Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso A 210Pb chronological study in sediments from poços de caldas alkaline massif (PCAM), Brazil F.R.M. Matamet, D.M. Bonotto⁎ Departamento de Petrologia e Metalogenia, Universidade Estadual Paulista (UNESP), Av. 24-A No. 1515, C.P. 178, CEP 13506-900, Rio Claro, São Paulo, Brazil H I G H L I G H T S • Sedimentation rates. • Pb-210 chronological method. • Osamu Utsumi uranium mine. • Poços de Caldas Alkaline Massif. A R T I C L E I N F O Keywords: Sedimentation rate Unsupported/excess 210Pb model Antas stream Poços de Caldas plateau A B S T R A C T The Constant Flux and Constant Sedimentation (CF:CS) of supported/excess 210Pb model was successfully used to study sediment profiles from Antas stream, located in the region of Poços de Caldas city, Minas Gerais State, Brazil. Historical changes in the region were tracked from evaluating the sedimentation rate by the 210Pb method. In that site, Osamu Utsumi mine was the first mining-industrial complex for the production of con- centrated uranium in Brazil. Four sediment testimonies were sampled along Antas stream in order to determine sedimentation rates using 210Pb as geochronometer. 210Pb and 238U activity concentrations were determined in sediment samples by alpha spectrometry, allowing to find the excess 210Pb present in the sediments. Additionally, the main oxides, organic matter, particles size and water composition were determined in order to assist the results interpretation from radionuclides data. The results allowed find one (profile PKS-4) or two (profiles PKS-1, PKS-2 and PKS-3) sedimentation rates, probably due to changes in the sediments input regime in the region. The sedimentation rates were in the range between 0.26 and 0.94 g/cm2.year, corresponding to the interval of linear sedimentation rate of 0.21 – 0.92 cm/year. The deposition year in the bottom of PKS-4 profile as estimated from the sedimentation rate coincided with the construction year of Bortolan dam (1956). Large touristic interventions carried out at Poços de Caldas city from 1920s coupled to unbridled urbanization, in- dustrialization and demographic growth there in the second half of the twentieth century possibly caused the changes found in the sedimentation rates. 1. Introduction Mining activities have contributed significantly to the growth and development of various countries. The importance of this sector to the Brazilian economy is significant, especially for iron, niobium, manga- nese, and aluminum (from bauxite) production (IBRAM, 2008). Besides the economic impact and the job creation, mining activities cause sig- nificant impacts to the environment, since their development often implies on the removal of vegetation resources and soil exposure to erosion. They also cause air pollution and changes on the quality of surface and groundwater resources (Mechi and Sanches, 2010). The water importance for the human subsistence and development has been widely recognized, where Brazil is a relative privileged country in terms of water resources abundance. Some years ago, the increase in the country for manufactured compounds promoted a rapid and disordered industrialization process, also increasing the demand for water (Lacerda, 1994). The urban and industrial occupation in areas of river basins may imply on greater inputs of pollutants like trace metals that can also cause destabilization and erosion in the environment, promoting the increase of materials in depositional environments and changing all the sediments dynamics. These changes can affect not only living organisms https://doi.org/10.1016/j.apradiso.2018.03.017 Received 30 March 2017; Received in revised form 18 February 2018; Accepted 19 March 2018 ⁎ Corresponding author. E-mail addresses: danielbonotto@yahoo.com.br, dbonotto@rc.unesp.br (D.M. Bonotto). Applied Radiation and Isotopes 137 (2018) 108–117 Available online 22 March 2018 0969-8043/ © 2018 Elsevier Ltd. All rights reserved. T http://www.sciencedirect.com/science/journal/09698043 https://www.elsevier.com/locate/apradiso https://doi.org/10.1016/j.apradiso.2018.03.017 https://doi.org/10.1016/j.apradiso.2018.03.017 mailto:danielbonotto@yahoo.com.br mailto:dbonotto@rc.unesp.br https://doi.org/10.1016/j.apradiso.2018.03.017 http://crossmark.crossref.org/dialog/?doi=10.1016/j.apradiso.2018.03.017&domain=pdf Fig. 1. Location of the study area at Minas Gerais State, Brazil. Adapted from Frayha (2010). F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 109 in such environments, but also human populations using water re- sources for food and recreation (Rosales-Hoz et al., 2003). Concerning to the mineral exploration impacts, the dispute for water and its re- sources is often one important point of conflict involving mining and society. According to Rebouças et al. (2006) mining activities involve major changes in the landscape contour, promoting chemical and bio- logical changes in the environment. The municipality of Poços de Caldas, within this scenario, is con- figured as a strategic point of environmental contamination, since it is the homebirth of the first mining-industrial complex for the production of concentrated uranium in Brazil, operating from 1982 to 1995. Radioactive wastes generated by acid mine drainage (AMD) occur there, which are chemically treated with calcium hydroxide and floc- culants before their release into Antas stream (Mata et al., 2002). Prior studies of the environmental characterization were developed in the region. However, they have only considered the current situation from the analysis of sediments samples from the surface drainage. In this paper, the results obtained for 210Pb allow reconstruct the environ- mental impact produced during the last 100–150 years, covering the largest industrial and population growth experienced in the region. 