Applied Geochemistry (v.19, #12)

Subject Index (XX-L).

Author Index (LI-LV).

A mineralogical study of 3 samples of municipal solid waste incineration bottom ash collected from different storage sites and with storage times varying from 3 weeks to 2 years, has enabled identification of the main secondary mineral species formed during weathering. The frequencies of the secondary phases were determined and a diagram is proposed for the relative distribution of the newly formed mineral phases: calcite ≫ Fe oxides quartz ⩾ sulphates and/or ettringite (depending on the amount of reactive Al present in the bottom ash). This approach, involving careful sampling, sample preparation and the combined use of various analytical techniques, also showed the high frequency of Al hydroxides and amorphous phases and helped to identify more than 30 sulphates s.l. (sulphates, chromates, vanadates, etc.). Most of the secondary minerals (carbonates and sulphates s.l.) have broad metal trapping capacities for heavy element uptake (Pb, Zn, Cd, As, V, Cr, etc.) due to their crystal-chemistry characteristics. Ca-oxalates were also identified. Mineralogical data from the study provide new input for thermochemical models. The relative stability of metal uptake and the extent of associated neogenesis occurring during bottom-ash decomposition is discussed. Sulphate minerals (and certain heavy metal oxides (zincite)), which are extremely sensitive to environmental conditions, can trap metals only temporarily, as opposed to Fe oxyhydroxides (As, etc.) and carbonates (Pb, Zn, Cd), which are more stable under atmospheric conditions and constitute more sustainable trapping media with higher liquid/solid (L/S) ratios. Finally, a composite predictive diagram is proposed for the mineralogical evolution of bottom ash that accounts for variations in L/S ratios.

The evolution of alkaline, saline ground- and surface waters in the southern Siberian steppes by D. Banks; V.P. Parnachev; B. Frengstad; W. Holden; O.V. Karnachuk; A.A. Vedernikov (1905-1926).
Groundwaters, river and lake waters have been sampled from the semi-arid Siberian Republic of Khakassia. Despite the relatively sparse data set, from a diversity of hydrological environments, clear salinity-related trends emerge that indicate the main hydrochemical evolutionary processes active in the region. Furthermore, the major ion chemistry of the evolution of groundwater baseflow, via rivers, to terminal saline lake water, can be adequately and simply modelled (using PHREEQCI) by invoking: (i) degassing of CO2 from groundwater as it emerges as baseflow in rivers (rise in pH); (ii) progressive evapoconcentration of waters (parallel accumulation of Cl, Na+, SO4 2−, and increase in pH due to common ion effect); and (iii) precipitation of calcite (depletion of Ca from waters, reduced rate of accumulation of alkalinity). Dolomite precipitation is ineffective at constraining Mg accumulation, due to kinetic factors. Silica saturation appears to control dissolved Si in low salinity waters and groundwaters, while sepiolite saturation and precipitation depletes Si from the more saline surface waters. Gypsum and sodium sulphate saturation are only approached in the most saline environments. Halite remains unsaturated in all waters. Sulphate reduction processes are important in the lower part of lakes.

Lead and uranium isotopic behavior in diagenetic and epigenetic manganese nodules, Timna Basin, Israel, determined by MC-ICP-MS by Sarah Ehrlich; Yehudit Harlavan; Miryam Bar-Matthews; Ludwik Halicz (1927-1936).
Isotope ratios of U and Pb were measured in two types of Mn nodules from the Cambrian Timna Formation, Israel. Type A nodules are mainly composed of pyrolusite and hollandite, with Mn, Ba, Pb and U concentrations of 30–60%, 0.2–2.5%, 0.2–1.0% and 500–3500 ppm, respectively, whereas type B nodules were formed by alteration of the former, and contain mainly coronadite, with Mn, Ba, Pb and U concentrations of 7–48%, 0.2–7%, 0.6–5% and 10–160 ppm, respectively. The isotopic composition of U and Pb was measured by MC-ICP-MS on Mn-rich solutions (up to 100 mg/L) without and with chromatographic separation. The values for the 207/206 and 208/206 ratios have been determined with precisions of up to 50 ppm and those of 206/204, 207/204 and 208/204 – up to 200 ppm. The values for the 234/238 ratios have been determined with precisions of 0.4–1%. The results of the separated and unseparated solutions were shown to be equal within the error. Thus there is no significant matrix effect while measuring U and Pb in Mn rich solution using the MC-ICP-MS.The isotopic composition of Pb and U support the distinction between the two types of Mn nodules. Type A nodules have a wide range of 206Pb/204Pb ratios (18.278–19.776), and an almost constant ratio of 208Pb/204Pb. In contrast, type B nodules have almost constant 206Pb/204Pb ratios and a wide range of 208Pb/204Pb ratios (37.986–38.079). Type A nodules form a linear array on a 207Pb/204Pb vs 206Pb/204Pb diagram, while type B nodules form a tight group characterized by lower Pb isotope ratios that slightly deviate from the type A array. The 234U/238U ratio differs between the two types of nodules; type A nodules exhibit a uniform and close to equilibrium 234U/238U ratio while type B nodules show a wide range of 234U/238U ratios above and below the equilibrium value. The isotopic composition of Pb in type A nodules might reflect Pb contributions from plutonic rock weathering, exposed at the time of deposition or later, to the Cambrian sea. These nodules have remained unaffected by processes that occurred since the Cambrian. The higher 208Pb/204Pb values of type B indicate that these nodules were formed from a Th-enriched solution probably during epigenetic processes which occurred also during the last 1 Ma.Thus the two isotopic systems of U and Pb can record formation, leaching and redeposition of Mn ores.

