HEAVY METALS IN SURFACE WATERS IN A STATE OF THE BRAZILIAN AMAZON: AN INTEGRATIVE REVIEW

Objective: The aim was to carry out a systematic literature review on studies and research into heavy metals (traces) in rivers in the Amazon region of Pará. Theoretical Framework: To have a chronological understanding of the situation of possible contamination by trace metals, affecting the quality of water in the Amazon, impacting ecosystems and public health. Industrial, agricultural and urban development has had a negative impact on rivers in Pará, contributing to the degradation of water resources. Method: This is a review, with a descriptive, qualitative and quantitative approach, using literature searches (descriptors) of research carried out in the state of Pará, published between 2005 and 2023. Articles with solid evidence were considered, in accordance with the parameters recommended by resolutions 274/2000 and 357/2005 and ordinance 888/2021 of the National Environment Council - CONAMA, expressing the results through descriptive statistics. Results and Discussion: It was possible to demonstrate the main environmental impacts of pollutant and contaminant sources in rivers in the Amazon region of Pará, such as high concentrations of Pb, Cu, As, Cd, Cr and Hg, especially Pb and Hg, which were present in 60% of the studies carried out in different aquatic environments over the last 20 years in the state of Pará. Research Implications: It helps to visualize the little research carried out in the Pará Amazon, as well as providing a better understanding of land use in the region, correlating it with the contamination of surface water by heavy metals. Originality/


INTRODUCTION
Metals, in relation to their essentiality to aquatic organisms, can be classified as essential and non-essential (Rodrigues et al., 2016).The essential ones such as copper (Cu), iron (Fe) and zinc (Zn) are those that have known biological function and are obligatory constituents of the metabolism of individuals, participating in processes involving enzymatic compounds, but depending on the amount assimilated can become toxic (Costa et al., 2020).On the other hand, non-essential elements such as chromium (Cr), mercury (Hg) and lead (Pb), for example, generally do not have a known biological function for metabolism, and the cofactors of SOD -Superoxide dismutase, an enzyme that prevents the release of hydrogen peroxide and free radicals such as zinc (Zn), copper (Cu) and Manganese (Mn) (Rodrigues et al., 2016).
The human being only needs small doses of a few metals, they are called micronutrients, as in the case of Cu and Fe (Cozzolino, 1997).The direct ingestion of heavy metals dissolved in water or indirectly accumulated in seafood, above the limit, is one of the main sources harmful to human beings, and causes disturbances in metabolism, besides carcinogenic activity (Cozzolino, 1997;Galarza et al., 2023).
Water is an essential resource for life forms, correlating with ecological systems, of vital importance for the survival of living organisms, besides directly influencing the economy, leisure, culture and social environment (Almeida & Souza, 2019;Simões et al., 2020) In socioeconomically poor or even emerging countries, such as Brazil, the levels of potability of this resource are sometimes compromised due, in part, to poor sanitary conditions, failure between water management and environmental management and the disorderly growth of large cities (Oliveira et al., 2017;Simões (...),(11) When discussing water resources in the Amazon there is an erroneous perception, in which quantity is mistaken for quality of available water, which ends up masking the problems related to the degradation of the rivers and springs of the region, since anthropic waste may be thrown in an irregular manner and without treatment, incapacitating the system's power of selfpurification, directly affecting the health of biological species and increase of diseases of water 4 circulation (Teixeira et al., 2017;Costa et al., 2020).In addition, in the Amazon rivers, there is a seasonality with a well-defined dry and rainy season that is reflected in the physical and chemical properties of the waters (Lopes et al., 2021).
In a general context, in the last two decades, rivers and springs of Pará have suffered strong impact and degradation due to industrial development, growth of urban disorderly area, lack of public policies and intensive use of agricultural land, which use high quantities of inputs, affecting the quality of natural resources (Teixeira et al., 2017;Moura et al., 2020).
The presence of anthropogenic chemical contaminants may not be considered as pollution unless it affects the environment or biota.According to Galarza et al. (2023), contamination occurs when the direct or indirect introduction of matter or energy into aquatic environments passes concentrations whose harmful effects are manifested, i.e. results in measurable impacts on individual organisms, populations or biological communities.Pollution, in turn, occurs when these concentrations in water, sediment, or organisms exceed the area's baseline levels, without causing measurable harmful effects (Pereira et al., 2019).
On the basis of the above, precise data were sought to assess the current situation of the rivers and effluents of the region in recent years.Thus, the present study aimed to carry out a systematic literature review on studies and research of heavy metals/traces in rivers of the Pará Amazon, providing the synthesis of knowledge, through the main periodical collections in the period 2005 to 2023.

