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A new biodevice with plants and local cork to control water eutrophication in urban lakes - nutrient remediation from urban lakes
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A demografia e a sócioeconomia das últimas décadas têm alterado o funcionamento dos recursos aquáticos, gerando entre outras consequências, eutrofização com consequente destruição de habitats, perda de biodiversidade e riscos para a saúde pública. Este trabalho de ecohidrologia urbana, procurou desenvolver uma Solução Baseada na Natureza (NbS) para melhorar o estado ecológico de um lago urbano, através de espécies macrófitas autóctones. fitorremediadoras de nutrientes na água. Pretendeu-se contribuir para melhorar o funcionamento do lago do Jardim das Comunidades – Almancil, Loulé, no âmbito de um projeto de investigação sobre a performance ambiental deste espaço urbano, do Instituto Superior de Engenharia - Universidade do Algarve e do Município de Loulé. Os protótipos do biodispositivo foram construídos com peças de cortiça, do interior de Loulé - Algarve, ligadas entre si com corda náutica, e onde se abriram orifícios para colocar exemplares de Typha latifolia, Phragmites australis e Juncus inflexus, selecionadas pela sua capacidade de fitorremediação. Caracterizou-se a cortiça (cor, textura, densidade e espessura) e avaliou-se o funcionamento do biodispositivo, com monitorização da qualidade da água do lago quantificando-se amónia, nitritos, nitratos, azoto total, fosfatos, fósforo total, clorofila a, oxigénio dissolvido, temperatura, pH e transparência ao Disco Secchi, antes e depois da sua instalação. Classificou-se o estado ecológico do lago através de um Índice de Estado Trófico (IET). Entre junho de 2022 e junho de 2023, não houve episódios de eutrofização, o biodevice terá contribuído para reduzir as concentrações de nutrientes na água, de 0,021 ± 0,007 para 0,002 ± 0,001 mg/L PO4, e de 0,050 ± 0,007 para 0,020 ± 0,006 mg/L NH4. A clorofila a manteve-se entre 4,00 ± 0,79 mg/m³ em junho de 2022 e 4,87 ± 0,20 mg/m³ em junho de 2023. A introdução indevida de espécimes presumivelmente exóticos de tartarugas e peixes no lago contribuiu para o aumento do azoto e do fósforo na água, dificultando a interpretação dos resultados obtidos. O azoto total aumentou de 1,59 ± 0,21 mg/L N para 68,05 ± 8,85 mg/L N, e por isso o IET (de 62,4 para 126). O fósforo total também aumentou de 0,03 ± 0,005 mg/L P para 0,08 ± 0,009 mg/L P, portanto, o IET passou de 37,4 para 53,3. Estes exemplares exóticos devem ser retirados e o biodevice deve continuar a ser testado, assegurando-se em simultâneo as condições hidrodinâmicas já definidas como ideais para o lago. Na construção do biodispositivo, deve ser testada outra corda que seja resistente à água e tenha uma pegada ecológica mais baixa.
