The influence of atmospheric n deposition on nitrous oxide and nitric oxide fluxes and soil ammonium and nitrate concentrations

The deposition of atmospheric N to soils provides sources of available N to the nitrifying and denitrifying microbial community and subsequently influences the rate of NO and N₂O emissions from soil. We have investigated the influence of three different sources of enhanced N deposition on NO and N₂O emissions 1) elevated NH₃ deposition to woodlands downwind of poultry and pig farms, 2) increased wet cloud and occult N deposition to upland forest and moorland and 3) enhanced N deposition to trees as NO^? ₃ and NH⁺ ₄ aerosol. Flux measurements of NO and N₂O were made using static chambers in the field or intact and repacked soil cores in the laboratory and determination of N₂O by gas chromatography and of NO by chemiluminescence analysis. Rates of N deposition to our study sites were derived from modelled estimates of N deposition, NH₃ concentrations measured by passive diffusion and inference from measurements of the ²¹⁰Pb inventory of soils under tree canopies compared with open grassland. NO and N₂O emissions and KCl-extractable soil NH⁺ ₄ and NO^? ₃ concentrations all increased with increasing N deposition rate. The extent of increase did not appear to be influenced by the chemical form of the N deposited. Systems dominated by dry-deposited NH₃ downwind of intensive livestock farms or wet-deposited NH⁺ ₄and NO^? ₃ in the upland regions of Britain resulted in approximately the same linear response. Emissions of NO and N₂O from these soils increased with both N deposition and KCl extractable NH⁺ ₄, but the relationship between NH⁺ ₄ and N deposition (ln NH⁺ ₄ = 0.62 ln N_deposition+0.21, r ² = 0.33, n = 43) was more robust than the relationship between N deposition and soil NO and N₂O fluxes.     

Correlating the Spatial Distribution of Atmospheric Ammonia with δ15N Values at an Ammonia Release Site

A field ammonia (NH₃) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH₃ or sprayed with NH₄Cl were used to assess the potential for using ¹⁵N values in determining the area of influence around a point NH₃ emission source. ¹⁵N values are being increasingly used as environmental tracers and we tested the hypothesis that the ¹⁵N signal from an NH₃ emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH₃ concentrations were found to decrease with distance from source, with ¹⁵N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of ¹⁵N values of Calluna vulgaris (L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis of Calluna shoots from the NH₃ release showed a similar trend of ¹⁵N enrichment. Significant linear correlations between ¹⁵N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH₃ release site, illustrating the possible use of this technique in N deposition biomonitoring.     

Selenium accumulation in the cockle Anadara trapezia

An extensive study on Se accumulation in a population of Anadara trapezia from a marine lake is reported. The effects of organism mass, gender, reproductive cycle, and season on Se accumulation and tissue distribution were investigated. Analyses showed that gender and reproductive cycle had no significant effect on Se accumulation. A. trapezia showed a strong positive correlation between Se burden and tissue mass. Constant Se concentrations were observed within individual populations but varied spatially with sediment Se concentrations. Se concentrations in tissues decreased from gills > gonad/intestine > mantle > muscle > foot, which remained constant over 12 months, however, significantly lower concentrations were observed in the summer compared to winter. A. trapezia is a good biomonitor for Se, as gender and size do not effect concentration, however, season of collection must be reported if changes in Se bioavailability are to be identified in short term studies, or during intersite comparisons.     

Part 1: The role of waste data in building knowledge: The South African waste information system

An empirical study was undertaken with 31 organisations submitting data to the South African Waste Information System (SAWIS) in order to explore the relationship between data and resultant waste knowledge generated through a process of learning. The results show that of the three constructs of knowledge (experience, data/information, and theory), experience has the greatest influence on building waste knowledge, nearly twice that of data/information and three times that of theory. Together the three constructs account for 54.1% of the variance in knowledge. Respondents from municipalities and private waste organisations reflect two distinct sub-groups in the data set. While the theoretical model remains the same for the two sub-groups, the way in which knowledge is constructed, and the variance in knowledge explained by the model, differs for the two. A mixed methods research design, combining quantitative statistical analysis and rich qualitative data, contributes to a comprehensive interpretation of the role of waste data in building knowledge in South Africa. While waste data has a minor influence on building knowledge, respondents acknowledge that waste data does have a positive impact on the way their organisations manage waste. However, it is not the data, but rather the resultant waste knowledge and raised level of awareness that causes the operational response. Experience is obtained predominantly through learning from others. Respondents in municipalities, emphasised learning from consultants, landfill site contractors, and colleagues in city-twinning programmes, while respondents in private waste companies, emphasised learning from experienced, senior colleagues.     

Air Pollution Control Expenditures in the Chemical Industry

As industry today analyzes its emissions with more sophisticated sampling and testing techniques, it is finding more often that the problems of gaseous and particulate contaminants occur simultaneously. Current legislation is rapidly becoming more stringent and where a particular industry formerly thought it primarily had a single contaminant problem, it now finds itself faced with the necessity to comply with multiple contaminant emission level requirements. Extensive field experience in a wide diversity of industries has shown that the simultaneous removal of both the gaseous and particulate contaminants can be effectively met by crossflow scrubbers utilizing filamentous-type packings. High efficiency collection can be achieved at low operating cost in a single piece of control equipment with reliable operating results.     

