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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

How does hydropeaking and geological substrate affect aquatic macroinvertebrates in a regulated river? / Hur påverkas akvatiska makroevertebrater av korttidsreglering och geologiskt substrat i ett reglerat vattendrag?

Vernby, Andreas January 2021 (has links)
Hydropower is an important source of renewable energy, but is often a cause of degradation to river ecosystems. Hydropeaking, i.e. the frequent alteration of discharge, is a process involved in hydropower generation and has been proven to affect aquatic organisms negatively. However, it’s unclear exactly what effects hydropeaking has on riverine ecology, in combination with important geomorphological characteristics. In this study, the interaction of hydropeaking and geological substrate (fine or coarse material) on aquatic macroinvertebrates was evaluated, while also assessing the influence of river width and water chemistry. Studies were conducted in 27 sites at rivers, 15 of which were exposed to hydropeaking, in central Sweden during June and August 2020. Sampling of macroinvertebrates was conducted using Hester-Dendy samplers. The following variables were investigated: i) total species richness, ii) species diversity, iii) macroinvertebrate density, iv) EPT (Ephemeroptera, Plecoptera, and Trichoptera) species richness, v) % EPT, vi) EPT/Chironomidae ratio, and vii) % Oligochaeta. The effects of hydropeaking and geological substrate on these variables were assessed using AIC model selection. Results did not indicate interaction effects of hydropeaking and geological substrate on any variable, and this did not concur with stated hypotheses. The results reaffirm the complexity of disentangling the effects that are in play during these processes. Studies of this kind is important in understanding how hydropower affects macroinvertebrates, and provides information on where and how most effective mitigation measures should be applied and provides valuable information for improving hydropower management protocols. / Vattenkraft är en viktig källa till förnybar energi, men är ofta en orsak till försämring av ekosystem hos älvar. Korttidsreglering, dvs. den frekventa förändringen av vattenflöde, är en process som är involverad i vattenkraftsproduktion och har visat sig påverka vattenlevande organismer negativt. Det är dock oklart exakt vilka effekter korttidsreglering har på älvens ekologi, i kombination med viktiga geomorfologiska egenskaper. I denna studie utvärderades interaktionen mellan korttidsreglering och geologiskt substrat (fint eller grovt material) på akvatiska makroevertebrater, samtidigt som påverkan av älvbredd och vattenkemi utvärderades. Studier utfördes på 27 platser lokaliserade vid älvar, av vilka 15 var utsatta för korttidsreglering, i centrala Sverige under juni och augusti 2020. Provtagning av makroevertebrater utfördes med Hester-Dendy-provtagare. Följande responsvariabler undersöktes: i) total artrikedom, ii) artdiversitet, iii) densitet av makroevertebrater, iv) artrikedom av EPT (Ephemeroptera, Plecoptera och Trichoptera), v) % EPT, vi) EPT/Chironomidae-förhållande samt vii) % Oligochaeta. Effekterna av korttidsreglering och geologiskt substrat på dessa variabler bedömdes med hjälp av AIC-modellval. Resultaten indikerade inte interaktionseffekter av korttidsreglering och geologiskt substrat på någon responsvariabel, och detta överensstämde inte med angivna hypoteser. Resultaten bekräftar komplexiteten i att utvärdera de effekter som har en påverkan under dessa processer. Studier av detta slag är viktiga för att förstå hur vattenkraft påverkar makroevertebrater, och ger information om var och hur de mest effektiva åtgärderna bör tillämpas och ger värdefull information för att förbättra hantering av vattenkraft. / Korttidsregleringens påverkan på biologin varierar med vattendragets geomorfologi
32

Biodegradation of Groundwater Pollutants (Chlorinated Hydrocarbons) in Vegetated Wetlands: Role of Aerobic Microbes Naturally Associated with Roots of Common Plants

Powell, Christina Lynn 01 December 2010 (has links)
No description available.
33

Use and Development of Diffusive Samplers to Analyse the Fate of Polycyclic Aromatic Compounds, Polychlorinated Biphenyls and Pharmaceuticals in Wastewater Treatment Processes