2. Methodological basis for 210Pb dating 210Pb is a radionuclide that presents itself naturally in aquatic se- diments, as a result of the 238U decay series. Its half-life is 22.26 years, which makes it especially suitable for studying sediments deposited over the last two centuries (Crikmore et al., 1990). 210Pb is formed by disintegration of the noble gas radon (222Rn, half-life = 3.8 days), which is produced by 226Ra-decay and escapes from rocks and soils of the earth's crust due to its gaseous nature. Once airborne, radon pro- duces several descendants, among them 210Pb that is deposited in the sediments. The 210Pb deposited in the sediments is known as unsupported (or excess) 210Pb, 210Pbxs, whereas the 210Pb formed by the 226Ra-decay has been named supported (or in situ produced) 210Pb, 210Pbs (Álvarez- Iglesias et al., 2007). The excess 210Pb can be achieved from the dif- ference of the total 210Pb, 210PbT, and in situ produced 210Pb (Bonotto and Lima, 2006). The total 210Pb activity concentration is equal to the 210Po activity concentration as a consequence of the radioactive equi- librium between 210Pb and 210Po in the 238U decay series (Lima, 2000). The in situ produced 210Pb may be obtained from the 238U specific ac- tivity and applying a correction factor due to escaping 222Rn (Bonotto and Lima, 2006; Sabaris and Bonotto, 2010; Nery and Bonotto, 2011). The analysis of the excess 210Pb in core sediments allows determine the sedimentation rate and deposition time of the sediments in the profile (El-Daoushy, 1988). The 210Pb quantification in this paper was indirectly performed by 210Po alpha spectrometry deposited upon copper discs, taking into ac- count the existence of radioactive equilibrium between 210Pb and 210Po (Appleby and Oldfield, 1978; Lima, 2000; Bonotto and Lima, 2006). This technique presents a series of advantages: high sensitivity to beta counting; possibility of using the 209Po to control the chemical se- paration yield; easy 210Po identification, without any error, due to the sensitivity of the alpha spectrometry; simple 210Po extraction from se- diments. Table 1 The pH, conductivity and ionic concentration (in mg/L) in the bulk composition of the water samples collected at the monitoring points PKS-1, PKS-2, PKS-3 and PKS-4 in Antas stream, Poços de Caldas city, Minas Gerais State, Brazil. Parameter PSK − 1 PSK − 2 PSK − 3 PSK − 4 pH 6.1 6.6 4.9 6.6 Conductivitya 502 161 110 75 Chloride 1.7 0.3 5.4 4,1 Nitrate 0.3 0.6 1.4 0,7 Sulfate 300 72 30 17 Bicarbonate 10.43 13 7.8 15.6 Calcium 7.0 27.6 13 6.7 Potassium 4.3 4.1 9.2 8.6 Magnesium 11.4 0.8 0.8 0.5 Sodium 1.9 1.7 4.2 3.3 a In µS/cm. Fig. 2. Results of the chemical analyses of waters from Antas stream in a Piper (1944) diagram. F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 110 3. Experimental 3.1. Study area The study area is located at the Poços de Caldas Alkaline Massif (PCAM), southeastern of Minas Gerais State, Brazil, on the São Paulo State border (Fig. 1). The research limited itself to Antas stream (Fig. 1), which belongs to the Pardo river hydrographic system. The city of Poços de Caldas in the plateau has a total area of 547 km2 and is si- tuated on a site whose average altitude ranges from 943m to 1575m (mean = 1300m). It consists of a single district, bordering with nine municipalities, one at São Paulo State (Águas da Prata). The Poços de Caldas region is geologically situated at the northeast limit of the Paraná sedimentary basin, bordering with the Precambrian terrains of the Brasiliano crystalline complex, on the western edge of Mantiqueira Scarp (Ellert, 1959). An intrusive body of Mesozoic-Cen- ozoic age consisting of alkaline rocks like nepheline (tinguatites, phonolites, foyaites) predominate in Poços de Caldas region. Several lithological types are of alkaline source, divided into three main groups: volcanic material; effusive and hypabyssal rocks; and plutonic rocks. Geomorphologically, the alkaline massif is inserted in areas of the Atlantic Highlands, with a slightly elliptical shape (major axis of 35 km in the NE-SW direction and lower axis of 30 km in the NW-SE direc- tion). Two large fault systems with predominant directions N60W and N40E are present in the alkaline complex: the first is related to regional tectonics and the last with the former fusion processes (Fraenkel et al., 1985). The soil covering the region is the result of in situ alteration rock. The soil materials and rock blocks are of variable proportion and composed by rocks with varying degrees of fracturing, alluvium, soft soils deposited with organic and clayey materials, tallus consisting of transported soil materials and rock fragments of various sizes (Poços de Caldas, 2006). Table 2 Size distribution of the sediments samples collected at the monitoring points PKS-1, PKS-2, PKS-3 and PKS-4 in Antas stream, Poços de Caldas city, Minas Gerais State, Brazil. Sampling Point Depth range (cm) Grain size (mm) 4.000 – 2.000 2.000 – 1.000 1.000 – 0.500 0.500 – 0.250 0.250 – 0.125 0.125 – 0.062 0.062 – 0.031 ˂ 0.031 0− 3 5.958 4.435 0.850 1.766 1.434 1.607 1.117 0.362 3− 6 5.684 3.350 0.779 1.608 1.129 0.928 0.450 0.073 6− 9 8.234 2.380 0.562 1.352 1.210 0.781 1.195 0.026 9− 12 9.181 6.919 1.242 2.843 2.541 3.575 0.906 0.517 12− 15 4.446 7.102 1.530 2.847 2.733 3.277 0.228 0.003 PKS − 1 15− 18 3.236 6.006 1.484 3.276 2.308 2.773 1.066 0.361 18− 21 3.676 9.261 1.763 3.653 3.168 3.572 0.829 0.174 21− 24 4.454 10.452 1.819 3.363 2.296 3.930 0.556 0.012 24− 27 2.234 9.658 2.212 4.605 2.945 4.176 1.567 0.512 27− 30 2.440 4.517 1.548 3.380 2.418 4.973 0.822 0.136 30− 33 2.333 6.245 1.911 3.974 4.091 3.461 0.408 0.002 33− 36 3.247 8.193 2.073 5.390 4.933 4.000 1.137 0.240 0− 3 