Applied Geochemistry (v.71, #C)

Stabilisation/solidification and bioaugmentation treatment of petroleum drill cuttings by Reginald B. Kogbara; Josiah M. Ayotamuno; Ikechukwu Onuomah; Victoria Ehio; ThankGod D. Damka (1-8).
Petroleum drill cuttings are usually treated by techniques suitable for particular contaminant groups. The significance of this study consists in the development of a treatment technology that can simultaneously handle the hydrocarbon and metal constituents of drill cuttings. Bioaugmentation is combined with stabilisation/solidification (S/S), within S/S monoliths and in granulated S/S monoliths. Portland cement was used for S/S treatment at 30% binder dosage. Bioaugmentation treatment involved two bacterial densities of a mixed culture bio-preparation. The effects of inclusion of compost, fertiliser and activated carbon were also evaluated. After 28 days, the combined S/S and bioaugmentation treatments recorded up to 15% higher total petroleum hydrocarbon (TPH) loss than control S/S treatment without bioaugmentation. Embedding fertiliser, activated carbon and higher bacterial density within S/S monoliths resulted in the highest (99%) TPH reduction but higher concentrations of metals. The addition of compost and lower bacterial density to granulated S/S monoliths led to similar (98%) TPH degradation and lower amounts of metals. The results suggest that with better mixture optimisation, combining S/S and bioaugmentation could engender more sustainable treatment of drill cuttings.
Keywords: Bioremediation; Hydrocarbon utilising bacteria; Metals; Portland cement; Stabilisation/solidification; Total petroleum hydrocarbons;

A foray into false positive results in mineral dissolution and precipitation studies by D. Wolff-Boenisch; I.M. Galeczka; K.G. Mesfin; S.R. Gislason (9-19).
This study presents and discusses several case studies of false positive results in mineral/rock dissolution and precipitation studies and the lessons that can be learned from them.

A natural cement analogue study to understand the long-term behaviour of cements in nuclear waste repositories: Maqarin (Jordan) by Lukas H.J. Martin; Andreas Leemann; Antoni E. Milodowski; Urs K. Mäder; Beat Münch; Niels Giroud (20-34).
The geological storage of nuclear waste includes multibarrier engineered systems where a large amount of cement-based material is used. Predicting the long term behaviour of cement is approached by reactive transport modelling, where some of the boundary conditions can be defined through studying natural cement analogues (e.g. at the Maqarin natural analogue site). At Maqarin, pyrometamorphism of clay biomicrites and siliceous chalks, caused by the in-situ combustion of organic matter, produced various clinker minerals. The interaction of infiltrating groundwater with these clinker phases resulted in a portlandite-buffered hyperalkaline leachate plume, which migrated into the adjacent biomicrite host rock, resulting in the precipitation of hydrated cement minerals.In this study, rock samples with different degrees of interaction with the hyperalkaline plume were investigated by various methods (mostly SEM-EDS). The observations have identified a paragenetic sequence of hydrous cement minerals, and reveal how the fractures and porosity in the biomicrite have become sequentially filled. In the alkaline disturbed zone, C-A-S-H (an unstoichiometric gel of Ca, Al, Si and OH) is observed to fill the pores of the biomicrite wallrock, as a consequence of reaction with a high pH Ca-rich fluid circulating in fractures. Porosity profiles indicate that in some cases the pores of the rock adjacent to the fractures became tightly sealed, whereas in the veins some porosity is preserved. Later pulses of sulphate-rich groundwater precipitated ettringite and occasionally thaumasite in the veins, whereas downstream in the lower pH distal regions of the hyperalkaline plume, zeolite was precipitated.Comparing our observations with the reactive transport modelling results reveals two major discrepancies: firstly, the models predict that ettringite is precipitated before C-A-S-H, whereas the C-A-S-H is observed as the earlier phase in Maqarin; and, secondly, the models predict that ettringite acts as the principal pore-filling phase in contrast to the C-A-S-H observed in the natural system. These discrepancies are related to the fact that our data were not available at the time the modelling studies were performed. However, all models succeeded in reproducing the porosity reduction observed at the fracture–rock interface in the natural analogue system.
Keywords: Natural analogue; Nuclear waste repository; Maqarin; Cement; Porosity; Hyperalkaline plume; Reactive transport model;

