Banca de DEFESA: VICTOR MARTINS GUEDES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : VICTOR MARTINS GUEDES
DATA : 19/02/2020
HORA: 14:00
LOCAL: Auditório NTB - Campus Tapajós
TÍTULO:

DYNAMICS OF CARBON AND NITROGEN DISSOLVED IN THE LOW AMAZON RIVER REGION

PALAVRAS-CHAVES:

Concentrations Flows. Tidally-influenced. Mass balance.

PÁGINAS: 63
GRANDE ÁREA: Outra
ÁREA: Ciências Ambientais
RESUMO:

The Amazon River play an important role in transporting and processing of nutrients towards the ocean. However, there is a gap in the understanding of this river as a link between the terrestrial and marine environment, due to few studies in this region, tidally influenced. Here, dissolved carbon and nitrogen concentrations and flows were measured from Óbidos to the last two well-defined channels near the mouth of the Amazon River, north and south channels (close to Macapá), during the period of 2014 and 2017, through six cruises. DOC, DIC and TDN concentrations were determined by infrared absorption generated after combustion at 690°. DIN fractions (nitrite, nitrate and ammonium) were determined by automated flow injection system calorimetry. DON concentrations were obtained by the difference between the TDN fraction and the DIN fractions. DOC and DON concentrations in the Amazon River mainstem and its clearwater tributaries are mainly influenced by the input of allochthonous material, varying their concentrations between 1,1 to 5,9 mg.L-1 and 0,01 to 0,21 mg N.L-1, respectively. Regarding DIC and DIN concentrations, their variation was less uniform when compared to dissolved organic fractions, varying between 1,1 to 5,9 mg.L-1 and 0,01 to 0,21 mg N.L-1, respectively. From Óbidos to Almeirim, decreases in average concentrations of DOC were observed during periods of high and falling water, with negative mass balances (ΔF%= -9% ~ 106 kg.s-1 and ΔF%= -12% ~ 125 kg.s-1, respectively). Regarding DIC, decrease in its average concentration was observed in the low water period, accompanied by unaccounted sinks (ΔF% = -47% ~ 206 kg.s-1). From Almeirim to mouth, decreases in DOC and DIC concentrations are observed only at the low water period, with positive mass balances for both fractions (ΔF% = + 30% ~ 156 kg.s-1; and ΔF% = + 170% ~ 408 kg.s-1, respectively). Longitudinal variations of DON were observed only in the falling water period, accompanied by unaccounted sinks from Óbidos to Almeirim (ΔF% = -42% ~ 13 kg.s-1) and unaccounted sources (ΔF% = + 94% ~ 17 kg.s-1) from Almeirim to the river mouth. Regarding the DIN, longitudinal variations were observed only between the Almeirim station and the mouth during the rising and high water periods, accompanied by positive flow balances (ΔF% = + 11% ~ 6 kg.s-1 and ΔF% = + 67% ~ 2 kg.s-1, respectively). An average flux of 59 Tg C.year-1 and 2 Tg N.year-1 in its dissolved forms, towards the ocean, were estimated.

MEMBROS DA BANCA:
Externa ao Programa - 2386579 - DIANI FERNANDA DA SILVA LESS
Presidente - 1794276 - JOSE MAURO SOUSA DE MOURA
Externo à Instituição - LUIZ ANTÔNIO MARTINELLI - USP
Interno - 1549120 - RODRIGO DA SILVA