4.063 2.965 0.543 1.590 1.913 1.044 0.382 0.064 3− 6 1.024 6.060 1.410 3.819 3.208 1.688 0.690 0.104 6− 9 0.173 3.652 1.002 2.840 2.421 2.000 0.640 0.005 9− 12 0.431 4.508 0.982 2.768 2.333 1.618 0.700 0.001 12− 15 0.317 3.915 0.803 2.058 1.619 1.263 0.480 0.001 PKS − 2 15− 18 0.180 4.219 1.136 3.108 2.361 1.397 0.690 0.025 18− 21 0.068 3.447 0.910 2.411 1.970 1.466 0.650 0.003 21− 24 0.203 3.998 0.868 2.554 2.398 2.148 0.467 0.001 24− 27 0.119 3.772 0.952 2.760 2.593 2.054 0.594 0.016 27− 30 0.035 3.447 0.945 3.054 3.502 2.973 0.813 0.014 30− 33 1.623 10.653 1.668 4.325 4.255 3.999 0.666 0.001 0− 3 0.172 2.820 0.753 0.869 1.652 1.266 0.526 0.134 3− 6 0.494 3.743 0.872 2.010 1.768 1.367 0.704 0.242 6− 9 1.795 4.159 0.886 2.149 1.996 1.751 0.811 0.249 9− 12 0.557 5.124 1.016 2.645 2.574 1.717 0.891 0.362 12− 15 0.335 0.709 1.276 3.608 3.824 2.461 1.158 0.292 15− 18 2.841 4.917 0.946 2.867 3.280 2.051 0.965 0.427 18− 21 0.803 4.966 1.026 2.788 2.803 2.424 1.160 0.158 PKS − 3 21− 24 2.217 4.436 0.786 2.256 2.571 2.175 1.289 0.310 24− 27 0.690 5.052 0.986 2.589 2.561 1.997 1.201 0.191 27− 30 0.378 3.639 0.960 3.082 3.451 2.486 1.463 0.322 30− 33 0.744 5.942 1.187 3.816 4.243 2.984 1.798 0.388 33− 36 0.993 2.335 0.733 2.924 3.826 2.590 1.317 0.554 36− 39 0.162 2.675 0.938 3.815 4.571 2.930 1.534 0.500 39− 42 1.374 6.271 1.440 4.340 4.052 2.510 1.069 0.552 42− 45 0.459 3.568 0.887 3.093 3.540 3.312 1.272 0.213 0− 3 0.437 1.681 0.713 2.554 2.492 1.332 0.456 0.174 3− 6 0.217 2.433 0.894 2.956 2.663 1.125 0.374 0.130 6− 9 1.392 3.182 0.885 2.881 2.592 1.515 0.657 0.182 PKS − 4 9− 12 0.072 2.805 0.793 1.871 1.845 3.330 1.048 0.268 12− 15 0.781 3.519 0.761 1.844 1.990 1.551 0.620 0.377 15− 18 0.073 0.894 0.544 2.872 4.182 2.794 1.518 1.361 18− 21 0.101 1.138 0.568 4.216 4.039 2.383 1.600 1.184 21− 24 0.031 1.399 0.754 3.672 4.615 2.783 1.411 1.385 Udden scale (in mm) and Wentworth classification: GRA =granule (> 2.0mm), VCS =very coarse sand (2.0 – 1.0 mm), CRS = coarse sand (1.0 – 0.5 mm), MES =medium sand (0.5 – 0.25mm), FIS = fine sand (0.25 – 0.125mm), VFS = very fine sand (0.125 – 0.063mm), CSI = coarse silt (0.063 – 0.031mm), MSI =medium silt (˂0.031mm). F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 111 3.2. Sampling The sediments sampling was carried out during the dry season in Antas stream, Poços de Caldas city, Minas Gerais State, Brazil, near its source and downstream monitoring points called PKS-1, PKS-2, PKS-3 and PKS-4 (Fig. 1). These sampling points were geo-referenced with GPS (Global Positioning System) in UTM coordinates system. Four ac- rylic tubes were used (~ 5 cm diameter and ~ 60 cm long) and pre- viously washed with an acid solution for decontamination. After col- lection, the tubes with the samples were kept under refrigeration (4 °C). One liter water samples were also collected in the same sediments collection points, using plastic bottles previously washed in the la- boratory. The sites choice was made considering the position of the polluting sources, effluents location and sites accessibility for sampling. In the laboratory, pellet samples were removed from the tubes, the testimonies were cut at 3 cm intervals, packed in sealed plastic bags and refrigerated until analysis. 3.3. Analytical methods The analysis of the water samples (~1 L) was done at LABIDRO – Isotopes and Hydrochemistry Laboratory (IGCE - Geosciences and Exacts Sciences Institute of UNESP – Rio Claro) by a Hach DR2000 spectrophotometer, among other equipments. The samples were ana- lyzed for pH, conductivity, anions (chloride, nitrate, sulfate, bicarbo- nate) and cations (calcium, magnesium, potassium). Sodium analysis was performed by Atomic Absorption Spectrometry (AAS). In order to obtain the excess 210Pb in the sediments, the samples were analyzed for 238U and 210Po at LABIDRO. For measuring 210Po in the sediments, 1 g of sample was attacked with different acids for the 210Po extraction. Such 210Pb ¨grandchild¨ was deposited in a copper disk. Each slice underwent counting in an alpha spectrometer. For the 238U determination, the slices passed through a series of chemical steps until electrodeposition on stainless steel discs (Lima, 2000). After ob- taining the dry disk, the next step was to count the uranium isotopes by alpha spectrometry that is a procedure requiring the use of thin sources containing the extracted material and prepared from the uniform 238U deposition. The grain size analysis of the sediments was also carried out at LABIDRO. The samples were thawed, dried and classified through sieving, based on the Udden-Wentworth scale (Lima, 2000). It was used a set of calibrated mesh sieves that allowed to obtain the dry weight in each grain size range. The determination of the main oxides levels in the sediments was carried out at LARIN (Ionizing Radiations Laboratory) of UNESPetro (Geosciences Center Applied to Petroleum), IGCE – UNESP – Rio Claro, through S8 TIGER X-rays Fluorescence Spectrometer of high end wa- velength dispersion from Bruker Co. The organic matter (OM) content analysis was held at LABIDRO according to the loss on ignition (LOI) method based on the Heiri et al. (2001) proposition. Dry samples (~ 1 g of total sediment) were used. The sediments were put in small porcelain crucibles. After weighing, the samples were dried at 110 °C for 12 h (overnight) in order to remove any moisture. In the next day, the samples, still hot, were cooled and kept in desiccators with silica gel until reaching the room temperature. After ~30min, they were weighed for obtaining the dry weight. The second part of the experiments consisted on inserting the sediments into an oven at 550 °C and keeping them there for 5 h (Dean, 1974; Bengtsson and Enell, 1986). Then, the sediments were cooled in a de- siccator to reach the room temperature. Finally, the pellet samples were weighed and the difference between this weight and the final weight of the sample (without moisture) corresponded to the organic matter percentage. 