Banca de DEFESA: DANIEL JÁDSON NORONHA LIMA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : DANIEL JÁDSON NORONHA LIMA
DATE: 19/06/2020
TIME: 09:00
LOCAL: Videoconferência
TITLE:

PHOSPHORUS FRACTIONS AND THEIR AVAILABILITY IN RESERVOIR SEDIMENTS IN THE BRAZILIAN TROPICAL SEMIARID

KEY WORDS:

Eutrophication. Internal loading. Phosphorus extraction. Elemental composition. Shallow artificial lakes.

PAGES: 36
BIG AREA: Engenharias
AREA: Engenharia Sanitária
SUMMARY:

The Phosphorus (P) stored in eutrophic lake sediments can be an important source of enrichment of this nutrient for the water column and contribute to the persistence of eutrophication in these environments, even after the reduction of external sources. Thus for the restoration of these water bodies to be successful, it is also necessary to control this internal load. For this, it is essential to know the elemental composition and the mobile load of P present in the sediments. In artificial lakes (reservoirs) in the tropical semiarid, this internal loading mechanism is especially important during periods of drought, where external input from P is reduced due to scarcity of rainfall. Thus, this study aimed to quantify the P fractions and the elemental composition in the superficial sediments of eight shallow eutrophic reservoirs located in the tropical semiarid of northeastern Brazil, in order to evaluate the internal load available for the maintenance of the trophic conditions of these water bodies. For this, chemical fractionation tests were performed to determine the fractions of P present in the sediments and the X-ray fluorescence (XRF) to analyze their elemental composition. The total phosphorus (PT) load in the sediments varied from 593,17 to 1222,12 µg g-1 DW,  about 35 to 46% of this content was associated with potentially mobile forms of P. The most abundant fractions were P-NaOH (25% to 37% of PT), representing non-reducible forms of P-Fe and -Al oxides, and P-BD (23% to 30% of PT), which is related to forms of P sensitive to redox conditions, mainly Fe and Mn oxides and hydroxides. The greater abundance of these two fractions is consistent with the elemental composition that points to a large presence of Al₂O₃ (25,27% ± 2,19%) and Fe₂O₃ (22,56% ± 2,95%) in the sediments. In general, the P fractions presented the following decreasing order in most reservoirs: P-NaOH> P-BD > P-Humic> NRP >P-Res> P-HCl> P-Water. The high P pool in the investigated sediments associated with potentially mobile forms and common environmental characteristics in these water bodies in the semiarid region, that normally favor their release, are factors that indicate that the internal loading mechanism may be acting in these environments.

BANKING MEMBERS:
Presidente - 052.716.174-83 - FABIANA OLIVEIRA DE ARAUJO SILVA - UFRN
Externa à Instituição - NATÁLIA PESSOA NOYMA - UERJ
Externo à Instituição - ROSEMBERG FERNANDES DE MENEZES - UFPB