RESUMO

The current emphasis of developing countries on policies that favor the intensification of mining exploitation as the main source of incomes, has generated negative consequences for ecosystems and rural communities, mainly due to the release of highly toxic elements into the environment. This study was carried out to evaluate the effect of the Vetas-California gold mining district on As distribution in stream sediments and surface water samples from Suratá River, located in the southwestern area of Santurbán paramo, Colombia. With this aim, samples distributed along the high Suratá River basin in areas near and far from mining areas were selected. Samples were chemically characterized. The As mobility, enrichment and sources were evaluated using sequential and single extractions, enrichment factor (EF), geoaccumulation index (Igeo), and hierarchical cluster analysis (HCA). The results highlight high As content (reaching up to 484 mg/kg) in stream sediment sampled near the gold mining district. For both sediment and water, the relative As content along the Suratá River exceeded the background content by 220 and 64.9 times, respectively. From the single-stage extractions performed, the reducible fractions found in As(NaOH) and As(HCl) were higher in all cases, meaning a high level of mobility and lixiviation of the As content in water samples by changes in pH and redox potentials. The correlations estimated using Spearman coefficients show that most of the bioavailable fraction of As(Exch) is related to main sediment constituents such as S, Fe2O3, SiO2, and Al2O3 and the relative As content. Calculation of the enrichment factor (EF) confirms high enrichments around active sites of gold mining such as the municipalities of Vetas, California and Matanza with EF values of 285, 204, and 133, respectively. In addition, the Igeo values suggest moderate to strong As pollution due to the high Igeo found at the major mining effect points. The findings from this study are valuable for providing effective management options for risk prevention and control of the persistent As accumulation in Santurbán paramo.

Assuntos

Arsênio , Metais Pesados , Poluentes Químicos da Água , California , Colômbia , Ecossistema , Monitoramento Ambiental , Sedimentos Geológicos , Rios , Dióxido de Silício , Água

RESUMO

In the title co-crystal, [Sn(4)(CH(3))(8)Cl(4)O(2)]·2[Sn(CH(3))(2)Cl(C(4)H(8)NS(2))], all the Sn(IV) atoms are in distorted trigonal-bipyramidal environments. In the mononuclear species, the carbodithio-ate ligand is unsymmetrically coordinated to the Sn(IV) atom, with Sn-S distances of 2.6722 (12) and 2.4706 (11) Å. All atoms with the exception of the methyl groups and one of the pyrrolidine ring CH(2) groups lie on a crystallographic mirror plane. The pyrrolidine ring exhibits an envelope conformation; the C atom at the flap is disordered above and below the plane of symmetry with fixed occupation factors of 0.50. The centrosymmetric dimer species consists of a central Sn(2)O(2) unit with two adjacent Sn(2)OCl four-membered rings.

RESUMO

In the title salt, [Sn(CH(3))(2)Cl(CH(4)N(3)S)]Cl, the Sn(IV) atom is five-coordinated in a distorted trigonal-bipyramidal geometry with two methyl groups and one S atom in the equatorial plane, and one N atom and one Cl atom occupying the apical positions. In the crystal, mol-ecules are linked by inter-molecular N-H⋯S hydrogen bonds with set graph-motif C(4) along [010]. N-H⋯ Cl hydrogen bonds with graph-set motif D(2) and D(3) (3)(10) link cations and anions.