4. Results and discussion 4.1. Hydrochemical analyzes The results of the water samples analysis are shown in Table 1. The parameters analyzed were pH, conductivity, cations (Ca2+, K+, Mg2+, Na+) and anions (Cl-, NO3 -, SO4 2-, HCO3 -) in order to classify them and verify if they fit the guideline reference values established by the Bra- zilian laws CONAMA 357/05 (Brasil, 2005) and Rule No. 2.914/11 of Health Ministry (Brasil, 2011). The sulfate concentration at PKS-1 monitoring point was greater than 250mg/L as established by them. Thus, the waters of Antas stream demonstrate inadequate sanitation for public health close to the uranium mine. The Piper (1944) diagram (Fig. 2) allows verify the total ions dis- tribution and to identify similarities and differences among the samples. In terms of dissolved anions, the waters are sulfated (PKS-1, PKS-2 and PKS-3) and mixed (PKS-4). In terms of dissolved cations, the waters are magnesian (PKS-1), calcic (PKS-2 and PKS-3) and mixed (PKS-4). Table 3 Maximum, minimum, mean, median and standard deviation (SD) of the major oxides in sediments samples collected at the monitoring points PKS-1, PKS-2, PKS-3 and PKS-4 in Antas stream, Poços de Caldas city, Minas Gerais State, Brazil. All values are in %. Sampling Point SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 OM PKS − 1 Mean 39.66 0.80 31.99 6.60 0.49 0.16 0.12 0.15 6.51 0.25 11.87 Median 39.14 0.79 31.85 6.11 0.19 0.14 0.04 0.11 6.59 0.27 11.77 SD 3.23 0.10 2.30 1.80 0.57 0.03 0.13 0.12 0.89 0.05 2.14 Maximum 45.60 1.01 35.13 10.12 1.92 0.22 0.36 0.48 8.37 0.32 17.05 Minimum 34.93 0.66 27.65 4.68 0.12 0.13 0.02 0.06 5.25 0.17 8.69 PKS − 2 Mean 26.99 2.10 39.46 7.54 0.07 0.21 0.09 0.07 2.22 0.12 19.73 Median 26.46 2.15 39.94 7.69 0.04 0.21 0.07 0.05 2.13 0.12 19.78 SD 1.61 0.17 1.64 0.34 0.09 0.01 0.06 0.09 0.37 0.01 0.71 Maximum 31.39 2.17 40.39 7.97 0.33 0.23 0.28 0.33 3.30 0.13 20.72 Minimum 25.70 1.60 34.57 7.11 0.04 0.19 0.06 0.04 2.01 0.10 18.60 PKS − 3 Mean 33.74 1.74 34.17 7.56 0.29 0.20 0.04 0.15 3.51 0.12 17.46 Median 34.10 1.73 34.20 7.52 0.29 0.20 0.02 0.15 3.48 0.11 17.22 SD 0.96 0.03 0.33 0.16 0.07 0.01 0.03 0.02 0.24 0.01 0.89 Maximum 34.93 1.81 34.55 7.88 0.39 0.22 0.10 0.19 3.86 0.13 19.00 Minimum 32.05 1.69 33.51 7.35 0.17 0.19 0.00 0.11 3.12 0.11 16.17 PKS − 4 Mean 28.07 3.31 27.54 16.46 0.13 0.13 0.04 0.04 0.61 0.65 22.72 Median 27.26 2.50 27.00 16.25 0.07 0.14 0.03 0.04 0.79 0.55 22.86 SD 2.26 1.23 3.13 2.00 0.10 0.03 0.04 0.02 0.40 0.15 1.16 Maximum 31.39 4.84 32.17 19.17 0.30 0.16 0.12 0.06 1.03 0.85 24.22 Minimum 25.44 2.36 24.17 14.02 0.06 0.09 0.01 0.01 0.12 0.53 20.98 F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 112 4.2. Size distribution and chemical analysis of the sediments The particle distribution carried out in the four sampling points is recorded in Table 2. It appears that there is predominance of the granule (GRA) and very coarse sand (VCS) fractions at all collection points. The maximum values of GRA are 51.36% (PKS-1), 31.59% (PKS- 2), 15.17% (PKS-3) and 10.18% (PKS-4). The maximum values of VCS are 37.86% (PKS-1), 38.22% (PKS-2), 36.52% (PKS-3) and 29.57% (PKS-4). The fine sand (FIS) and very fine sand (VFS) fractions increase towards the base of the sediments profiles, reaching a maximum value of 30.55% (Table 2). Table 3 reports the maximum, minimum, mean, median and stan- dard deviation of the major oxides and OM in the sediments. OM was detected in all sampled profiles, with maximum values of 17.05% (PKS- 1), 20.72% (PKS-2), 19% (PKS-3) and 24.22% (PKS-4). The Pearson correlation coefficient was evaluated among the oxides analyzed and OM, indicating the following significant correlations: silica (PKS-2: r=−0.81; PKS-3: r=−0.96; PKS-4: r=−0.80), TiO2 (PKS-4: r= 0.73), Al2O3 (PKS-3: r= 0.79), Fe2O3 (PKS-2: r= 0.83), MnO (PKS- 4: r=−0.87), MgO (PKS-3: r= 0.77), CaO (PKS-4: r=−0.82), Na2O (PKS-3: r=−0.71; PKS-4: r=−0.85), K2O (PKS-2: r=−0.67; PKS-3: r=−0.96), and P2O5 (PKS-3: r= 0.92; PKS-4: r= 0.73). Thus, the significant correlations with OM were found at the profiles PKS-2, PKS- 3 and PKS-4, whereas inverse relationships were characterized for si- lica, confirming the trends pointed out by Bonotto and Lima (2006). The correlations may suggest a similar behavior during transpor- tation of the evaluated components (Thornton, 1983). In general, it was observed that the OM favors the retention up to a certain limit of some oxides in all profiles. Thus, the organic matter in these environments behaves as a complexing factor acting as a regulator of the chemical components in the sediments, thus, taking an important role in fixing or releasing metals into the water column (Aiken et al., 1985). Table 4 Radiochemical analyses of the sediments samples collected at the monitoring points PKS-1, PKS-2, PKS-3 and PKS-4 in Antas stream, Poços de Caldas city, Minas Gerais State, Brazil. Depth range (cm) Dry weight (g) Po-210 activity (dpm/g) Cumulative dry weight/area (g/cm2) Total Pb-210 activity 210PbT (dpm/g) U-238 Specific Activity (dpm/g) In-situ Pb-210 activity PbS (dpm/ g) Excess Pb-210 activity PbXS (dpm/g) ln (Pbxs) (dpm/g) Profile PKS− 1 0− 3 62.06 6.38 3.16 6.38 3.99 0.64 5.74 1.75 3− 6 58.06 9.33 6.12 9.33 1.89 0.30 9.03 2.20 6− 9 94.92 4.43 10.95 4.43 9.71 1.55 2.88 1.06 9− 12 96.40 3.01 15.87 3.01 11.15 1.78 1.23 0.20 12− 15 75.11 3.45 19.69 3.45 6.12 0.98 2.47 0.90 15− 18 77.07 3.42 23.62 3.42 3.68 0.59 2.83 1.04 18− 21 71.58 3.85 27.26 3.85 5.13 0.82 3.03 1.11 21− 24 97.75 3.45 32.24 3.45 5.68 0.91 2.54 0.93 24− 27 89.63 1.55 36.81 1.55 9.16 1.47 