Evolution of groundwater geochemistry in the Sulaimani-Warmawa Sub-basin in the Kurdistan Region of Iraq has been investigated using hydrogeochemical and isotopic methods. This is a semiarid region with seasonal precipitation in winter. Water chemistry generally evolves from Ca-HCO3 groundwater type close to the basin boundaries towards Ca-Mg-HCO3 groundwater type close to the Tanjero River along the axis of the basin. Some samples have increased concentrations of Na, Cl, and SO4 as a consequence of dissolution of halite and gypsum embedded in carbonates. Values of pH are slightly alkaline or alkaline, and redox parameters indicate a moderately reducing environment. Isotopes δ2H and δ18O indicate recharge from winter precipitation with no evaporation. Values of dissolved 13C(DIC) correspond to equilibrium with carbonates and C4 plants as the source of CO2. Values of 87Sr/86Sr in groundwater are in a good agreement with carbonate dissolution as a principal process. The principal geogenic contaminant is Ba with concentrations up to 0.383 mg/L. Dissolved concentrations of other geogenic contaminants such as As, F, Mn, and Cr are low or below the detection limit as expected based on their low contents in carbonate rocks. Inverse geochemical modeling on selected profiles calibrated using δ13C values provided mass transfer coefficients for possible geochemical reactions. Future work should focus on interactions in the hyporheic zone of the Tanjero River.
- Klíčová slova
- Clastic aquifer, Environmental isotopes, Geochemical modeling, Kurdistan Region of Iraq,
- MeSH
- chemické látky znečišťující vodu * analýza MeSH
- monitorování životního prostředí metody MeSH
- podzemní voda * chemie MeSH
- uhličitany analýza MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Irák MeSH
- Názvy látek
- chemické látky znečišťující vodu * MeSH
- uhličitany MeSH
The impact of a natural wetland ("dambo" in Zambia) on neutral mine drainage at Luanshya in the Zambian Copperbelt has been investigated during an intermediate discharge period (July) using a multi-method characterization of solid phase samples, sequential extraction analysis, X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy combined with water analyses, isotopic analyses, and geochemical modeling. In the wetland, the principal identified solid phases in sediments were carbonates, gypsum, and ferric oxyhydroxides. A significant portion of the ochres was present as insoluble hematite. Mine drainage pH values decrease, and log [Formula: see text] values increase after inflow of water into the wetland; dissolved and suspended concentrations of Fe, Mn, Cu, and Co also decrease. Based on speciation calculations, there is no precipitation of secondary Cu and Co minerals in the period of sampling, but it can occur later in dry period when the flow rate is reduced. Concentrations of sulfate decrease, and values of δ34S(SO4) in the wetland increase in parallel, suggesting sulfate reduction is occurring. In more advanced dry period, the discharge in mine drainage stream is probably much lower and water can reach supersaturation with respect to minerals such as gypsum, which has been found in sediments. Wetlands have a positive impact on mine drainage water quality due to the removal of metals by adsorption, co-precipitation, and filtration of colloids. However, there can also be a rebound of contamination by seepage inflow downstream from the wetland. Ongoing climate change with extreme hydrologic events may enhance differences between dry and rainy seasons with resulting faster mobilization of contaminants.
- Klíčová slova
- Adsorption, Climate change, Neutral mine drainage, Ochres, Wetland, Zambia,
- MeSH
- adsorpce MeSH
- chemická precipitace MeSH
- chemické látky znečišťující vodu analýza MeSH
- difrakce rentgenového záření MeSH
- filtrace MeSH
- hornictví * MeSH
- klimatické změny * MeSH
- koloidy MeSH
- minerály chemie MeSH
- mokřady * MeSH
- monitorování životního prostředí * metody MeSH
- odpadní voda chemie MeSH
- počasí MeSH
- roční období MeSH
- síran vápenatý chemie MeSH
- sírany analýza MeSH
- těžké kovy analýza MeSH
- uhličitany chemie MeSH
- železité sloučeniny MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Zambie MeSH
- Názvy látek
- chemické látky znečišťující vodu MeSH
- ferric oxide MeSH Prohlížeč
- ferric oxyhydroxide MeSH Prohlížeč
- koloidy MeSH
- minerály MeSH
- odpadní voda MeSH
- síran vápenatý MeSH
- sírany MeSH
- těžké kovy MeSH
- uhličitany MeSH
- železité sloučeniny MeSH
We studied arid desert soils from Namibia (Rosh Pinah) that were contaminated with up to 7 mg kg-1 of thallium (Tl) via dust emitted from a local flotation tailing dam. Chemical extractions of waste and soil materials indicated that most of the Tl is strongly bound, in accordance with X-ray diffraction and X-ray absorption spectroscopy data that point to the predominant association of Tl with metal sulfides and phyllosilicates. The isotope fractionation factor ε205Tl of the soil samples (from -0.4 to +3.8) shows a positive linear relationship (R2 = 0.62) with 1/Tl, indicative for the mixing of two major Tl pools, presumably anthropogenic Tl and geogenic Tl. The ε205Tl value for the topmost soil samples (∼+3) closely matches the ε205Tl value for post-flotation waste particles with a diameter of <0.05 mm, whereas the bulk flotation waste exhibits a significantly larger ε205Tl value (∼+6). These variations are in accordance with predominant atmospheric transfer of Tl from the tailings to the adjacent soils via fine (dust) particles. The identified minimal Tl alteration in soils indicates that only a small part of the Tl could be potentially released and passively enter the vegetation, local population and/or food chain in the long term. From this viewpoint, Tl does not represent such an important environmental concern as other (abundant) contaminants at the locality. Furthermore, there could be a relevance for other alkaline desert soils, including those where Tl pollution plays a major role.
