results indicate that the deepest penetration (over 2000 m) is found in the northwest North Pacific. The shallowest penetration (to less than 400 m) is found in the eastern equatorial Pacific. Depth of penetration of anthropogenic CO₂ appears to have been controlled by such factors as deep water formation in the Northwest Pacific; upwelling in the equatorial Pacific and; vertical mixing in the western boundary areas. These results compare well with results implied from tritium, C-14, and freons distributions. The total inventory of excess carbon in the North Pacific was 14.7±4×10¹⁵ g around 1980.