0.08 − 2.47 27− 30 97.66 2.49 41.79 2.49 4.06 0.65 1.84 0.61 30− 33 96.25 3.24 46.69 3.24 11.40 1.82 1.42 0.35 33 – 36 91.13 2.95 51.33 2.95 2.45 0.39 2.56 0.94 Profile PKS− 2 0− 3 40.01 9.10 2.04 9.10 5.04 0.81 8.29 2.12 3− 6 50.98 9.24 4.64 9.24 2.35 0.38 8.86 2.18 6− 9 57.85 13.00 7.58 13.00 0.85 0.14 12.86 2.55 9− 12 58.03 6.47 10.54 6.47 1.17 0.19 6.28 1.84 12− 15 52.08 8.30 13.19 8.30 0.78 0.12 8.18 2.10 15− 18 49.93 9.50 15.74 9.50 1.05 0.17 9.33 2.23 18− 21 52.61 13.65 18.42 13.65 1.15 0.18 13.47 2.60 21− 24 50.62 7.76 20.99 7.76 1.26 0.20 7.56 2.02 24− 27 57.70 9.44 23.93 9.44 0.87 0.14 9.30 2.23 27− 30 69.82 12.54 27.49 12.54 1.26 0.20 12.34 2.51 30 – 33 75.64 14.40 31.34 14.40 1.18 0.19 14.21 2.65 Profile PKS− 3 0− 3 39.91 11.08 2.36 11.08 2.22 0.36 10.72 2.37 3− 6 45.08 10.07 5.02 10.07 1.51 0.24 9.83 2.29 6− 9 42.49 12.11 7.53 12.11 1.23 0.20 11.91 2.48 9− 12 54.50 16.70 10.75 16.70 1.22 0.20 16.50 2.80 12− 15 60.58 14.53 14.33 14.53 0.96 0.15 14.38 2.67 15− 18 61.76 18.67 17.98 18.67 0.92 0.15 18.52 2.92 18− 21 62.62 12.27 21.67 12.27 0.78 0.12 12.15 2.50 21− 24 54.37 9.93 24.89 9.93 0.93 0.15 9.78 2.28 24− 27 62.81 12.00 28.60 12.00 1.73 0.28 11.72 2.46 27− 30 52.57 15.20 31.70 15.20 0.94 0.15 15.05 2.71 30− 33 63.01 13.71 35.42 13.71 1.13 0.18 13.53 2.60 33− 36 53.35 14.48 38.57 14.48 1.25 0.20 14.28 2.66 36− 39 56.71 19.52 41.92 19.52 0.98 0.16 19.36 2.96 39− 42 55.87 14.59 45.22 14.59 0.61 0.10 14.49 2.67 42 – 45 51.49 12.65 48.26 12.65 1.37 0.22 12.43 2.52 Profile PKS− 4 0− 3 39.34 7.64 2.00 7.64 1.59 0.25 7.39 2.00 3− 6 37.83 7.74 3.93 7.74 3.95 0.63 7.11 1.96 6− 9 40.39 8.55 5.99 8.55 2.19 0.35 8.20 2.10 9− 12 37.37 7.06 7.89 7.06 3.33 0.53 6.53 1.88 12− 15 37.80 5.60 9.82 5.60 2.72 0.44 5.16 1.64 15− 18 43.97 8.00 12.06 8.00 1.75 0.28 7.72 2.04 18− 21 48.16 8.84 14.51 8.84 2.35 0.38 8.46 2.14 21− 24 43.37 8.77 16.72 8.77 2.05 0.33 8.44 2.13 F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 113 The analysis showed that silica (SiO2) is the main constituent in all testimonies, ranging from mean values of 27–39.7% (Table 3). Sig- nificant Pearson correlation coefficient were also found among silica and other analyzed compounds, for instance: TiO2 (PKS-2: r=−0.91), Al2O3 (PKS-2: r=−0.88; PKS-3: r=−0.78), Fe2O3 (PKS-1: r=−0.80), MnO (PKS-2: r= 0.89; PKS-4: r= 0.95), MgO (PKS-2: r= 0.77; PKS-3: r=−0.73), CaO (PKS-2: r= 0.93; PKS-4: r= 0.86), Na2O (PKS-2: r= 0.91), K2O (PKS-1: r= 0.69; PKS-2: 0.97; PKS-3: r= 0.92), and P2O5 (PKS-3: r=−0.92). 4.3. Sedimentation rates by the 210Pb method The results of the total 210Pb activity, supported 210Pb and excess 210Pb of the PKS-1, PKS-2, PKS-3 and PKS-4 profiles are shown in Table 4. The sediment excess profiles of 210Pb activities are shown in Fig. 3. The excess 210Pb activity in PKS-1 core shows a tendency to decrease from the top towards the core bottom. However, some dis- continuities can be scanned along the profile, perhaps indicating changes in the settling rate and/or sudden variation of the granulo- metric composition of the sediments. The excess 210Pb in the profiles PKS-2, PKS-3 and PKS-4 (Fig. 3) show no reduction in its activity from the top towards the bottom core. This may reflect the high momentum of the Antas stream, with oscil- lations on the sedimentation over time, indicating an environment with much variable annual sedimentation rate. Such situation has been pointed out by Ruiz-Fernández et al. (2003, 2007) that considered that the excess 210Pb flow in sedimentary environments is controlled by the climatic characteristics of the region, runoff and origin of the prevailing air mass in the region (oceanic or continental). The CF:CS (Constant Flux: Constant Sedimentation) model (Crozaz et al., 1964; Krishnaswamy et al., 1971; Koide et al., 1973; Brugam, 1978; Appleby and Oldfield, 1983) takes into account the concentration of excess 210Pb in each slice of the sedimentary column per dry weight. The 210Pb activity, P(x), varies with the dry mass of sediment, m, at a certain depth, according to the equation: Fig. 3. The excess 210Pb plotted against core depth in sampling points (a) PKS-1, (b) PKS-2, (c) PKS-3 and (d) PKS-4. F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 114 Fig. 4. The logarithm of the excess 210Pb plotted against the cumulative dry weight per area in sampling points (a) PKS-1, (b) PKS-2, (c) PKS-3 and (d) PKS-4. Fig. 5. The deposition time plotted against core depth in sampling points (a) PKS-1, (b) PKS-2, (c) PKS-3 and (d) PKS-4. F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 115 = × −P x P e( ) (0) λ m r( 210. / ) where: P (0) and P (x) = total inventory of the excess 210Pb at the surface and below the layer x (Bq/cm2), m is the cumulative dry weight per unit area (g/cm2), r is the flow sediment or sedimentation rate (g/ cm2.year) and λ210 is the decay constant of 210Pb (0.03114 year−1). The equation can be written as: = −lnP x lnP λ r m( )– (0) ( / )210 Fig. 4 shows the ln 210Pbxs (dpm/g) plotted against the cumulative dry weight per area in the PKS-1, PKS-2, PKS-3, and PKS-4 profiles. Some straight lines were fitted to the experimental data, allowing find the sedimentation rate on dividing the 210Pb decay constant by the slope modulus. Two distinct sedimentation rates were obtained in three profiles: 0.28 and 0.58 g/cm2.year (PKS-1); 0.38 and 0.49 g/cm2.year (PKS-2); 0.45 and 0.94 g/cm2.year (PKS-3). One sedimentation rate (0.26 g/ cm2.year) was found for (PKS-4) (Fig. 4). The variable sedimentation rates in the profiles PKS-1, PKS-2 and PKS-3 show the existence of differentiated events as also demonstrated by Monteiro (2008)), Sabaris and Bonotto (2010) and Nery and Bonotto (2011), among other. The sedimentation rates reported in this paper are similar to some de- termined elsewhere, for