Evaluation and application of micro-sampling system for inductively coupled plasma mass spectrometry

Two Meinhard microconcentric nebulizers, model AR30-07-FM02 and AR 30-07-FM005, were employed as a self-installed micro-sampling system for inductively coupled plasma-mass spectrometry (ICP-MS). The FM02 nebulizer at 22 muL/min of solution uptake rate gave the relative standard deviations of 7.6%, 3.0%, 2.7%, 1.8% for determinations (n = 10) of 20 mug/L Be, Co, In and Bi, respectively, and the detection limits (3s) of 0.14, 0.10, 0.02 and 0.01 mug/L for Be, Co In and Bi, respectively. The mass intensity of In-115 obtained by this micro-sampling system was 60% of that by conventional pneumatic nebulizer system at 1.3 mL/min. The analytical results for La, Ce, Pr and Nd in 20 muL Wistar rat amniotic fluid obtained by the present micro-sampling system were precisely in good agreement with those obtained using conventional pneumatic nebulization system.

Potential of the seaweed Gracilaria lemaneiformis for integrated multi-trophic aquaculture with scallop Chlamys farreri in North China

In this study the red alga, Gracilaria lemaneiformis, was cultivated with the scallop Chlamys farreri in an integrated multi-trophic aquaculture (IMTA) system for 3 weeks at the Marine Aquaculture Laboratory of the Institute of Oceanology, Chinese Academy of Sciences (IOCAS) in Qingdao, Shandong Province, North China. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus from scallop excretion were determined. The experiment included four treatments each with three replicates, and three scallop monoculture systems served as the control. Scallop density (407.9 +/- 2.84 g m(-3)) remained the same in all treatments while seaweed density differed. The seaweed density was set at four levels (treatments 1, 2, 3, 4) with thallus wet weight of 69.3 +/- 3.21, 139.1 +/- 3.80, 263.5 +/- 6.83, and 347.6 +/- 6.30 g m(-3), respectively. There were no significant differences in the initial nitrogen and phosphorus concentration between each treatment and the control group (ANOVA, p > 0.05). The results showed that at the end of the experiment, the nitrogen concentration in the control group and treatment 1 was significantly higher than in the other treatments. There was also a significant difference in phosphorus concentration between the control group and the IMTA treatments (ANOVA, p < 0.05). Growth rate, C and N content of the thallus, and mortality of scallop was different between the IMTA treatments. The nutrient uptake rate and nutrient reduction efficiency of ammonium and phosphorus changed with different cultivation density and time. The maximum reduction efficiency of ammonium and phosphorus was 83.7% and 70.4%, respectively. The maximum uptake rate of ammonium and phosphorus was 6.3 and 3.3 A mu mol g(-1) DW h(-1). A bivalve/seaweed biomass ratio from 1:0.33 to 1:0.80 (treatments 2, 3, and 4) was preferable for efficient nutrient uptake and for maintaining lower nutrient levels. Results indicate that G. lemaneiformis can efficiently absorb the ammonium and phosphorus from scallop excretion and is a suitable candidate for IMTA.

Response of chlorophyll fluorescence to dynamic light in three alpine species differing in plant architecture

A study was carried out to examine the effect of dynamic photosynthetically active photon flux density (PPFD) on photoinhibition and energy use in three herbaceous species, prostrate Saussurea superba, erect-leaved S. katochaete, and half-erect-leaved Gentiana straminea, from the Qinghai-Tibet Plateau. Chlorophyll fluorescence response was measured under each of three sets of high-low PPFD combinations: 1700-0, 1400-300, and 1200-500 mu mol m(-2) s(-1), illuminating in four dynamic frequencies: 1, 5, 15, and 60 cycles per 2 h. The total light exposure time was 2h and the integrated PPFD was the same in all treatments. The highest frequency of PPFD fluctuation resulted in the lowest photochemical activity, the highest level of non-photochemical quenching, and the greatest decrease of F-v/F-m (maximal photochemical efficiency of PSII). The 5 and 15 cycles per 2h treatments resulted in higher photochemical activity than the 1 cycle per 2h treatment. The 1700-0 PPFD combination led to the lowest photochemical activity and more serious photoinhibition in all species. S. superba usually exhibited the highest photochemical activity and CO2 uptake rate, the lowest reduction of F-v/F-m,F- and the smallest fraction of energy in thermal dissipation. With similar fractions of thermal dissipation, S. katochaete had relatively less photoinhibition than G. straminea owing to effective F-o quenching. The results suggest that high frequency of fluctuating PPFD generally results in photoinhibition, which is more serious under periods of irradiation with high light intensity. (c) 2005 Elsevier B.V. All rights reserved.

