bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesosphere inversion layers and stratosphere temperature enhancements
Authors: Meriwether John W. , Gerrard Andrew J.
Published: September 2004

It has been known for at least 30 years that vertically narrow thermal layers form within the middle atmosphere. Two types of temperature enhancements, the low‐latitude to midlatitude mesosphere inversion layer (MIL) and the high‐latitude winter stratosphere temperature enhancement (STE), have both received much attention within the atmospheric science community because of their unexplained formation mechanisms and potential impacts on the middle‐atmosphere global circulation. Numerous experimental, numerical, and theoretical studies have attempted to explain certain aspects of these respective thermal layers, but no one theory consistently and satisfactorily describes all the features observed. We present a review of the literature and explicitly propose a classification scheme based on the different formation mechanisms suspected to cause these events. For the MIL we demonstrate that there are two subtypes. The first one is tidally driven and tends to occur above ∼85 km. This MIL originates from large‐amplitude tidal waves propagating into the mesosphere and their subsequent nonlinear interactions with gravity waves, which can often create the appearance of a “double MIL” separated by approximately one vertical tidal wavelength (∼25 km). The other subtype of MIL is formed by a climatological planetary wave dissipation mechanism that occurs at a zero‐wind line. The dissipation of the planetary wave tends to generate a mesoscale (∼1000 km) inversion layer in the range of 65–80 km. These two formation mechanisms explain a host of observed characteristics, including the reason behind the downward progression of some MILs and not others, the different climatological nature of the two forms of MIL events, and the relative scarcity of MIL observations at high latitudes. The STE is believed to be generated by an altogether different process, namely, the nonlinear interaction between the polar vortex and planetary waves/Aleutian High. The induced temperatures typically peak around 40 km and often exceed 300 K, generating what appears to be a “low, hot stratopause.” When vertical temperature profiles are combined with synoptic analyses, one observes that the STE is the consequence of high‐latitude vortex interactions creating a baroclinic atmosphere, i.e., a downward adiabatic compression induced by an ageostropic flow. We summarize the details of the relationship between this feature and sudden stratospheric warmings, as well as the potential for in situ gravity wave generation. We close with a review of currently unexplained MIL/STE features and offer new directions for future middle‐atmosphere thermal layer research.
Microlite textures and volatile contents of obsidian from the Inyo volcanic chain, California
Authors: Castro Jonathan M. , Mercer Celestine
Published: September 2004

We test the hypothesis that microlite textures record progressive degassing during magma ascent. We compare microlite number density (NV) and H2O concentrations in pyroclastic and effusive obsidian (OBS) from the Inyo Volcanic Chain, CA. Comparisons reveal a weak correlation between microlite NV and H2O; however, most obsidians (OBSs) of a given volatile content exhibit a wide range of NV. Factors other than degassing must also influence final groundmass texture. We postulate that OBS textures record different ascent rates and residence histories prior to eruption from the conduit. We conclude that microlites do not sensitively indicate the extent of magmatic degassing, rather, they provide qualitative indications of magma ascent and residence time.
The fraction of interplanetary coronal mass ejections that are magnetic clouds: Evidence for a solar cycle variation
Authors: Richardson I. G. , Cane H. V.
Published: September 2004

“Magnetic clouds” (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized by enhanced magnetic fields with an organized rotation in direction, and low plasma β. Though intensely studied, MCs only constitute a fraction of all ICMEs detected in the solar wind. A comprehensive survey of ICMEs in the near‐Earth solar wind during the ascending, maximum and early declining phases of solar cycle 23 in 1996–2003 shows that the MC fraction varied with the phase of the solar cycle, from ∼100% (though with low statistics) at solar minimum to ∼15% at solar maximum. A similar trend is evident in near‐Earth observations during solar cycles 20–21, while Helios 1/2 observations at 0.3–1.0 AU show a weaker trend and larger MC fraction.
Did melting glaciers cause volcanic eruptions in eastern California? Probing the mechanics of dike formation
Authors: Jellinek A. Mark , Manga Michael , Saar Martin O.
Published: September 2004

A comparison of time series of basaltic and silicic eruptions in eastern California over the last 400 kyr with the contemporaneous global record of glaciation suggests that this volcanism is influenced by the growth and retreat of glaciers occurring over periods of about 40 kyr. Statistically significant cross correlations between changes in eruption frequency and the first derivative of the glacial time series imply that the temporal pattern of volcanism is influenced by the rate of change in ice volume. Moreover, calculated time lags for the effects of glacial unloading on silicic and basaltic volcanism are distinct and are 3.2 ± 4.2 kyr and 11.2 ± 2.3 kyr, respectively. A theoretical model is developed to investigate whether the increases in eruption frequency following periods of glacial unloading are a response ultimately controlled by the dynamics of dike formation. Applying results from the time series analysis leads, in turn, to estimates for the critical magma chamber overpressure required for eruption as well as constraints on the effective viscosity of the wall rocks governing dike propagation.
Rates of sediment recycling beneath the Acapulco trench: Constraints from (U‐Th)/He thermochronology
Authors: Ducea Mihai N. , Valencia Victor A. , Shoemaker Sarah , Reiners Peter W. , DeCelles Peter G. , Campa Maria Fernanda , Morán‐Zenteno Dante , Ruiz Joaquin
Published: September 2004