instance: Corumbataí River – 2.22 g/cm2.year (Lima, 2000); Grande Curuaí lake – 0.42 g/cm2.year (Turcq et al., 2004); Amisk lake (0.02 g/cm2.year) and Elwater lake (0.27 g/ cm2.year) in Canada (Turner and Delorme, 1996); Chapala lake, Mexico – 0.44 g/cm2.year (Fernex et al., 2001). The deposition time of the sedimentary layers was estimated by dividing the accumulated mass/area by the sedimentation rate. These values were obtained with reference to the sampling year (2014). They corresponded to: PKS-1= 138 years; PKS-2=78 years; PKS-3=79 years; PKS-4=64 years. Fig. 5 shows the linear sedimentation rate for each sampled profile: PKS-1=0.21 and 0.33 cm/year; PKS-2=0.41 and 0.43 cm/year; PKS-3=0.40 and 0.92 cm/year; PKS-4=0.38 cm/ year. Fig. 5 also shows the deposition time plotted against the core depth. Fig. 6 shows the deposition age of the sedimentary layers plotted in relation to the core depth. The PKS-1 profile presents a rate of 3.3 mm/ year from 18 to 36 cm depth (equivalent to year 1930). Above 18 cm depth, the sedimentation rate decreases (2.1 mm/year) (Fig. 6a). This change in the sedimentation rate may be related to the large touristic interventions carried out in the Poços de Caldas city from 1920s that contributed to the spa apogee on the 1930 decade (Frayha, 2010). The PKS-2 profile presents a sedimentation rate of 4.1 mm/year from 15 to 33 cm depth (equivalent to 1974). Above 15 cm depth, there is a slight increase in the sedimentation rate (4.3 mm/year) (Fig. 6b). The PKS-3 profile (near the urban area of Poços de Caldas city) presents a sedimentation rate of 4.0mm/year from 24 to 45 cm depth (equiva- lent to 1979), and, above 24 cm depth, there is an increase in the se- dimentation rate (9.2 mm/year) (Fig. 6c), larger than at other points. According to Poços de Caldas (1992), Ferreira (1996), Megale (2002), Gonçalves (2010) and IBGE (2010), in the second half of the twentieth century, the Poços de Caldas unbridled urbanization, industrialization and demographic growth began. According to Oliveira (2012), the largest population growth is related to the main cycle of expansion and industrial diversification experienced between 1960 and 1990 and concentrated mainly in the peripheries of the city. Finally, the PKS-4 profile (near Bortolan dam) presents an unique sedimentation rate (3.8 mm/year) (Fig. 6d), practically coinciding the deposition year at the core bottom (1950) with the construction of Bortolan dam in 1956 (Frayha, 2010). 5. Conclusion This paper reports the results performed over four sediments Fig. 6. The deposition year plotted against core depth in sampling points (a) PKS-1, (b) PKS-2, (c) PKS-3 and (d) PKS-4. F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 116 profiles (PKS-1, PKS-2, PKS-3 and PKS-4) collected at Antas stream, Poços de Caldas city, Minas Gerais, State, Brazil. The oxides analysis showed a significant correlation between the Organic Matter (OM) and oxides analyzed in the four profiles, especially silica, which was the major constituent. This indicates that the OM presence can constrain the major oxides concentration in the sediments. The size sediments analysis showed higher levels of the larger fractions (granule and very coarse sand) in the four collection points. The finer fractions take an important role on the metals aggregation. Regarding the 210Pb model for estimating the sedimentation rate, it was possible to find the fol- lowing values: 0.28 and 0.58 g/cm2.year (PKS-1); 0.38 and 0.49 g/ cm2.year (PKS-2); 0.45 and 0.94 g/cm2.year (PKS-3) and 0.26 g/ cm2.year (PKS-4). They indicate that the rainfall 210Pb deposition in the study area was enough to quantify this radionuclide, allowing to use the CF:CS (Constant Flux: Constant Sedimentation) model to different time scales. The ages of the sedimentary layers seemed to agree with his- torical events that occurred at Poços de Caldas city, which influenced the studied environments. In addition, the analysis of the physical and chemical parameters in the waters indicated that they exhibit un- favorable conditions for human consumption, according to the Brazilian guidelines for water quality. Acknowledgments CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) in Brazil, is thanked by the scholarship to FRMM. References Aiken, G.R., McNight, D., Wershw, R.L., MacCarthy, 1985. Humic substances in soil, sediment and water. John Wiley & Sons, New York, pp. 691. Álvarez-Iglesias, P., Quintana, B., Rubio, B., Pérez-Arlucea, M., 2007. Sedimentation rates and trace metal input history in intertidal sediments from San Simón Bay (Ría de Vigo, NW Spain) derived from 210Pb and 137Cs chronology. J. Environ. Radioact. 98, 229–250. Appleby, P.G., Oldfield, F., 1978. The calculation of lead-210 dates assuming a constant rate of supply of unsupported 210Pb to the sediment. Catena 5, 1–8. Appleby, P.G., Oldfield, F., 1983. The assessment of 210Pb data from sites with varying sediment accumulation rates. Hydrobiologia 103, 29–35. Bengtsson, L., Enell, M., 1986. Chemical analysis. In: Berglund, B.E. (Ed.), Handbook of Holocene Paleoecology and Paleohydrology. John Wiley & Sons, Chichester, pp. 423–451. Bonotto, D.M., Lima, J.L.N., 2006. 210Pb-derived chronology in sediment cores evidencing the anthropogenic occupation history at Corumbataí River basin, Brazil. Environ. Geol. 50 (4), 595–611. Brasil, 2005. Resolução Conama No. 357, de 17 de março de 2005 - Dispõe sobre a classificação dos corpos de água e diretrizes ambientais para seu enquadramento bem como estabelecer as condições e padrões de lançamento de efluentes, e dá outras providências. 〈http://www.mma.gov.br/conama〉. Brasil, 2011. Portaria No. 2914 do Ministério de Saúde, de 12 de dezembro de 2011. 