Photosynthesis of Saussurea superba and Gentiana straminea is not reduced after long-term enhancement of UV-B radiation

Experiments were conducted in an alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37degrees29'-37degrees45'N, 101degrees12'-101degrees33'E; altitude 3200 m). Effects of enhanced ultraviolet-B (UV-B) radiation on photosynthesis of the alpine plants of Saussurea superba and Gentiana straminea were investigated. Both species were exposed to a UV-B-BE density at 15.80 kJ m(-2) per day, simulating nearly 14% ozone (O-3) reduction during the plant growing season. Neither photosynthetic CO2 uptake rate nor photosynthetic O-2 evolution rate were decreased after a long period of enhanced UV-B radiation treatment. On the contrary, there was a tendency to increase of both parameters in both species. The photosynthetic pigments were also increased, when expressed on a leaf area basis. UV-B absorbing compounds, detected by the absorbance values at 300 mm, had a tendency to increase in both species after enhanced UV-B radiation. After long-term exposure of plants to enhanced UV-B radiation, leaf morphology was also affected. Leaf thickness in both S. superba and G. straminea were increased significantly (P < 0.001). This supports our hypothesis that the increase of leaf thickness in both species after long-term exposure of enhanced UV-B radiation could compensate for the photodestruction of photosynthetic pigments when light passes through the leaf. Therefore, photosynthesis is not reduced in either species when expressed on leaf area basis. (C) 2003 Elsevier B.V. All rights reserved.

Evaluation of a new peat-based sorbent for metals capture

A new peat-based sorbent was evaluated for the capture of heavy metals from waste streams. The media is a pelletted blend of organic humic material targeted for the capture of soluble metals from industrial waste streams and stormwater. The metals chosen for the media evaluation were Cd, Cu, Ni, and Zn due to their occurrence and abundance in waste streams and runoff. Sorption tests included an evaluation of the rate and extent of metals capture by the media, single versus multicomponent metals uptake, pH, anion influence, leaching effects and the effect of media moisture content on uptake rate and capacity. Isotherms of the sorption results showed that the presence of multiple metals increased the total sorption capacity of the media compared to the single component metal capacity; a result of site selectivity within the media. However the capacity for an individual metal in a multicomponent metal matrix was reduced compared to its single component capacity, due to competition for sites. Evidence of ion exchange behavior was observed but did not account for all metals capture. The media also provided a buffering action to counter the pH drop typically associated with metals capture.

Can arsenic-phytochelatin complex formation be used as an indicator for toxicity in Helianthus annuus?

The formation of arsenic-phytochelatin (As-PC) complexes is thought to be part of the plant detoxification strategy for arsenic. This work examines (i) the arsenic (As) concentration-dependent formation of As-PC complex formation and (ii) redistribution and metabolism of As after arrested As uptake in Helianthus annuus. HPLC with parallel ICP-MS/ES-MS detection was used to identify and quantify the species present in plant extracts exposed to arsenate (As(V)) (between 0 and 66.7 micromol As l-1 for 24 h). At As concentrations below the EC50 value for root growth (22 micromol As l-1) As uptake is exponential, but it is reduced at concentrations above. Translocation between root and shoot seemed to be limited to the uptake phase of arsenic. No redistribution of As between root and shoot was observed after arresting As exposure. The formation of As-PC complexes was concentration-dependent. The amount and number of As-PC complexes increased exponentially with concentration up to 13.7 micromol As l-1. As(III)-PC3 and GS-As(III)-PC2 complexes were the dominant species in all samples. The ratio of PC-bound As to unbound As increased up to 1.3 micromol As l-1 and decreased at higher concentrations. Methylation of inorganic As was only a minor pathway in H. annuus with about 1% As methylated over a 32 d period. The concentration dependence of As-PC complex formation, amount of unbound reduced and oxidized PC2, and the relative uptake rate showed that As starts to influence the cellular metabolism of H. annuus negatively at As concentrations well below the EC50 value determined by more traditional means. Generally, As-PC complexes and PC-synthesis rate seem to be the more sensitive parameters to be studied when As toxicity values are to be estimated.

