Experimental studies of near-surface temperature cycling and surface wetting of stone and its implications for salt weathering

It has long been accepted that thermal and moisture regimes within stonework exert a major influence upon patterns of salt movement and, subsequently, the type and severity of salt-induced decay. For example, it is suggested that slow drying is more likely to bring dissolved salts to the surface, whereas rapid drying could result in the retention of some salt at or near the frequent wetting depth. In reality however, patterns of heating, cooling and surface wetting regimes that drive them – are complex and inconsistent responses to a wide range of environmental controls. As a first step to understanding the complexity of these relationships, this paper reports a series of experiments within a climatic cabinet designed to replicate the effects of short-term temperature fluctuations on the surface and sub-surface temperature regimes of a porous Jurassic limestone, and how they are influenced by surface wetting, ambient temperature and surface airflow. Preliminary results confirm the significance of very steep temperature/stress gradients within the outer centimetre or less of exposed stone under short-duration cycles of heating and cooling. This is important because this is the zone in which many stone decay processes, particularly salt weathering, operate, these processes invariably respond to temperature and moisture fluctuations, and short-term interruptions to insolation could, for example,
trigger these fluctuations on numerous occasions over a day. The data also indicate that there are complex patterns of temperature reversal with depth that are influenced in their intensity and location by surface wetting and moisture penetration, airflow across the surface and ambient air temperature. The presence of multiple temperature reversals and their variation over the course of heating and cooling phases belies previous assumtions of smooth, exponential increases and decreases in subsurface temperatures in response, for example to diurnal patterns of heating and cooling

A new landscape of arts-based buildings and comparative cultural policies on the island of Ireland: the curse of Jocasta's necklace

Much current cultural policy research focuses on activity traditionally viewed as arts practice: visual arts, music, literature and dance. Architecture’s role in the discussion of cultural policy is, however, less certain and thus less frequently interrogated. The study presented here both addresses this dearth of in-depth research while also contributing to the interdisciplinary discussion of cultural policy in wider terms. In seeking to better understand how architectural culture is regulated and administered in a specific case study, it unpacks how the complicated relationships of nominal and explicit policies on both sides of the Irish/Northern Irish border contributed to the significant expansion of arts-based buildings 1995-2008. It contrasts political and cultural motivations behind these projects during a period of significant economic growth, investment and inward immigration. Data has been gathered from both official published policies as well as interviews with elite actors in the decision-making field and architects who produced the buildings of interest in both countries. With the sizeable number of arts-based buildings now completed in both Republic of Ireland and Northern Ireland, one must wonder if this necklace of buildings is, like Jocasta’s, a thing of both beauty and redolent with a potential future curse. It is the goal of this project to contribute to the larger applied and critical discussion of these issues and to engage with future policy design, administration and, certainly, evaluation.

A study of the use of the trimesium salt of glyphosate to desiccate and ret flax and linseed (Linum usitatissimum) and of its effects on the yield of straw, seed and fibre

A replicated field plot experiment was carried out in Northern Ireland in 1996 with flax, cv Ariane, and linseed, cv Flanders, each grown at seed rates of 500, 1000 and 1500 seeds/m(2), in which a comparison was made between netting of the standing crop, following desiccation by the trimesium salt of glyphosate (Touchdown, Zeneca Ltd.), and water or dew retting of the pulled crop. Application at 4 litres/ha on 9 August, 33 days after the mid-point of flowering (MPF), achieved both desiccation and partial retting of the crop within 14 days. Over 16 % clean long fibre was extracted by scutching the stand-netted flax straw, yielding 800 kg/ha fibre, while water retting achieved 20 extraction and 980 kg/ha yield and dew netting 8.5 % and 420 kg/ha respectively. The dew retting was uneven, resulting in high losses during fibre extraction, while water retting for 7 days at 25 degreesC did not achieve complete retting resulting in a high content of woody fragments in the fibre. Fibre yields increased by almost 50 % with the high v. low seed rate. Linseed was less well retted than flax and contained higher levels of impurity in the extracted long fibre which, after retting, yielded 120 to 310 kg/ha at extraction rates of 2.9 % to 7.5 %.

