Anthropogenic influence on the degradation of an urban lake – The Pampulha reservoir in Belo Horizonte, Minas Gerais, Brazil

Abstract

a b s t r a c tThe artificial reservoir Lagoa da Pampulha in central Brazil has been increasingly affected by sediment deposition and pollution from urban and industrial sources. This study investigates water chemistry and heavy metal concentrations and their fractionation in the lake sediment using ICP-OES, ICP-MS, and XRD analyses. Fractionation analysis was done by sequential extraction under inert gas as well as after oxidation. The lake exhibits a permanent stratification with an oxygen-free hypolimnion below 2 m depth. Nutrient concentrations are enriched for phosphorous components (SRP, PO 4 ). In the sediment it was not possible to detect oxygen. Carbon, sulfur, and most of the analyzed heavy metals are enriched in the top sediment layer with a pronounced downward decrease, indicating the presence of an anthropogenic influence. Statistical analysis, including correlations and a Principal Component Analysis (PCA) of depth-related total concentration data, helps to distinguish presumably anthropogenic heavy metals from geogenic components. Some samples with high element concentrations in the sediment also show elevated concentrations in their pore water. Analyses of element distribution between sediment and pore water suggest a strong bonding of heavy metals to the anoxic sediment. The trend towards elevated solubility in the pore water of oxidized samples is clear for most of the analyzed elements. Fractionation analysis reveals characteristic associations of selected elements to specific mineral bonding forms. In addition, it indicates that the behavior of heavy metals in the sediment is strongly influenced by organic substances. These substances provide buffering against oxidation, acidification, and metal release. The high nutrient loading causes reducing conditions in the lake sediment. These conditions trigger the accumulation of sediments rich in S 2 À , which stabilizes the fixation of heavy elements. In the future, care must be taken to reduce the supply of contaminants and to prevent the release of heavy metals from sediments dredged for remediation purposes.

From intermittent to persistent cyanobacterial blooms: identifying the main drivers in an urban tropical reservoir

“…An increasing TP input may also be explained by a higher contribution from untreated streams (those that are not primarily treated by the treatment plant) as a consequence of a growing urbanization and more dense population in the reservoir's catchment (source: www.ibge.gov.br -accessed on January 2013). Finally, the internal P recycling rate from the sediments may also contribute to higher TP concentrations due to more episodes of low DO concentrations and even hypoxia in the hypolimnion in recent years (Friese et al, 2010). A similar situation was observed in Lake Kinneret, Israel (Zohary, 2004), where external nutrient inputs declined, but internal loading and recycling were important to maintain the already altered phytoplankton community.…”

Dissolved organic N in shallow tropical lakes and reservoirs: Contribution to total dissolved N and relationships with eutrophication

“…Differences between studied systems, regardless of season, appeared to be primarily dictated by land use, with urbanization being especially important. The Pampulha reservoir differed greatly from all other studied systems due to its persistent hypereutrophic status (Boëchat & Giani, ; Friese, Schmidt, Lena, Nalini, & Zachmann, ). Concentrations of nutrients, as well as values of pH and EC were extremely high in this urban reservoir.…”

Concentrações de metais pesados nos sedimentos do lago Água Preta (Pará, Brasil)

“…A cidade de Belém, de acordo com a classificação de Koppen (KOTTEK et al, 2006), está na categoria Af, caracterizada pela alta temperatura (sempre acima de 18º) e distinção entre dois períodos, um mais chuvoso (conhecido na região como inverno) e outro menos chuvoso (DE SOUZA et al, 2016 ) apontam para a contaminação dos sedimentos para esse metal, apesar de não existir índices internacionais que confirmem essa suposição (AN & KAMPBELL, 2003;FRIESE et al, 2010;NGUYEN et al, 2005). …”