Metais na Amazônia: um panorama da literatura científica entre 1984 e 2023

Abstract

The Amazon is a region of enormous natural wealth, including a vast quantity of minerals and metals, both naturally occurring, concentrated in different mineral deposits and distributed in the environment by natural processes, and mobilized by the exploitation of these resources and introduced by various socioeconomic activities. Given its mineral, cultural, and biodiversity importance, and as one of the main regulators of the global climate, the Amazon has attracted growing interest from various areas of scientific research, among which the area of metal contamination stands out in this study, due to the intensification and diversification over the last thirty years of socioeconomic activities that are potential sources of these substances. Metals are substances naturally present in the Earth's crust, but their concentration and distribution can be significantly altered by anthropogenic activities, generating impacts on human health and ecosystems. The scientific literature on metals in soils, water, and sediments in the Amazon between 1984 and 2023 was compiled using bibliometric analysis and a systematic review of the Scopus online collection. The results indicated that scientific production on the topic follows an exponential growth pattern, according to Price's Law (R² = 0.8525). The Price Index pointed to the high relevance of recent literature, while the third-order polynomial model predicted more than 150 annual publications by 2034 and more than 200 by 2044. The systematic review, based on 61 studies published between 2014 and 2023, identified Brazil as the country with the highest number of articles (45), followed by Ecuador (9), Peru (5), and Colombia (2). Among the Amazonian institutions with the highest number of publications, UFPA stood out as the one that publishes the most works on metals, with 71 articles, followed by USP with 63 and UFRJ and UNESP with 37 articles each. Among the areas most affected by metal contamination are the Carajás region and the Parauapebas River basin (Brazil), the Zamora River Basin (Ecuador), the Province of San Martín (Peru), and the Taraira Region (Colombia). The most studied metals, by number of citations, were Cu (41) > Pb (40) > Zn (38) > Fe (33) > Mn (32) > Cd (30) > Cr (30) > Ni (28) > Hg (24) > Al (21), with a predominance of anthropogenic sources, especially mining. When compared with the quality standards established for ecosystem protection, significant enrichment was shown (i) in soil: Cu (726 μg/g), Pb (523 μg/g), Zn (589 μg/g), Cr (141 μg/g), and Hg (19.4 μg/g); (ii) in sediment: Cu (141 μg/g), Pb (902 μg/g), Zn (3,067 μg/g), Cd (5.9 μg/g), Cr (549 μg/g) and (Hg 18.6 μg/g); (iii) in surface water: Cu (103 μg/L), Zn (4,800 μg/L), Fe (408 μg/L), Mn (980 μg/L), Ni (183 μg/L), Hg (100 μg/L), Al (5.74 μg/L); and in groundwater: Pb (2,002 μg/L). Soil was the most investigated environmental matrix, followed by sediments and water, highlighting the need for continuous monitoring and public policies aimed at preventing metal contamination in the region.