Variation in oxygen consumption among 'living fossils' (Mollusca: Polyplacophora)

Polyplacophoran molluscs (chitons) are phylogenetically ancient and morphologically constrained, yet multiple living species are often found co-occurring within widely overlapping ecological niches. This study used two sets of experiments to compare interspecific variation among co-occurring species in the North Atlantic (Ireland) and separately in the North Pacific (British Columbia, Canada) chiton faunas. A complementary review of historical literature on polyplacophoran physiology provides an overview of the high level of metabolic variability in this group of 'living fossils'. Species examined in de novo experiments showed significant variation in oxygen consumption both under air-saturated water conditions (normoxia), and in response to decreasing oxygen availability (hypoxia). Some species demonstrate an ability to maintain constant oxygen uptake rates despite hypoxia (oxyregulators), while others oxyconform, with uptake rate dependent on ambient oxygen tension. These organisms are often amalgamated in studies of benthic communities, yet show obvious physiological difference that may impact their response or tolerance to environmental change.

Existing and emerging high impact invasive species are characterized by higher functional responses than natives

Predicting ecological impacts of invasive species and identifying potentially damaging future invaders are research priorities. Since damage by invaders is characterized by their depletion of resources, comparisons of the ‘functional response’ (FR; resource uptake rate as a function of resource density) of invaders and natives might predict invader impact. We tested this by comparing FRs of the ecologically damaging ‘world's worst’ invasive fish, the largemouth bass (Micropterus salmoides), with a native equivalent, the Cape kurper (Sandelia capensis), and an emerging invader, the sharptooth catfish (Clarias gariepinus), with the native river goby (Glossogobius callidus), in South Africa, a global invasion hotspot. Using tadpoles (Hyperolius marmoratus) as prey, we found that the invaders consumed significantly more than natives. Attack rates at low prey densities within invader/native comparisons reflected similarities in predatory strategies; however, both invasive species displayed significantly higher Type II FRs than the native comparators. This was driven by significantly lower prey handling times by invaders, resulting in significantly higher maximum feeding rates. The higher FRs of these invaders are thus congruent with, and can predict, their impacts on native communities. Comparative FRs may be a rapid and reliable method for predicting ecological impacts of emerging and future invasive species.

Differential ecological impacts of an invader and a native under environmental change are revealed by comparative functional responses.

Predicting the ecological impacts of damaging invasive species under relevant environmental contexts is a major challenge, for which comparative functional responses (the relationship between resource availability and consumer uptake rate) have great potential. Here, the functional responses of Gammarus pulex, an ecologically damaging invader in freshwaters in Ireland and other islands, were compared with those of a native trophic equivalent Gammarus duebeni celticus. Experiments were conducted at two dissolved oxygen concentrations (80 and 50 % saturation), representative of anthropogenic water quality changes, using two larval prey, blackfly (Simuliidae spp.) and mayfly (Baetis rhodani). Overall, G. pulex had higher Type II functional responses and hence predatory impacts than G. d. celticus and the functional responses of both predators were reduced by lowered oxygen concentration. However, this reduction was of lower magnitude for the invader as compared to the native. Further, the invader functional response at low oxygen was comparable to that of the native at high oxygen. Attack rates of the two predators were similar, with low oxygen reducing these attack rates, but this effect occurred more strongly for blackfly than mayfly prey. Handling times were significantly lower for the invader compared with the native, and significantly higher at low oxygen, however, the effect of lowered oxygen on handling times was minimal for the invader and pronounced for the native. Maximum feeding rates were significantly greater for the invader compared with the native, and significantly reduced at low oxygen, with this effect again lesser for the invader as compared to the native. The greater functional responses of the invader corroborate with its impacts on recipient macroinvertebrate communities when it replaces the native. Further, our experiments predict that the impact of the invader will be less affected than the native under altered oxygen regimes driven by anthropogenic influences.