The Sierra Madre del Sur mountain range is an uplifted forearc associated with the subduction of the Cocos plate along the Acapulco trench beneath mainland southern Mexico. The shallow subduction angle, the truncation of geologic features along the modern Acapulco trench, and direct seismic and drill hole observations in the trench through deep sea drilling data suggest that subduction erosion is an important process during the evolution of this margin. Turbidites derived from the uplifted forearc are the predominant sedimentary input into this trench, while pelagic sediments are subordinate. Apatite (U‐Th)/He ages were obtained on 23 samples from two transects across the Sierra Madre del Sur (Acapulco and Puerto Escondido) and reveal slow cooling during the Miocene. (U‐Th)/He ages range between ∼25 and 8 Ma and correlate inversely with elevation. Long‐term erosional exhumation rates inferred from these ages range from 0.11 to 0.33 km/m.y., with higher rates in the range core, and suggest that the Sierra Madre del Sur has been a slowly decaying mountain range, since at least the early Miocene. Apparent Miocene‐Pliocene sedimentation (“preservation”) rates in the Acapulco trench derived from Deep Sea Drilling Project data are about an order of magnitude smaller than the Miocene forearc erosion rates estimated from (U‐Th)/He ages, suggesting that the terrigenous input to the trench was almost entirely recycled via subduction erosion, at least during the Miocene. The Miocene subducted flux per unit length of the margin is about 30 km3/(km m.y.), or a subducted volume per unit time of 44 × 103km3/m.y., when integrated over the length of the trench.
Interpretation of pressure recovery data from packer inflation
Authors: Illman Walter A.
Published: September 2004

A packer test conducted in porous or fractured medium includes a stage prior to the actual test in which packers are inflated. If the packers are inflated quickly, the pressure within the injection interval rises in a near‐instantaneous fashion and decays with time as it comes into equilibrium with the surrounding formation. These pressure recovery data are commonly not collected and never analyzed. However, the pressure transient resulting from packer inflation is akin to a pressurized slug test conducted within a packed off interval. Here we interpret 18 records of such pressure recovery data obtained prior to a cross‐hole pneumatic injection test conducted in unsaturated fractured tuff at the Apache Leap Research Site (ALRS) in central Arizona. We analyze these records by modifying the M. J. Hvorslev's method to account for airflow. Results from the analysis are compared against permeability (k) estimates obtained from a pneumatic slug test as well as several single‐ and cross‐hole pneumatic injection tests at the ALRS. This comparison shows that the k determined from the pressure recovery compares well with the result from the pneumatic slug test, but the estimates are noticeably smaller than the values determined from single‐ and cross‐hole tests, suggesting a k scale effect. In addition, the basic time lag (tB) obtained from the analysis of the pressure recovery data using M. J. Hvorslev's method is smaller than what was previously determined from the type curve interpretation of a cross‐hole pneumatic injection test. These results collectively suggest that the pressure transients from single‐ and cross‐hole tests conducted over a longer period at higher flow rates sample a much larger volume of the rock compared to the pressure recovery data from packer inflation at the ALRS.
‘Settled in Mobility’: Engendering Post-Wall Migration in Europe
Authors: Morokvasic Mirjana
Published: September 2004

The end of the bi-polar world and the collapse of communist regimes triggered an unprecedented mobility of people and heralded a new phase in European migrations. Eastern Europeans were now not only ‘ free to leave’ to the West but more exactly ‘free to leave and to come back’. In this text I will focus on gendered transnational, cross-border practices and capabilities of Central and Eastern Europeans on the move, who use their spatial mobility to adapt to the new context of post-communist transition. We are dealing here with practices that are very different from those which the literature on ‘immigrant transnationalism’ is mostly about. Rather than relying on transnational networking for improving their condition in the country of their settlement, they tend to ‘settle within mobility,’ staying mobile ‘as long as they can’ in order to improve or maintain the quality of life at home. Their experience of migration thus becomes their lifestyle, their leaving home and going away, paradoxically, a strategy of staying at home, and, thus, an alternative to what migration is usually considered to be — emigration/immigration. Access to and management of mobility is gendered and dependent on institutional context. Mobility as a strategy can be empowering, a resource, a tool for social innovation and agency and an important dimension of social capital — if under the migrants’ own control. However, mobility may reflect increased dependencies, proliferation of precarious jobs and, as in the case of trafficking in women, lack of mobility and freedom.
Florence Nightingale and the Irish Uncanny
Authors: Nagai Kaori
Published: September 2004

