Name: THAISHI LEONARDO DA SILVA
Publication date: 29/09/2025
Examining board:
Name |
Role |
|---|---|
| ANA CHRISTINA WIGNERON GIMENES | Presidente |
| ANDRE LUIZ NASCENTES COELHO | Examinador Interno |
| FÁBIO LUIZ MAÇÃO CAMPOS | Examinador Externo |
Summary: The Doce River floodplain, which extends through Minas Gerais and Espírito Santo, has
ecological, productive, and social importance, harboring soils that regulate water flow, retain
contaminants, store carbon, and sustain biodiversity. The collapse of the Fundão dam in 2015
released 39.2 million m3 of mining tailings that reached the Doce River via the Gualaxo do
Norte and Carmo rivers. For this research, the affected area was delimited from the flood zone
of January 2022, which totaled approximately 1,213 km2 and allowed for the analysis of recent
connectivity between the main channel and the floodplain. The study aimed to understand how
variations in iron (Fe), pedogenetic processes, and socioeconomic conditions influence the
functional susceptibility of soils after the disaster. The approach integrated a literature review,
multicriteria analysis, and spatial processing in GIS. Secondary iron (Fe) data from pre- and
post-dam rupture scenarios were converted to a common unit and standardized to allow for
temporal comparison. Iron surfaces were interpolated using IDW and reclassified into five
percentile-based classes (P25–P95), representing relative gradations of accumulation. These
classes were cross-referenced with soil information, land use, and socioeconomic indicators,
composing the Criticality Index (Icrit), structured as a synthesis metric to represent the
functional susceptibility of soils. The interpretation of criticality was guided by the categories
of soil ecosystem services (provision, regulation, support, and cultural), allowing the correlation
of critical areas to potential functional losses. The results revealed distinct patterns among the
floodplain sectors. In the Upper Rio Doce, the highest proportions of areas in the upper
percentiles of Fe were observed, associated with the presence of technosols and agricultural
use, resulting in the highest Icrit values. The Middle Doce River presented marked
heterogeneity, combining stable areas with critical stretches near the channel, reflecting the
interaction between young alluvial soils and land use patterns. In the Lower Doce River, lower
percentiles of Fe and lower pedological pressure prevailed, although the sector concentrates
municipalities with high social vulnerability, which increased the final criticality in specific
portions. The Icrit synthesized these patterns by integrating pedological and geochemical
attributes, land use, and socioeconomic vulnerability, allowing for the spatial identification of
the stretches most susceptible to the loss of ecosystem services. The final result of the research
consists of a functional matrix that relates each Icrit class to the soil's ecosystem services,
structured from international literature on functional landscape assessment. The matrix
synthesizes the intensity of alteration of the functions of water regulation, filtration and
retention, nutrient cycling, biological support, and provision along the criticality gradient. The
lower classes (1 and 2) are associated with lower intensity of functional alteration; The
intermediate class (3) exhibits greater expression of filtering, retention, and support; and the
higher classes (4 and 5) simultaneously concentrate the most sensitive functions. This
functional synthesis allows us to understand how ecosystem services respond to pedogenetic
and geochemical reorganization after a breach, constituting the main integrating product of the
study.
