O Lago das Garças (23°39\'S, 46°37\'W) está situado dentro da área do Parque Estadual das Fontes do Ipiranga, cidade de São Paulo (SP). Com o objetivo de identificar as principais fontes de aporte de nutrientes (nitrogênio e fósforo) e a quantificação das cargas do entorno do corpo d\'água, o lago foi dividido em dois compartimentos. Foram realizadas amostragens mensais de janeiro de 1997 a junho de 1998, em dez estações de coleta. Foram feitas medidas de temperatura, pH, condutividade elétrica e concentrações de fósforo total, nitrogênio total, amônio, clorofila a, material em suspensão total, oxigênio dissolvido, em cinco profundidades no lago. Nos afluentes foram determinadas as concentrações de nitrogênio total e fósforo total. Os perfis obtidos na coluna d\'água em conjunto com os dados climatológicos e morfométricos do lago, indicaram que o aquecimento térmico pela radiação solar e a profundidade do sistema foram as principais funções de força nos processos de estratificação térmica e química. No período de estudo, as cargas de entrada no reservatório, foram de 6.519 Kg de fósforo e 37.156 Kg de nitrogênio, sendo que os afluentes representaram 99% e 34% da carga total de fósforo e nitrogênio, respectivamente. A eficiência de retenção do Lago das Garças foi de 61% para o fósforo total e 85% para o nitrogênio total. Em relação a trofia o lago foi classificado como eutrófico em todo o período de estudo. Através de equação matemática baseada na carga anual de fósforo, tempo de residência e profundidade média, foi possível estimar as concentrações de fósforo no reservatório, além de fazer simulações na redução das cargas. Considerando que a carga média de fósforo total foi de 4.891 mg/m2 ano, a simulação matemática indicou que reduções superiores a 90% da carga (valores máximos de 300 mg/m2 ano) alterariam o nível de trofia no sistema para oligotrófico/mesotrófico. / The Lago das Garças (23°39\'S, 46°37\'W) is located in Parque Estadual das Fontes do Ipiranga, São Paufo city (SP). In order to identify the main sources of nutrients (nitrogen and phosphorus) and to quantify of the nutrient loads of its tributaries, the lake was divided in two compartments. Water sample were collected monthly from January 1997 to June 1998, in ten sampling station. Measurements of temperature, pH and electric conductivity and concentrations of totaf phosphorus, total nitrogen, ammonium, chlorophyll a,suspended solids, dissolved oxigen, were done in five depth of in the lake. ln each tributarys it was established only one sampling station where it was measured the concentration of total phosphorus and nitrogen. The profiles obtained in the water column, associated with the climatological data and morphological features of the lake, showed that the thermaI heating by the solar irradiation and depth of the system were the main force functions in the processes of thermal and chemical stratification. In the period study, the entrance loads into the Iake were of 6,519 Kg of pnosphorus and 37,156 Kg of nitrogen. The tributaries represented 99% and 34% of the total load of phosphorus and nitrogen, respectively. The retention efficiency of the Lago das Garças was 61% for total phosphorus and 85% for total nitrogen. In relation to the trophic status, this lake was cfassified as eutrophic all over the studied time. Using a mathematical equation based on the annual load of phosphorus, residence time and medium depth, it was possible to evaluate the phosphorus concentration in the lake and also to verify the effect of the redution of the loads. Considering that average load of total phosphorus was of 4.891 mg/m2.year, the mathematical model indicated there more than 90% of the load (maximum 300 mg/m2.year) should be reduced, to alter the trophic status in the system for oligotrophic/mesotrophic.

