Batch autotrophic ammonia oxidation tracked through oxygen uptake measurements displays a preliminary acceleration phase. Failure to recognize the acceleration phase and fitting batch ammonia oxidation profiles with standard Monod-type mathematical models can result in meaningless kinetic parameter estimates. The objectives of this study were to examine the factors controlling the acceleration ...

BACKGROUND Soil/dust ingestion rates are important variables in assessing children's health risks in contaminated environments. Current estimates are based largely on soil tracer methodology, which is limited by analytical uncertainty, small sample size, and short study duration. OBJECTIVES The objective was to estimate site-specific soil/dust ingestion rates through reevaluation of the lead ...

Mercury (Hg) is a global environmental pollutant that has been the cause of many public concerns. One particular concern about Hg in aquatic systems is its trophic transfer and biomagnification in food chains. For example, the Hg concentration increases with the increase of food chain level. Fish at the top of food chain can accumulate high concentrations of Hg (especially the toxic form, methy...

The body concentrations of Ag in a top marine predator, the whelk Thais clavigera, varied significantly (1.10 to 4.67 μg g–1 dry wt) in individuals collected from 3 intertidal rocky shores in Hong Kong, whereas there was no significant difference in Ag concentrations in species from lower trophic levels (macroalgae Ulva sp. and rocky oyster Saccostrea cucullata). We compared the variation in Ag...

A dynamic model that links biokinetics and consumer-resource dynamics for describing zinc (Zn) accumulation in abalone Haliotis diversicolor supertexta has been developed and then applied to Zn data from real abalone farms. The biokinetic parameters used in this study, uptake and depuration rate constants of abalone and their food source, red alga Gracilaria tenuistipitata var. liui, were obtai...

Although considerable progress has been made in recent years in reducing human exposures to lead, the potential for high intake of this contaminant still exists in millions of homes and in many occupational settings. Moreover, there is growing evidence that levels of lead intake considered inconsequential just a few years ago can result in subtle, adverse health effects, particularly in childre...

The paper reports recent observations among Czech uranium miners. The study includes two groups of underground miners exposed in periods 1948-63 and 1968-88. A total of 9960 workers have been followed to the end of 1999 representing 267 thousands person-years. By the end of 1999, a total of 29 cases of leukaemia were observed. The standardized mortality ratio is 1.31, 90%CI: 0.88-1.88. In relat...

Random coe cient regression models have been applied in di erent elds and they constitute a unifying setup for many statistical problems. The nonparametric study of this model started with Beran and Hall (1992) and it has become a fruitful framework. In this paper we propose and study statistics for testing a basic hypothesis concerning this model: the constancy of coe cients. The asymptotic be...