Biovalorização de soro de queijo por processos anaeróbios/aeróbios

Este trabalho abordou a valorização de um subproduto da indústria de lacticínios (soro de queijo) através da alteração do funcionamento de processos habitualmente utilizados no contexto do tratamento biológico. Foi avaliada a fermentação acidogénica deste subproduto para maximizar a conversão do seu elevado teor de matéria orgânica em ácidos orgânicos voláteis (AOV) que actualmente são produtos com elevada procura, nomeadamente para produção de polihidroxialcanoatos (PHA). Em ensaios descontínuos e semi-contínuos foi caracterizada a produção e composição de AOV a partir de soro de queijo variando a razão food-to-microorganism (F/M) e a concentração de alcalinidade. Recorrendo à modelação dos resultados através de superfícies de resposta, demonstrou-se que condições de F/M = 4 gCQO g-1SSV combinadas com uma adição elevada de alcalinidade (8 g L-1 expresso como CaCO3) resultaram na conversão de 72% da CQO alimentada em AOV. O acetato e o butirato foram os AOV predominantes (60%), mas elevadas razões F/M combinadas com elevadas alcalinidades promoveram o alongamento da cadeia carboxílica, tendo sido produzidos AOV de maior massa molecular (iso-valerato e n-caproato). O processo de fermentação acidogénica foi posteriormente desenvolvido em modo contínuo num reactor MBBR acidogénico operado a longo prazo. Cargas orgânicas entre 30 e 50 gCQO L-1d-1 permitiram obter um grau de acidificação máximo de 68% no efluente fermentado. Foi ainda demonstrado que uma adição dinâmica de alcalinidade (0 – 4,8 g CaCO3 L-1) nestas condições estimulou a produção de AOV de cadeia ímpar (propionato e n-valerato) até 42%. O efluente acidificado no processo anaeróbio foi usado como substrato em reactores SBR operados para selecção de culturas microbianas mistas acumuladoras de PHA, nos quais foi aplicado um regime de alimentação dinâmica em condições aeróbias (“fartura-fome”). Estes sistemas operaram também a longo prazo, e demonstraram ser capazes de remover mais de 96% da CQO alimentada e simultaneamente convertê-la em PHA, até 36% do peso celular seco. A velocidade de remoção de substrato (valor máximo de 1,33 gCQO g-1SSV h-1) foi proporcional ao teor de polímero acumulado, evidenciando o estabelecimento de uma fase de “fome” prolongada que estimulou a selecção de microrganismos com elevada capacidade de acumulação de PHA. Além disso, o teor molar de hidroxivalerato (HV) no copolímero produzido [P(HB-co-HV)] foi directamente proporcional ao teor de AOV de cadeia ímpar (propionato e n-valerato) presente no soro fermentado que serviu de substrato. Uma estratégia de operação do reactor SBR com variação da carga orgânica, aliada ao regime “fartura-fome” estabelecido, permitiu ainda simular a realidade dos processos de tratamento biológico de efluentes, nos quais a composição e concentração inicial de matéria orgânica variam frequentemente. Este modo de operação do sistema estimulou notavelmente o processo de selecção de culturas acumuladoras de PHA tendo resultado num aumento da acumulação de PHA de 7% para 36%. Os resultados demonstraram com sucesso a possibilidade de valorização do soro de queijo através de eco-biotecnologia, contribuindo para uma mudança de paradigma no tratamento convencional de efluentes: ao invés de serem eliminados enquanto poluentes, os componentes orgânicos presentes neste subproduto industrial podem assim ser convertidos em materiais de valor acrescentado.

Determination of the Change in Anthropogenic Carbon Content in the Kuroshio Extension over the past 20 years using the C* Method

Senior thesis written for Oceanography 445

Copper and lead removal by peanut hulls: equilibrium and kinetic studies

This research work aims to study the use of peanut hulls, an agricultural and food industry waste, for copper and lead removal through equilibrium and kinetic parameters evaluation. Equilibrium batch studies were performed in a batch adsorber. The influence of initial pH was evaluated (3–5) and it was selected between 4.0 and 4.5. The maximum sorption capacities obtained for the Langmuir model were 0.21 ± 0.03 and 0.18 ± 0.02 mmol/g, respectively for copper and lead. In bi-component systems, competitive sorption of copper and lead was verified, the total amount adsorbed being around 0.21 mmol of metal per gram of material in both mono and bi-component systems. In the kinetic studies equilibrium was reached after 200 min contact time using a 400 rpm stirring rate, achieving 78% and 58% removal, in mono-component system, for copper and lead respectively. Their removal follows a pseudo-second-order kinetics. These studies show that most of the metals removal occurred in the first 20 min of contact, which shows a good uptake rate in all systems.