This article characterizes Florence Nightingale's nursing reform as the cleaning of the Victorian home which she found unheimlich. She laid strong emphasis on an improvement in the hygiene of the house as a significant part of nursing, and, by establishing the nurse as a new occupation, gave the surplus of unmarried women a decent means of escape from the stifling domesticity in which they had been helplessly trapped. Her nursing at once reformed and reinforced the traditional role of woman as a domestic figure, for she created the nurse as a mother figure in charge of the home space. In the Crimean War, Nightingale successfully nursed the idea of England as Home by attending to the dying soldiers at the front. Her crusade to nurse the unhomely space into a home, however, dismissed one uncanny place inside the imperial Home that needed urgent nursing, that is, Ireland, which had been suffering from the Great Famine and its aftermath. Nightingale confronted Irish Sisters of Mercy, who came to the Crimea to save the lives and souls of the Irish soldiers. These Irish nuns not only embodied the memories of the Famine which they had recently relieved, but also threatened Nightingale's single female authority by representing Ireland as a nation through their equally motherly presence. The service of the Irish nuns in the Crimean War was erased from the myth of the Lady with the Lamp. Nightingale could establish herself as an authoritative female subject and assumed the voice of England only by suppressing another female voice which challenged England's competence in Home management.
A Dialogue with ‘Global Care Chain’ Analysis: Nurse Migration in the Irish Context
Authors: Yeates Nicola
Published: September 2004

This article examines the relationship between globalization, care and migration, with specific reference to the ‘global care chain’ concept. The utility of this concept is explored in the light of its current and potential contributions to research on the international division of reproductive labour and transnational care economies. The article asserts the validity of global care chain analysis but argues that its present application to migrant domestic care workers must be broadened in order that its potential may be fully realized. Accordingly, five ways in which the concept could be more broadly applied are outlined and applications of this expanded framework are illustrated through a case study of nurse migration in the Irish context. Finally, the discussion considers future directions for empirical and theoretical research into global care chains and suggests various lines of enquiry.
‘Big Sisters’ are Better Domestic Servants?! Comments on the booming au Pair Business
Authors: Hess Sabine , Puckhaber Annette
Published: September 2004

The au pair program in general is still known as a form of cultural exchange program and a good possibility for young women to spend a year abroad, although it has undergone great changes during the last 10 years. This article argues that due to different socio-economic and cultural processes in Western postindustrial societies as well as in the eastern and southern parts of the world the au pair program is becoming a form of domestic work with quite similar working and living conditions to that of live-in migrant domestic workers. This article which is based on two empirical studies on the globalizing au pair business in Eastern and Western Europe as well in the United States looks into the motivations and expectations, the living conditions and interactions between the au pairs and the employer families and contrasts these findings with the discourse of the au pair agencies still advertising au pair as a form of cultural exchange. In doing so the paper can show that it is the still dominant image of au-pair as a cultural exchange program (disarticulating the work aspect) that leaves the young au pair women even more vulnerable to exploitation: ‘big sisters’ are the best domestic servants. This article draws attention to the racialized economization of the private sphere and care work, the inherent traps and exploitative features of this very specific work place.
An Ethnography of Global Labour Migration
Authors: Pai Hsiao-Hung
Published: September 2004

An ever more aggressive anti-migration propaganda war is being waged by the majority of British media, where migration in any form is consistently portrayed on the basis of forming and consolidating a response to a security threat. While tens of thousands of migrant workers are exchanging their sweated labour for meagre wages in the 3-D jobs — dirty, dangerous and degrading — in Britain's food-processing, electronic manufacturing, catering, cleaning and hospitality industries outside any mechanism of labour protection, Britain today is still declining to at least ratify the UN Convention on the Rights of Migrant Workers and Their Families in effect since last year. In the post-Morecambe debate on migration and demand for regularizing gangmasters, policing and immigration raids are seen as the quick cure for migrant labour exploitation. The argument sounds as if the only way to get rid of employers’ violation of minimum labour rights is to get rid of migrant workers. Britain has forgotten to ask — who are the migrant workers? They are the ones who sweep British roads, clean British supermarkets and serve you food in restaurants in every high street. They are the ones who sew the clothes you wear, put together your microwaves and process the British salads that you have on your dinner table everyday. Migrant workers are people you don't meet everyday but upon whom you depend. To find out about the chain of exploitation in which migrant workers live and the impact of British immigration controls that are fundamental to their lives, I lived undercover among the Chinese workers from whom I learnt a great deal.
Effect of hormonal growth promotant implants in weaner and hogget ewes on subsequent growth and reproductive performance
Authors: Bortolussi G. , Bird A. R. , Playford C. L. , Moore J.
Published: September 2004