The use of multiple partially penetrating wells (MPPW) during aquifer storage and recovery (ASR) in brackish aquifers can significantly improve the recovery efficiency (RE) of unmixed injected water. The water quality changes by reactive transport processes in a field MPPW-ASR system and their impact on RE were analyzed. The oxic freshwater injected in the deepest of four wells was continuously enriched with sodium (Na+) and other dominant cations from the brackish groundwater due to cation exchange by repeating cycles of ‘freshening’. During recovery periods, the breakthrough of Na+ was retarded in the deeper and central parts of the aquifer by ‘salinization’. Cation exchange can therefore either increase or decrease the RE of MPPW-ASR compared to the RE based on conservative Cl, depending on the maximum limits set for Na+, the aquifer’s cation exchange capacity, and the native groundwater and injected water composition. Dissolution of Fe and Mn-containing carbonates was stimulated by acidifying oxidation reactions, involving adsorbed Fe2+ and Mn2+ and pyrite in the pyrite-rich deeper aquifer sections. Fe2+ and Mn2+ remained mobile in anoxic water upon approaching the recovery proximal zone, where Fe2+ precipitated via MnO2 reduction, resulting in a dominating Mn2+ contamination. Recovery of Mn2+ and Fe2+ was counteracted by frequent injections of oxygen-rich water via the recovering well to form Fe and Mn-precipitates and increase sorption. The MPPW-ASR strategy exposes a much larger part of the injected water to the deeper geochemical units first, which may therefore control the mobilization of undesired elements during MPPW-ASR, rather than the average geochemical composition of the target aquifer.
Keywords: Aquifer storage and recovery; ASR; Multiple partially penetrating wells; MPPW; Reactive transport; Water quality; Cation exchange; Arsenic; Subsurface iron removal; Coastal aquifers;

Groundwater recharge and salinization in the arid coastal plain aquifer of the Wadi Watir delta, Sinai, Egypt by Mustafa A. Eissa; James M. Thomas; Greg Pohll; Orfan Shouakar-Stash; Ronald L. Hershey; Maher Dawoud (48-62).
The Quaternary coastal plain aquifer down gradient of the Wadi Watir catchment is the main source of potable groundwater in the arid region of south Sinai, Egypt. The scarcity of rainfall over the last decade, combined with high groundwater pumping rates, have resulted in water-quality degradation in the main well field and in wells along the coast. Understanding the sources of groundwater salinization and amount of average annual recharge is critical for developing sustainable groundwater management strategies for the long-term prevention of groundwater quality deterioration. A combination of geochemistry, conservative ions (Cl and Br), and isotopic tracers (87/86Sr, δ81Br, δ37Cl), in conjunction with groundwater modeling, is an effective method to assess and manage groundwater resources in the Wadi Watir delta aquifers. High groundwater salinity, including high Cl and Br concentrations, is recorded inland in the deep drilled wells located in the main well field and in wells along the coast. The range of Cl/Br ratios for shallow and deep groundwaters in the delta (∼50–97) fall between the end member values of the recharge water that comes from the up gradient watershed, and evaporated seawater of marine origin, which is significantly different than the ratio in modern seawater (228). The 87/86Sr and δ81Br isotopic values were higher in the recharge water (0.70,723 < 87/86Sr < 0.70,894, +0.94 < δ81Br < +1.28‰), and lower in the deep groundwater (0.70,698 < 87/86Sr < 0.70,705, +0.22‰ < δ81Br < +0.41‰). The δ37Cl isotopic values were lower in the recharge water (−0.48 < δ37Cl < −0.06‰) and higher in the deep groundwater (−0.01 < δ37Cl < +0.22‰). The isotopic values of strontium, chloride, and bromide in groundwater from the Wadi Watir delta aquifers indicate that the main groundwater recharge source comes from the up gradient catchment along the main stream channel entering the delta. The solute-weighted mass balance mixing models show that groundwater in the main well field contains 4–10% deep saline groundwater, and groundwater in some wells along the coast contain 2–6% seawater and 18–29% deep saline groundwater.A three-dimensional, variable-density, flow-and-transport SEAWAT model was developed using groundwater isotopes (87Sr/86Sr, δ37Cl and δ81Br) and calibrated using historical records of groundwater level and salinity. δ18O was used to normalize the evaporative effect on shallow groundwater salinity for model calibration. The model shows how groundwater salinity and hydrologic data can be used in SEAWAT to understand recharge mechanisms, estimate groundwater recharge rates, and simulate the upwelling of deep saline groundwater and seawater intrusion. The model indicates that most of the groundwater recharge occurs near the outlet of the main channel. Average annual recharge to delta alluvial aquifers for 1982 to 2009 is estimated to be 2.16 × 106 m3/yr. The main factors that control groundwater salinity are overpumping and recharge availability.
Keywords: Salinization; Groundwater sustainability; Groundwater modeling; Seawater intrusion; Water chemistry; Isotopes; Wadi Watir Egypt;

