Journal
JOURNAL OF SOILS AND SEDIMENTS
Volume 22, Issue 3, Pages 982-993Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11368-021-03128-1
Keywords
Eutrophication; Internal loading; Phosphorus extraction; Chemical composition; Extreme drought
Categories
Funding
- Brazilian National Council for Scientific and Technological Development (CNPq) [442484/2014-3/MCTI/CNPq/Universal 14/2014 a, 446138/2015-0/MCTI/CNPq/ANA/23/2015]
- Coordination for the Improvement of Higher Educational Personnel (CAPES/PNPDProject) [2304/2011]
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This study quantified the phosphorus fractions and oxide content in the sediment of eight tropical semiarid reservoirs, and evaluated how water-level decreases affect the potential phosphorus internal loading. The results showed that a significant proportion of total phosphorus in the sediment was associated with potentially mobile forms, and the chemical composition of the sediments played a role in determining the phosphorus fractions.
Purpose We quantified the phosphorus (P) fractions and oxide content in the sediment of eight tropical semiarid reservoirs to assess how water-level decreases affect the potential P internal loading. Methods Chemical fractionation analyses were carried out to determine the P fractions in the reservoirs' sediment, and their chemical composition was evaluated via X-ray fluorescence. Linear regressions were performed to evaluate how changes in the oxide content in the reservoirs' sediment and percentage of the maximum volume stored (%MVS) affected the P fractions. Results About 35 to 46% of the content of the sediment load of the total phosphorus (TP) was associated with potentially mobile P forms (NaOH-P and BD-P). The chemical composition of the sediments indicated a strong presence of Al2O3 and Fe2O3. The regressions showed that the lower the proportions of Al2O3 content, the lower was both P mobile (Total-P and BD-P) and non-mobile forms (HCl-P and Res-P) in the reservoirs sediment, whereas the proportions of Fe2O3 content were positively related to NaOH-P and Res-P. Moreover, the proportions of SiO2 and CaO content in the sediment were respectively negatively related to NaOH-P and positively related to HCl-P. The decrease in the %MVS in the reservoirs favored both the accumulation of non-mobile forms of P (HCl-P and Res-P) and CaO in the sediments, whereas an opposite pattern was observed for Al2O3. Conclusion The high P load in the sediments, associated with potentially mobile forms and low water level, indicates that an internal loading mechanism may be present in the environments observed.
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