Inorganic nitrogen metabolism inUlva rigida illuminated with blue light

Inorganic nitrogen metabolism in blue light was studied for the green algaUlva rigida C. Agardh collected in the south of Spain (Punta Carnero, Algeciras) in the winter of 1987. NH₄ ⁺ has been reported to inhibit NO₃ ^- uptake; however,U. rigida showed a net NO₃ ^- uptake even when the NH₄ ⁺ concentration of the external medium was three or four times greater than the concentration of NO₃ ^-. NO₃ ^- uptake rates were similar in both darkness and in blue light of various photon fluence rates (PFR) ranging from 17 to 160 mol m^-2 s^-1. Since NO₃ ^- uptake is an active mechanism involving the consumption of ATP, respiratory metabolism can provide enough ATP to maintain the energetic requirement of NO₃ ^- transport even in darkness. In contrast, NO₃ ^- reduction inU. rigida was highly dependent on the net photosynthetic rate. After 7 h in blue light, intracellular NO₃ ^- concentrations ([NO₃ ^-] _i ) were higher in specimens exposed to intensities below the light compensation point (LCP) than in those incubated at a PFR above the LCP. When PFR is below the light compensation point, NO₃ ^- reduction is low, probably because all the NADH produced by the cells is oxidized in the respiratory chain in order to produce ATP to maintain a steady NO₃ ^- transport rate. The total nitrogen (TN) and carbon (TC) contents decreased from darkness to 33 mol m^-2 s^-1 in blue light. In this range, catabolic processes prevailed over anabolic ones. In contrast, increases in TN and TC contents were observed above the light compensation point. The C : N ratio increased with light intensity, reaching a stable value of 17 at 78 mol m^-2 s^-1 in blue light. Intracellular NO₃ ^- concentration and NO₃ ^- reduction appear to be directly controlled by light intensity. This external control of [NO₃ ^-]_i and the small capacity ofU. rigida to retain incorporated NO₃ ^-, NO₂ ^- and NH₄ ⁺ ions may explain its nitrophilic character.     

The effect of selenium on fluoride — clay interactions: Possible environmental health implications

Previous epidemiological studies have shown that dental fluorosis is endemic in the lowland, dry zone of Sri Lanka, which is considered to be an area in which excessive quantities of fluorides are present in the drinking water supplies. It has been found that kaolinitic clay forms a suitable raw material in the defluoridation of water.It is shown that there is a noticeable effect of selenium and media pH on the reactions involved in the interaction of fluoride with clay. In this study, 1 mM fluoride solutions containing SeO ₃ ^2– (selenite) concentrations of 0 mM, 0.1 mM, 0.5 mM and 1 mM were used in the reactions with kaolinitic clay. The effect of pH was monitored in the range 4 to 8. It was observed that fluoride adsorption was maximum at a pH of 5.6 without either SeO ₃ ^2– or SeO ₄ ^2– , the adsorption capacity being 15.2 mol F^– g^–1 clay. However, when the SeO ₃ ^2– concentration was increased up to 0.5 mM at this optimum pH, the adsorption capacity reduced to 12.8 mol F^– g^–1 clay. Monitoring of the effect of SeO ₄ ^2– and media pH on fluoride adsorption showed that when the SeO ₄ ^2– concentration increases from zero to 0.1 mM, there is a reduction of fluoride adsorption capacity. However, when the SeO ₄ ^2– concentration is further increased from 0.1 mM to 1.0 mM, there was an increase in the fluoride adsorption capacity, indicating a more consistent effect of SeO ₃ ^2– on fluoride-kaolinitic clay interaction than SeO ₄ ^2– .Fluoride concentrations in drinking water supplies have a marked effect on dental health and the geochemistry of selenium appears to play an important role in the geochemical mobility of fluoride ions.     

Effect of nickel on some aspects of protein metabolism in the gill and kidney of the freshwater fish, Cyprinus carpio L

Nickel has an adverse effect on some aspects of protein metabolism of the freshwater fish, Cyprinus carpio. The main changes observed were: (a) Decrease in soluble, structural and total proteins, AlAT and AAT activities with an increase in the levels of free amino acids, protease and GDH activities and ammonia in the gill and kidney at 1, 2, 3, and 4 days of exposure to a lethal concentration, 40 mg litre(-1) of nickel; (b) Increase in soluble, structural and total proteins, free amino acids and the activities of protease, AlAT, AAT and GDH with a decrease in ammonia and urea in these organs at 1, 5, 10 and 15 days of exposure to sublethal concentration, 8 mg litre(-1); (c) The magnitude in these changes increased over time with both concentrations of the metal, and was more marked in gill than in kidney.     

Contribution of canopy leaching to sulphate deposition in a Scots pine forest

Radioactive sulphate (35SO4) was applied to the soil below a Scots pine forest on 23 June 1989, and its movement into the canopy and into throughfall and stemflow was measured over 4 months. The specific activity, Bq (mg S)(-1), of the canopy increased monotonically; uptake by current-year (1989) expanding needles was initially twice as fast as by older needles or live twigs. By 10 October the canopy average specific activity was 62 Bq (mg S)(-1). The specific activity of net throughfall (throughfall + stemflow - rain), deduced from measurements from six throughfall collectors, six stemflow collectors and two rain collectors, fell rapidly from 12.6 Bq (mg S)(-1) in late July to <1 Bq (mg S)(-1) in mid-August. The results suggest (assuming rapid equilibration of 35S with sulphate in soil) that root-derived sulphate contributed c. 3% of sulphate in net throughfall and that dry deposition of SO2 and sulphate particles contributed c. 97% of the 0.56 g S m(-2) measured in net throughfall over the period. Simultaneous measurements of SO2 at canopy height and of NH3 above and within the canopy gave mean concentrations of 5.9 and 0.86 microg m(-3), respectively, sufficient to account for the sulphate measured in net throughfall only if codeposition of NH3 and SO2 occurred to canopy surfaces. The large values of specific activity observed in July, however, indicate that throughfall composition may be closely related to recent soil input of sulphate, and that equilibrium cannot be safely assumed. The possibility of a significant contribution of soil-derived sulphate to sulphate deposition in net throughfall cannot be ruled out on the basis of this experiment.     