FIELD OF STUDY
The literary searches were of surveys carried out under the State of Pará, one of the 27 federative units of Brazil, occupying an area of 1,245,870,704 km².According to the 2022 census, it has 8,116,132 million inhabitants, with a population density of 6.51 inhabitants/m2 distributed in 144 municipalities.The local Human Development Index (HDI) is 0.646, occupying the 24th position in the country; monthly nominal household income per capita is R$1,061.The capital Belém, along with five other municipalities, encompasses the metropolitan region with about 2.6 million inhabitants (Ibge, 2022).
The region has a hot and humid climate, with average annual relative air humidity of 86.8 ± 3.05%, average annual precipitation of 2,921.7 ± 122.145 mm and average annual temperature of 25.9 ± 0.33 ºC (Inmet, 2014).

TYPE OF STUDY
This is a review research, a descriptive approach, of a qualitative-quantitative nature, through the analysis of content proposed by Bardin (2016).The use of different databases occurred in order to expand the rationale of the research, eliminating possible biases during the selection of articles.

DATA COLLECTION
An online search was carried out in the aforementioned journals by means of the descriptors established for the selection of articles, being: Amazon estuary; Pará rivers; contamination by heavy metals; Amazon surface waters; water quality index; environmental impacts in the waters of Amazonia; Metals and water; Metals in the Amazon; AmazonAmazon and metals; River and amazon.
The data extracted from the articles covered the following items: title, journal, authors/ year/ country, study design and level of evidence.

DATA ANALYSIS
It was organized in a database in Microsoft Office Excel software 2021, through which the pertinent results were selected with the question guiding the integrative review, besides the construction of figure and table to express the results better, using descriptive statistics with percentage values (%).

RESULTS AND DISCUSSION
In a search carried out through the crossings of the descriptors, twenty-three (23) studies were found on the theme addressed.After establishing the desired period of research, the preselected works were tabulated and organized, in which corresponded to the years 2005 to 2023, where ten (10) jobs were found in the Pubmed base, seven (7) in the Scielo base, three (4) in Google scholar and others.
After a thorough reading of the articles, the 23 made up the database for analysis and discussion, since they answered the questions of research (Table 1).The selected articles were characterized by database, year of publication, author(s) and main results.They aimed to evaluate the concentrations of nutrients and heavy metals in the sediments at the bottom of the Água Preta lake, Belém, Pará.The metals with the highest concentration were chromium (245 mg.Kg -1 ) and nickel (97 mg.Kg -1 ), which were above the index that determines the probable effect level (locallyProbable Effect Level -PEL).