Adsorption of U(VI) on 6 samples of natural Fe-rich sands from Oyster, VA was studied over a range of U(VI) concentrations (0.1–100 μM), pH values (3–7.6), and dithionite–citrate–bicarbonate (DCB) extractable amounts of Fe (3.1–12.3 μmol/g). Four modeling approaches were applied to represent the U(VI) adsorption data. Model I was a two-site, diffuse double layer, surface complexation model based on data for synthetic ferrihydrite [Geochim. Cosmochim. Acta 58 (1994) 5465–5478]. Considering the magnitude of approximations necessary for application of the laboratory-based model to natural sands, Model I was surprisingly accurate, as determined by the goodness of fit parameter, χ 2/N of 53.1–22.2. Model II was based on the reactions and diffuse double layer treatment of Model I, but was calibrated to a portion of U(VI) adsorption data for each sand, and then used to predict adsorption data for the same sand under different experimental conditions. Model II did not increase the accuracy of the predictions made with Model I, χ 2/N of 42.4–27.6. Models III and IV were four-site affinity spectrum models, without an explicit electric double layer model or explicit surface hydrolysis reactions. Model III was based on a discrete log K spectrum approach, and Model IV was obtained from adjusting all surface stability constants and site concentrations for all surface sites. Models III and IV represented the U(VI) adsorption data with the greatest accuracy, χ 2/N ranged from 13.8 to 4.4. Model I provides evidence supporting the practice of using pure phase thermodynamic reaction constants for describing the adsorption characteristics of environmentally important sorbents in certain simple cases. Yet, affinity spectrum approaches (Models III and IV) become increasingly important as more accurate interpolation of adsorption data is necessary, the sorbent becomes increasingly complex, or the range of experimental conditions expands.

Geochemical effects of oxidation products and framboidal pyrite oxidation in acid mine drainage prediction techniques by P.A. Weber; W.A. Stewart; W.M. Skinner; C.G. Weisener; J.E. Thomas; R.St.C. Smart (1953-1974).
Acid mine drainage predictive testwork associated with the Australian Mineral Industries Research Association (AMIRA) P387A Project: Prediction and Kinetic Control of Acid Mine Drainage (AMD) has critically examined static acid assessment and kinetic information from acid–base accounting techniques, including net acid production potential (NAPP), net acid generation (NAG) and column leach tests. This paper compares results on two waste rock samples that were obtained from the Kaltim Prima Coal mine (KPC) containing significant quantities of fine-grained framboidal pyrite. In agreement with other research, the authors' results indicated that framboidal pyrite is more reactive than euhedral forms due to the greater specific surface area of framboidal pyrite. This is evidenced by optical microscopy of reacted samples. Importantly, the results showed that NAPP testing is biased by the rapid acid generating oxidation of framboidal pyrite prior to, and during the acid neutralisation capacity (ANC) test. This can result in negative ANC values for samples containing significant framboidal pyrite (often “corrected” to zero kg H2SO4/t) when significant ANC is actually present in the sample. NAG testing using H2O2 indicated that samples containing a significant quantity of framboidal pyrite can result in the catalytic decomposition of the H2O2 prior to complete oxidation of the sulfide minerals present, requiring sequential addition of H2O2 for completion. A benefit of the NAG test, however, is that it assesses the net acid generation capacity of the sample without bias towards acid generation as is observed using NAPP methods. The kinetic NAG test also gives information on the reaction sequence of framboidal and euhedral pyrite. Periodic (kinetic) analysis of sub-samples from column leach tests indicated rapid oxidation of the framboidal pyrite compared to the euhedral pyrite, which was correlated with the greater framboidal pyrite surface area.Calculations to determine the sulfide/sulfate acidity derived from the oxidation of framboidal pyrite prior to; and during the ANC test have been developed to provide a better indication of the actual ANC (ANCActual) of the sample. Paste pH values of <pH 4–5 may be one suitable trigger mechanism for the implementation of this new method. This has led to an improved NAPP estimation of total acid production. Together with NAG and column leach testing this improved methodology has resulted in accurate AMD characterisation of samples containing acidic oxidation products and framboidal pyrite.

Geochemistry of the Kola River, northwestern Russia by Larisa Pekka; Johan Ingri; Anders Widerlund; Olga Mokrotovarova; Margarita Riabtseva; Björn Öhlander (1975-1995).
The Kola River in the northern part of the Kola Peninsula, northwestern Russia, flows into the Barents Sea via the Kola Bay. The river is a unique place for reproduction of salmon and an important source of drinking water for more than 500,000 people in Murmansk and the surrounding municipalities. To evaluate the environmental status of the Kola River water, sampling of the dissolved (<0.22 μm) and suspended (>0.22 μm) phases was performed at 12 sites along the Kola River and its tributaries during 2001 and 2002. Major (Ca, K, Mg, Na, S, Si, HCO3 and Cl) and trace (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sr, Ti, and Zn) elements, total and particulate organic C (TOC and POC), N and P were analysed. Comparison with the boreal pristine Kalix River, Northern Sweden, shows that, except for Na, Cl, Al, Cu and Ni, which exceed the concentrations in the Kalix River by as much as 2–3 times, the levels of other major and trace elements are close to or even below the levels in the Kalix River. However, the results also demonstrate that pollutants from the three major sources: (1) the Cu–Ni smelter in Monchegorsk, (2) the open-pit Fe mine and ore concentration plant in Olenegorsk, and (3) the Varlamov, the Medveziy and the Zemlanoy creeks, draining the area of the large agricultural enterprises in the lower part of the watershed, have a major influence on the water quality of the Kola River.