Modelling the effect of climate change on recovery of acidified freshwaters: relative sensitivity of individual processes in the MAGIC model.

The MAGIC model was used to evaluate the relative sensitivity of several possible climate-induced effects on the recovery of soil and surface water from acidification. A common protocol was used at 14 intensively studied sites in Europe and eastern North America. The results show that several of the factors are of only minor importance (increase in pCO(2) in soil air and runoff, for example), several are important at only a few sites (seasalts at near-coastal sites, for example) and several are important at nearly all sites (increased concentrations of organic acids in soil solution and runoff, for example). In addition changes in forest growth and decomposition of soil organic matter are important at forested sites and sites at risk of nitrogen saturation. The trials suggest that in future modelling of recovery from acidification should take into account possible concurrent climate changes and focus specially on the climate-induced changes in organic acids and nitrogen retention.

Climate variability and forecasting surface water recovery from acidification: modelling drought-induced sulphate release from wetlands.

Climate-induced drought events have been shown to have a significant influence on sulphate (SO(4)(2-)) export from forested catchments in central Ontario, subsequently delaying recovery of surface waters from acidification. Field and modelling studies have demonstrated that water table drawdown during drought periods promotes oxidation of previously stored (reduced) sulphur (S) compounds in wetlands, with subsequent efflux of SO(4)(2-) upon re-wetting. Although climate-induced changes in processes are generally not integrated into soil-acidification models, MAGIC (Model of Acidification of Groundwater in Catchments) includes a wetland compartment that incorporates redox processes driven by drought events. The potential confounding influence of climate-induced drought events on acidification recovery at Plastic Lake, south-central Ontario (under proposed future S emission reductions) was investigated using MAGIC and two climate scenarios: monthly precipitation and runoff based on long-term means (average-climate scenario), and variable precipitation and runoff based on the past 20 years of observed monthly data (variable-climate scenario). The variable-climate scenario included several periods of summer drought owing to lower than average rainfall and higher then average temperature. Nonetheless, long-term regional trends in precipitation and temperature suggest that the variable-climate scenario may be a conservative estimate of future climate. The average-climate scenario indicated good recovery potential with acid neutralising capacity (ANC) reaching approximately 40 micromol(c)L(-1) by 2020 and 50 micromol(c)L(-1) by 2080. In contrast, the forecasted recovery potential under the variable-climate scenario was very much reduced. By 2080, ANC was forecasted to increase to 2.6 micromol(c)L(-1) from -10.0 micromol(c)L(-1) in 2000. Elevated SO(4)(2-) efflux following drought events (introduced under the variable-climate scenario) has a dramatic impact on simulated future surface water chemistry. The results clearly demonstrate that prediction of future water quality, using models such as MAGIC, should take into account changes or variability in climate as well as acid deposition.

Steady state critical loads of acidity for sulphur and nitrogen: a multi-receptor, multi-criterion approach.

The critical load approach to emission reductions has become an important element of the United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution (CLRTAP). The steady state mass balance approach (SSMB) is the most widely used method in Europe for estimating critical loads, typically applied to forest ecosystems on mineral soils in conjunction with a base cation to aluminium (Bc:Al) ratio using a default critical limit of 1.0. The 'typical' approach has been expanded in this paper by: inclusion of a broader range of natural and semi-natural receptor ecosystems; inclusion of multiple chemical criterion for each receptor; and an attempt to include organic soils (peatlands). Critical loads of acidity were estimated for the Republic of Ireland using four receptor ecosystems (coniferous forest, deciduous forest, natural grasslands and moors and heathlands) and seven chemical criteria. The dominant chemical criteria, in the determination of critical loads, were based on a critical pH limit for mineral soils or a critical pH shift in relation to pristine conditions for organic soils. Approximately 68 and 26% of the final distribution of critical loads were estimated using these criteria, respectively. The 5th-percentile critical loads of acidity were more sensitive than those previously estimated for Ireland due to the inclusion of organic soils. Furthermore, coniferous ecosystems had the lowest critical loads due to the high percentage occurring on organic soils, and the removal of base cations through harvesting. The results demonstrate that it may be more appropriate to use multiple criteria and receptors to ensure adequate protection of biological indicators. However, it is important that appropriate critical limits are chosen to protect the biological indicators and receptor ecosystems from long-term damage.

Parallelisation and application of a multi-layer atmospheric transport model to quantify dispersion and deposition of ammonia over the British Isles.