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Google scholar 2014 Lima Furo da Laura is the main watercourse of the municipality of Vigia (PA), with large extension, daily flow of vessels and sharp urbanization on the right bank, pouring daily domestic sewage into this estuary, can lead to deterioration of water quality and sediment.As for heavy metals, sediments were found to be impacted by Cd, Cr, Ni and Fe higher than recommended by CONAMA.In the light of the current reality of the Amazon rivers, it was possible to observe a characteristic pattern as to the main metals most researched (Table 1), since knowing the reality, industrial/economic processes, mining areas, exploitation of natural resources for various purposes.As Figure 1 points out, in recent years in rivers of the Pará Amazon, exposure to lead and mercury has been more prevalent based on the scientific literature, which is widely recognized as a global public health problem, affecting children in developing countries, such as Brazil (Brazil, 2012;Obregón et al., 20214).
In the State of Pará, mercury contamination is linked to artisanal and small-scale gold mining, where it is used in the purification process (Sacramento et al., 2021).In relation to lead contamination in the broader region, it is caused mainly by exposure to electronic waste, battery recycling or the manufacturing of enameled ceramics, according to the studies of Freitas et al. (2018) and Sacramento et al. (2021).Based on these analyzes, the concentrations of heavy metals such as Pb, Hg, Al and Cr were determined in bottom sediment samples in streams and rivers and surface waters, present in the body of fish and human hair in most studies, mainly in pará municipalities where the economic base is based on mineral resources and mining, as well as large steel mills and leather production, as the case of Cr (Nevado et al., 2010, Doimeadios et al.,¹ 2014).In large urban centers, there is the issue of disorderly occupation, poor distribution of sanitation and industrial networks close to rivers, combined with deforestation and the construction of dams, causes serious environmental impacts in the region, increasing the accumulation of heavy metals in the Amazon soils and rivers (Arrifano et al., 2018b, Lopes et al., 2021).Lopes et al. (2021) point out that the consumption of fish contaminated by illegal miners, from the upper and middle Tapajós river, for example, is indicated as the origin of the presence of high levels of mercury in the blood of the population of about 306 thousand inhabitants of the municipality of Santarém, in Pará.Rivers and streams were contaminated and around 40 thousand citizens of indigenous, riverside and quilombo communities had their health and way of life affected by aluminum production in Barcarena and Abaetetuba, northeast of the state (Arrifano et al., 2018a).Another example, the Amazon River and its tributaries suffer from the presence of chemical contamination, by pesticides, microplastics, pharmaceuticals and other types of contaminants (Lopes et al., 2021).Fabregat et al. (2021) in Environment International, shows the first quantitative analysis of pharmaceuticals and other urban contaminants in freshwater ecosystems in the Amazon as to exposure patterns in four major cities in the Brazilian Amazon, including Belém and Santarém, where the chemical load created by the emission of untreated wastewater from urban areas poses significant long-term risks to freshwater ecosystems, with chemical mixtures that can affect up to 50-80% of species.

