Sensitivity of benthic community respiration and primary production to changes in temperature and light

In-situ measurements of benthic community respiration and primary production on an intertidal sandflat in Nova Scotia, Canada were used to test the hypothesis that community responses to light and temperature were similar within and between seasons. Multiple regression indicated that mean incubation temperature explained 57% of the variance in total sediment oxygen demand (TOD). The logarithmic relationship between TOD and temperature (Q₁₀=6.5) was not significantly different between fall and spring, suggesting no acclimation within season. Chemical oxygen demand measured in formalin-poisoned cores averaged 30% of TOD. Microalgal gross primary production (GROSS) was measured as oxygen production in light cores. Mean incubation temperature and sediment chlorophylla explained 56% of the variance. The linear relationship between GROSS and temperature had Q₁₀=2.0. When production was normalized to chlorophylla [GROSS(SP)], seasonal production-temperature curves were significantly different. The spring curve had Q₁₀=3.3; in the fall, production and temperature were not related. GROSS(SP)-light curves derived from Plexiglas shade experiments in the field were linear and not significantly different between fall and spring. Temperature alone was a better predictor of GROSS(SP) than light, even when P/I curves were adjusted for temperature. One can therefore model community respiration and photosynthesis at this site using daily averages in temperature, which are then summed over longer time scales to estimate monthly or seasonal rates.     

Insecticidal and growth-reducing activity of foliar extracts from Meliaceae

Summary Thirty-one species in twenty genera of the plant family Meliaceae were assayed for the production of growth-inhibiting phytochemicals, using the generalist herbivorePeridroma saucia. Most species were inhibitory when methanolic extracts were incorporated into artificial diets at concentrations at or below those occurring naturally. In general members of the subfamily Melioideae were more inhibitory than members of the Swietenioideae. Extracts of deciduous species with short leaf lifetimes were significantly more inhibitory than those of evergreen species with longer leaf lifetimes. In a smaller sample of species, evergreen species showed a trend towards having tougher leaves than deciduous species. These results support the resource availability hypothesis of Coleyet al. (1985), and suggest that life history attributes may be of some value in selecting plants for phytochemical prospecting.     

Aggressiveness and foraging mode of young-of-the-year brook charr,Salvelinus fontinalis (Pisces,Salmonidae)

Summary Young-of-the-year brook charr in streams use either an active or a sit-and-wait foraging tactic and exhibit a range of resource defense from territoriality to tolerating conspecifics. We use simple graphical models, based on encounter rate with drift and the theory of economic defendability, to predict qualitative changes in the aggressiveness and mobility of brook charr in relation to current velocity. Aggressiveness (percent of conspecifics eliciting an overt response) initially increases with increasing current velocity, as does drift rate and foraging rate. However, aggressiveness decreases at high current velocities, probably because of increased costs of defense at these velocities. In standing water areas, brook charr use primarily an active foraging tactic, but mobility (percent time spent moving) decreases rapidly as current velocity increases. These results are generally consistent with the simple graphical models. A literature survey suggests that the models can be generalized for most species of stream salmonids.     

Cluster detection using Bayes factors from overparameterized cluster models

In this paper, we consider the use of a partition model to estimate regional disease rates and to detect spatial clusters. Formal inference regarding the number of partitions (or clusters) can be obtained with a reversible jump Markov chain Monte Carlo algorithm. As an alternative, we consider the ability of models with a fixed, but overly large, number of partitions to estimate regional disease rates and to provide informal inferences about the number and locations of clusters using local Bayes factors. We illustrate and compare these two approaches using data on leukemia incidence in upstate New York and data on breast cancer incidence in Wisconsin.     

Removal of NOM from drinking water: Fenton's and photo-Fenton's processes

The control of disinfection by-products during water treatment is primarily undertaken by reducing the levels of precursor species prior to chlorination. As many waters contain natural organic matter at levels of up to 15 mgl(-1) there is a need for a range of control methods to support conventional coagulation. Two such processes are the Fenton and photo-Fenton's processes and in this paper they are assessed for their potential to remove NOM from organic rich waters. The performance of both processes is shown to be depentent on pH, Fe: H2O2 ratio as well as Fe2+ dose. Under optimum conditions both processes achieved greater than 90% removal of DOC and UV254 absorbance. This removal lead to the trihalomethane formation potential of the water being reduced from 140 to below 10 microgl(-1), well below UK and US standards.     