〈http://bvsms.saude.gov.br/bvs/saudelegis/gm/2011/prt2914_12_12_2011.html〉. Brugam, R.B., 1978. Pollen indicators of land-use change in Southern Connecticut. Quatern. Res. 9, 349–362. Crozaz, G., Picciotto, E., de Breuck, W., 1964. Antarctic snow chronology with Pb-210. J. Geophys. Res. 69, 2597–2604. Crikmore, M.J., Tazioli, P.G., Appleby, P.G., Oldfield, F., 1990. The use of nuclear tech- niques in sediment transport and sediment problems. UNESCO-International Hydrological Program, Paris, 170 pp. Dean, W.E.J.R., 1974. Determination of carbonate and organic matter in calcareous se- diments and sedimentary rocks by loss ignition: comparison with other methods. J. Sed. Petrol. 44, 242–248. El-Daoushy, F.A., 1988. A summary on the lead-210 cycle in nature and related appli- cations in Scandinavia. Environ. Int. 14, 305–319. Ellert, R., 1959. Contribuição à geologia do maciço alcalino de Poços de Caldas. Geologia FFCL-USP 18, 5-63. Fernex, F., Valle, P.Z., Sanchez, H.R., Michaud, F., Parron, P., Dalmasso, J., Funel, G.B., Arroyo, M.G., 2001. Sedimentation rates in Lake Chapala (Western Mexico): possible active tectonic control. Chem. Geol. 177, 213–228. Ferreira, J., 1996. Um hectare na história de Poços de Caldas. 11th ed., Gráfica Brasil, Poços de Caldas. Fraenkel, M.O., Santos, R.C., Lourenço, F.E.V.L., Muniz, W.S., 1985. Jazida de urânio no planalto de Poços de Caldas, Minas Gerais. In: DNPM (Departamento Nacional de Produção Mineral) (Ed.) Principais Depósitos Minerais do Brasil, v. 1, pp. 89–103. Frayha, G.Z., 2010. Poços de Caldas polo mesorregional: ambiente, planejamento e qualidade de vida na articulação dos municípios da Média Mogiana e do Sul de Minas Gerais. M.Sc. Dissertation. UNICAMP-Universidade Estadual de Campinas, Campinas (SP), pp. 228. Gonçalves, Y.A., 2010. Poços de Caldas: uma leitura econômica. Sul Mineira, Varginha. Heiri, O., Lotter, A.F., Lemcke, G., 2001. Loss on ignition as a method for estimating organic and carbonate content in sediments: reprodutibility of results. J. Paleolimnol. 25, 101–110. IBGE (Instituto Brasileiro de Geografia e Estatística), 2010. Densidade demográfica nos censos demográficos de 1872 a 2010, segundo as regiões do Estado de Minas Gerais. 〈http://biblioteca.ibge.gov.br/visualizacao/dtbs/minasgerais/pocosdecaldas.pdf〉. IBRAM (Instituto Brasileiro de Mineração), 2008. Informações e Análises da Economia Mineral Brasileira. 〈http://www.ibram.org.br/sites〉. Koide, M., Bruland, K.W., Goldberg, E.D., 1973. Th-228/Th-232 and Pb-210 geo- chronologies in marine and lake sediments. Geochim. Cosmochim. Acta 37, 1171–1187. Krishnaswamy, S., Lal, D., Martin, J., Meybeck, M., 1971. Geochronology of lake sedi- ments. Earth Planet. Sci. Lett. 11, 407–414. Lacerda, L.D.D., 1994. Biogeoquímica de metais pesados em ecossistemas de manguezal. Ph.D. Thesis. UFF-Universidade Federal Fluminense, Niterói (RJ), pp. 68. Lima, J.L.N., 2000. Hidroquímica pluvial e fluvial na Bacía do Rio Corumbataí (SP) e relações com o uso do Pb-210 como geocronômetro. Ph.D. Thesis. UNESP- Universidade Estadual Paulista, Rio Claro (SP), pp. 260. Mata, Y.M., González, F., Ballester, A., Blásquez, M.L., Muñoz, J.A., 2002. Inhibition of acid rock drainage from uranium ore waste using a conventional neutralization and precipitation treatment. Miner. Eng. 15, 1141–1150. Megale, N.B., 2002. Memórias históricas de Poços de Caldas. 2nd ed., Sulminas, Poços de Caldas. Mechi, A., Sanches, D.L., 2010. Impactos ambientais da mineração no Estado de São Paulo. Estud. Av. 24 (68), 209–220. Monteiro, F.F., 2008. Histórico de acumulação de metais-traço em sedimentos estuarinos do Rio Iguaçu e da região da área de Proteção Ambiental de Guapimirim, Baía de Guanabara (RJ. (RJ. M.Sc. Dissertation. UFF-Universidade Federal Fluminense, Niterói (RJ), pp. 88. Nery, J.R.C., Bonotto, D.M., 2011. 210Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil. J. Environ. Radioact. 102, 348–362. Oliveira, E.M., 2012. Dinâmica locacional das indústrias e a produção do espaço urbano em Poços de Caldas (MG). Oliveira, E.M., 2012. Dinâmica locacional das indústrias e a produção do espaço urbano em Poços de Caldas (MG). M.Sc. Dissertation, UNESP- Universidade Estadual Paulista, Rio Claro, Rio Claro (SP), 177 pp., UNESP- Universidade Estadual Paulista, Rio Claro, Rio Claro (SP), 177 pp. Piper, A.M.A., 1944. A graphic procedure in the geochemical interpretation of water- analyses. Trans. Am. Geophys. Union 25, 914–928. Poços de Caldas, 1992. Plano Diretor. Secretaria de Planejamento e Coordenação, Poços de Caldas. Poços de Caldas, 2006. Plano Diretor (Documento de 2002, revisado de acordo com a Lei Federal 10.257/10). Secretaria de Planejamento e Coordenação, Poços de Caldas. Rebouças, A.C., Braga, B., Tundisi, J.G., 2006. Águas doces do Brasil: capital ecológico, uso e conservação, 3rd ed. Editora Escrituras, São Paulo, pp. 748. Rosales-Hoz, L., Cundy, A.B., Bahena-Manjarrez, J.L., 2003. Heavy metals in sediment cores from a tropical estuary affected by anthropogenic discharges: coatzacoalcos estuary, Mexico. Estuar. Coast. Shelf Sci. 58, 117–126. Ruiz-Fernández, A.C., Hillaire-Marcel, C., Paez-Osuna, F., Ghaleb, B., Soto-Jiménez, M., 2003. Historical trends of metal pollution recorded in the sediments of the Culiacan River Estuary, Northwestern Mexico. Appl. Geochem. 18, 577–588. Ruiz-Fernández, A.C., Hillaire-Marcel, C., Paez-Osuna, F., Ghaleb, B., Caballero, M., 2007. 210Pb chronology and trace metal geochemistry at Los Tuxtlas, Mexico, as evidences by a sedimentary record from the Lago Verde crater lake. Quatern. Res. 67 (2), 181–192. Sabaris, T.P.P., Bonotto, D.M., 2010. Sedimentation rates in Atibaia River basin, São Paulo State, Brazil, using 210Pb as geochronometer. Appl. Radiat. Isot. 69, 275–288. Thornton, I., 1983. Applied Environmental Geochemistry. Academic Press, London, pp. 501. Turcq, P.M., Jouanneau, J.M., Turcq, B., Seyler, P., Weber, O., Guyot, J.L., 2004. Carbon sedimentation at Lago Grande de Curuaí, a floodplain lake it the low Amazon region: in sight into sedimentation rates. Palaeogeogr. Palaeoclimatol. Palaeoecol. 