Parameterization of a dynamic specific activity model of 14C transfer from surface water-to-humans

Carbon-14 is a particularly interesting radionuclide from the perspective of dose estimation because it mixes readily with stable CO2, and hence enters the food-chain as fundamental biomolecules. A model was developed for the situation of 14C releases to surface waters, where there are distinct changes in the water 14C activity concentrations throughout the year. The model computes the specific activity in water, phytoplankton, fish, crops, meat, milk and air, following a typical irrigation-based food-chain scenario. This paper describes the derivation of the required 14C-specific parameter values. Many of the key parameters are not commonly measured, at least not in the context of dose assessment. Thus, inference from other sources of data was required, and this is the scientific contribution described in this paper. The best estimates and appropriate measures of statistical dispersion are provided. This required consideration of both the temporal and spatial averaging domains to ensure they were correct for parameters as defined in the model. The model coupled with these parameter values represents several new developments for modelling 14C transfers.     

Estimated hourly personal exposures to ambient and nonambient particulate matter among sensitive populations in Seattle, Washington

Epidemiological studies of particulate matter (PM) routinely use concentrations measured with stationary outdoor monitors as surrogates for personal exposure. Despite the frequently reported poor correlations between ambient concentrations and total personal exposure, the epidemiologic associations between ambient concentrations and health effects depend on the correlation between ambient concentrations and personal exposure to ambient-generated PM. This paper separates personal PM exposure into ambient and nonambient components and estimates the outdoor contribution to personal PM exposures with continuous light scattering data collected from 38 subjects in Seattle, WA. Across all subjects, the average exposure encountered indoors at home was lower than in all other microenvironments. Cooking and being at school were associated with elevated levels of exposure. Previously published estimates of particle infiltration (Finf) were combined with time-location data to estimate an ambient contribution fraction (alpha, mean = 0.66+/-0.21) for each subject. The mean alpha was significantly lower for subjects monitored during the heating season (0.55+/-0.16) than for those monitored during the nonheating season (0.80+/-0.17). Our modeled alpha estimates agreed well with those estimated with the sulfur-tracer method (slope = 1.08; R2 = 0.67). We modeled exposure to ambient and nonambient PM with both continuous light scattering and 24-hr gravimetric data and found good agreement between the two methods. On average, ambient particles accounted for 48% of total personal exposure (range = 21-80%). The personal activity exposure was highly influenced by time spent away from monitored microenvironments. The median hourly longitudinal correlation between central site concentrations and personal exposures was 0.30. Although both alpha and the nonambient sources influence the personal-central relationship, the latter seems to dominate. Thus, total personal exposure may be poorly predicted by stationary outdoor monitors, particularly among persons whose PM exposure is dominated by nonambient exposures, for example, those living in tightly sealed homes, those who cook, and children.     

Effects of acid mist on mature grafts of Sitka spruce. Part I. Frost hardiness and foliar nutrient concentrations

Mature grafts of five clones of Sitka spruce (Picea sitchensis Bong. Sarg.) were exposed to simulated acid mist composed of an equimolar mixture of sulphuric acid and ammonium nitrate at pH 2.5 and pH 5.0 in open-top chambers from May to November 1991. Treatments were applied on consecutive days, four times a week. The pH 2.5 treatment provided an overall dose three times higher than that received by forests in upland areas of Britain. Frost hardiness was assessed in November by freezing detached current year shoots at a range of temperatures and assessing the rate of electrolyte leakage Foliar nutrient concentrations were determined on the same shoots. Acid mist at pH 2.5 significantly reduced frost hardiness in four of the five clones; the temperature causing 50% shoot death (LT50) was increased by 0 to 7 degrees C. The clones varied in their level of hardiness, one clone being exceptionally frost sensitive. The frost hardiness of the frost sensitive clone was found to be less perturbed by acid mist than the hardiness of the more frost resistant clones. Mature grafts showed a smaller reduction in hardiness at an equivalent dose than that found previously with Sitka spruce seedlings. Compared with seedlings, grafts had lower absolute concentrations of foliar sulphur. Exposure to acid mist at pH 2.5 increased %S in current year foliage by <0.05% compared with absolute increases of more than 0.10% in current year foliage of seedlings. We conclude that the effect of acid mist on frost hardiness is likely to be less on mature trees than on seedlings and that the increased frost risk to mature trees of Sitka spruce from occult deposition alone is small.     

Hierarchical dominance structure in reintroduced California condors: correlates, consequences, and dynamics

Populations of reintroduced California condors (Gymnogyps californianus) develop complex social structures and dynamics to maintain stable group cohesion, and birds that do not successfully integrate into group hierarchies have highly impaired survivability. Consequently, improved understanding of condor socioecology is needed to inform conservation management strategies. We report on the dominance structure of free-ranging condors and identify the causes and consequences of rank in condor populations by matching social status with the behavioral and physical correlates of individual birds. We characterized the hierarchical social structure of wild condor populations as mildly linear, despotic, and dynamic. Condor social groups were not egalitarian and dominance hierarchies regulated competitive access to food resources. Absence of kin-based social groups also indicated that condor social structure is individualistic. Agonistic interactions among condors were strongly unidirectional, but the overall linearity and steepness of their hierarchies was low. Although one aggressive male maintained the highest dominance rank across the 3-year observation period, there was considerable fluidity in social status among condors within middle and lower rank orders. Older condors were more dominant than younger birds and younger males supplanted older females over time to achieve higher status. Dominance rank did not predict the amount of time that a bird spent feeding at a carcass or the frequency that a bird was interrupted while feeding. Thus, younger, less dominant birds are able to obtain sufficient nutrition in wild social populations.