Growth and nutrient uptake of green alga, Scenedesmus dimorphus, under a wide range of nitrogen/phosphorus ratio—I. Experimental study

In order to elucidate the relation between algal growth and nutrients such as nitrogen and phosphorus, a chemostat culture experiment using Scenedesmus dimorphus was performed under the conditions of T-N/T-P ratio of 2–50 mg N mg⁻¹ P and dilution rate of 1–4 day⁻¹. It was ensured from the results that nitrogen and/or phosphorus is the limiting nutrient for the growth of this alga under these conditions. The optimum T-N/T-P ratio for its growth was observed to change from 20 to 5 mg N mg⁻¹ P as the dilution rate varied from 1 to 4 day⁻¹ and, in most of the range of T-N/T-P ratio and dilution rate, its growth rate was not regulated by only one of the available nitrogen and phosphorus concentrations in the medium and algal nitrogen and phosphorus contents. Based on these facts, the multiplicative effect rather than the threshold effect of these two nutrients on its growth was considered to exist. It has been suggested, however, that algal nitrogen and phosphorus contents, especially nitrogen content, are the most important factors regulating its growth. Nitrogen uptake rate of this alga increased at a given concentration of available nitrogen in the medium as T-N/T-P ratio decreased down to 2 or 5 mg N mg⁻¹ P. It is also suggested that a multiplicative effect of nitrogen and phosphorus on uptake of these nutrients by S. dimorphus may exist.     

Fecal bacteria and sex hormones in soil and runoff from cropped watersheds amended with poultry litter

The application of poultry litter to agricultural fields can provide plant nutrients for crops and forage production, but fecal bacteria and the sex hormones estradiol and testosterone are components of litter that can be detrimental to the environment. Our objective was to determine if applications of poultry litter to small watersheds would contribute to the load of fecal bacteria and sex hormones to soil and runoff. We, therefore, investigated the fate and transport of fecal bacteria, estradiol and testosterone from surface applied poultry litter to four small cropped watersheds. Poultry litter was applied to meet the nitrogen requirements of pearl millet (Pennisetum glaucum L.) in 2000 and grain sorghum [Sorghum bicolor (L.) Moench] in 2001. Neither Salmonella nor Campylobacter were detected in the litter but the fecal indicator bacteria were. The average load of total coliforms, Escherichia coli, and fecal enterococci applied with the litter was 12.2, 11.9, and 12.7 log(10) cells ha(-1), respectively. The average load of estradiol and testosterone was 3.1 and 0.09 mg ha(-1), respectively. Runoff events first occurred 7 months after the first litter application in 2000, and 3 weeks after the second application in 2001. Only for the 25 July 2001 runoff event 3 weeks after the second litter application were the concentrations of total coliforms, E. coli, and fecal enterococci in runoff greater than background concentrations which were on average 5.2, 2.9, and 1.1 log(10) MPN 100 ml(-1), respectively. Average background levels of total coliforms, fecal enterococci, and E. coli in surface soil were 8.2, 7.9, and 3.5 log(10) cells kg(-1) soil. At the rate of litter application the concentrations of estradiol and testosterone in the litter did not appear to impact the background levels in the soil and runoff. Because concentrations of sex hormones in litter from other broiler operations are known to be greater than in the litter we applied, further study on the connection between concentrations of sex hormones in poultry litter and operational practices is recommended.     

Limit analysis solutions for the bearing capacity of rock masses using the generalised Hoek–Brown criterion

This paper applies numerical limit analyses to evaluate the ultimate bearing capacity of a surface footing resting on a rock mass whose strength can be described by the generalised Hoek–Brown failure criterion [Hoek E, Carranza-Torres C, Corkum B. Hoek–Brown failure criterion—2002 edition. In: Proceedings of the North American rock mechanics society meeting in Toronto, 2002]. This criterion is applicable to intact rock or heavily jointed rock masses that can be considered homogeneous and isotropic. Rigorous bounds on the ultimate bearing capacity are obtained by employing finite elements in conjunction with the upper and lower bound limit theorems of classical plasticity. Results from the limit theorems are found to bracket the true collapse load to within approximately 2%, and have been presented in the form of bearing capacity factors for a range of material properties. Where possible, a comparison is made between existing numerical analyses, empirical and semi-empirical solutions.     

The spatial and temporal variations in PM10 mass from six UK homes

People spend the majority of their time indoors mostly in the domestic environment, where their health may be effected by significant airborne particulate pollution. The indoor/outdoor air quality at six homes in Wales and Cornwall was investigated, based on different locations (urban, suburban, rural) and household characteristics (smokers, non-smokers). The spatial and temporal variations in PM10 mass were monitored for a calendar year, including ambient weather conditions. The activities of individuals within a household were also recorded. Monitoring of PM10 took place inside (kitchen, living room, bedroom) homes, along with concomitant collections outdoors. Samples were subjected to gravimetric analysis to determine PM10 concentrations and examined by scanning electron microscopy to identify the types of particles present on the filters. The results of the study show there are greater masses of PM10 indoors, and that the composition of the indoor PM10 is controlled by outdoor sources, and to a lesser extent by indoor anthropogenic activities, except in the presence of tobacco smokers. The indoor and outdoor PM10 collected was characterised as being a heterogeneous mixture of particles (soot, fibres, sea salt, smelter, gypsum, pollen and fungal spores).     

