Use of kriging models to predict 12-hour mean ozone concentrations in Metropolitan Toronto-A pilot study

Ozone concentrations exhibit spatial variability within metropolitan areas, resulting in significantly different personal exposures among individuals. This paper uses the statistical technique, kriging, to explore the 12-h daytime (8am–8pm) ozone spatial variation and to predict mean outdoor ozone levels at home sites within the Toronto metropolitan area. Outdoor ozone measurements taken in the Toronto metropolitan area between June and August 1992 are used in kriging models to predict outdoor ozone concentrations. The performance of the model is evaluated by comparing actual home outdoor measurements with predicted values. Results indicate that kriging predictions are more accurate than using only the closest stationary ambient site measurements for determining home outdoor ozone concentrations within the metropolitan area. The average variogram obtained from pooling data throughout the entire sampling period shows a clear spatial trend in the outdoor ozone variation. Kriging predictions using the parameters from the average variogram perform as well as those using variograms from individual days. An approach for minimizing sample bias can be used to increase the accuracy of the predictions; cross-validation suggests that it is a reasonable procedure.     

Residential mobility and personal well-being

This research examines the relationship between personal mobility rate (number of lifetime moves/respondent's age) and health status. A contextual analysis is proposed in which the health consequences of relocation depend not only on the immediate circumstances surrounding a move, but also on the broader context of the individual's residential history, current life situation, and aspirations for the future. Two hundred and forty-two adult employees completed an initial survey of lifetime residential history, current residential desirability, employment experience, and perceived housing options for the future. Three months later, a panel group of 121 respondents completed a follow-up survey of emotional and physical well-being. Frequent relocation was directly associated with a greater number of illness-related symptoms, but the impact of mobility rate was largely mediated by psychological factors. Health problems were more prevalent among high-mobility individuals characterized by low rather than high levels of environmental exploratory tendency; among low-mobility persons reporting low versus high levels of residential choice and congruence; and among low residential-quality individuals who perceived future residential options to be unavailable rather than available.     

Employability of environmental science graduates in Australia

Since the 1970s, there has been a global proliferation of environmental courses. The types of courses are described, as are the structures, philosophies and objectives of courses which have stood the test of time. Employment of environmental graduates is discussed. The degree in Australian Environmental Studies (AES) from Griffith University is described and discussed with reference to pitfalls described in the literature. In Australia, there has been an increased demand for graduates in the environmental area. The trend in employers has been widening the field of potential recruits by keeping the degree specification broad and using the duty statements in the advertisements to specify the environmental skills and knowledge required. The number of graduates from AES has increased steadily since the course was established, and despite global and national trends of proliferation of environmental courses and graduates, survey results indicated that graduates from AES are professionally employed in a wide range of employment sectors, with female and male graduates being equally successful in obtaining employment.     

Malnutrition and anaemia among Somali refugee children in long term camps

In a long term Somali refugee camp where nutritional and general health status of children is now considered satisfactory and stable, a randomized community based survey of 300 children under five years was undertaken. Results indicate that the prevalence of protein-energy malnutrition is rising again: 17.3% of children are <80% median weight/height and 1.7% are <70%median weight/height. In addition, there is a high prevalence of anaemia: 50.5% have a haemoglobin level <9g% and 10.8%≤6g%. This cannot be explained by chronic malaria as the spleen rate is only 2%. Stool examination of 161 children show 29.8% to have evidence of Giardia Lamblia infection but this is not statistically correlated with either anaemia or with protein-energy malnutrition. Other potentially pathogenic parasites are uncommon and no hookworm is seen. Examination of blood films of anaemic children shows hypochromia as a striking feature.
It is concluded that nutritional deficiencies are a likely major factor in the aetiology of the anaemia. Both protein-energy malnutrition and anaemia seem related to the weaning period. Food rations for refugees, although adequate for short term needs, may be qualitatively deficient for long term subsistence, especially as regards young children.     

