The impact of a chromium smelter on pollution was evaluated by determining Cr(VI) in topsoil, grass and tree bark by electhrothermal atomic absorption spectrometry (ETAAS). It was found that bark reflected the levels of air pollution better than soil and grass due to its high accumulative ability of Cr(VI). The tree bark was contaminated with Cr(VI) by a factor of 9 than in soil. It is therefore suggested that the bark be used as an indicator of air pollution for long-term exposure. The concentration of Cr(VI) in the bark was always a fraction of the total concentration of Cr and ranges between 1.6 and 3%. The method used in the preparation of samples was validated by the analysis of certified reference materials.

South Africa is a semi arid country and the provision of water clean water to a steadily growing population is currently one of the major challenges facing governmental organisations. Water resources in South Africa are subject to many forms of pollution. resulting in eutrophication and salinisation. Hence, there is a need to monitor chemical and organic pollution in South African rivers. Chemical monitoring is expensive and not all the elements of water quality can be monitored and measured in a particular sample. The synergistic effects of water quality determinants cannot be demonstrated if only the chemical composition of a water resource is monitored. Biological monitoring can provide a rapid indication of water quality and at a lower cost than traditional monitoring. Organisms within a river are exposed to all water quality variables present in a system and can provide an integrated reflection of the health of their environment. Diatoms are found in all aquatic ecosystems and have demonstrable responses to many of the elements of water quality that have been identified as causing aquatic pollution. These elements include total dissolved solids, pH and plant nutrients such as nitrates and phosphates. The relationship between the structure of a given diatom community and the water quality to which the community is exposed, has lead to the development of several indices of water quality. Diatom indices of aquatic pollution have been developed in France, Belgium, Germany, Britain and Japan. Existing diatom indices have been tested for use in Finland, Poland, Britain, the Himalayas and South America. Several diatom indices were tested in this study for application in the Vaal and Wilge Rivers. The tested diatom indices correlated well with measured water quality variables such as pH and the chemical variables responsible for eutrophication and salinisation. The demonstrated correlations were comparable to those demonstrated by European authors. Several indices proved successful in indicating general water quality, namely the Biological Diatom lndex (BDI), the Specific Pollution sensitivity lndex (SPI) and the Generic Diatom lndex (GDI). The Eutrophication and Pollution lndex (EPI) successfully indicated levels of plant nutrients together with the ionic composition measured at various sites in the Vaal and Wilge Rivers. It is recommended that these indices be further tested in different regions within South Africa. / Thesis (M. Omgewingswetenskappe)--North-West University, Potchefstroom Campus, 2004.

South Africa is a semi arid country and the provision of water clean water to a steadily growing population is currently one of the major challenges facing governmental organisations. Water resources in South Africa are subject to many forms of pollution. resulting in eutrophication and salinisation. Hence, there is a need to monitor chemical and organic pollution in South African rivers. Chemical monitoring is expensive and not all the elements of water quality can be monitored and measured in a particular sample. The synergistic effects of water quality determinants cannot be demonstrated if only the chemical composition of a water resource is monitored. Biological monitoring can provide a rapid indication of water quality and at a lower cost than traditional monitoring. Organisms within a river are exposed to all water quality variables present in a system and can provide an integrated reflection of the health of their environment. Diatoms are found in all aquatic ecosystems and have demonstrable responses to many of the elements of water quality that have been identified as causing aquatic pollution. These elements include total dissolved solids, pH and plant nutrients such as nitrates and phosphates. The relationship between the structure of a given diatom community and the water quality to which the community is exposed, has lead to the development of several indices of water quality. Diatom indices of aquatic pollution have been developed in France, Belgium, Germany, Britain and Japan. Existing diatom indices have been tested for use in Finland, Poland, Britain, the Himalayas and South America. Several diatom indices were tested in this study for application in the Vaal and Wilge Rivers. The tested diatom indices correlated well with measured water quality variables such as pH and the chemical variables responsible for eutrophication and salinisation. The demonstrated correlations were comparable to those demonstrated by European authors. Several indices proved successful in indicating general water quality, namely the Biological Diatom lndex (BDI), the Specific Pollution sensitivity lndex (SPI) and the Generic Diatom lndex (GDI). The Eutrophication and Pollution lndex (EPI) successfully indicated levels of plant nutrients together with the ionic composition measured at various sites in the Vaal and Wilge Rivers. It is recommended that these indices be further tested in different regions within South Africa. / Thesis (M. Omgewingswetenskappe)--North-West University, Potchefstroom Campus, 2004.

No description available.