Research published by
Exposure to metals or mixtures of metalloids is of particular interest in environmental quality, human and animal health; and from a public health point of view the presence of Pb, Hg and As, for example, continue to be the target of attention, since they are compounds that are found in 95% of the residues and are diffused in Amazon rivers (Sousa et al., 2022), corroborating with the information highlighted in the research.Carvalho et al. (2017), report that poisoning by Pb (saturnism) seems to affect more intensively aquatic fauna and the riverside population, since they directly or indirectly consume these animals and water.As for the main forms and contaminating agents, according to the literary results, the rivers of the Amazon suffer strong silting, deforestation of the banks and the large quantity of material of anthropogenic origin poured into their beds (Sandin et al., 2018).11 Thus, metals can be introduced into aquatic ecosystems in a natural or artificial way, where Santos et al. (2012), highlight that naturally, by means of atmospheric intake and rainfall, leaching processes due to high rainfall index and favorable topography, by release and transport from the parent rock or other soil compartments.Artificially, by anthropogenic sources of various branches: sewage in natura urban areas, effluents from industries, agricultural activities, and waste from mining and mining areas, minerals and reserves very abundant in the region's soils, as well as scraping of vessels and industrial accidents (Pereira et al., 2023;Teixeira et al., 2017).
Agriculture, for example, is one of the most important non-point sources of metal pollution in bodies of water.The main sources of release are fertilizers (Cd, Cr, Pb, Zn), active ingredients (Cu, Pb, Mn, Zn) and intensive production waste of cattle, pigs and poultry (Cu, As and Zn).In addition, the metals released into the soil from this activity are carried to the rivers by the runoff of surface waters coming from the rains, persisting in the aquatic environment because they are free-form, or ionic, which facilitates their accumulation in biota (Santos et al., 2023).
The main results evidenced in Table 1, considering the review metadata demonstrate the cited by Barreto et al. (2023), where the problems generated by high concentrations of metals are numerous.In addition to harming the environment, these elements have a negative influence on human life.Human beings often interfere as a potentiator of the concentration of these materials in nature, which causes significant changes in the environment, mainly due to the degradation of natural resources.
The observations of Santos et al. (2012), as shown in Table 1, report that the waters of rivers, lakes and seas can be polluted directly by the discharge of industrial or domestic effluents, as well as in the work of Botle et al. (2023), who, when assessing the levels of heavy metals in surface water of Indian rivers from 1991 to 2021, confirmed that the levels of Fe, Cr, Pb, Ni, Cd, Mn, Hg, Co exceeded by far the permitted limits established by the World Health Organization and the Bureau of Indian Standards, indicating a high risk of cancer development in adults and children via ingestion for Cr, Pb, Ni, Cd and As, results also reinforced by Alaboudi et al. (2018).
Water can also be polluted by substances present in the soil, such as pesticides and fertilizers used in agriculture and transported by rain to rivers, lakes and eventually to the sea (Bernstein et al., 2022).As demonstrated by Qin et al. (2021), rain accumulates and transports substances from the atmosphere to the waters.Furthermore, at the end the traditional processes of water treatment and purification are not efficient when we talk about contamination by heavy metals like lead (Pb), arsenic (As) or mercury (Hg) (Faial et al., 2015), often as observed in Figure 1.
The presence of mercury (Hg) in various compartments of the rivers and surface waters of the northern region is an increasingly worrying problem in the Amazon basin.The first studies on this issue date back more or less two decades, and since then, it is possible to verify a correlation between the regions of gold mining and mines as being the main sources responsible for the contamination of these compounds, as can be observed in the research of Siqueira et al. (2005) 1).
In addition, when evaluating the distribution of total mercury (THg) and methyl (MeHg) in the Tapajós river basin, described in Table 1, Lino et al. (2019) observed that suspended particles were the main carrier of Hg in the water column and sediment, and that such values were far above the recommended by CONAMA/2006.In the context, it was possible to conclude that the increase in erosion, caused by anthropic activities, led to higher concentrations of Hg in the water of the most impacted areas.Hg is transported mainly in particulate matter; therefore, anthropic disorders influence the concentrations of Hg downstream, being ubiquitous component of different industrial, agricultural effluents and presenting high natural levels in various regions of the Amazon, be sequestered by the Amazon forest and concentrated in the soils and later eroded and climate changes and Hg input in the forests.Limnological parameters, such as the organic matter content, which are very present in soils in Pará, have influenced the concentrations of MeHg in the water in the Tapajós basin (Fostier et al., 2015).
The dangers of this type of contamination in water are not only limited to the direct consumption of this contaminated water but also to the direct consequences in the food chain when referring to bioaccumulative toxins, the pollution of the water by mercury is associated especially with the possibility of methylation in the environment of its inorganic form Hg 2+ by bacteria and the complexation with dissolved organic compounds that makes it possible to maintain relatively high concentrations in the water column and preferential access to biota.An example is the presence of methylmercury in the waters, in fish and consequently in all the higher trophic levels, being the fish, an important food base and one of the main economic means of the Amazon region, as Jesus et al. state. (2021) and Sousa et al. (2022).Soares and Signor (2021), highlighted concerns about water scarcity, groundwater contamination, reduced rainfall with consequent reduction of water volumes in rivers and increased pollution from inappropriate or unconscious use of the good.The historical problem in the region calls for priority change, as this is a vast region that needs public policies of socio-environmental development and monitoring, so that it can mitigate such negative effects on these aquatic environments.Furthermore, with local economic growth, rivers of the state have been the target of a high load of effluents and solid waste of the most varied companies, whether in the manufature of leather, local commerce, industrial production, urbanization and among others.
There are several studies concerning the biogeochemical composition according to the seasonality typical of the region, so it is important to carry out more and more studies and research of this range, in order to contribute and disseminate knowledge about the socioenvironmental impacts in the Amazon waters due to the dumping of chemical components and sanitary sewage freely, resulting in greater vulnerability in the region.

