Phosphorus release from sediments and the role of oxygen and trophic state
Phosphorous (P) is a limiting nutrient of algal growth. Reducing input of point P sources of surface waters, although essential, is not enough towards mitigating eutrophication due to the P internal loading. There are numerous factors that can interfere on P release, including oxygen presence and...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/25291 |
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| Resumo: | Phosphorous (P) is a limiting nutrient of algal growth. Reducing input of point P sources of
surface waters, although essential, is not enough towards mitigating eutrophication due to the P
internal loading. There are numerous factors that can interfere on P release, including oxygen
presence and trophic state of overlying water. Hence, our study aimed to analyze P fluxes
concerning the oxygen presence (low and high oxygen) and the phosphorus concentrations of
overlying water (natural and deionized water) utilizing several microcosms in order to simulate
the proposed conditions. Overall, P fluxes were higher when a low P concentration overlying
water situation was simulated under hypoxic conditions for both soluble reactive phosphorus
(SRP) and dissolved organic phosphorus (DOP) fluxes. With natural overlying water, P release
was greater also under hypoxic conditions, which is an indicative of higher inorganic P bonded
to Al and FeOOH. When the P fluxes are analyzed temporally, we could notice that P fluxes
were positive at the first seven days, then, mostly negative for the rest of the experiment. This
indicates that, although P release is significant throughout the experiment, phosphorus behavior
is dynamic in time. SRP fluxes for the 0-7 day interval showed interaction only with variation of
P concentration in overlying water, while DOP fluxes exhibit only interaction with both O2 and P
concentrations. The 7-14 day interval indicates higher phosphorus retention in oxic conditions
for both SRP and DOP fluxes. SRP fluxes were significantly changed with oxygen conditions,
while DOP fluxes, with P concentration. Both SRP and DOP fluxes showed significant
interaction between categorical factors. Thus, in semiarid regions such as Gargalheiras’, P
release might continue being a serious problem due to its high temperature and pH, low depth
and elevated evaporation rates, which contributes to concentrate P in overlying water and induce
anoxic conditions in sediment. Also, even if the rainy season come to dilute P in water, P release
may be favored due to P gradient concentration due to the large P pool in sediments. |
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