O Lago das Garças (23°39\'S, 46°37\'W) está situado dentro da área do Parque Estadual das Fontes do Ipiranga, cidade de São Paulo (SP). Com o objetivo de identificar as principais fontes de aporte de nutrientes (nitrogênio e fósforo) e a quantificação das cargas do entorno do corpo d\'água, o lago foi dividido em dois compartimentos. Foram realizadas amostragens mensais de janeiro de 1997 a junho de 1998, em dez estações de coleta. Foram feitas medidas de temperatura, pH, condutividade elétrica e concentrações de fósforo total, nitrogênio total, amônio, clorofila a, material em suspensão total, oxigênio dissolvido, em cinco profundidades no lago. Nos afluentes foram determinadas as concentrações de nitrogênio total e fósforo total. Os perfis obtidos na coluna d\'água em conjunto com os dados climatológicos e morfométricos do lago, indicaram que o aquecimento térmico pela radiação solar e a profundidade do sistema foram as principais funções de força nos processos de estratificação térmica e química. No período de estudo, as cargas de entrada no reservatório, foram de 6.519 Kg de fósforo e 37.156 Kg de nitrogênio, sendo que os afluentes representaram 99% e 34% da carga total de fósforo e nitrogênio, respectivamente. A eficiência de retenção do Lago das Garças foi de 61% para o fósforo total e 85% para o nitrogênio total. Em relação a trofia o lago foi classificado como eutrófico em todo o período de estudo. Através de equação matemática baseada na carga anual de fósforo, tempo de residência e profundidade média, foi possível estimar as concentrações de fósforo no reservatório, além de fazer simulações na redução das cargas. Considerando que a carga média de fósforo total foi de 4.891 mg/m2 ano, a simulação matemática indicou que reduções superiores a 90% da carga (valores máximos de 300 mg/m2 ano) alterariam o nível de trofia no sistema para oligotrófico/mesotrófico. / The Lago das Garças (23°39\'S, 46°37\'W) is located in Parque Estadual das Fontes do Ipiranga, São Paufo city (SP). In order to identify the main sources of nutrients (nitrogen and phosphorus) and to quantify of the nutrient loads of its tributaries, the lake was divided in two compartments. Water sample were collected monthly from January 1997 to June 1998, in ten sampling station. Measurements of temperature, pH and electric conductivity and concentrations of totaf phosphorus, total nitrogen, ammonium, chlorophyll a,suspended solids, dissolved oxigen, were done in five depth of in the lake. ln each tributarys it was established only one sampling station where it was measured the concentration of total phosphorus and nitrogen. The profiles obtained in the water column, associated with the climatological data and morphological features of the lake, showed that the thermaI heating by the solar irradiation and depth of the system were the main force functions in the processes of thermal and chemical stratification. In the period study, the entrance loads into the Iake were of 6,519 Kg of pnosphorus and 37,156 Kg of nitrogen. The tributaries represented 99% and 34% of the total load of phosphorus and nitrogen, respectively. The retention efficiency of the Lago das Garças was 61% for total phosphorus and 85% for total nitrogen. In relation to the trophic status, this lake was cfassified as eutrophic all over the studied time. Using a mathematical equation based on the annual load of phosphorus, residence time and medium depth, it was possible to evaluate the phosphorus concentration in the lake and also to verify the effect of the redution of the loads. Considering that average load of total phosphorus was of 4.891 mg/m2.year, the mathematical model indicated there more than 90% of the load (maximum 300 mg/m2.year) should be reduced, to alter the trophic status in the system for oligotrophic/mesotrophic.

Les lacs urbains, souvent artificiels, sont complètement intégrés dans le tissu urbain et exercent des fonctions variées, très importantes pour le fonctionnement durable des villes. Ces écosystèmes sont fortement affectés par les activités anthropiques, par l'urbanisation accompagnée du changement de l'occupation du sol et de l'imperméabilisation du bassin versant, à l'origine d'un ruissellement plus important et plus chargé en polluants. En raison de ces pressions anthropiques, de nombreux plans d'eau dans le monde souffrent d'eutrophisation et sont fréquemment touchés par des proliférations de cyanobactéries, dont certaines espèces sont potentiellement toxiques. L'objectif de cette thèse est de contribuer à une meilleure compréhension des facteurs impliqués dans la dynamique des cyanobactéries dans les lacs urbains. Notre recherche a été menée sur deux sites d'études : le lac d'Enghien en France et le lac de Pampulha au Brésil. Dans le site d'étude français, nous avons bénéficié de nouvelles technologies de suivi du phytoplancton pour modéliser la dynamique des cyanobactéries à courte échelle de temps. Dans le lac brésilien, notre site d'étude principal, la modélisation de la dynamique des cyanobactéries a été réalisée, en prenant en considération l'insertion du lac dans son bassin versant grâce à une modélisation intégrée : le modèle