Development and characterization of concentric capillary nebulizer used in inductively coupled plasma analysis /

A simple, low-cost concentric capillary nebulizer (CCN) was developed and evaluated for ICP spectrometry. The CCN could be operated at sample uptake rates of 0.050-1.00 ml min'^ and under oscillating and non-oscillating conditions. Aerosol characteristics for the CCN were studied using a laser Fraunhofter diffraction analyzer. Solvent transport efficiencies and transport rates, detection limits, and short- and long-term stabilities were evaluated for the CCN with a modified cyclonic spray chamber at different sample uptake rates. The Mg II (280.2nm)/l\/lg 1(285.2nm) ratio was used for matrix effect studies. Results were compared to those with conventional nebulizers, a cross-flow nebulizer with a Scott-type spray chamber, a GemCone nebulizer with a cyclonic spray chamber, and a Meinhard TR-30-K3 concentric nebulizer with a cyclonic spray chamber. Transport efficiencies of up to 57% were obtained for the CCN. For the elements tested, short- and long-term precisions and detection limits obtained with the CCN at 0.050-0.500 ml min'^ are similar to, or better than, those obtained on the same instrument using the conventional nebulizers (at 1.0 ml min'^). The depressive and enhancement effects of easily ionizable element Na, sulfuric acid, and dodecylamine surfactant on analyte signals with the CCN are similar to, or better than, those obtained with the conventional nebulizers. However, capillary clog was observed when the sample solution with high dissolved solids was nebulized for more than 40 min. The effects of data acquisition and data processing on detection limits were studied using inductively coupled plasma-atomic emission spectrometry. The study examined the effects of different detection limit approaches, the effects of data integration modes, the effects of regression modes, the effects of the standard concentration range and the number of standards, the effects of sample uptake rate, and the effect of Integration time. All the experiments followed the same protocols. Three detection limit approaches were examined, lUPAC method, the residual standard deviation (RSD), and the signal-to-background ratio and relative standard deviation of the background (SBR-RSDB). The study demonstrated that the different approaches, the integration modes, the regression methods, and the sample uptake rates can have an effect on detection limits. The study also showed that the different approaches give different detection limits and some methods (for example, RSD) are susceptible to the quality of calibration curves. Multicomponents spectral fitting (MSF) gave the best results among these three integration modes, peak height, peak area, and MSF. Weighted least squares method showed the ability to obtain better quality calibration curves. Although an effect of the number of standards on detection limits was not observed, multiple standards are recommended because they provide more reliable calibration curves. An increase of sample uptake rate and integration time could improve detection limits. However, an improvement with increased integration time on detection limits was not observed because the auto integration mode was used.

Modélisation toxicocinétique du benzo(a)pyrène et 3-hydroxybenzo(a)pyrène pour l’interprétation des données de surveillance biologique de l’exposition chez les travailleurs