Ninety young Merino ewes, depastured on Mitchell (Astrebla spp.) grass pastures in North West Queensland, were used in a hormonal growth promotant implantation study. The ewes were given 1 implant of Compudose, Ralgro, Revalor or Synovex-H, either at lamb marking (mid-dry season) or the start of the following summer wet season, which was ~180 days post-marking.
The hormonal growth promotant implanted groups had greater (P<0.05) liveweights than the control group early in the trial (days 22 and 57) and also from the end of the period of activity of the wet season implant (day 277) until the middle of the dry season (day 412). Dry season (at lamb marking) implantation did not improve average daily gain. From the end of the wet season onwards, ewes with a wet season implant were heavier (P<0.05) than those ewes implanted at lamb marking. This liveweight advantage had diminished by the start of the autumn mating. Hormonal growth promotant implantation had a favourable (P<0.05) effect on growth rate, but adversely affected reproduction in the ewes, regardless of time of implantation. Implantation with Compudose or Synovex-H significantly (P<0.001) reduced the demonstration of oestrus, while Revalor or Synovex-H reduced pregnancy rates by up to 100%. Despite Ralgro reducing these variables by up to 25%, its effect was not significant. All ewes that were diagnosed as pregnant at 140 days later produced lambs.
It was concluded from this study that hormonal growth promotant implantation at lamb marking provides no later-life advantage, while wet season implantation provides a growth or liveweight advantage to young Merino ewes and this persists for a long period after implantation. Despite the lack of an effect of Ralgro on oestrus and pregnancy results, however, implantation of young breeding ewes of any age should not be carried out, due to the long term and negative effects on reproductive performance. Wet season implantation may be best used for animals intended for slaughter.
Observations on environmental control of flowering of Qualup bell (Pimelea physodes)
Authors: Seaton K. A. , Plummer J. A.
Published: September 2004

The attractive Western Australian native cut flower, Pimelea physodes (Qualup bell), was grown in a cooler climate at Mt Barker and a warmer climate at Medina. Buds appeared much earlier (7 weeks) at Mt Barker and flower opening was earlier but the time between these events was greater (i.e. the duration of flower development was 1.7 times longer) at Mt Barker compared with Medina. Temperatures at Mt Barker were lower than at Medina, but at both latitudes the temperature averaged over the 2 weeks up to when buds appeared was similar (i.e. about 20/10°C day/night). During bud appearance daylength was 10 h or less at both sites. Plants at Mt Barker produced fewer flowering stems but more stems per plant compared with Medina. Since there were more stems and a longer development period for the plants at Mt Barker, the total number of flowers per plant was 3.7 times higher than those at the Medina site. Longer flower development did not affect flower size at Mt Barker with flower size remaining the same at both latitudes. Flower opening occurred at a similar rate at both latitudes and could be described by a linear function with about 3% change in opening per day. Bud appearance and flowering was promoted by a short-term pulse of cooling (10/15°C day/night) followed by warmer conditions (day/night temperature range; 20/11°C to 17/7°C over 5 weeks), with a longer cool pulse giving earlier bud appearance but not affecting flower appearance. Under cold pulse treatment flowers opened more rapidly giving a fuller flower display. A 2-week cold pulse resulted in an increase in flower production while a longer 4-week pulse reduced flower production. The impact on floral display is discussed. Results from trials indicated that by choosing sites with different temperature conditions such as at different latitudes or altitudes or subjecting plants to a cold pulse it should be possible to spread the flowering time of P. physodes.
Additives to reduce phosphorus excretion and phosphorus solubility in poultry and swine manure
Authors: Nahm K. H.
Published: September 2004

In the past 20 years, scientists have realised that environmental contamination by non-point source nutrients is a significant problem and its control is not easily managed. Manure phosphorus was found to be a primary pollutant of surface water, so methods to reduce manure phosphorus runoff have been a research focus. This review concentrates on approaches developed to reduce the excretion of manure phosphorus and to reduce the soluble phosphorus content of manure by poultry and swine. Addition of phytase to poultry and swine diets reduces phosphorus excretion dramatically. For example, phytase addition lowered broiler manure phosphorus by 10–56%, hen manure phosphorus by 41%, growing–finishing pig manure phosphorus by 21–51% and weaning–growing pig manure phosphorus by 20–25%. Phytase also improves the availability of other nutrients. Addition of vitamin D and its metabolites increases phosphorus retention by 31–79%, while use of this vitamin and its metabolites with phytase improved phosphorus retention by 79%. Further research is needed in the use of organic acids, probiotics and starch and their impact on manure phosphorus reduction. Ratios of dietary calcium:total phosphorus in the range of 1.1:1 to 1.4:1 appear to provide the best efficiency of supplemental phytase and D3 in broilers. Determination of dietary phosphorus requirements for each growth phase is vital, as is accurate and quick measurement of phosphorus contents in feeds. Certain chemical reagents containing aluminium, calcium or iron have been found effective in reducing the solubility of phosphorus, when added to manure or litter. Research reports have shown that reagents containing aluminium reduced phosphorus solubility in manure by 39–100%. Compounds containing iron decreased phosphorus solubility by 48–95%, while calcium compounds reduced soluble phosphorus by 65%. Fly ash containing aluminium, iron and calcium may also be used to lower soluble phosphorus content in manures.
An exploratory evaluation of APSIM to simulate growth and yield processes for winter cereals in rotation systems in South Australia
Authors: Yunusa I. A. M. , Bellotti W. D. , Moore A. D. , Probert M. E. , Baldock J. A. , Miyan S. M.
Published: September 2004