214, 27–40. Turner, L.J., Delorme, L.D., 1996. Assessment of 210Pb data from Canadian lakes using the CIC and CRS models. Environ. Geol. 28, 78–87. F.R.M. Matamet, D.M. Bonotto Applied Radiation and Isotopes 137 (2018) 108–117 117 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref1 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref1 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref2 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref2 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref2 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref2 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref3 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref3 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref4 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref4 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref5 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref5 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref5 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref6 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref6 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref6 http://www.mma.gov.br/conama http://bvsms.saude.gov.br/bvs/saudelegis/gm/2011/prt2914_12_12_2011.html http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref7 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref7 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref8 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref8 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref9 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref9 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref9 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref10 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref10 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref11 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref11 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref11 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref12 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref12 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref12 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref12 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref13 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref13 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref13 http://biblioteca.ibge.gov.br/visualizacao/dtbs/minasgerais/pocosdecaldas.pdf http://www.ibram.org.br/sites http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref14 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref14 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref14 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref15 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref15 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref16 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref16 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref17 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref17 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref17 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref18 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref18 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref18 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref19 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref19 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref20 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref20 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref20 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref20 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref21 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref21 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref21 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref22 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref22 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref23 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref23 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref24 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref24 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref24 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref25 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref25 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref25 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref26 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref26 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref26 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref26 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref27 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref27 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref28 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref28 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref29 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref29 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref29 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref29 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref30 http://refhub.elsevier.com/S0969-8043(17)30473-6/sbref30 A 210Pb chronological study in sediments from poços de caldas alkaline massif (PCAM), Brazil Introduction Methodological basis for 210Pb dating Experimental Study area Sampling Analytical methods Results and discussion Hydrochemical analyzes Size distribution and chemical analysis of the sediments Sedimentation rates by the 210Pb method Conclusion Acknowledgments References