An atmospheric transport model, FRAME (Fine Resolution AMmonia Exchange), has been used to model the spatial pattern of ammonia concentrations and deposition over the British Isles for the first time. The model uses a multi-layer approach with diffusion through 33 layers to describe vertical concentration profiles in the atmosphere explicitly. Together with the necessary description of atmospheric reactions with sulphur and oxidised nitrogen, this imposes a major computational requirement, with the model having a run-time of 8.5 days on a mid-range workstation. Improvement in the model run-time was sought by developing a parallel implementation coded in a data-parallel approach using High Performance Fortran. Running the code on a Cray T3E with 128 processors provided a speedup by a factor of 69. The code's portability, its validation with measurements and new maps of its application to the British Isles, are presented. Good agreement is found with measured NH3 concentrations, while wet de-position is underestimated. In addition to model uncertainties, this may be due to an underestimation of the NH3 emissions input data.

Modelling the spatial distribution of SO2 and NOx emissions in Ireland.

The spatial distributions of sulphur dioxide (SO2) and nitrogen oxides (NOx) emissions are essential inputs to models of atmospheric transport and deposition. Information of this type is required for international negotiations on emission reduction through the critical load approach. High-resolution emission maps for the Republic of Ireland have been created using emission totals and a geographical information system, supported by surrogate statistics and landcover information. Data have been subsequently allocated to the EMEP 50 x 50-km grid, used in long-range transport models for the investigation of transboundary air pollution. Approximately two-thirds of SO2 emissions in Ireland emanate from two grid-squares. Over 50% of total SO2 emissions originate from one grid-square in the west of Ireland, where the largest point sources of SO2 are located. Approximately 15% of the total SO2 emissions originate from the grid-square containing Dublin. SO2 emission densities for the remaining areas are very low, < 1 t km-2 year-1 for most grid-squares. NOx emissions show a very similar distribution pattern. However, NOx emissions are more evenly spread over the country, as about 40% of total NOx emissions originate from road transport.

Clinical and endocrine effects of leuprorelin acetate in pre- and postmenopausal patients with advanced breast cancer.

Premenopausal Study. Twenty-five pre- or perimenopausal patients with advanced breast cancer were treated with leuprorelin acetate 3.75 mg (n = 9) or 7.5 mg (n = 16) every 4 weeks. Serum levels of gonadotrophins and oestrogens were suppressed markedly by both doses and there was no indication that the lower dose was less effective as an oestrogen suppressant. There were four objective responders to the 3.75 mg dose and six to the 7.5 mg dose. Toxicity was confined almost entirely to hot flushes, which occurred in 17 patients. Leuprorelin acetate is therefore an effective agent in the treatment of premenopausal breast cancer patients. There appears to be no major detriment to the use of 3.75 mg rather than the 7.5 mg dose. Postmenopausal Study. Fifteen postmenopausal patients with advanced breast cancer were treated with monthly injections of leuprorelin acetate 7.5 mg to assess the clinical activity and endocrine responses to treatment. None of the 15 patients showed an objective response to treatment, although four patients had stable disease for at least 6 months. Endocrine effects after 4 weeks' treatment included major suppression of serum gonadotrophins to below 10% of pretreatment values and decreases in the level of serum testosterone in 12 of 14 patients. In this group there were no changes in oestradiol levels, although we had previously observed suppression in postmenopausal patients treated with goserelin. In common with other gonadotrophin-releasing hormone analogues, leuprorelin acetate cannot be recommended as a treatment for postmenopausal breast cancer.

In vitro fertilisation and allied techniques. The initial experiences of the first Irish service.

Since 1986 in vitro fertilisation and allied techniques have formed a part of the fertility service at St. James's Hospital. By June 1988 using routine methodology, IVF or GIFT has been attempted at least once in 94 women with a further 17 having one repeat procedure and 4 two repeat procedures performed. Although embryos were cultured from 54% of oocytes in which fertilisation was attempted, no pregnancies were achieved during that period with IVF. Ten pregnancies had occurred during a GIFT cycle (9 at first attempt, 16%) 60% of these are on-going. Also continuing were pregnancies where ovulation induction was abandoned on day 8 (1) and where conception occurred spontaneously whilst on the waiting list for the procedure (8) and in untreated cycles following the procedure (4) (16%). Seventy percent of patients who failed the first time expressed a wish to try again.