The demographics and socio-economics of recent decades have altered the functioning of aquatic resources, generating, among other consequences, eutrophication with the consequent destruction of habitats, loss of biodiversity and risks to public health. This work on urban ecohydrology sought to develop a Nature-Based Solution (NbS) to improve the ecological status of an urban lake, using native macrophyte species that are phytoremediators of nutrients in the water. The aim was to help improve the functioning of the lake at Jardim das Comunidades - Almancil, Loulé, as part of a research project on the environmental performance of this urban space, organised by the Instituto Superior de Engenharia - Universidade do Algarve and the Loulé municipality. The prototypes of the bio-device were built with pieces of cork from the interior of Loulé - Algarve, connected to each other with nautical rope, in which holes were drilled to place specimens of Typha latifolia, Phragmites australis and Juncus inflexus, selected for their phytoremediation capacity. The cork was characterised (colour, texture, density and thickness) and the functioning of the biodevice was assessed by monitoring the lake's water quality, quantifying ammonia, nitrites, nitrates, total nitrogen, phosphates, total phosphorus, chlorophyll a, dissolved oxygen, temperature, pH and Secchi disk transparency before and after its installation. The ecological status of the lake was classified using a Trophic State Index (TSI). Between June 2022 and June 2023 there were no eutrophication episodes, the biodevice is considered to have contributed to the reduction of nutrient concentrations in the water from 0.021 ± 0.007 to 0.002 ± 0.001 mg/L PO4 and from 0.050 ± 0.007 to 0.020 ± 0.006 mg/L NH4. Chlorophyll a remained between 4.00 ± 0.79 mg/m³ in June 2022 and 4.87 ± 0.20 mg/m³ in June 2023. The improper introduction of presumably exotic specimens of turtles and fish into the lake contributed to the increase in nitrogen and phosphorus in the water, making it difficult to interpret the results obtained. Total nitrogen increased from 1.59 ± 0.21 mg/L N to 68.05 ± 8.85 mg/L N, and the TSI from 62.4 to 126. Total phosphorus also increased from 0.03 ± 0.005 mg/L P to 0.08 ± 0.009 mg/L P, so the TSI rose from 37.4 to 53.3. The exotic specimens should be removed and the biodevice should continue to be tested, while ensuring the hydrodynamic conditions already defined as ideal for the lake. In the construction of the biodevice, another rope should be tested that is water-resistant and has a lower ecological footprint.
The demographics and socio-economics of recent decades have altered the functioning of aquatic resources, generating, among other consequences, eutrophication with the consequent destruction of habitats, loss of biodiversity and risks to public health. This work on urban ecohydrology sought to develop a Nature-Based Solution (NbS) to improve the ecological status of an urban lake, using native macrophyte species that are phytoremediators of nutrients in the water. The aim was to help improve the functioning of the lake at Jardim das Comunidades - Almancil, Loulé, as part of a research project on the environmental performance of this urban space, organised by the Instituto Superior de Engenharia - Universidade do Algarve and the Loulé municipality. The prototypes of the bio-device were built with pieces of cork from the interior of Loulé - Algarve, connected to each other with nautical rope, in which holes were drilled to place specimens of Typha latifolia, Phragmites australis and Juncus inflexus, selected for their phytoremediation capacity. The cork was characterised (colour, texture, density and thickness) and the functioning of the biodevice was assessed by monitoring the lake's water quality, quantifying ammonia, nitrites, nitrates, total nitrogen, phosphates, total phosphorus, chlorophyll a, dissolved oxygen, temperature, pH and Secchi disk transparency before and after its installation. The ecological status of the lake was classified using a Trophic State Index (TSI). Between June 2022 and June 2023 there were no eutrophication episodes, the biodevice is considered to have contributed to the reduction of nutrient concentrations in the water from 0.021 ± 0.007 to 0.002 ± 0.001 mg/L PO4 and from 0.050 ± 0.007 to 0.020 ± 0.006 mg/L NH4. Chlorophyll a remained between 4.00 ± 0.79 mg/m³ in June 2022 and 4.87 ± 0.20 mg/m³ in June 2023. The improper introduction of presumably exotic specimens of turtles and fish into the lake contributed to the increase in nitrogen and phosphorus in the water, making it difficult to interpret the results obtained. Total nitrogen increased from 1.59 ± 0.21 mg/L N to 68.05 ± 8.85 mg/L N, and the TSI from 62.4 to 126. Total phosphorus also increased from 0.03 ± 0.005 mg/L P to 0.08 ± 0.009 mg/L P, so the TSI rose from 37.4 to 53.3. The exotic specimens should be removed and the biodevice should continue to be tested, while ensuring the hydrodynamic conditions already defined as ideal for the lake. In the construction of the biodevice, another rope should be tested that is water-resistant and has a lower ecological footprint.
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Keywords
Fitoremediação Eutrofização Cortiça Soluções baseadas na natureza