Tree cover in sub-Saharan Africa: rainfall and fire constrain forest and savanna as alternative stable states

Savannas are known as ecosystems with tree cover below climate-defined equilibrium values. However, a predictive framework for understanding constraints on tree cover is lacking. We present (a) a spatially extensive analysis of tree cover and fire distribution in sub-Saharan Africa, and (b) a model, based on empirical results, demonstrating that savanna and forest may be alternative stable states in parts of Africa, with implications for understanding savanna distributions. Tree cover does not increase continuously with rainfall, but rather is constrained to low (<50%, "savanna") or high tree cover (>75%, "forest"). Intermediate tree cover rarely occurs. Fire, which prevents trees from establishing, differentiates high and low tree cover, especially in areas with rainfall between 1000 mm and 2000 mm. Fire is less important at low rainfall (<1000 mm), where rainfall limits tree cover, and at high rainfall (>2000 mm), where fire is rare. This pattern suggests that complex interactions between climate and disturbance produce emergent alternative states in tree cover. The relationship between tree cover and fire was incorporated into a dynamic model including grass, savanna tree saplings, and savanna trees. Only recruitment from sapling to adult tree varied depending on the amount of grass in the system. Based on our empirical analysis and previous work, fires spread only at tree cover of 40% or less, producing a sigmoidal fire probability distribution as a function of grass cover and therefore a sigmoidal sapling to tree recruitment function. This model demonstrates that, given relatively conservative and empirically supported assumptions about the establishment of trees in savannas, alternative stable states for the same set of environmental conditions (i.e., model parameters) are possible via a fire feedback mechanism. Integrating alternative stable state dynamics into models of biome distributions could improve our ability to predict changes in biome distributions and in carbon storage under climate and global change scenarios.     

Book reviews

Making Cities Work: the role of local government in the urban environment. Richard Gilbert, Don Stevenson, Herbert Girardet &; Richard Stren, 1996, London, Earthscan, 203pp. ISBN 1 85383 354 1, £13.95 pbk

Environmental Policy in an International Context, Vols 1–3: Perspectives, Conflicts and Prospects. P. Glasbergen &; A. Blowers (Series Eds) London, Arnold

Rhetoric and Reality in Environmental Policy. M. Wintle &; R. Reeve (Eds), 1994, Aldershot, Avebury Studies in Green Research, 154 pp. ISBN 1 85628 927 3

FutureNatural: Nature, Science, Culture. G. Roberston et al. (Eds) 1996, London, Routledge, ISBN 0415 070139, £40.00 hbk

Environmental Policy with Political Integration: the European Union and the United States. New horizons in environmental economics. John B. Braden, Henk Folmer &; Thomas S. Ulen (Eds), 1996, Cheltenham, Elgar Publishing, 477 pp. ISBN 1 85898 217 0     

Arbuscular mycorrhizal fungi can alleviate the adverse effects of chlorothalonil on Oryza sativa L

A glasshouse pot experiment was conducted to investigate the effect of the fungicide chlorothalonil on the growth of upland rice, in the absence or presence of the arbuscular mycorrhizal fungus (AMF) Glomus mosseae (NM and GM treatments). The plants were grown with three concentrations of chlorothalonil (0, 50 and 100 mg kg(-1) soil). Mycorrhizal colonization decreased significantly with increasing chlorothalonil concentrations. Plant biomass decreases were smaller in GM plants than in non-mycorrhizal (NM) plants. Mycorrhizal dependency was the highest with 50 mg kg(-1) chlorothalonil. Chlorothalonil affected physiological processes in upland rice irrespective of inoculation. Chlorothalonil at 50 and 100 mg kg(-1) increased ascorbate peroxidase (APX) activity and soluble protein concentrations in shoots and roots of NM upland rice. However, values of APX, catalase (CAT) and peroxidase (POD) were reduced more in GM plants than in NM plants. These results showed that chlorothalonil induced oxidative stress in upland rice and it is needed to evaluate the side effects of chlorothalonil on rice and AMF.