The Agricultural Production Systems Simulator (APSIM) suite of models was used to predict dynamics in water and nitrogen in soil, as well as the growth and yield of sequential crops of wheat and barley in pasture–wheat–barley rotations, between 1995 and 1997 at Roseworthy, South Australia. The NWHEAT model satisfactorily predicted above-ground dry matter, leaf area index and grain yields for both crops in rotations with either grassy (Grass) or medic (Medic) pastures, including the lack of significant response of yield to nitrogen fertiliser applied to wheat at sowing. Simulation data for soil water, from SOILWAT2, was consistent with measured data. Simulation with SOILN2, however, largely underestimated soil nitrogen, due to excessive uptake by the simulated wheat during the season when nitrogen was abundant and water supply readily available. Thus, the soil nitrate had to be reset at sowing for the following barley crop; simulated soil nitrate agreed with the measured data in this season when this nutrient was low. For most variables of crop growth and soil water, the simulated data were mostly within 2 standard errors of the measured means. Prediction of grain protein was underestimated in all cases, including where nitrogen in the shoot was overestimated. This was possibly due to inadequate remobilisation of nitrogen from the straw and roots to the grain by the simulated crop. A satisfactory prediction of dry matter, grain yield and grain weight was obtained for wheat when the models were extended to other trials at Roseworthy (Lower North), Minnipa (Upper Eyre Peninsula) and Wunkar (Murray Mallee), based on limited soil data. Long-term simulations of wheat yields showed that, with early sowing in the Lower North, median wheat yield increased by 50 kg/ha for every kilogram of nitrogen applied at sowing, up to a maximum nitrogen rate of 50 kg/ha. In the drier districts of the Upper Eyre Peninsula and the Murray Mallee, nitrogen fertiliser of no more than 25 kg/ha, applied at sowing, was enough to achieve yield benefits in any given season. At these drier sites, crop failures occurred in 5% (Upper Eyre Peninsula) and 10% (Murray Mallee) of the seasons simulated. Median sowing dates from these simulations were 15 May for the Lower North, 30 May for the Upper Eyre Peninsula and 24 May for Murray Mallee. This suggested that sowing could be conducted at least a week earlier than currently practised in the 3 environments. This study demonstrated the capability of APSIM to predict growth and grain yield of wheat and barley, as well as the associated dynamics of soil water in the main cereal belts of South Australia.
Delay in ripening of Gala and Pink Lady apples in commercial orchards following pre-harvest applications of aminoethoxyvinylglycine
Authors: Phan-Thien K-Y. , Wargo J. M. , Mitchell L. W. , Collett M. G. , Rath A. C.
Published: September 2004

Aminoethoxyvinylglycine (AVG) was applied to Gala and Pink Lady apple trees on commercial orchards at label rates (830 g/ha ReTain with 0.1% v/v organosilicone surfactant) 21–28 days before anticipated first harvest. Fruit from treated and untreated trees in each orchard were sampled weekly during the commercial harvest period (2–6 times) and assessed for starch pattern index, background colour, soluble solids and flesh firmness. Ripening of AVG-treated Gala apples was delayed by 9–12 days based on starch pattern index and background colour whereas fruit softening was delayed by 5 days. Ripening of AVG-treated Pink Lady apples was delayed by 5 days based on SPI and fruit softening was delayed by 7 days. These differential delays for starch pattern index and fruit softening did not adversely affect the fruit quality of either apple variety, as there was no difference between the flesh firmness of treated and untreated fruit when fruit of the same starch pattern index were compared. Regardless of treatment, Gala apples grew an average 1.16 g per day during the harvest period whereas Pink Lady apples grew an average 0.22 g per day. These results suggest AVG has major benefits as a harvest management tool, as it allows growers to regulate fruit ripening.
Development of acid sulfate soil in sub-aerially disposed dredge spoil at Fisherman Islands, Brisbane, Australia
Authors: Clark M. W. , McConchie D. M.
Published: September 2004

During disposal of Brisbane River estuary dredge sediments into the reclamation paddocks at Fisherman Islands, a size separation of the fine (<63 µm) pyrite-rich silts and clays from the coarser (>63 µm) pyrite-poor sands and gravels occurs. The sand and gravel fractions contain most of the shell material and, therefore, most of the acid-neutralising capacity. In the most recently reclaimed paddock this size separation is of little consequence because sediments remain well buffered and acid produced from sulfides contained in the oxidising estuarine sediments is readily neutralised by the large volume of seawater and fine-grained carbonate minerals. However, as more sediment is added to the paddock, sediments become anoxic and sulfate reduction within the sedimentary pile occurs. This reduction rapidly produces pyrite and black monosulfides, consequently the pyrite content and degree of pyritisation and sulfidisation (DOP, DOS) of the sediment increase. Sulfide production rapidly removes sulfate from sediment pore waters and the process quickly becomes sulfate-limited because the fine-grained sediment texture restricts sediment permeability and therefore sulfate replenishment. Consequently, a clear relationship between DOP and DOS is observed for the reclamation paddock sediments. However, pre-existing mud-flat, and older unbunded dredge spoil sediments from the 1960s and 1970s, have no clear relationship between DOP and DOS values because they contain fewer fines and the production of pyrite was not limited by sulfate availability, but was constrained by other geochemical factors (e.g. redox potential, organic matter, or iron availability). Because of the increasing pyrite content of the paddock sediments as they age, the carbonate-buffering capacity provided by the sediment is readily exceeded, and the sediments become potentially acid sulfate. Should these sediments subsequently be disturbed and allowed to oxidise, the surrounding environment could be subject to large quantities of metal-rich acidic waters.
Groundwater acidification caused by urban development in Perth, Western Australia: source, distribution, and implications for management
Authors: Appleyard S. , Wong S. , Willis-Jones B. , Angeloni J. , Watkins R.
Published: September 2004