The joint action of sulphur dioxide and hydrogen fluoride on the yield and quality of wheat and barley

The effects of joint action of SO(2) and HF on the yield and quality of wheat and barley were studied by exposing them to combinations of <13,130 or 267 microg m(-3) SO(2) and 0.03 or 0.38 microg m(-3) HF in open top chambers for 90 days. At the concentrations used, SO(2) had greater effects than HF. All responses were marked by compensatory changes. The treatments had no effect on wheat yield, although SO(2) reduced shoot weight. SO(2) increased the growth and yield of barley, and HF or SO(2) increased the grain protein concentration of barley and wheat. The effects of mixtures of SO(2) and HF were complex, but often antagonistic, as the addition of HF counteracted the effect of SO(2) alone.     

Optical remote measurement of toxic gases.

Enactment of the Clean Air Act Amendments (CAAA) of 1990 has resulted in increased ambient air monitoring needs for industry, some of which may be met efficiently using open-path optical remote sensing techniques. These techniques include Fourier transform spectroscopy, differential optical absorption spectroscopy, laser long-path absorption, differential absorption lidar, and gas cell correlation spectroscopy. With this regulatory impetus, it is an opportune time to consider applying these technologies to the remote and/or path-averaged measurement and monitoring of toxic gases covered by the CAAA. This article reviews the optical remote sensing technology and literature for that application.     

Assessment of human exposure to ambient particulate matter

Recent epidemiological studies have consistently shown that the acute mortality effects of high concentrations of ambient particulate matter (PM), documented in historic air pollution episodes, may also be occurring at the low to moderate concentrations of ambient PM found in modern urban areas. In London in December 1952, the unexpected deaths due to PM exposure could be identified and counted as integers by the coroners. In modern times, the PM-related deaths cannot be as readily identified, and they can only be inferred as fractional average daily increases in mortality rates using sophisticated statistical filtering and analyses of the air quality and mortality data. The causality of the relationship between exposure to ambient PM and acute mortality at these lower modern PM concentrations has been questioned because of a perception that there is little significant correlation in time between the ambient PM concentrations and measured personal exposure to PM from all sources (ambient PM plus indoor-generated PM). This article shows that the critical factor supporting the plausibility of a linear PM mortality relationship is the expected high correlation in time of people's exposure to PM of ambient origin with measured ambient PM concentrations, as used in the epidemiological time series studies. The presence of indoor and personal sources of PM masks this underlying relationship, leading to confusion in the scientific literature about the strong underlying temporal relationship between personal exposure to PM of ambient origin and ambient PM concentration. The authors show that the sources of PM of non-ambient origin operate independently of the ambient PM concentrations, so that the mortality effect of non-ambient PM, if any, must be independent of the effects of the ambient PM exposures.     

Reduction of silver solubility by humic acid and thiol ligands during acanthite (beta-Ag2S) dissolution

Precipitation of highly insoluble metal sulfide minerals like acanthite (beta-Ag2S) or red cinnabar (HgS) is in principle an effective means to reduce metal availability and toxicity in contaminated soils. Unfortunately, experiments have shown that red cinnabar may be solubilized in the presence of dissolved organic matter or thiol ligands. To determine whether the same applies to acanthite, a laboratory synthesized beta-Ag2S mineral was incubated for up to 3 weeks in the presence of KNO3, dissolved humic acids, cysteine, methionine and thiosulfate. XPS analysis identified Ag2O (52%), Ag2SO4 (8%) and Ag2S (40%) on the particle surfaces. Ag was released into solution in the presence of KNO3 and methionine, presumably from mixed-oxidation surface layers. Contrary to earlier results with cinnabar, however, humic acids reduced Ag concentrations in solution by about 75%, and cysteine and thiosulfate, each containing a free -SH functional group, almost completely suppressed Ag release into solution.