La digestion anaérobie est un processus de transformation de la matière organique en biogaz riche en méthane. Les déchets solides sont le plus souvent traités par une technologie par voie sèche qui est caractérisée par des teneurs en matières sèches supérieures à 20%. Du fait de la faible teneur en eau, la digestion sèche présente de nombreuses inconnus scientifiques, tant au niveau microbiologique et physico-chimique. Le but de cette thèse est de comprendre l'influence des parametres opératoires spécifiques à la digestion anaérobie par voie sèche sur les performances et le comportement des communautés microbiennes de ce processus. Les résultats obtenus montrent que l'augmentation de la teneur en matières sèches au-delà de 30% et la diminution de la surface spécifique d'échange ont un effet négatif sur le processus de digestion anaérobie. En effet lorsque la teneur en matière sèche est supérieure à 30%, le transfert des gaz dissous du milieu réactionnel vers le ciel gazeux peut limiter la méthanisation. L'analyse des populations microbiennes montre la présence de bio-indicateurs bactériens liés au non fonctionnement de la digestion anaérobie. Ces bio-indicateurs sont des clostridium et sont présents quel que soit l'inoculum utilisé. L'étude des populations méthanogènes montre une sensibilité de ces microorganismes à leur environnement : des shifts de populations méthanogènes ont été observés en fonction de la concentration en matières sèches. Ce travail a permis d'accroître les connaissances dans le domaine de la digestion anaérobie sèche, ces connaissances pouvant contribuer à améliorer les performances des procédés. / Anaerobic digestion is the transformation of organic matter into biogas rich in methane. Solid waste is treated by dry anaerobic digestion process with a total solid content higher than 20%. The high solids content make the process difficult to control. The aim of this work is to study the influence of operating parameters specific to dry anaerobic digestion on performances and behavior of microbial communities. The results show that increasing the solids content higher than 30% and decreasing the specific surface area of change have a negative effect on the anaerobic digestion process. Indeed, when the solids content exceeds 30%, the transfer of dissolved gas from the reaction mixture to the headspace can limit anaerobic digestion. The analysis of microbial populations demonstrates the presence of bacterial bio-indicators related to no-functioning anaerobic digestion. These bio-indicators correspond to the clostridium genus and are present regardless of the inoculum source. The study of methanogenic Archaea shows a sensitivity of these microorganisms. Shifts in the methanogenic populations related to the concentration of total solids were observed. This work has improved the fundamental knowledge of dry anaerobic digestion which can help improve the performance of this process.

We evaluated the effect of cyanobacterial crude extracts containing microcystin (CCEMC+) from a natural bloom on seed germination and initial development of three economically important legume species: green mung bean Vigna radiata, cowpea Vigna cylindrical and red mung bean Vigna angularis and compared it to crude extracts of cyanobacteria without the toxin (CCEMC–). Results showed that CCEMC+ and CCEMC– caused different effects on seed germination and initial development of the three species. There was a clear inhibition on germination and root growth of the green mung bean exposed to the CCEMC+ (20, 200 and 500 μg/L), indicating that the green mung bean being more sensitive to CCEMC+ when compared to the cowpea and red mung bean. CCEMC+ induced a greater occurrence of abnormal seedlings in the green mung bean, duce to inhibition the germination as well as reduction of fresh weight and root length. The CCEMC– extract caused no harmful effects to germination and seedlings growth of the green mung bean and red mung bean. However, it reduced shoot and root length in cowpea bean, suggesting that the cowpea being more sensitive to both extracts. Our results indicated that the sensitivity in germination and root growth of the green mung bean V. radiata could be used as an indicator to evaluate the toxic effect and monitor the toxin concentration of water contaminated with microcystins. / Nghiên cứu này khảo sát và so sánh các tác động bất lợi của ly trích vi khuẩn lam có chứa và không chứa độc tố lên sự nẩy mầm và sự phát triển ở giai đoạn đầu của ba loại cây họ đậu gồm đậu xanh Vigna radiata, đậu đỏ Vigna angularis và đậu đen Vigna cylindrical. Kết quả cho thấy hai loại ly trích gây ra các tác động khác nhau lên ba loại cây đậu thí nghiệm. Ly trích vi khuẩn lam có chứa độc tố ở nồng độ 20, 200 và 500 μg/L ngăn chặn đáng kể sự nẩy mầm và sự phát triển rể ở đậu xanh. Cả hai loại ly trích có chứa và không chứa độc tố đều ngăn chặn sự nẩy mầm và sự phát triển rể ở đậu đen. Ngược lại ly trích vi khuẩn lam có chứa độc tố ở nồng độ 500 μg/L lại kích thích chiều dài rể, thân mầm và trọng lượng tươi ở đậu đỏ. Kết quả cho thấy đậu đen khá nhạy cảm với cả hai loại ly trích có chứa và không chứa độc tố, trong khi đó đậu xanh nhạy cảm hơn với ly trích có chứa độc tố. Tính nhạy cảm của các loại cây họ đậu khi phơi nhiễm với ly trích vi khuẩn lam có thể được sử dụng để chỉ thị cho sự ô nhiễm và quan trắc độc tố vi khuẩn lam trong môi trường.