Modeling phosphorus exchange between bottom sediment and water in tropical semiarid reservoirs

Abstract

This study investigated phosphorus (P) dynamics in the sediment-water interface of three distinct reservoirs located in a tropical semiarid region. Sequential chemical fractioning of the P content in the sediment and controlled experiments of the sedimentwater interface were performed to understand and model the effect of the different P fractions on the exchange dynamics under anoxic and oxic scenarios. The results revealed that the older the reservoir, the higher the amount of iron and aluminum-bound P in the sediment, and that this fraction was responsible for a 10-fold increase in P concentration in the water during anoxic conditions. After aeration, P in water decreased but did not return to its initial concentration. The most recently constructed reservoir showed the lowest P concentration in the sediment and dominance of the unavailable P fraction, resulting in no potential impact on water quality. Phosphorus release and precipitation rates were well described by zero-and first-order models, respectively.Reservoirs with high P availability in the sediment, not only released more phosphorus but also presented a lower precipitation rate, resulting in higher potential damage to water quality and making some in-lake treatment techniques ineffective.

Phosphorus mass balance and input load estimation from the wet and dry periods in tropical semiarid reservoirs

“…Figure 4 also shows the mean modeled TP load for each semester throughout the studied period. As already mentioned, the load during the dry period can be caused by both sediment release and/or resuspension (Mesquita et al 2020;Moura et al 2020). Particularly in shallow lakes, internal loading can promote elevated TP values in the epilimnion (Horppila et al 2017).…”

“…Internal TP load production is expected to be stronger in the dry season, as dissolved oxygen concentration in the hypolimnion usually falls below 1.0 mg/L (Souza , potentially causing P release from sediments (Moura et al 2020), while, on the other hand, water volume is lower and wind speed is stronger, potentially causing wind-induced resuspension (Mesquita et al 2020). Note that in larger reservoirs such as Castanhão (71 m deep), periods of low hypolimnetic dissolved oxygen (about 2 mg/L) are also expected during the rainy season (Santos et al 2017).…”

“…Commonly, external P load represents a higher percentage in an annual P budget and its relevance have formed the basis for classic predictive models such as the P model of Vollenweider (1968) (Lepori and Roberts 2017). The majority of P that comes to a lake ecosystem, however, is usually stored in the bottom sediment (Kiani et al 2020), which in appropriate conditions return to the water column (Moura et al 2020). P releasing from sediments, the internal loading, results from physical and/or biogeochemical mechanisms that operate on different temporal and spatial scales in a complex process (Orihel et al 2017).…”

Avaliação de nutriente limitante da produção algal em reservatórios do semiárido brasileiro

“…Dessa forma, nos reservatórios eutrofizados do NEB, onde vivem cerca de 50 milhões de pessoas, a identificação do nutriente limitante do crescimento algal é fundamental para o seu gerenciamento. Apesar do conhecimento acumulado sobre a limnologia e o manejo desses reservatórios LIMA NETO, 2017;LACERDA et al, 2018;MOURA et al, 2019), que envolvem as fontes de cargas de nutrientes (FREITAS; RIGHETTO; ATTAYDE, 2011; VIDAL; CAPELO NETO, 2014; ARAÚJO; LIMA NETO; BECKER, 2019) e a influência da seca na qualidade da água (BRASIL et al, 2016;ROCHA JÚNIOR et al, 2018;LIRA;LIMA NETO, 2020), as pesquisas que avaliaram o nutriente limitante da produtividade primária e seus fatores associados são raras e locais. Assim, o presente estudo teve por objetivo testar a hipótese de que o fósforo total seria o principal nutriente limitante do crescimento fitoplanctônico em reservatórios do NEB.…”

Análise E Modelagem Das Relações Entre Nutrientes E Fitoplâncton Em Reservatórios Do Ceará

“…A eutrofização tem provocado sérios impactos socioeconômicos e ambientais relacionados à proliferação de algas em diversos lagos e reservatórios do planeta (SMITH;SCHINDLER, 2009;PAERL;OTTEN, 2013;IBELINGS et al, 2016). No Brasil, esse problema tem sido potencializado principalmente pelas elevadas cargas de nutrientes lançadas nos corpos hídricos, além da escassez hídrica recorrente na região semiárida (VON SPERLING, 1996;CIRILO, 2015;WIEGAND;PIEDRA;ARAÚJO, 2016;LOPES et al, 2017;PACHECO;LIMA NETO, 2017;MOURA et al, 2019; FRAGA; ROCHA; LIMA NETO, 2020; LIRA; MEDEIROS; LIMA NETO, 2020; MESQUITA; PEREIRA; LIMA NETO, 2020).…”