Banca de DEFESA: DJENNYFER KAROLAINE DE MELO FERREIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : DJENNYFER KAROLAINE DE MELO FERREIRA
DATE: 30/07/2021
TIME: 09:00
LOCAL: Defesa remota pelo Google Meet
TITLE:

Geochemical alterations in contaminated mangrove soils and effects on the bioavailability of metals and microbial community

KEY WORDS:

contamination, heavy metals, microorganisms, redox.

PAGES: 42
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Química do Solo
SUMMARY:

Mangrove soils in their natural conditions are known as a sink of contamination for retaining heavy metals in solid and organic particles in non available forms. In the northern littoral of Pernambuco, the Botafogo river estuary has a history of contamination by mercury (Hg) but it is needed to evaluate how changes on the characteristics of these soils can affect the availability of metals and microbial communities. The objectives of this study were to determine mercury (Hg), Chromium (Cr) and Zinc (Zn) contents in mangrove soils and analyse changes in compartmentalization of Hg after 120 days of exposure to oxic conditions, as well as the interferences on microbial respiration and soil carbon biomass. Soils from three areas (A1, A2 and A3) of the Botafogo River were collected and selected for ten times of incubation (0, 5, 15, 30, 45, 60, 75, 90, 105 and 120 days). After incubation times the samples were divided in two depths (0-5cm and 5-10cm), each one homogenized and put inside plastic recipients under refrigeration (-18°C) until the moment of being analyzed. Potential redox (Eh) and pH were determined on site and after every collection from incubation times. The humidity of soils was gradually decreased to half of the initial humidity. Soil particle size distribution was performed for each area. The chemical analysis performed were total contents of Hg, Zn, Cr and Fe and Hg sequential extraction. For the microbial analysis, soil carbon biomass and soil respiration were conducted. These soils are classified as clay and silty clay. After 120 days of decreased humidity, all areas showed acidification and an increase in Eh from anoxic/suboxic to oxic conditions. Chromium and Zn main values were found below international limits for these metals (TEL and PEL). These two metals were highly correlated to iron (Fe). Mercury contents are above international limits (TEL and PEL), confirming the contamination status of the Botafogo River. Sequential extraction of Hg showed a tendency of Hg release from non available fractions (residual) to less stable fractions (organo-chelated and elementar Hg). This could mean a risk of availability of Hg when the mangrove soil is exposed to longer times of alterations on their natural conditions of humidity, pH and Eh. Soil carbon biomass increased with incubation times in all areas, while soil respiration decreased in A3, the most contaminated area, and increased in A1 and A2, the less contaminated areas. Acidification had a higher impact on the microbial communities than the other parameters, showing that there might have resistant populations in these areas. These results show a potential risk of a second source of Hg contamination from the Botafogo River estuary and the need to study microbial populations existing in the area to better understand the impacts of alterations to the microorganisms.

BANKING MEMBERS:
Presidente - 2584833 - CAROLINE MIRANDA BIONDI
Interna - 1929733 - GISELLE GOMES MONTEIRO FRACETTO
Externa à Instituição - PAULA RENATA MUNIZ ARAUJO - UFRPE