Banca de QUALIFICAÇÃO: WENDEL VALTER DA SILVEIRA PEREIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : WENDEL VALTER DA SILVEIRA PEREIRA
DATE: 17/02/2023
TIME: 11:00
LOCAL: Por videoconferência
TITLE:

"Contamination and risks of rare earth elements in gold mining areas in the eastern Amazon"

KEY WORDS:

Emerging contaminants; environmental contamination; pollution indices;
ecological risks; lanthanides.

PAGES: 62
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUMMARY:

Gold (Au) is exploited by rudimentary methods in several artisanal mines in the eastern
Amazon, which generates residuesthat can harm the ecosystem and public health through
contamination by rare earth elements (REEs). This study is divided into two chapters. In
the first chapter, the objectives were to determine the concentrations of cerium (Ce),
lanthanum (La), scandium (Sc), and yttrium (Y) in the area of influence of the Serra
Pelada mine, as well as the environmental risks of these elements. For this purpose, 27
samples were collected in agricultural, forest, mining, and urban areas, and submitted to
chemical and granulometric characterization. The concentrations of REEs were
quantified by inductively coupled plasma mass spectrometry (ICP-MS) and used to
estimate pollution indices and environmental risks. All REEs had higher concentrations
in anthropized areas than in the forest areas, except Sc in mining and urban areas.
Pollution load indices revealed that all areas are contaminated (>1) by the combined effect
of REEs, especially agricultural areas (index of 2.3). The element with the highest
enrichment was Y, with enrichment factors from 18.2 to 44.4 in anthropized areas.
However, ecological risk indices were low (<150) in all areas, indicating that there are no
current environmental risks from REEs in Serra Pelada. In the second chapter, the
objectives were to quantify the concentrations of REEs and assess their risks to the
environment and human health in artisanal Au mining areas in Cachoeira do Piriá,
northeastern Amazon. Thus, 25 samples were collected in underground, colluvial, and
cyanidation mining areas, as well as in a natural forest. The concentrations of REEs were
quantified using alkaline fusion and ICP-MS, and the results were used to estimate
pollution indices and risks associated with the contaminants. All REEs had higher
concentrations in the waste disposal areas than in the forest areas, especially light REEs.
Pollution and enrichment levels were higher in the underground and cyanidation mining
areas, with very high contamination factors (6.2 – 27) for Ce, europium (Eu), La,
neodymium (Nd), praseodymium (Pr), samarium (Sm) and Sc, and significant to very
high enrichment factors (5.5 – 20) for Ce, La, Nd, Pr and Sc. Ecological risk indices
ranged from moderate (167.3) to high (365.7) in the most polluted areas, but human health
risks were low. The results of this study indicate that mitigating measures must be
implemented to protect the environment from the impacts of REEs, considering the levels
of contamination, enrichment, and ecological risks of these elements in the studied areas.

BANKING MEMBERS:
Externa à Instituição - FRANCIELLE ROBERTA DIAS DE LIMA - UFLA
Externa à Instituição - CYNTHIA DE OLIVEIRA - UFLA
Presidente - 6388356 - ANTONIO RODRIGUES FERNANDES
Externo ao Programa - 388426 - FRANCISCO DE ASSIS OLIVEIRA