Dynamic analysis of partially prismatic thin-walled structures

A mixed-mode method is investigated for the dynamic analysis of partially prismatic structures, such as box girders with intermediate diaphragms and supports, or with variable-depth webs. Thus the prismatic ‘main structure’ is discretised by finite strips, and the non-prismatic ‘sub-structure’ by finite elements. After dynamic reduction of the finite element degrees of freedom, advantage may be taken of the finite strip harmonic expansions in determining mode shapes. The method is tested by a variety of examples. Thus for structures with transverse substructures (e.g. diaphragms), the method is shown to be successful, being up to an order of magnitude faster than finite elements. However, for structures with longitudinal substructures (e.g. variable-depth webs) the method is shown to be unreliable. This is because for such structures, approximations in the dynamic reduction procedure are found to be significant.     

Photocatalytic oxidation of DBP precursors using UV with suspended and fixed TiO2

French River water (Nova Scotia, Canada) was separated into six different natural organic matter (NOM) fractions, including hydrophobic acids, bases and neutrals and hydrophilic acids, bases and neutrals. The raw water, as well as each of the NOM fractions were analysed for disinfection by-product (DBP) formation potential before and after advanced oxidation with UV/TiO₂ to determine the efficacy of this treatment for the removal of DBP precursors. The UV/TiO₂ treatment was carried out with a nanostructured thin film (NSTF), coated with TiO₂ which is compared with the use of a TiO₂ suspension. For the raw river water, removals of total trihalomethane formation potential (TTHMFP) and total haloacetic acid formation potential (THAA₉FP) were found to be approximately 20% and 90%, respectively, with 50 mJ/cm² UV exposure and 1 mg/L TiO₂. For the fractionated samples, approximately 75% of both trihalomethane (THM) and haloacetic acid (HAA) precursors were found to be associated with the hydrophobic acid fraction. For this individual fraction the same UV/TiO₂ treatments exhibited approximately 20-25% removal of both TTHMFP and THAA₉FP, suggesting that the fractionation process may have affected the treatability of HAA precursors or may have altered the results of the oxidation processes.     

Kinetics of microbial nitrification: nitrite-nitrogen oxidation

The kinetics of nitrite-nitrogen oxidation by enriched Nitrobacter cultures were examined under various temperatures (9°–35°C), pH (6.0–8.5), and microbial concentrations. For the substrate concentrations examined (100–1100 mg N1⁻¹) the reaction was zero order and correlations between temperature, pH, microbial concentrations and reaction rates were formulated. Inhibition by free ammonia and nitrous acid is discussed. This study of enriched cultures of nitrobacter organisms also provide some insight into the growth characteristics of this fastideous organism under conditions of dense population and severe environmental conditions (temperature and pH).     

The fate of fenitrothion in a stream environment and its effect on the fauna,following aerial spraying of a Scottish forest

In order to control an infestation of Pine Beauty moth (Panolis flammea Schiff.) fenitrothion was applied at a rate of 300 g ha^?1 to a forest plantation consisting primarily of Lodgepole Pine (Pinus contorta Loud.) and Sitka Spruce (Picea sitchensis Carriere) using the ultra-low volume spraying technique. The concentration of fenitrothion in the forest stream rose to a maximum of 18μgl^?1 within the treated area an hour after spraying, but fell to 0.5 μgl^?1 after 24 hs. There was no evidence that the resident fish population was disturbed by the treatment and no short term effects were noticeable in caged fish. The concentration—time profile in the fish followed closely the profile in the water, and in each of the four fish tissues studied fell to 0.02 mg kg^?1 after 24 hs. Invertebrate drift increased markedly 12–16 hs after spraying, but decreased to around pretreatment levels within 48 hs. Caged insects remained alive during the five-day post-spray observation period, suggesting that drifting insects were displaced rather than killed by the insecticide. Concentration of fenitrothion in Willow Moss (Fontinalis antipyretica) fell from 0.139 mg kg^?1 to 0.003 mg kg^?1 (wet weight) after 48 hs. Fenitrothion was not detected in sediment but his was possibly due to the low surface area/weight ratio of the particles.     

Mercury and methylmercury concentrations in high altitude lakes and fish (Arctic charr) from the French Alps related to watershed characteristics

Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220 mm, a standardized age of 5 years or for individualuals did not exceed the 0.5 mg kg^− 1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes.     

Atmospheric pollution for trace elements in the remote high-altitude atmosphere in central Asia as recorded in snow from Mt. Qomolangma (Everest) of the Himalayas

A series of 42 snow samples covering over a one-year period from the fall of 2004 to the summer of 2005 were collected from a 2.1-m snow pit at a high-altitude site on the northeastern slope of Mt. Everest. These samples were analyzed for Al, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Cd, Sb, Pb, and Bi in order to characterize the relative contributions from anthropogenic and natural sources to the fallout of these elements in central Himalayas. Our data were also considered in the context of monsoon versus non-monsoon seasons. The mean concentrations of the majority of the elements were determined to be at the pg g(-1) level with a strong variation in concentration with snow depth. While the mean concentrations of most of the elements were significantly higher during the non-monsoon season than during the monsoon season, considerable variability in the trace element inputs to the snow was observed during both periods. Cu, Zn, As, Cd, Sb, and Bi displayed high crustal enrichment factors (EF(c)) in most samples, while Cr, Ni, Rb, and Pb show high EF(c) values in some of the samples. Our data indicate that anthropogenic inputs are potentially important for these elements in the remote high-altitude atmosphere in the central Himalayas. The relationship between the EF(c) of each element and the Al concentration indicates that a dominant input of anthropogenic trace elements occurs during both the monsoon and non-monsoon seasons, when crustal contribution is relatively minor. Finally, a comparison of the trace element fallout fluxes calculated in our samples with those recently obtained at Mont Blanc, Greenland, and Antarctica provides direct evidence for a geographical gradient of the atmospheric pollution with trace elements on a global scale.