A
bibliographic survey was carried out in the following databases: Latin American and Caribbean Literature in Health Sciences (LILACS), Google Scholar, Scielo, Medline (PUBMED), published between the period 2005 to 2023, for analysis and discussion of the final study, available online in full text, in the languages: Portuguese and English, related to the proposed theme.Articles were selected whose theme was related to the core research questioning and which offered solid evidence about the data collected, according to the parameters recommended by resolutions 274/2000 and 357/2005 and ordinance 888/2021 of the National Council for the Environment -CONAMA, considering the publications of literature in English and Portuguese in the defined period.
The water samples were collected for 800 hours at intervals of 48 hours in a river in the northeast of Pará.The results show that the presence of heavy metals in the following order Cr > Ni > Cu > Fe > Zn > Mn, as well as low pH and electrical conductivity, with significant changes over the years.8Medline2007 BirthThe analyzes showed total and partial concentrations in the samples of the right bank of the Guamá River: total Pb (11 -23 mg Kg-1); partial Pb (9 -18 mg Kg-1); total Cr (26 -69 mg Kg-1); partial Cr (11 -33 mg Kg-1); total Ni (7 -29 mg Kg-1); partial Ni (6 -26 mg Kg-1); total Cu (7 -23 mg Kg-1); partial Cu (6 -17 -1) ).For the 7 left-margin samples, total and partial concentrations were: Total Pb (16-20 mg kg-1), Partial Pb (13-19 mg kg-1); Total Cr (34-56 mg kg-1), Partial Cr (16-26 mg kg-1); Total Ni (12-21 mg kg-1), Partial Ni (12-16 mg kg-1), Cutotal (9-14 mg kg-1) and Partial Cu (7-12 mg kg-1).Thus, the sediments of the Guamá River, although in contact with domestic effluents, pose no risk to the aquatic ecosystem for the Pb and Cu metals.The total content of Cr (69 and 56 mg.Kg-¹) and Ni (29 and 21 mg Kg-¹) in the sediment on the right and left banks is greater than or equal to the respective TEL values of 37 and 18 mg Kg-1 and may pose a possible risk to aquatic organisms in this river.9 Google scholar 2005 Siqueira et al Samples of bottom sediments were collected in the Amazon River, in the stretch that comprises Cape Maguari (PA) and analyzed in relation to the occurrence of selected metals (Li, Sr, Ba, V, Cr, Co, Ni, As, Zn, Pb and As).The dominant metals Fe, Mn and Al were also analyzed and used as support for the geochemical study.Important correlations between Al and most of the selected metals were observed, justifying the occurrence of these metals in mineralogical matrix.Lilacs 2009 Miranda et al.The Tapajós river Ca, Mg, Al, Fe, Ba, Mn, Sr, Ti, Ag, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb and Zn were evaluated and determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), the As was determined by ICP-AES with hydride generation, Hg was determined by atomic absorption with cold vapor and the physico-chemical parameters, presenting non-compliance for Al and Fe, averaging 280.01±294.69μg/L and 564,89±326,5 μg/L, respectively.Scielo 2013 Siqueira & Aprile The Aurá River basin is located in the metropolitan region of Belém do Pará.The results showed that the main contribution of Al and Fe ions was landfill; Mn and Ni came mainly from adjacent soils; Cr was modified (III/VI) by alobiochemical process and Cu by bioinduced process.Pubmed 2007 Pereira et al.The Murucupi River is located in the Amazon region near an aluminum production plant (Al).Thirteen points were selected along the river.The macroelements, microelements, trace elements (Ca, Mg, Na, K, Fe, Al, Ba, Mn, Sr, Zn, Ni, Pb and Cu) and the physicochemical parameters, acidity, total alkalinity, organic matter, pH, turbidity, temperature, conductivity, dissolved oxygen (OD) and total hardness were analyzed.As for the chemical elements Al only: 356.04 μg/L and iron (Fe: 1080.80 μg/L), they were in non-compliance with the legislation.Scielo 2006 Siqueira et al.Research developed in the Maguari (PA) River to determine Zn, Co and Ni levels in surface sediments, identifying the role of sediments as a source or reserve of trace elements.The concentration of the metals was associated as follows: Zn > Ni > Co.The sediments located in the PCA can be considered as the natural occurrence site of the metals, and there is no influence of polluting sources on their release into the system.Scielo 2017 Pereira et al.The samples were collected in Canal Sul and Rio Pará (PA).Inductively coupled plasma atomic emission spectrometry (ICPAES) was used to evaluate Al, Mn and Pb levels and hydride generation atomic absorption spectrophotometry (HGAAS) was used for the analysis of As.As rangedfrom <0.35 to 50.60 µg/L, Al from <1.88 to 3347.70 µg/L, Mn from 0.13 to 403.39 µg/L, and Pb from <0.18 to 57.78 µg/L.On average As (South channel), Al (all regions), Mn (North and South channel) and Pb (North and South channel) met in values above what is allowed by Brazilian legislation.Pubmed 2023 Santos et al.The concentrations of metals (Al, Cr, Pb, Ba, Ni and Mn) in water and the biochemical biomarkers (total antioxidant capacity, ACAP and lipid peroxidation, LPO) were analyzed along 5 points in the Pará river with different distances from a center of anthropogenic activity, in three seasonal periods (rainy, transition and dry).Metal concentrations were similar between sites in each seasonal period, but aluminum (Al) showed the highest concentrations among all metals analyzed at all points and seasonal periods.Pubmed 2022 Sousa et al When assessing land uses in the catchment area and determining water quality through turbidity, total solids and metals (Cd, Cu, Fe, Mn, Pb, Zn and Hg) measurements in the Xingu River, Pará, he observed that the Fresco River inputs impacted the water quality of the Xingu River, leading to reductions in local biodiversity due to anthropic factors.Pubmed 2017 Ribeiro et al The concentrations of As, Cd, Cu, Cr, Pb, Hg and Ni were analyzed during the wet and dry seasons in the water of the Xingu River.The total concentration of As (>0.14μg/L) was higher than the local reference values at all sampling points and at both stations.The ordering analysis (PCA) highlighted the elements As and Cu in water mainly in mining regions.Pubmed 2019 Lino et al.The distribution of total mercury (THg) and methyl (MeHg) was evaluated in unfiltered water (n = 47), suspended particulate matter (SPM, n = 30), surface sediment (BS, n = 29) of the Tapajós river basin.The suspended particles were the main carrier of Hg in the water column and sediment.The increase in erosion, caused by anthropic activities, led to higher concentrations of Hg in the water of the most impacted areas.Pubmed 2020 Lino et al.When evaluating dietary networks of the Tapajós River basin and its relationship with mercury, they observed that Selenium (Se) concentrations in the sediment were significantly higher in Taplow (345-664 μg kg -1 ) than in Tapup/mi (60-424 μg kg -1).The seasonal flooding of the Amazon River probably helps transport selenium-rich sediments to the mouth of the Tapajós river (part of the Taplow).We suggest that Se in sediment could decrease the bioavailability of Hg, resulting in lower concentrations of MeHg in fish, according to Taplow (45-934 μg kg -1 ).Pubmed 2006 Telmer et al.Mercury analysis in the Tapajós river basin.The Hg bound to the suspended sediment was approximately 600 and 200 times the concentration of Hg dissolved per liter of water in impacted and untouched areas.Suspended sediments represent the main Hg pathway transported by the river.The average concentrations of Hg in the suspended charge of the impacted and untouched waters were 134 ppb, and 80% of the samples were below 300 ppb -in the range of surface materials of natural occurrence in the tropics.Pubmed 2015 Faial et al.He evaluated the levels of mercury (Hg) and Selenium (Se) in surface waters of the Tapajós river, PA.The surface water quality variables at the sampling points showed values according to the range established by the legislation.Pubmed 2023 Cantanhêde Sampling was carried out in the post-rain and post-drought periods and at three points, located in two rivers: one in the environs of the mining area (P1) and the other inside the mining area, upstream (P2) and downstream (P3).The water samples were acidic, with dissolved Al concentrations above the values established by federal legislation at all points.Google scholar 2018 Santos et al.In the total sediment, Cadmium Cd showed values above those allowed by PEL and CONAMA No. 454/2012.In the leachate phase, all the metals remained within the limits allowed by the legislation, showing low to moderate contamination.Source: Search protocol Heavy Metals in Surface Waters in A State of The Brazilian Amazon: An Integrative Review ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.6 | p.1-17 | e06952 | 2024.9 Considering the total of collections analyzed, the Pubmed and Scielo database has had more evidence in the search, according to pre-established criteria, corresponding together in 80% of the articles, with homogeneous distribution of publications between the years 2005 and 2023.The main chemical compounds discussed by the periodicals in recent years in the state of Pará were Lead (Pb) and Mercury (Hg), followed by Chromium (Cr) and Aluminum (Al), respectively (Figure1).