Because of their frequent association with man-made products, increasing SO 4 2 − and Cl concentrations are often important indicators of deterioration of groundwater quality. The integrated use of hydrochemistry and multi-isotopic approaches (δ34S, δ18O and δ37Cl) was applied in Shijiazhuang area, China, to characterize SO 4 2 − and Cl sources; and to evaluate factors, including natural processes and anthropogenic activities, that affect groundwater quality. In the plain area, the SO 4 2 − concentrations of the surface water and shallow groundwater (mean 2.42 mmol/L and 2.06 mmol/L, respectively) were generally higher than those of the deep groundwater (mean 0.69 mmol/L). The natural waters in the mountain area (mean 4.36 mmol/L) had higher SO 4 2 − contents than those in the plain area (mean 1.73 mmol/L). The shallow groundwater samples collected in the southern part of the plain area had higher Cl concentrations than other samples. The SO 4 2 − in natural waters showed variable δ34S and δ18O values, ranging from +8.7‰ to +21.7‰ and from +5.9‰ to +11.4‰, respectively. The δ37Cl values fell in a narrow range of −0.22‰ to +0.64‰ with a mean value of +0.14‰. The hydrochemistry of samples is in part controlled by water-rock interaction processes, but also influenced by anthropogenic activities. The variations of δ34S and δ18O values indicate gypsum, oxidation of inorganic sulfide minerals, and detergents are the primary sources of sulfate in the samples. Bacterial SO 4 2 − reduction is an important reaction affecting the SO 4 2 − concentrations in the deep groundwater of the plain area. The plot of δ37Cl and 1/Cl combined with the δ37Cl information of potential Cl sources suggests that the dissolved Cl in natural waters is mainly sourced from dissolution of Cl-bearing minerals, import of wastewater, and precipitation. Given the above, the elevated concentration of SO 4 2 − and Cl in the groundwater could be mainly attributed to mining activities in the mountain area and input of wastewater from domestic and industrial activities.
Keywords: Groundwater pollution; δ34SSO4 and δ18OSO4; δ37Cl; Multiple solute sources; Bacterial sulfate reduction;