Deposition of atmospheric ammonia to moorlands

Micrometeorological methods were applied to measure fluxes of atmospheric ammonia (NH3) to moorlands. Measurements were made in a wide variety of surface conditions and included both Calluna vulgaris (L.) Hull and Eriophorum vaginatum L. dominated sites. NH3 was found to deposit rapidly to all the sites investigated, providing large deposition velocities (Vd, typically 10-40 mm s(-1)) and usually minimal surface resistances (rc). A small number of measurements were made in frozen conditions and suggest a possible exception to this pattern with mean rc of 50-200 s m(-1). The effect of vegetation drying was also investigated and a possible increase in rc observed, though this was small (< 10 s m(-1)). The results are interpreted in terms of the processes controlling exchange; it is shown that NH3 deposition is predominantly to the leaf surfaces and that the net NH3 compensation point approaches zero. Annual estimates show that dry deposition of NH3 is a major source of atmospheric nitrogen to moorland ecosystems. For two typical UK sites subject to background air concentrations, NH3 dry deposition is of similar magnitude to equivalent NH4+ inputs in wet deposition. In the vicinity of emission sources, NH3 dry deposition is expected to dominate inputs of atmospheric nitrogen.     

Effects of clearfelling on stream and soil water aluminium chemistry in three UK forests

Data are presented demonstrating how clearfelling has changed soil and stream water aluminium chemistry. For soil waters, a strong empirical relationship was observed between inorganic aluminium (Al(inorg)) and total inorganic anion (TIA) concentrations. Before felling, chloride and sulphate accounted for the largest proportion of the TIA concentration. After felling, in soils where nitrification was active, nitrate became increasingly important. Where this led to an increase in TIA, Al(inorg) concentrations increased. Over five years, nitrate concentrations have fallen, along with TIA, resulting in a sympathetic decline in Al(inorg). Streams draining clearfelled areas initially became more acid, although chloride and sulphate concentrations decreased. Stream water nitrate concentrations increased soon after felling and remained higher than controls for up to four years. While nitrate concentrations were high, Al(inorg) remained unchanged. Subsequently, as nitrate and TIA decreased, Al(inorg) also declined to concentrations below those in the control stream. Clearfelling upland forests will not necessarily result in immediate improvements in water quality, although long-term benefits may be seen before canopy-closure of the next crop.     

Cadmium availability to the cyanobacterium Synechocystis aquatilis in solutions containing chloride

Availability of cadmium to Synechocystis aquatilis (estimated by 109Cd sorption and cadmium toxicity-14C method) in solutions containing cadmium and complexing (KCl) or non-complexing (KNO3) salts, in the range of 0-0.5 m was investigated. Both cadmium surface adsorption and transport into the cells were lower in solutions containing cadmium chloride complexes (CdCl+, CdCl2, CdCl3-) than in those containing cadmium in the form of Cd2+. Also, cadmium toxicity in solutions of higher KCl concentrations, in which CdCl+ and CdCl2 forms predominated, was significantly limited.     

Response of the Plastic Lake catchment, Ontario, to reduced sulphur deposition

As a consequence of decreases in the emission rate of sulphur in eastern North America in the late 1970s and early 1980s, sulphate deposition in central Ontario declined by about 40%, but has remained constant for about six years. Plastic Lake, a small, dilute lake on the Precambrian shield that the authors have studied since 1979, acidified between the start of the study and about 1986, but since then has not changed. The authors also monitored the chemistry of streamwater draining the Plastic Lake catchment. Water quality of runoff from an upland site improved rapidly (pH and alkalinity increased, SO4(2-) and Al decreased), but two factors offset these improvements. A small wetland area downstream reversed most of these changes, resulting in a constant output of strong acid from the catchment. In addition, in extremely dry years (1983, 1987, 1989) there were very high concentrations of SO4(2-) in the streamwater, suggesting substantial re-oxidation of reduced S in the catchment.     

The impact of refugees on the health status and health services of host communities: Compounding bad with worse?

Although there have been a number of recent developments in our understanding of refugee health problems that have influenced policies and action, the effects of refugees on the health status and services of host communities remain relatively neglected. This article sets out to explain why this is an important issue with implications for policy, planning surveillance and evaluation, training and research.
The first sections outline some of the problems facing host governments and communities in Africa and discuss the changing rhetoric between the first and second International Conferences for Assistance to Refugees in Africa. A number of possible ways in which refugees could affect the individual, agent and environmental causes of disease are considered, as are the characteristics of the refugees, the host communities and the response which may all modify this impact.
Policy implications of the impact of the refugees, both negative and positive, are discussed, and detailed consideration is given to the pros and cons of integrated and parallel approaches to health care provision. The need to monitor carefully the health status and services of host communities is emphasized and recommendations are made for this and other essential developments relating to training and research.     

Training refugees as primary health care workers: Past imperfect, future conditional

Many problems have been encountered in the planning and implementation of health care in refugee camps, and more specifically in the training of refugees as primary health care workers. A review of the published literature and a "survey" of the opinions and experiences of refugee, national and international health personnel regarding training has therefore been undertaken to provide an overview of what has been done and to make recommendations for future work.
The review highlights the need to reallocate resources away from high visibility emergency aid to development activities, such as training, that will create an infrastructure for primary health care and promote self-reliance.