A decline in the watertable due to a long period of low rainfall, and the disturbance of sulfidic peat soils by dewatering and excavation in the Perth suburb of Stirling, has led to widespread acidification of groundwater at the watertable in a residential area and contamination of groundwater by arsenic and metals. The acidification has been caused by the oxidation of sulfide minerals within the peat, which contains up to 15% by weight of oxidiseable sulfur. Groundwater of pH 1.9 has been measured in shallow monitoring bores in the area, as well as high arsenic (up to 7 mg/L), aluminium (up to 290 mg/L), and iron (up to 1300 mg/L) concentrations. Contaminated groundwater pumped from affected domestic garden bores caused plant deaths in gardens and has given rise to health concerns because of high arsenic and metal concentrations. Drilling has indicated that acidic groundwater generally extends 5–10 m below the watertable, and that deeper groundwater is currently unaffected by contamination. As groundwater forms 70% of Perth’s total water usage and sulfide-rich peat soils are common in the region, acid sulfate soil risk maps and management policies need to be developed and implemented as a matter of urgency to prevent similar acidity problems occurring elsewhere in Perth.
Factors contributing to the acid sulfate soil scalding process in the coastal floodplains of New South Wales, Australia
Authors: Rosicky Mark A. , Sullivan Leigh A. , Slavich Peter G. , Hughes Mike
Published: September 2004

Acid sulfate soil (ASS) scalds are persistently bare areas of land, occurring in the coastal backswamps of New South Wales (NSW), Australia. This study aims to understand why particular areas become ASS scalds, while adjacent areas remain vegetated. Some important soil parameters are compared and field observations are summarised. Soil core sampling in both ASS-scalded land and surrounding areas of permanently vegetated paddocks has demonstrated similar pyrite concentrations and depth occurrence, soil salinity, and soil acidity (pH). As conditions are similar beneath both vegetated and non-vegetated land, there must be some additional factors influencing which areas become denuded. Several disparate (usually human-induced) events were found to cause initial loss of vegetative cover. Once the soil is bare, surface evaporation causes toxic solutes to build up quickly at the soil surface and ASS scalding is perpetuated. Some of the intervening events include fire, flood, flood-scouring, deliberate topsoil removal, surface pyrite oxidation, saltwater inundation of freshwater paddocks, saltwater exclusion from saltmarsh or mangroves, changes to the vegetation regimes, excessive vehicular traffic, and over-grazing. Backswamp management needs to ensure that land underlain by shallow pyritic layers (or with soil-water that is enriched with the toxic by-products of pyrite oxidation) is not laid bare by accident or design. Similar soil chemical conditions underlying both ASS scalds and the surrounding permanently vegetated paddocks suggest that much larger areas are potentially at risk of ASS scalding.
Occurrence of marcasite in an organic-rich Holocene estuarine mud
Authors: Bush Richard T. , McGrath Roger , Sullivan Leigh A.
Published: September 2004

Substantial marcasite and pyrite were recently identified in the upper-most unoxidised Holocene clay–peat sediments at Bungawalbin Swamp, a coastal backswamp on the Richmond River floodplain, north-east New South Wales, Australia. Marcasite (FeS2), the mineral dimorph of pyrite, is considered a rare secondary mineral in estuarine sediments and its abundance at Bungawalbin Swamp is highly unusual. The morphology and distribution of marcasite in the sulfidic sedimentary profile was examined and compared with the palynological record. Marcasite, recognised by its distinctive platy morphology and disulfide composition, occurred exclusively within organic remnants in only the upper most 1 m of the sulfidic sediment layer. Pyrite occurred throughout the sulfidic profile. A dramatic change in the sedimentary conditions at Bungawalbin Swamp from a marine environment, characterised by the presence of avicenniaceae (i.e. mangrove), to a fresh–brackish environment correlates directly with the occurrence of marcasite. The occurrence of substantial marcasite may provide a valuable environmental proxy of fresh–brackish depositional swamp environments.
Acid neutralising capacity of two different bauxite residues (red mud) and their potential applications for treating acid sulfate water and soils
Authors: Lin Chuxia , Maddocks Greg , Lin Jing , Lancaster Graham , Chu Chengxing
Published: September 2004