In a second experiment in 1998 flax cvs. Viola and Evelyn were treated with the timesium salt of glyphosate at rates of 2, 4 or 6 litres/ha 10, 20, 30 or 40 days after MPF on 5 July. Viola desiccated satisfactorily at all spray dates with 4 and 6 litres/ha glyphosate. The 20-day treatment desiccated more slowly than the 30-day and the 2 litres/ha rate did not achieve complete desiccation, but the trimesium salt of glyphosate achieved better desiccation at this timing than that found in earlier studies with the original form of glyphosate. Evelyn desiccated more slowly and less evenly than Viola particularly at the 20-day and 40-day timings. Spraying at MPF + 10 days interrupted early development of the seed and fibre significantly reducing yields. Due to slower desiccation the 20-day timing was no better than the 30-day, which was well retted by harvest 44 days after spraying, and gave the highest yield of clean long fibre. The spraying 40 days after MPF was considered too late in the season to be of practical use. It was concluded that retting of standing flax following desiccation with the trimesium salt of glyphosate was more effective than with the earlier formulation and that resting of the standing crop could achieve equivalent or better retting with similar fibre yields to traditional retting methods. The optimum spray timing was found to be about 30 days after MPF with 4 or 6 litres/ha, the lower rate being adequate for glyphosate responsive varieties such as Viola.

The Doñana ecological disaster:contamination of a world heritage estuarine marsh ecosystem with acidified pyrite mine waste

One of the most important bird breeding and over wintering sites in the west of Europe, the Coto Doñana, was severely impacted by the release of 5 million cubic meters of acid waste from the processing of pyrite ore. The waste entered ecologically sensitive areas of the park (including breeding areas for internationally endangered bird species) causing sustained pH decreases from pH 8.5 to 4.5 and resulting in massive metal contamination of the impacted ecosystem. The contaminating sludge waste contained arsenic at 0.6%, lead at 1.2% and zinc at 0.8% on a dry weight basis. The acid conditions facilitated the solubilization of these metals, leading to water concentrations lethal for aquatic wildlife. The accident caused considerable fish and invertebrate kills and has severe consequences for the protected bird species dependent on the impacted habitats and adjacent areas.

Changing climate, changing process: implications for salt transportation and weathering within building sandstones in the UK

Salt weathering is a crucial process that brings about a change in stone, from the scale of landscapes to stone outcrops and natural building stone facades. It is acknowledged that salt weathering is controlled by fluctuations in temperature and moisture, where repeated oscillations in these parameters can cause re-crystallisation, hydration/de-hydration of salts, bringing about stone surface loss in the form of, for example, granular disaggregation, scaling, and multiple flaking. However, this ‘traditional’ view of how salt weathering proceeds may need to be re-evaluated in the light of current and future climatic trends. Indeed, there is considerable scope for the investigation of consequences of climate change on geomorphological processes in general. Building on contemporary research on the ‘deep wetting’ of natural building stones, it is proposed that (as stone may be wetter for longer), ion diffusion may become a more prominent mechanism for the mixing of molecular constituents, and a shift in focus from physical damage to chemical change is suggested. Data from ion diffusion cell experiments are presented for three different sandstone types, demonstrating that salts may diffuse through porous stone relatively rapidly (in comparison to, for example, dense concrete). Pore water from stones undergoing diffusion experiments was extracted and analysed. Factors controlling ion diffusion
relating to ‘time of wetness’ within stones are discussed, (continued saturation, connectivity of pores, mineralogy, behaviour of salts, sedimentary structure), and potential changes in system dynamics as a result of climate change are addressed. System inputs may change in terms of increased moisture input, translating into a greater depth of wetting front. Salts are likely to be ‘stored’ differently in stones, with salt being in solution for longer periods (during prolonged winter wetness). This has myriad implications in terms of the movement of ions by diffusion and the potential for chemical change in the stone (especially in more mobile constituents), leading to a weakening of the stone matrix/grain boundary cementing. The ‘output’ may be mobilisation and precipitation of elements leading to, for example, uneven cementing in the stone. This reduced strength of the stone, or compromised ability of the stone to absorb stress, is likely to make crystallisation a more efficacious mechanism of decay when it does occur. Thus, a delay in the onset of crystallisation while stonework is wet does not preclude exaggerated or accelerated material loss when it finally happens.