Augulyte, Lijana January 2008 (has links)
The efficiency of wastewater treatment systems is commonly measured by the reductions of parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS) and/or reductions in levels of selected macro compounds (e.g. long-chained hydrocarbons and inorganic compounds). Less attention has generally been paid to micropollutants with high potential toxic effects, such as polycyclic aromatic compounds (PACs), including unsubstituted and alkylated polycyclic aromatic hydrocarbons (PAHs) and dibenzothiophenes, polychlorinated biphenyls (PCBs), human pharmaceuticals and by-products formed during the treatment process. These organic micropollutants occur in wastewaters at trace and ultra-trace levels, therefore their detection requires advanced, costly analyses and large sample volumes. Furthermore, concentrations of micropollutants can fluctuate widely both diurnally and between days. Thus, in order to understand the fate of micropollutants in wastewaters there is a need to develop sampling techniques that allow representative samples to be readily collected. In the work underlying this thesis two types of diffusive passive samplers, semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCISs), were used to monitor non-polar and polar organic micropollutants in wastewaters subjected to various treatment processes. The pollutants sequestered in these samplers represent micropollutants in the dissolved phase that are available for aquatic organisms. Further, since they collect pollutants in an integrative manner, i.e. they sample continuously during the selected exposure time (usually approx. one to ca. three weeks), the results provide time-weighted average (TWA) concentrations. In addition, the effects of various environmental factors on the uptake of analyzed micropollutants in POCISs and SPMDs were investigated using laboratory calibration and in situ calibration with performance reference compounds (PRCs). The results confirm that SPMDs are good sampling tools for investigating the efficacy of wastewater treatment processes for removing non-polar PACs and PCBs, and the effects of varying the process settings. In addition, analyses of process streams in municipal sewage treatment plants demonstrated that conventional sewage treatment processes are not optimized for removing dissolved four-ringed PAHs, some of the five-ringed PAHs, and tri- to hexa-chlorinated biphenyls. The removal of bioavailable PACs was enhanced by adding sorbents with high sorption capacities to the sludge used in the activated sludge treatment step, and a biologically activated carbon system was designed that robustly removed bioavailable PACs, with removal efficiencies of 96.9-99.7 percent across the tested ranges of five varied process parameters. In situ SPMD calibration data acquired show that uptake of PACs, described by SPMD sampling rates (Rs), were four to eight times higher than published laboratory calibrated Rs values, mainly due to strong (bio)fouling and turbulence effects. In addition, the laboratory calibration study demonstrated that temperature affects the POCIS uptake of pharmaceuticals. The uptake of four pharmaceuticals was higher, by 10-56 percent, at 18 °C compared to 5 °C. For two of the pharmaceuticals our data indicate that the uptake was lower by 18-25 percent at 18 °C. Our results also indicate that uptake of the studied pharmaceuticals was in the linear phase throughout the 35 day exposure period at both temperatures. Finally, calibration studies enabled aqueous concentrations of micropollutants to be more accurately estimated from amounts collected in the passive samplers.
34

Využití pasivního vzorkování při analýze hormonů v pitných vodách / Application of passive sampling for the analysis of hormones in drinking water

Remerová, Martina January 2013 (has links)
The thesis focuses on the use of passive sampling during an analysis of hormones in drinkable water. In the theoretical part there are described selected passive samplers and the sample of the type of POCIS is described at fuller length. The next chapter engages with steroid hormones and an input of estrogenic hormone into the environment. The thesis contains chapters dealing with possibilities of the determination of hormones in water. It is specialized on the analysis of drinkable and surface water. In the last chapter of the theoretical part there are introduced water works where samples for an experimental assessment were collected from. The experimental part of the thesis presents the specification of the extraction of analytes and an adjustment of used device. In the thesis there are specific calibrations for individual assessment of hormones. The results of the assessment for each collection point are ordered to a well-arranged table. Increased levels of targeted estrogens were not approved in most of sampling points.
35

Semipermeable membrane devices as integrative tools for monitoring nonpolar aromatic compounds in air