The acid neutralising capacity (ANC) and potential beneficial uses of 2 different bauxite residues (red mud) were investigated. The results show that the ANC is much higher in the red mud disposed of using a dry stacking method at the Pingguo Alumina Refinery (China) than in the red mud disposed of by a wet method using seawater at the Queensland Alumina Ltd Refinery (Australia). The higher ANC in the Pingguo red mud is attributable to its high CaO and low SiO2. An incubation experiment showed that leaching of alkaline materials from the lime-treated sample was much greater than that from the red mud-treated sample. This suggests that red mud may be superior to lime for treating potential acid sulfate soils, which contain sulfide minerals that could take a long time to oxidise and release soluble acid. The effects of 2 acid-filtering systems were tested, both of which used red mud as the main material for removal of acid from passing acidic water. The results showed that the red mud–CaCO3 filter performed better than the red mud–Mg(OH)2 filter. Results from pot trials in Australia further demonstrated that the application of combined red mud and sewage sludge significantly improved the soil conditions for the growth of 5 Australian native tree species, in addition to Eucalyptus paniculata, which successfully grew in the same mine soil amended with the red mud and sewage sludge in previous work of G. Maddocks et al. The results from the pot experiment in China showed that the application of combined neutralising agents (red mud/lime blends) and sewage sludge to the extremely acidic mine soil was insufficient for creating appropriate ecological conditions for the growth of vetiver grass. In this experiment, additional application of zeolitic rock powder significantly improved the growth performance of the plant.
Applying mixed manure and inorganic phosphorus fertiliser to improve rice yield on acid sulfate soil (Hydraquentic Sulfaquept)
Authors: Ren Do Thi Thanh , Tinh Tran Kim , Minh Nguyen Thi Ngoc , Linh Tran Ba
Published: September 2004

In order to improve the yield of rice cultivated on acid sulfate soil, 2 field experiments and 1 pot experiment were conducted continuously for 5 and 2 crops, respectively (1997–2000), in Tri Ton district, An Giang province, Vietnam. Soil for the pot experiment was taken from the 2 field experiments to study the residual effect on phosphorus availability.
Both organic and inorganic phosphorus had a possitive effect on the rice yield. Compared with the treatments being fertilised at the same doses of P, a significantly higher yield was obtained in the treatment of mixed inorganic P fertiliser and manure. This effect was found only in the first crop. From the second crop onward, rice yields were not different among treatments (mixed fertilisers, inorganic P fertiliser, and manure only). Manure-only treatment resulted in rice yield equal to the treatment with 60 kg P2O5 in the form of superphosphate. Supplying phosphorus in both organic and inorganic forms over several crops resulted in an accumulation of phosphorus in soil, which became available for rice growth in the following crop season. Adding P fertiliser modified the P fraction in acid sulfate soil mainly to the form of Fe-P.
Mechanisms of acid sulfate soil oxidation and leaching under sugarcane cropping
Authors: Kinsela A. S. , Melville M. D.
Published: September 2004

Analysis of acid sulfate soils (ASS) under sugarcane cropping at a site on the Tweed River, north-eastern New South Wales, showed that the majority of the acidity and higher valence ions generated through pyrite oxidation was retained within an individual caneblock. It appears that the oxidation products generated >1 m away from the field drain edge primarily remain where they were formed, and are not exported to the adjacent field drain. Capillary rise and diffusion control the transfer of oxidation products within this area. Leaching and mass movement dominate the transport of ionic species in the topsoil and close to the field drain edge (~1 m). Soluble ion movement within the unsaturated zone also appears to be influenced by nutrient uptake of the growing sugarcane, adsorption and exchange reactions, and convective/dispersive forces.
The almost ubiquitous degree and depth of oxidation of ASS profiles along most of the coast, even where no artificial drainage has occurred, leads us to propose natural hydrological and pedogenic processes as the cause. While artificial drainage systems may not have caused the acidity that is stored in backswamps, they do provide the conduit for acidity export. Therefore, management regimes should focus on maximising the retention of acidity in the backswamp and treating that which is exported. Whilst a reduction in the drain frequency appears a logical solution to a reduction in the acidity export from the site, consideration must be given to the benefits field drainage provides before any subsequent changes can be made. An integrated approach of drain minimisation, laser levelling, and active watertable control would appear to be the most appropriate policy in containing the acidity within the soil profile. This approach, combined with the strategic application of lime, offers a means for minimising acid export from the sampled site.
Upland active acid sulfate soils from construction of new Stafford County, Virginia, USA, Airport
Authors: Fanning D. S. , Coppock Cary , Orndorff Z. W. , Daniels W. L. , Rabenhorst M. C.
Published: September 2004

