Dados da Submissão

Título

Methodological approach and general guidelines to geochemical mapping and background-baseline analysis for environmental assessment: a study case in the Carajás Mineral Province

Texto do resumo

Regional geochemical surveys have been used in mineral exploration since the mid-20th century for the location of mineral deposits. In the 1990s, an international project was created to stimulate geochemical surveys on all continents, following a standardized methodology to ensure comparability of the data from different areas and countries.
The aim of this study is to present the methodological approach and general guidelines to support geochemical mapping and background-baseline projects for environmental assessment. A study case was developed in the Itacaiúnas River watershed (IRW), Eastern Amazon, to fulfil a knowledge gap about the distribution of chemical elements, particularly those potentially toxic, in the near-surface environment of the area. The high -impact research achievements obtained from the project “Itacaiúnas Geochemical Mapping and Background Project” - ItacGMBP revealed the need for this scientific investigation across the globe, following a systematic methodology of the implementation.
The methodological approach includes: SAMPLE METHODOLOGICAL APPROACH - i) construction of the Geographic Information Systems (GIS) database, ii) data collection and GIS computer-based framework for sampling and data validation, iii) general strategies for site selection based on GIS tools, iv) sample collection and documentation; LABORATORY PROTOCOLS, ANALYTICAL METHODS, AND QUALITY CONTROL – v) chemical and mineralogical analyses of soil and sediment samples, vi) analyses of physico-chemical parameters in stream water samples, vii) quality assurance and quality control (QA/QC) of the geochemical data; GENERAL ASPECTS ON DATA PROCESSING AND STATISTICAL TREATMENT OF GEOCHEMICAL DATA – viii) data preparation and statistical treatment, ix) geochemical mapping, and x) statistical methods used for the calculation of geochemical background values.
The results obtained by the ItacGMBP indicate that regional geochemical background values along with high-density spatial mapping should always be considered as a tool for identifying pollution hotspots and the accurate assessment of metal contamination. It was concluded that the maximum values proposed as a reference of quality in the Brazilian environmental regulations, proposed by the Conselho Nacional do Meio Ambiente (CONAMA), are not realistic for the Amazonian region. The results show the importance of a well-planned field activities, multimedium sampling, analytical methods, laboratory procedures, database construction, and general aspects on data processing and statistical treatment.
We conclude that the information given herein is an important contribution to the scientific community, which can be used as a reference to support geospatial analysis in research conducted within the scope of the geochemical mapping and background-baseline projects. The database is accessible through a web-based geographic information system GIS front-end and a Geochemical Atlas of the IRW.

Palavras Chave

geochemical mapping; soil; stream sediment; stream water; GIS