## 3 Results
### Metal and Metalloid Contents in FHA, BHA, and FA  
3.4.1. Copper, Chromium, Zinc, and Arsenic  
The highest concentration in HS was reached by Cu (Figure 6). Concentration ranges were:  
* FHA: 57.4-580 ug g\({}^{-1}\) (mean = 176 \(\mu\)g g\({}^{-1}\));
* BHA: 65.0-171 ug g\({}^{-1}\) (mean = 115 \(\mu\)g g\({}^{-1}\));
* FA: 10.6-80.1 ug g\({}^{-1}\) (mean = 37.9 \(\mu\)g g\({}^{-1}\)). Figure 4: Spatial distribution of the concentrations (mg g\({}^{-1}\)) of: (**a**) Humic Substances; (**b**) Free Humic Acids; (**c**) Bound Humic Acids; (**d**) Fulvic Acids. Copper contents were highest in FHA, where they presented the highest dispersion of values about the mean. The absolute maximum of 580 \(\upmu\)g g\({}^{-1}\) was observed in the NE sector of Mar de Cubatao (Figure 6a). This value stood out considerably, exceeding the 1\(\sigma\) standard deviation of Cu concentrations in FHA. Copper concentration was relatively high also in FHA from the Trapande Bay (424 \(\upmu\)g g\({}^{-1}\)), Mar de Cananeia (227 \(\upmu\)g g\({}^{-1}\)), and Mar Pequeno (108-222 \(\upmu\)g g\({}^{-1}\)). Chromium was the second-most abundant metal associated with HS (Figure 7). Concentrations ranges were:  
* FHA: 19.1-81.2 \(\upmu\)g g\({}^{-1}\) (mean = 47.4 \(\upmu\)g g\({}^{-1}\));
* BHA: 53.1-132 \(\upmu\)g g\({}^{-1}\) (mean = 86.3 \(\upmu\)g g\({}^{-1}\));
* FA: 20.5-104 \(\upmu\)g g\({}^{-1}\) (mean = 43.9 \(\upmu\)g g\({}^{-1}\)). Chromium concentration was highest in BHA, particularly near the city of Cananeia, at the Ararapira inlet and in the SW sector of Mar de Cubatao (Figure 7b). Zinc and As showed comparable concentrations and areal distributions (Figures 8 and 9). Zn concentration ranges were:  
* FHA: 16.8-104 \(\upmu\)g g\({}^{-1}\) (mean = 33.4 \(\upmu\)g g\({}^{-1}\));
* BHA: 15.4-59.7 \(\upmu\)g g\({}^{-1}\) (mean = 32.6 \(\upmu\)g g\({}^{-1}\));
* FA: 11.2-63.7 \(\upmu\)g g\({}^{-1}\) (mean = 24.0 \(\upmu\)g g\({}^{-1}\)). Figure 5: Spatial distribution of the \(\upxi^{13}\)C values (% vs. V-PDB) of: (**a**) Sedimentary Organic Matter; (**b**) Free Humic Acids; (**c**) Bound Humic Acids; (**d**) Fulvic Acids. As concentration ranges were:  
* FHA: 6.00-205 \(\upmu\)g g\({}^{-1}\) (mean = 35.8 \(\upmu\)g g\({}^{-1}\));
* BHA: 4.22-12.4 \(\upmu\)g\({}^{-1}\) (mean = 7.53 \(\upmu\)g g\({}^{-1}\));
* FA: 2.11-55.9 \(\upmu\)g g\({}^{-1}\) (mean = 14.8 \(\upmu\)g g\({}^{-1}\)). Both Zn and As showed maximum concentrations in FHA and relatively similar abundances in the three fractions of HS (Figures 8 and 9). In terms of location, the maximum Zn and As concentrations were observed near the Ararapira inlet and in the Trapande Bay, respectively. The results for each station are also reported in Table S2. Figure 6: Spatial distribution of Cu concentrations (\(\upmu\)g g\({}^{-1}\)) in: (**a**) Free Humic Acids; (**b**) Bound Humic Acids; (**c**) Fulvic Acids. (**d**) Box plots of Cu concentrations (\(\upmu\)g g\({}^{-1}\)) in the three fractions. Horizontal lines in whiskers represent the median, upper, and lower quartiles, respectively. Solid squares represent mean values. Solid circles represent the maximum and minimum values. Vertical bars represent 1\(\sigma\) standard deviations. Figure 8: _Conts_. Figure 7: Spatial distribution of Cr concentrations (\(\mu\)g g\({}^{-1}\)) in: (**a**) Free Humic Acids; (**b**) Bound Humic Acids; (**c**) Fulvic Acids. (**d**) Box plots of Cr concentrations (\(\mu\)g g\({}^{-1}\)) in the three fractions. Horizontal lines in whiskers represent the median, upper, and lower quartiles, respectively. Solid squares represent mean values. Solid circles represent the maximum and minimum values. Vertical bars represent 1\(\sigma\) standard deviations. Figure 8: Spatial distribution of Zn concentrations (\(\mu\)g g\({}^{-1}\)) in: (**a**) Free Humic Acids; (**b**) Bound Humic Acids; (**c**) Fulvic Acids. (**d**) Box plots of Zn concentrations (\(\mu\)g g\({}^{-1}\)) in the three fractions. Horizontal lines in whiskers represent the median, upper, and lower quartiles, respectively.