Chemical and isotope compositions of shallow groundwater in areas impacted by hydraulic fracturing and surface mining in the Central Appalachian Basin, Eastern United States by St. Thomas M. LeDoux; Anna Szynkiewicz; Anthony M. Faiia; Melanie A. Mayes; Michael L. McKinney; William G. Dean (73-85).
Hydraulic fracturing of shale deposits has greatly increased the productivity of the natural gas industry by allowing it to exploit previously inaccessible reservoirs. Previous research has demonstrated that this practice has the potential to contaminate shallow aquifers with methane (CH4) from deeper formations. This study compares concentrations and isotopic compositions of CH4 sampled from domestic groundwater wells in Letcher County, Eastern Kentucky in order to characterize its occurrence and origins in relation to both neighboring hydraulically fractured natural gas wells and surface coal mines. The studied groundwater showed concentrations of CH4 ranging from 0.05 mg/L to 10 mg/L, thus, no immediate remediation is required. The δ13C values of CH4 ranged from −66‰ to −16‰, and δ2H values ranged from −286‰ to −86‰, suggesting an immature thermogenic and mixed biogenic/thermogenic origin. The occurrence of CH4 was not correlated with proximity to hydraulically fractured natural gas wells. Generally, CH4 occurrence corresponded with groundwater abundant in Na+, Cl, and HCO3 , and with low concentrations of SO4 2−. The CH4 and SO4 2−concentrations were best predicted by the oxidation/reduction potential of the studied groundwater. CH4 was abundant in more reducing waters, and SO4 2− was abundant in more oxidizing waters. Additionally, groundwater in greater proximity to surface mining was more likely to be oxidized. This, in turn, might have increased the likelihood of CH4 oxidation in shallow groundwater.
Keywords: Methane; Groundwater; Isotopes; Hydraulic fracturing; Surface mining;

The Wabigoon River (Ontario, Canada) was affected by dams starting in 1898 and was polluted with pulp and paper mill wastes starting in 1913 and mercury from a chlor-alkali plant from 1962 to 1975. A dated sediment core from a riverine lake was analysed to investigate resultant changes in the biogeochemistry of mercury as revealed by variations in mercury isotope ratios and sediment chemistry. A total mercury maximum formed by the mercury pollution coincided with minimums in the δ-values of the 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, and 201Hg/202Hg ratios, and the δ-values decreased in the order δ201Hg > δ200Hg > δ199Hg > δ198Hg. Thus, mass-dependent fractionation caused depletion in lighter isotopes, implying evaporation of Hg(0) and pollution of the atmosphere as well as the river-lake system. Concurrently, mass-independent fractionation caused 199Hg enrichment, possibly reflecting an independently documented upsurge in methylmercury production, and 201Hg depletion, suggesting removal of methylmercury with anomalously high 201Hg/199Hg ratios by aquatic organisms and accumulation of 201Hg-depleted inorganic Hg(II) in sediments. The δ201Hg/δ199Hg ratio rose abruptly when mercury pollution began, reflecting the resultant increase in methylmercury production, and remained high but gradually declined as the pollution abated, paralleling trends shown by methylmercury in aquatic organisms. The δ201Hg/δ199Hg ratio of pre-1962 background mercury increased ca. 1898 and ca. 1913–1929, suggesting accelerated methylmercury production due to stimulation of microbial activities by the damming of the river and the input of pulp and paper mill wastes, respectively. Other variations were linked to economic and technological factors that affected pulp and paper manufacture.
Keywords: Mercury isotopes; Mercury pollution from chlor-alkali plant; Pulp and paper mill wastes; Damming of rivers; Riverine lake sediments;