De nombreux travailleurs sont exposés aux hydrocarbures aromatiques polycycliques (HAP). Le benzo(a)pyrène (BaP) fait partie de ce groupe de polluants. Cette substance a été classée cancérogène reconnu chez l’humain. Pour évaluer l'exposition aux HAP cancérogènes, plusieurs chercheurs ont proposé d’utiliser la mesure du 3-hydroxybenzo(a)pyrène (3-OHBaP) dans l’urine des travailleurs exposés. Dans le cadre du présent projet, deux approches de modélisation ont été développées et appliquées pour permettre une meilleure compréhension de la toxicocinétique du BaP et son biomarqueur d’intérêt actuel, le 3-OHBaP, et pour aider à interpréter les résultats de surveillance biologique. Un modèle toxicocinétique à plusieurs compartiments a été développé sur la base des données préalablement obtenues sur le rat par notre groupe. Selon le modèle, le BaP injecté par voie intraveineuse est rapidement distribué du sang vers les tissus (t½ ≈ 4 h), avec une affinité particulière pour les poumons et les composantes lipidiques des tissus. Le BaP est ensuite distribué vers la peau et le foie. Au foie, le BaP est promptement métabolisé et le 3-OHBaP est formé avec une demi-vie de ≈ 3 h. Le métabolisme pulmonaire du BaP a également été pris en compte, mais sa contribution à la cinétique globale du BaP a été jugée négligeable. Une fois formé, le 3-OHBaP est distribué vers les différents organes presque aussi rapidement que la molécule mère (t½ ≈ 2 h). Le profil temporel du 3-OHBaP dans le rein montre une accumulation transitoire en raison de la différence observée entre le taux d’entrée (t½ = 28 min) et le taux de sortie (t½ = 4,5 h). La clairance totale de 3-OHBaP du corps est principalement gouvernée par le taux de transfert de la bile vers le tractus gastro-intestinal (t½ ≈ 4 h). Le modèle toxicocinétique à plusieurs compartiments a réussi à simuler un ensemble indépendant de profils urinaires publiés sur le 3-OHBaP. Ce modèle toxicocinétique à compartiments s'est avéré utile pour la determination des facteurs biologiques déterminants de la cinétique du BaP et du 3-OHBaP. Par la suite, un modèle pharmacocinétique à base physiologique (PCBP) reproduisant le devenir du BaP et du 3-OHBaP chez le rat a été construit. Les organes (ou tissus) représentés comme des compartiments ont été choisis en fonction de données expérimentales obtenues in vivo chez le rat. Les coefficients de partition, les coefficients de perméabilité, les taux de métabolisation, les paramètres d'excrétion, les fractions absorbées et les taux d'absorption pour différentes voies d’exposition ont été obtenus directement à partir des profils sanguins, tissulaires, urinaires et fécaux du BaP et du 3-OHBaP. Les valeurs de ces derniers paramètres ont été calculées par des procédures Monte-Carlo. Des analyses de sensibilité ont ensuite été réalisées pour s’assurer de la stabilité du modèle et pour établir les paramètres les plus sensibles de la cinétique globale. Cette modélisation a permis d’identifier les facteurs déterminants de la cinétique: 1) la sensibilité élevée des paramètres de la métabolisation hépatique du BaP et du 3-OHBaP ainsi que du taux d'élimination; 2) la forte distribution du BaP dans les poumons par rapport à d'autres tissus; 3) la distribution considérable du BaP dans les tissus adipeux et le foie; 4) la forte distribution du 3-OHBaP dans les reins; 5) le transfert limité du BaP par la diffusion tissulaire dans les poumons; 6) le transfert limité du 3-OHBaP par la diffusion tissulaire dans les poumons, les tissus adipeux et les reins; 7) la recirculation entéro-hépatique significative du 3-OHBaP. Suite à des analyses de qualité des ajustements des équations du modèle aux données observées, les probabilités que les simulations reproduisent les données expérimentales par pur hasard se sont avérées toujours inférieures à 10% pour les quatre voies d’exposition : intraveineuse, orale, cutanée et respiratoire. Nous avons extrapolé les modèles cinétiques du rat à l’humain afin de se doter d’un outil permettant de reconstituer les doses absorbées chez des travailleurs exposés dans diverses industries à partir de mesures de l'évolution temporelle du 3-OHBaP dans leur urine. Les résultats de ces modélisations ont ensuite été comparés à ceux de simulations obtenues avec un modèle toxicocinétique à compartiment unique pour vérifier l’utilité comparative d’un modèle simple et complexe. Les deux types de modèle ont ainsi été construits à partir de profils sanguins, tissulaires, urinaires et fécaux du BaP et du 3-OHBaP sur des rats exposés. Ces données ont été obtenues in vivo par voie intraveineuse, cutanée, respiratoire et orale. Ensuite, les modèles ont été extrapolés à l’humain en tenant compte des déterminants biologiques essentiels des différences cinétiques entre le rat et l’humain. Les résultats ont montré que l'inhalation n'était pas la principale voie d'exposition pour plusieurs travailleurs étudiés. Les valeurs de concentrations de BaP dans l’air utilisées afin de simuler les profils d’excrétion urinaire chez les travailleurs étaient différentes des valeurs de concentrations de BaP mesurées dans l’air. Une exposition au BaP par voie cutanée semblait mieux prédire les profils temporels observés. Finalement, les deux types de modélisation se sont avérés utiles pour reproduire et pour interpréter les données disponibles chez des travailleurs.

Identificació de paràmetres cinètics i estequiomètrics del procés de depuració de fangs actius mitjançant tècniques respiromètriques

El sistema de depuració de tipus Fangs Actius constitueix una de les tècniques més esteses arreu del món pel tractament biològic de les aigües residuals. Els softwares de modelització i simulació permeten adquirir coneixements de forma ràpida i senzilla sobre el funcionament dels processos de fangs actius, dur a terme la comparació entre diferents tecnologies de tractament i determinar les estratègies d'operació més rentables d'una EDAR minimitzant els costos. L'objectiu de la present tesi consisteix en la identificació dels principals paràmetres cinètics i coeficients estequiomètrics que caracteritzen el procés de fangs actius a partir de la mesura de la velocitat de consum d'oxigen de la biomassa. En aquest sentit s'ha dissenyat i desenvolupat un Respiròmetre Tancat Seqüencial (RTS), un Respiròmetre Tancat (RT) i un Programa d'Anàlisi de Respirometries (PAR) per la determinació dels paràmetres cinètics més representatius i característics dels sistemes de fangs actius en diferents casos.