Figure 1
Figure 1Main metals analyzed in the databases between 2005 and 2023.

Heavy
Metals in Surface Waters in A State of The Brazilian Amazon: An Integrative Review ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.6 | p.1-17 | e06952 | 2024.13 4 CONCLUSION By means of the literary findings with respect to the theme covered over the last few years, it was possible to demonstrate the main environmental impacts of pollutant and contaminating sources in rivers of the Pará Amazon, such as large concentrations of Pb, Cu, As, Cd, Cr, and Hg, especially Pb and Hg, present in 60% of the studies carried out in different aquatic environments over the last 20 years in the ambit of the state of Pará, numbers that were underestimated, due to the great abundance of effluents.

Table 1
Characterization of articles according to metadata assigned in the review, between 2005 and2023.The exchangeable concentrations of Cu, Cr, Ni, Pb and Zn below the reference value indicate that the metals do not cause harmful effects to biota.A comparison with the levels of the same metals in the sediments on the edge of Belém points to a greater contribution, in the latter, of domestic effluents and industrial waste for Pb and Ni, followed by Cr and practically nonexistent for Cu and Zn, the west bank of the Guajará Bay.
Scielo 2012 Santos et al.Analyzes of lead (Pb) in bottom sediments of the hydrographic system of Belém indicated low levels of this metal in the sediments of the Guamá River, without significant anthropogenic contribution.Levels of Pb in the sediments of Guajará Bay, along with the decrease of the 206Pb/207Pb relations point to an anthropogenic contribution of metal, by the industrial and urban activities of the city of Belém.Isotopic signatures of the suspended material on the eastern (206Pb/207Pb=1,188) and western (206Pb/207Pb=1,174) shores of Guajará Bay show that the suspended material is an efficient mechanism for transporting Pb from the domestic and industrial effluents of the city of Belém to the west bank.Cu, Zn, Pb, Ni, Cr, Ba, V, Li, Fe and Al were analyzed in the Guajará Bay and Maguari River, in Belém do Pará.The average concentrations of Cu found in the sediment at two sites: 28,3 mg kg and 41,0 mg kg.The highest concentrations of metals found in paint fragments from abandoned vessels were 29,588 mg kg of Ba, 9,350 mg kg of Zn, 1,097 mg kg of Pb and 548 mg kg of Cr, far higher than those stipulated by federal law.