du lac destiné à la simulation des cyanobactéries est couplé à un modèle hydrologique qui simule les débits et la qualité de l'eau des affluents entrant dans le lac. La modélisation s'est basée sur des mesures de terrain recueillies durant un suivi de 21 mois. La performance d'une sonde spectrofluorométrique dans l'estimation de la biomasse phytoplanctonique dans ce lac hypereutrophe a été évaluée. Sur ce site d'étude, nos résultats ont montré que :• La sonde spectrofluorométrique sous-estime la biomasse cyanobactérienne quand (i) des cyanobactéries de l'ordre Oscillatoriales sont présentes car elles ont une fluorescence moindre par unité de chl-a, (ii) des cyanobactéries coloniales représentent plus de 20% de la biomasse cyanobactérienne et (iii) la chlorophylle total spectrofluorométrique est au-dessus de 100 μg chl-a.L-1.• Le modèle hydrologique a montré une bonne performance pour la simulation du débit (coefficient de Nash entre 0.70 et 0.88 en calage et 0.72 et 0.78 en validation) et des résultats moyennement satisfaisants pour la simulation des polluants. Le modèle du lac, développé par étapes, a présenté une bonne capacité prédictive de la dynamique des cyanobactéries, dans sa version plus complète, NMAE = 0.26 en calage et 0.55 en validation.• Les apports par temps de pluie sont une source importante de matières en suspension, phosphate et nitrates pour le lac de Pampulha. L'ammonium provient surtout des eaux usées rejetées dans les cours d'eau. Les épisodes pluvieux sont responsables des brassages de la colonne d'eau qui perturbent la croissance algale durant la saison humide.• Les cyanobactéries dans le lac de Pampulha étaient limitées par le phosphore pendant la majeure partie de notre suivi. Les épisodes de mélange du lac ont un effet important sur la disponibilité des nutriments dans les couches superficielles. Le travail mené dans le lac de Pampulha a permis d'avancer sur le couplage entre les aspects quantitatifs et qualitatifs du cycle de l'eau en milieu urbain et a fourni un outil qui peut être utilisé dans la simulation des scénarios de changement du bassin versant et leur impact sur le lac. La méthodologie développée dans cette thèse peut être appliquée ailleurs, en profitant des connaissances déjà acquises sur le lac de Pampulha / Urban lakes, often artificial, are fully integrated into the urban environment and perform several roles that are important for the sustainable functioning of cities. These ecosystems are strongly affected by human activities such as urbanization, land use changes and surface imperviousness which raise runoff in volume and speed, causing greater carrying capacity and greater pollutant load to aquatic receptors. Because of these anthropogenic activities, many lakes in the world are eutrophic and frequently affected by cyanobacterial blooms, some species of which are potentially toxic. The objective of this thesis is to contribute to a better understanding of the factors involved in the dynamics of cyanobacteria in urban lakes. Our research was conducted on two study sites: Lake Enghien in France and Lake Pampulha in Brazil. In the French study site, we benefited from new technologies for monitoring phytoplankton to model the dynamics of cyanobacteria in short-term scale. In the Brazilian lake, our main study site, the modelling of the cyanobacteria dynamics was carried out taking into account the inclusion of the lake in its catchment through and integrated modelling: the model used to simule lake cyanobacteria is coupled to a hydrological model for simulating the runoff quantity and the quality, which is inputted into the lake. Both models were calibrated and validated using measurements collected during a 21-month monitoring program. The performance of a spectrofluorometric probe in estimating phytoplankton biomass in this hypertrophic lake was evaluated. On this study site, our results showed that:• The spectrofluorometric probe underestimates the cyanobacterial biomass when (i) Oscillatoria cyanobacteria are present because they have a lower fluorescence per unit of chl-a, (ii) colonial cyanobacteria represent more than 20% of the cyanobacterial biomass and (iii) spectrofluorometric total chlorophyll is above 100 μg chl-a.L-1.• The hydrological model showed a good performance for runoff simulation (Nash coefficient is between 0.70 and 0.88 in calibration and 0.72 and 0.78 in validation) and moderately satisfactory results for pollutants simulation. The lake model, developed in steps, showed good predictive ability of the cyanobacteria dynamics in its most complete version, NMAE = 0.26 (calibration) and 0.55(validation).• Runoff is a major source for suspended solids, phosphate and nitrate influxes into Lake Pampulha. Ammonium comes mainly from wastewater discharged into tributaries. Rainfall events are responsible for the mixing of the water column and disrupting algal growth during the wet season.• Cyanobacteria in Lake Pampulha were limited by phosphorus during most of our monitoring. Mixing episodes of the lake water column have different effects on the availability of nutrients in the surface layers. The research carried out in Lake Pampulha allows us to progress on the coupling between the quantitative and qualitative aspects of the water cycle in urban areas and provides a tool that can be used in the simulation of scenarios of the catchment changements and their impact on the lake. The methodology developed in this thesis can be applied elsewhere, taking advantage of existing knowledge on Lake Pampulha