To assess microbial behavior at anticipated repositories of nitrate-containing radioactive waste such as TRU waste, we set up an anoxic single horizontal column filled with Pleistocene sand with indigenous microorganisms as model samples. The column was supplied with artificial groundwater containing nitrate and acetate for 9 weeks (Run 1) or nitrate-amended groundwater from the same Pleistocene stratum for 6 weeks (Run 2). Bacterial communities, including culturable denitrifiers, were established in the sand bed, resulting in acridine orange direct counts per pore water of 3 × 108 cell mL−1 in Run 1 and 5 × 107 cell mL−1 in Run 2 and nitrate-reducing activity per pore water of roughly 13 mg L−1 d−1 in Run 1 and 1–4 mg L−1 d−1 in Run 2. Eh and hydraulic conductivity declined in Run 1, indicating microbial activity capable of retarding radionuclide transport. However, the ratio of bacterial cell concentration found in the effluent water (free-living bacteria) to the total bacterial concentration in sand (R mobile) exceeded 2%. This finding is relevant to the increase in radionuclide transport associated with free-living cells. As a tool for quantifying this influence, we introduced an index, K d,att (distribution coefficient for microbes on sand particles), and calculated this value from the R mobile value. By sensitivity analysis using a numerical simulation model (MINT), we then demonstrated that higher K d,att values would suppress the detrimental effects of the free-living bacteria. Quantification of microbial influences can be made more realistic by obtaining K d,att values in a column experiment and incorporating this index into radionuclide transport models.
Keywords: Bacteria; Column; Denitrification; Radioactive waste;

Oxidative Ce3+ sequestration by fungal manganese oxides with an associated Mn(II) oxidase activity by Haisu Zheng; Yukinori Tani; Hirotaka Naitou; Naoyuki Miyata; Fuyumi Tojo (110-122).
Sequestration of Ce3+ by biogenic manganese oxides (BMOs) formed by a Mn(II)-oxidizing fungus, Acremonium strictum strain KR21-2, was examined at pH 6.0. In anaerobic Ce3+ solution, newly formed BMOs exhibited stoichiometric Ce3+ oxidation, where the molar ratio of Ce3+ sequestered (Ceseq) relative to Mn2+ released (Mnrel) was maintained at approximately two throughout the reaction. A similar Ce3+ sequestration trend was observed in anaerobic treatment of BMOs in which the associated Mn(II) oxidase was completely inactivated by heating at 85 °C for 1 h or by adding 50 mM NaN3. Aerobic Ce3+ treatment of newly formed BMO (enzymatically active) resulted in excessive Ce3+ sequestration over Mn2+ release, yielding Ceseq/Mnrel > 200, whereas heated or poisoned BMOs released a significant amount of Mn2+ with lower Ce3+ sequestration efficiency. Consequently, self-regeneration by the Mn(II) oxidase in newly formed BMO effectively suppressed Mn2+ release and enhanced oxidative Ce3+ sequestration under aerobic conditions. Repeated treatments of heated or poisoned BMOs under aerobic conditions confirmed that oxidative Ce3+ sequestration continued even after most Mn oxide was released from the solid phase, indicating auto-catalytic Ce3+ oxidation at the solid phase produced through primary Ce3+ oxidation by BMO. From X-ray diffraction analysis, the resultant solid phases formed through Ce3+ oxidation by BMO under both aerobic and anaerobic conditions consisted of cerianite with crystal sizes of 5.00–7.23 Å. Such nano-sized CeO2 (CeO2,BMO) showed faster auto-catalytic Ce3+ oxidation than that on well-crystalized cerianite under aerobic conditions, where the normalized pseudo-first order rate constants for auto-catalytic Ce3+ oxidation on CeO2,BMO was two orders of magnitude higher. Consequently, we concluded that Ce3+ contact with BMOs sequesters Ce3+ through two oxidation paths: primary Ce3+ oxidation by BMOs produces nano-sized crystalline cerianite, and subsequent auto-catalytic Ce3+ oxidation efficiently occurs using dissolved oxygen as the oxidizing agent. Pretreatment of newly formed BMOs with La3+ solution resulted in decreased rate constants for primary Ce3+ oxidation by BMO due to site blocking by La3+ sorption. The results presented herein increase our understanding of the role of BMO in oxidative Ce3+ sequestration process(es) through enzymatic and abiotic paths in natural environments and provide supporting evidence for the potential application of BMOs towards the recovery of Ce3+ from contaminated waters.Display Omitted
Keywords: Ce sequestration; Oxidation; Cerianite; CeO2; Biogenic manganese oxide; Mn(II)-oxidizing fungi;