- Klíčová slova
- Contamination, Mining waste, Soil, Tl isotopes,
- MeSH
- izotopy MeSH
- látky znečišťující půdu analýza MeSH
- monitorování životního prostředí metody MeSH
- potravní řetězec MeSH
- pouštní klima MeSH
- půda chemie MeSH
- thallium analýza MeSH
- znečištění životního prostředí MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Namibie MeSH
- Názvy látek
- izotopy MeSH
- látky znečišťující půdu MeSH
- půda MeSH
- thallium MeSH
Acid mine drainage from mine tailings at Selebi Phikwe, eastern Botswana, has been investigated using a combination of total decomposition, sequential extraction, X-ray diffraction, Mössbauer spectroscopy, and SEM analyses of solid phase samples, water analyses, isotopic analyses, and geochemical modeling. The principal ferric phases in the seepage stream sediments are jarosite and goethite, which incorporate Ni and Cu. The Mössbauer spectroscopy (MS) indicated exclusively 3+ oxidation state of iron with typical features of ferric hydroxides/sulfates. A fraction of dissolved sulfate is also sequestered in gypsum which precipitates further downstream. Significant portions of Fe, Ni, and Cu are transported in suspension. Values of pH decreased downstream due to H+ generated by the precipitation of jarosite. Values of δ2H and δ18O indicate evaporation of pore water in the mine tailings before seepage. Values of δ34S(SO4) are consistent with the oxidation of sulfides, but sample from the seepage face is affected by dissolution of gypsum. No minerals of Ni and Cu were detected and the principal attenuation processes seem to be adsorption and co-precipitation with jarosite. Higher contents of Cu are sequestered in solid phases compared to Ni, in spite of much higher dissolved Ni concentrations. Based on the speciation calculations, seepage water is undersaturated with respect to all Ni and Cu phases and adsorption and co-precipitation with jarosite seems to be the principal attenuation processes. Direct geochemical modeling was able to reproduce downstream pH trends, thus confirming the precipitation of jarosite as the principal pH-controlling process.
- Klíčová slova
- Attenuation, Cu, Jarosite, Mine tailings, Ni, Ochres, Seepage,
- MeSH
- adsorpce MeSH
- chemické látky znečišťující vodu analýza chemie MeSH
- chemické modely * MeSH
- difrakce rentgenového záření MeSH
- hornictví * MeSH
- koncentrace vodíkových iontů MeSH
- měď analýza chemie MeSH
- minerály MeSH
- monitorování životního prostředí metody MeSH
- nikl analýza chemie MeSH
- průmyslový odpad analýza MeSH
- sírany MeSH
- sloučeniny železa MeSH
- sulfidy analýza MeSH
- železité sloučeniny MeSH
- železo analýza MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Botswana MeSH
- Názvy látek
- chemické látky znečišťující vodu MeSH
- ferric hydroxide MeSH Prohlížeč
- ferric sulfate MeSH Prohlížeč
- goethite MeSH Prohlížeč
- jarosite MeSH Prohlížeč
- měď MeSH
- minerály MeSH
- nikl MeSH
- průmyslový odpad MeSH
- sírany MeSH
- sloučeniny železa MeSH
- sulfidy MeSH
- železité sloučeniny MeSH
- železo MeSH
We report, for the first time, a detailed study at river water and hyporheic zone systems through collection and analyses of shallow sediments and selected source rocks, pore water, and river water from forty-two locations at the Chianan Plain (CP), SW Taiwan. The study was focused to understand the possible changes in the river water and sediment chemistry as a consequence of high arsenic (mean±SD=71.28±16.24μg/L, n=46) groundwater discharge to three major rivers in the plain. The study shows, except few locations, As concentration in river sediments corresponds to average As concentration in soil and upper crustal abundance and of source rock. Sequential extraction indicates that As is mostly bound to FeOOH. No enrichment of arsenic in river sediments or depletion of aqueous As and iron in pore water was observed down to the maximum sampling depth of 1.7m although manganese is enriched in sediments. Dissolved As concentrations in the river sediments are much lower compared to the hotspots in the CP aquifers. This suggests that no As attenuation processes are active or they cannot be detected in this zone. Mn precipitates at higher redox level compared to Fe and As and thus attenuates in the studied zone.
- Klíčová slova
- Arsenic attenuation, Groundwater discharge, Redox reactions, Sediment-water interaction, Sr-Nd isotopes,
- Publikační typ
- časopisecké články MeSH
