Generation of internal waves by sheared turbulence: experiments

A series of experiments is presented that model the generation of internal gravity waves in the ocean by the forcing of turbulent eddies in the surface mixed layer.The experimental setup consists of a shallow mixed upper layer and a deep continuously stratified lower layer. A source of turbulence is dragged through the upper layer. Internal waves can freely propagate in the lower layer. The internal waves are measured using synthetic schlieren to determine the frequencies of the generated waves. Consistent with other studies, it is found that the characteristic frequencies of internal waves generated by turbulence are an approximate constant fraction of the buoyancy frequency.     

Trampling Impacts on Thermotolerant Vegetation of Geothermal Areas in New Zealand

Geothermal features such as geysers, mud pools, sinter terraces, fumaroles, hot springs, and steaming ground are natural attractions often visited by tourists. Visitation rates for such areas in the Taupo Volcanic Zone of New Zealand are in the order of hundreds of thousands annually. These areas are also habitat for rare and specialized plant and microbial communities that live in the steam-heated soils of unusual chemical composition. We evaluated historical and current trampling impacts of tourists on the thermotolerant vegetation of the Waimangu and Waiotapu geothermal areas near Rotorua, and compared the results to experimental trampling at a third site (Taheke) not used by tourists. Historical tourism has removed vegetation and soil from around key features, and remaining subsoil is compacted into an impervious pavement on which vegetation recolonization is unlikely in the short term. Social tracks made by tourists were present at both tourist sites often leading them onto hotter soils than constructed tracks. Vegetation height and cover were lower on and adjacent to social tracks than further from them. Thermotolerant vegetation showed extremely low resistance to experimental trampling. This confirms and extends previous research that also shows that thallophytes and woody shrubs, life forms that dominate in thermotolerant vegetation, are vulnerable to trampling damage. Preservation of these vulnerable ecosystems must ensure that tourist traffic is confined to existing tracks or boardwalks, and active restoration of impacted sites may be warranted.     

Monitoring the fate of chlorine from MSW sampling through combustion Part II: Combustion studies

Combustion measurements were carried out in a multi-kilogram capacity flow calorimeter on cellulose and cellulose/sand samples in 100% oxygen and several oxygen/nitrogen mixtures. Some measurements were made on cellulose/sand samples, which had 1 mass % of polyvinylchloride (PVC) as part of their composition, to study the conditions related to the formation/destruction of chlorinated organic compounds as combustion products. Qualitative identifications of a significant variety of chlorinated organic compounds have been made.     

The backward incidence of pollution control: A dual approach

The backward incidence of pollution control is reexamined using the techniques of duality theory. The simple geometry used establishes the results and clarifies them without the complicated mathematical manipulations required in earlier works, thereby making the material more attractive for classroom presentation.     

A team approach to implementing MACT standards

The requirements of the MACT Standards for Emissions from Leaking Equipment and the requirements of the amended Clean Air Act will change how environmental control programs are administered within plants. No longer will the programs be the responsibility solely of the separate environmental function. The programs will need to be administered via a team of personnel that involves maintenance, computer systems, environmental, emissions measurement specialists, and planning personnel as well as management. Compliance with the rules will be based on an inspection of paper records and computer databases. The enforcement penalties will not be trivial. The ability of the plant to grow and be modified will need to be balanced against the potential benefits from early reduction programs, which will allow for delayed implementation of some programs.     

Comparison of biomass production and biological nitrogen fixation of multi-species pastures (mixed herb leys) with perennial ryegrass-white clover pasture with and without irrigation in Canterbury, New Zealand

Legume-based pastures in Australasia are predominantly perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). These pastures have disadvantages such as limitations in the production and persistence of white clover and ryegrass in drought prone regions. With the increasing interest in organic agriculture, more complex pasture mixtures are seen as an alternative to the standard ryegrass-white clover (RWC) pasture. Although anecdotal evidence exists to support the benefits of alternative pastures, there is insufficient scientific evidence to support or refute these claims. The present study was conducted to compare three different alternative multi-species (mixed herb leys) (MSP) pastures with the standard RWC pasture with and without irrigation, in terms of biomass and biological nitrogen fixation (BNF) over a period of 1 year under field conditions in Canterbury, New Zealand. Isotopic dilution technique involving field ¹⁵N-microplots were used to measure BNF. Irrigation doubled dry matter yields (DMY) of all pastures compared with those under dryland. There was no significant difference between DMY of all pastures under dryland. However, under irrigation, MSP pastures out-yield RWC pasture in total and legume DMY. Red clover MSP produced significantly lower DMY than the comprehensive or lucerne MSP treatment, probably due to the ability of lucerne in extracting water from deeper soil depth. Seasonal changes in plant composition varied according to the species sown, soil moisture status and temperature. Total and seasonal amounts of N₂ fixed followed the same trend as the DMY and were related to the DMY of legumes. On average, about 26–34 kg N was fixed per tonne of legume DMY, showing a uniformity across all pastures. Overall, based on the present results of 1-year study, the MSP pastures tend to result in higher DMY, BNF and legume growth compared with that of the RWC pasture, provided irrigation is available. With increased BNF, these irrigated MSP pastures may provide high quality feed to grazing animals.     

Integrating agricultural and forestry GHG mitigation response into general economy frameworks: Developing a family of response functions

An econometrically estimated family ofresponse functions is developed forcharacterizing potential responses togreenhouse gas mitigation policies by theagriculture and forestry sectors in theU.S. The response functions are estimatedbased on results of anagricultural/forestry sector model. Theyprovide estimates of sequestration andemission reductions in forestry andagriculture along with levels of sectoralproduction, prices, welfare, andenvironmental attributes given a carbonprice, levels of demand for agriculturalgoods, and the energy price. Sixalternative mitigation policiesrepresenting types of greenhouse gasoffsets allowed are considered. Resultsindicate that the largest quantity ofgreenhouse gas offset consistently appearswith the mitigation policy that pays forall opportunities. Restricting carbonpayments (emission tax or sequestrationsubsidy) only to aff/deforestation or onlyto agricultural sequestration substantiallyreduces potential mitigation. Highercarbon prices lead to more sequestration,less emissions, reduced consumer and totalwelfare, improved environmental indicatorsand increased producer welfare.