Vegetation changes and human settlement of Easter Island during the last millennia: a multiproxy study of the Lake Raraku sediments

Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.

Rapid succession of plant associations on the small ocean island of Mauritius at the onset of the Holocene

The island of Mauritius offers the opportunity to study the poorly understood vegetation response to climate change on a small tropical oceanic island. A high-resolution pollen record from a 10 m long peat core from Kanaka Crater (560 m elevation, Mauritius, Indian Ocean) shows that vegetation shifted from a stable open wet forest Last Glacial state to a stable closed-stratified-tall-forest Holocene state. An ecological threshold was crossed at ∼11.5 cal ka BP, propelling the forest ecosystem into an unstable period lasting ∼4000 years. The shift between the two steady states involves a cascade of four abrupt (<150 years) forest transitions in which different tree species dominated the vegetation for a quasi-stable period of respectively ∼1900, ∼1100 and ∼900 years. We interpret the first forest transition as climate-driven, reflecting the response of a small low topography oceanic island where significant spatial biome migration is impossible. The three subsequent forest transitions are not evidently linked to climate events, and are suggested to be driven by internal forest dynamics. The cascade of four consecutive events of species turnover occurred at a remarkably fast rate compared to changes during the preceding and following periods, and might therefore be considered as a composite tipping point in the ecosystem. We hypothesize that wet gallery forest, spatially and temporally stabilized by the drainage system, served as a long lasting reservoir of biodiversity and facilitated a rapid exchange of species with the montane forests to allow for a rapid cascade of plant associations.

Beyond the boundaries in the island of Ireland

The review essay opens with positive attributes of Ireland but then considers that the island has been subject to centuries of bitter dispute and unrest. The historical background to this is outlined, particularly the interactions between Ireland and its neighbouring island, Great Britain, which dominated Irish affairs. One policy adopted by the British was to encourage migration of Protestants into the largely Catholic island in the vain hope that this would reduce unrest. The
two islands were then united from 1801 as the United Kingdom of Great Britain and Ireland but demands from indigenous Irish Catholics for independence continued, resisted by the Protestant minority who wished to remain inside the UK. After the Great War a solution was imposed that granted most of Ireland independence but left the largely Protestant northeast corner within the UK as Northern Ireland. Reaction to and life with the Irish border are considered and the paper concludes with musings about its future.

Comparative performances of birnessite and cryptomelane MnO as electrode material in neutral aqueous lithium salt for supercapacitor application

Na-doped Birnessite-type manganese oxide (d-MnO) has been synthesized using the chemical method and characterized through X-ray diffraction and SEM, showing the lamellar structure and high crystal structure. A comparative study of the electrochemical performances of this material with those of the commercial Cryptomelane-type MnO has then been undertaken in ten neutral aqueous electrolytes for supercapacitor applications. Aqueous electrolytes, containing a lithium salt, LiX (where X = SO , NO, CHCO , CHSO, ClO , CHCO, TFSI, Beti, BOB, or Lact), have been first prepared under neutral pH conditions to reach the salt concentration, providing the maximum in conductivity. Their transport properties are then investigated through conductivities, viscosities, and self-diffusion coefficient measurements. Second, the thermal behaviors of these electrolytic aqueous solutions are then evaluated by using a differential scanning calorimeter from (213.15 to 473.15) K in order to access their liquid range temperatures. Cyclic voltammograms (CV) in three electrode configurations are thereafter investigated using Na Birnessite and Cryptomelane as working electrode material from (-0.05 to 1.5) V versus Ag/AgCl at various sweep rates from (2 to 100) mV·s. According to anion nature/structure and manganese oxide material type, different CV responses are observed, presenting a pure capacitive profile for Beti or CH CO and an additional pseudocapacitive signal for the smallest anions, such as ClO and NO . The capacitances, energies, and efficiencies are finally calculated. These results indicate clearly that electrolytes based on a mineral lithium salt under neutral pH condition and high salt concentration (up to 5 mol·L) have better electrochemical performances than organic ones, up to 1.4 V with good material stability and capacity retention. The relationship between transport properties, electrostatic and steric hindrance considerations of hydrated ions, and their electrochemical performances is discussed in order to understand further the lithium intercalation-deintercalation processes in the lamellar or tunnel structure of investigated MnO. © 2013 American Chemical Society.