Söderström, Hanna January 2004 (has links)
<p>Air pollutants pose a high risk for humans, and the environment, and this pollution is one of the major environmental problems facing modern society. Active air sampling is the technique that has been traditionally used to monitor nonpolar aromatic air pollutants. However, active high volume samplers (HiVols) require a power supply, maintenance and specialist operators, and the equipment is often expensive. Thus, there is a need to develop new, less complicated sampling techniques that can increase the monitoring frequency, the geographical distribution of the measurements, and the number of sites used in air monitoring programs. In the work underlying this thesis, the use of semipermeable membrane devices (SPMDs) as tools for monitoring gas phase concentrations of nonpolar aromatic compound was evaluated using the compound classes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs) and nitrated PAHs (nitro-PAHs) as test compounds. </p><p>High wind-speeds increased the uptake and release in SPMDs of PAHs and PCBs with log K<sub>OA</sub> values > 7.9, demonstrating that the uptake of most nonpolar aromatic compounds is controlled by the boundary layer at the membrane-air interface. The use of a metal umbrella to shelter the SPMDs decreased the uptake of PAHs and PCBs by 38 and 55 percent, respectively, at high wind/turbulence, and thus reduced the wind effect. Further, the use of performance reference compounds (PRCs) to assess the site effect of wind on the uptake in SPMDs reduced the between-site differences to less than 50 percent from as much as three times differences in uptake of PCBs and PAHs. However, analytical interferences reduced the precision of some PRCs, showing the importance of using robust analytical quality control.</p><p>SPMDs were shown to be efficient samplers of gas phase nonpolar aromatic compounds, and were able to determine local, continental and indoor spatial distributions of PAHs, alkyl- PAHs and nitro-PAHs. In addition, the use of the SPMDs, which do not require electricity, made sampling possible at remote/rural areas where the infrastructure was limited. SPMDs were also used to determine the source of PAH pollution, and different approaches were discussed. Finally, SPMDs were used to estimate the importance of the gas phase exposure route to the uptake of PAHs in plants. The results demonstrate that SPMDs have several advantages compared with HiVols, including integrative capacity over long times, reduced costs, and no need of special operators, maintenance or power supply for sampling. However, calibration data of SPMDs in air are limited, and spatial differences are often only semi-quantitatively determined by comparing amounts and profiles in the SPMDs, which have limited their use in air monitoring programs. In future work, it is therefore important that SPMDs are properly sheltered, PRCs are used in the sampling protocols, and that calibrated sampling rate data, or the SPMD-air partition data, of specific compounds are further developed to make determination of time weighted average (TWA) concentrations possible.</p>
36

Semipermeable membrane devices as integrative tools for monitoring nonpolar aromatic compounds in air

Söderström, Hanna January 2004 (has links)
Air pollutants pose a high risk for humans, and the environment, and this pollution is one of the major environmental problems facing modern society. Active air sampling is the technique that has been traditionally used to monitor nonpolar aromatic air pollutants. However, active high volume samplers (HiVols) require a power supply, maintenance and specialist operators, and the equipment is often expensive. Thus, there is a need to develop new, less complicated sampling techniques that can increase the monitoring frequency, the geographical distribution of the measurements, and the number of sites used in air monitoring programs. In the work underlying this thesis, the use of semipermeable membrane devices (SPMDs) as tools for monitoring gas phase concentrations of nonpolar aromatic compound was evaluated using the compound classes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs) and nitrated PAHs (nitro-PAHs) as test compounds. High wind-speeds increased the uptake and release in SPMDs of PAHs and PCBs with log KOA values &gt; 7.9, demonstrating that the uptake of most nonpolar aromatic compounds is controlled by the boundary layer at the membrane-air interface. The use of a metal umbrella to shelter the SPMDs decreased the uptake of PAHs and PCBs by 38 and 55 percent, respectively, at high wind/turbulence, and thus reduced the wind effect. Further, the use of performance reference compounds (PRCs) to assess the site effect of wind on the uptake in SPMDs reduced the between-site differences to less than 50 percent from as much as three times differences in uptake of PCBs and PAHs. However, analytical interferences reduced the precision of some PRCs, showing the importance of using robust analytical quality control. SPMDs were shown to be efficient samplers of gas phase nonpolar aromatic compounds, and were able to determine local, continental and indoor spatial distributions of PAHs, alkyl- PAHs and nitro-PAHs. In addition, the use of the SPMDs, which do not require electricity, made sampling possible at remote/rural areas where the infrastructure was limited. SPMDs were also used to determine the source of PAH pollution, and different approaches were discussed. Finally, SPMDs were used to estimate the importance of the gas phase exposure route to the uptake of PAHs in plants. The results demonstrate that SPMDs have several advantages compared with HiVols, including integrative capacity over long times, reduced costs, and no need of special operators, maintenance or power supply for sampling. However, calibration data of SPMDs in air are limited, and spatial differences are often only semi-quantitatively determined by comparing amounts and profiles in the SPMDs, which have limited their use in air monitoring programs. In future work, it is therefore important that SPMDs are properly sheltered, PRCs are used in the sampling protocols, and that calibrated sampling rate data, or the SPMD-air partition data, of specific compounds are further developed to make determination of time weighted average (TWA) concentrations possible.

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