Copper remains at elevated levels in the aquatic environment of Stockholm due to diffuse urban sources. Management of these diffuse sources requires their quantification but they cannot be measured directly by field observations. The working hypothesis of this thesis was that Copper levels in the sediments of urban lakes would reflect diffuse emissions within their catchment areas. In order to test this hypothesis, a source – transport – storage conceptual model was developed for tracing the urban diffuse sources of Copper to the sediment in the urbanised catchment. A substance flow analysis (SFA) approach was taken in the source module and a fate, mass-balance model was applied in the lake module. Five separate urban lakes (Judarn, Laduviken, Långsjön, Råcksta Träsk and Trekanten) within the Stockholm area and a main water flow pathway from Lake Mälaren to the inner archipelago of the Baltic Sea, through Stockholm, were selected as case studies.  In comparison to actual source strength data in the literature for the five case study lakes, the SFA approach gave similar results to previous models, but with reduced uncertainty. The SFA approach was also able to indicate the actual sources of urban copper, which was not accomplished by the other approaches and which is a great advantage in managing the sources. For the five lakes in Stockholm, traffic and copper roofs were found to be major contributors of Copper. For the three more polluted lakes, good agreement was obtained between simulated sediment copper contents and independent field observations, thereby supporting the applicability of the model in such cases. Furthermore, simulation results showed sediment copper content to be linearly dependent on the urban load. While this suggests that the urban copper sediment level reflects the urban load, considerable integration of this load over time (decade(s)) was suggested by the simulation results, so time must be allowed in order to detect a change in the urban load by field monitoring of the sediments.  Published data on the main water flow pathway from Lake Mälaren to the archipelago showed a peak in sediment copper content close to the city centre, confirming a considerable urban influence. An approach to quantitatively follow Cu from its urban source through such a complex, aquatic system was developed and applied to Stockholm. The compliance of future quantitative model results with monitoring data may help test the choices made in this conceptual model and the applicability of the model. Data availability proved to be a major obstacle to achieving a quantitative model, particularly as several municipalities with different levels of data availability surround the main water flow pathway studied.  Finally, the applicability of the quantitative, coupled source – transport – storage was demonstrated in a simplified scenario analysis. The ability of the model to estimate the copper load to air and soil and to the urban aquatic environment was also demonstrated. / QC 20110324

Lakes in Hanoi play an important role in local human life. However, along with the economic and social development, some urban lakes have been polluted, especially organic pollution. This paper presents the monthly survey results for organic pollution assessment of ten selected lakes in Ha Noi city: the Ho Tay, Truc Bach, Thien Quang, Ba Mau, Bay Mau, Hoan Kiem, Ngoc Khanh, Giang Vo, Thanh Cong and Thu Le lakes during the period from March 2014 to February 2015. The survey results showed that the Ba Mau lake was organic polluted at level IV whereas other lakes were contaminated by organic matters at level III. Organic pollution may come from both autochthonous and allochthonous sources. Compared with the results of previous studies, the water quality of 10 lakes in the period from March 2014 to February 2015 has been improved thank for the recent application of some positive solutions for lake environmental protection. / Hệ thống hồ ở Hà Nội đóng vai trò quan trọng trong đời sống của người dân. Tuy nhiên, cùng với sự phát triển kinh tế xã hội, nhiều hồ trong nội đô đã và đang bị ô nhiễm, đặc biệt là ô nhiễm hữu cơ. Bài báo này trình bày kết quả khảo sát ô nhiễm hữu cơ tại 10 hồ trong thành phố Hà Nội: hồ Tây, Trúc Bạch, Thiền Quang, Ba Mẫu, Bảy Mẫu, Hoàn Kiếm, Ngọc Khánh, Giảng Võ, Thành Công và Thủ Lệ trong thời gian từ tháng 3 năm 2014 đến tháng 2 năm 2015. Kết quả khảo sát cho thấy hồ Ba Mẫu bị ô nhiễm hữu cơ ở mức IV, các hồ còn lại bị ô nhiễm hữu cơ ở mức III. Ô nhiễm hữu cơ tại các hồ có thể do cả hai nguồn cung cấp chất hữu cơ, ngoại lai và nội sinh. So với kết quả quan trắc trước đây, chất lượng nước 10 hồ Hà Nội đã được cải thiện do gần đây đã áp dụng một số biện pháp bảo vệ môi trường cho các hồ.

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