This paper reports on a situation where severe active acid sulfate soils were brought into existence by the construction of a new (opened in 2002) airport in Stafford County, VA, approximately 60 km south-west of Washington, DC. About 290 ha of new land surface was brought into existence that consisted of both scalped land surfaces on steep slopes, and spoil (fill), some of which was graded to provide level land surfaces for paved runways. Over 150 ha of ultra acidic (pH <3.5 at soil surface) post-construction acid sulfate soils remained barren for over 2 years before the acid sulfate soil situation was properly recognised. Construction took place in an originally dissected landscape with about 30 m of local relief. The construction was designed to balance the cut and fill areas so that soil materials would not need to be taken from the area or brought to it from other locations. This resulted in some deep cuts (scalped surfaces) in the higher parts of the landscapes, which retained slopes of about 25%. Great difficulty was encountered in establishing vegetation on these surfaces. The exposed sulfidic materials were dense, commonly on steep slopes, and developed low pHs, some <pH 2, after exposure. After a dry period in the autumn of 2001, sulfuric horizons crusted over with bitter hydrated sulfate salt minerals had formed in the surface of sulfidic materials originally exposed in 1999. By X-ray diffraction, halotrychite, Fe2+Al2(SO4)4.22H2O, was identified as a main white salt mineral and copiapite group minerals, e.g. Al2/3Fe3+4(SO4)6(OH)2.20H2O for aluminocopiapite, were identified as a yellow salt minerals. Information about, and photographs of, the site, soils, and drainage waters are presented, including examples of deleterious environmental impacts.
Intensive reclamation/revegetation measures were initiated in 2002. These involved the application of high rates of lime stabilised biosolids (sewage sludge) incorporated to a depth of about 0.15 m to neutralise acidity and add organic matter and nutrients to the soils. These measures permitted the establishment of acid- and salt-tolerant grasses on the acid sulfate soils and caused dramatic increases in pH and drops in Fe and Al levels in stream waters leaving the site. However, they also caused initial large increases in ammonia/ammonium-N in the waters and subsequent increases in NO3-N in the waters.
Experience with this and other similar sites demonstrates the need for engineers involved with earth-moving construction activities to be educated in the principles of acid sulfate soils so that the number of such disturbances that result in the creation of active acid sulfate soils can be lessened or, preferably, eliminated. Plans for recognition and reclamation of acid sulfate soil situations should be built into the construction plans and designs when it is necessary to disturb sulfidic materials.
Chemical changes during oxidation of iron monosulfide-rich sediments
Authors: Smith J.
Published: September 2004

Iron monosulfide-rich sediments are commonly found in drains in acid sulfate soil (ASS) areas in eastern Australia. Sulfides represent an important sink for contaminants (including acidity and metals) and play an important role in improving water quality. However, these sediments are prone to oxidation during drain cleaning or drought, releasing acidity and metals into the drainage system, and are a potential environmental hazard in ASS landscapes. Chemical changes during oxidation of iron monosulfide-rich sediments have been studied in an incubation experiment. The effect of lime and mill mud/ash (an alkaline sugar mill byproduct) as neutralising agents has been examined. Oxidation of untreated sediments resulted in decreased pH, the production of acidity, and release of SO4 and metals, including iron, aluminium, and manganese. The large concentration and highly reactive nature of iron monosulfides suggest that the chemical changes observed are mostly a result of iron monosulfide oxidation, although the contribution of pyrite oxidation cannot be totally excluded. Lime appears to be an effective neutralising agent by maintaining pH and low acidity concentrations throughout the incubation experiment. The mill mud/ash initially prevented oxidation but its effectiveness was limited. These findings are important in terms of drain management in ASS environments.
Physiological and biochemical studies on aluminum tolerance in pineapple
Authors: Le Van H. , Masuda T.
Published: September 2004

Aluminum is rhizotoxic and is often present in acidic soils at activities high enough to inhibit root growth. The objectives of present study were to screen for Al-sensitive and Al-tolerant pineapple (Ananas comosus (L.) Merrill) cultivars and to investigate the potential mechanism(s) of Al tolerance. Seven cultivars were analysed and found to differ considerably in Al tolerance. The cultivars Soft Touch (Al-sensitive) and Cayenne (Al-tolerant) were selected for further analysis of physiological mechanism(s) of Al tolerance. The root elongation of Soft Touch was 80% compared with 120% for Cayenne in response to 300 μm AlCl3 at pH 4.5 for 72 h. Al accumulation and Al-induced callose formation in root apices were 50 and 15% of that in Cayenne, respectively. It is clearly shown that Al only inhibited Soft Touch during the treatment, whereas it enhanced root growth of Cayenne, suggesting an Al-induced Al-tolerance mechanism operating in Cayenne. There was no significantly difference in total protein in root exudates between cultivars treated with or without 300 μm AlCl3. However, 2D SDS–PAGE analysis could detect an acidic and low molecular weight protein in Al-treated Cayenne root tips, but not in control Cayenne or in Soft Touch both in the presence and absence of Al. The identification of organic acids in collected root exudates was conducted on Al-tolerant Cayenne. Citrate, malate, and succinate were found in Cayenne root exudates, and citrate was induced by Al exposure. Changes in organic acids from root exudates and soluble protein of root tips may be involved in the Al-tolerance mechanism. Further studies are, however, needed to clarify their functions on detoxification of Al in the pineapple roots.