ALBERT

Description: A simple process-based approach to predict regional-scale loading of nitrate at the water table was implemented in a GIS for Great Britain. This links a nitrate input function, unsaturated zone thickness and lithologically-dependent rate of nitrate unsaturated zone travel to estimate arrival time of nitrate at the water table. The nitrate input function is the loading at the base of the soil and has been validated using unsaturated zone pore-water profiles. The unsaturated zone thickness uses groundwater levels based on regional-scale observations infilled by interpolated river base levels. Estimates of the rate of unsaturated zone travel are attributed from regional-scale hydrogeological mapping. The results indicate that peak nitrate loading may have already arrived at the water table for many aquifers, but that it has not where the unsaturated zone is relatively thick There are contrasting outcomes for the two main aquifers which have similar unsaturated zone velocities, the predominantly low relief Permo-Triassic sandstones and the Chalk, which forms significant topographic features. For about 60% of the Chalk, the peak input has not yet reached the water table and will continue to arrive over the next 60 years. The methodology is readily transferable and provides a robust method for estimating peak arrival time for any diffuse conservative pollutant where an input function can be defined at a regional scale and requires only depth to groundwater and a hydrogeological classification. The methodology is extendable in that if additional information is available this can easily be incorporated into the model scheme. Copyright © 2011 John Wiley & Sons, Ltd.

Description: This study investigates fluctuations in nitrate concentration at the water table to improve understanding of unsaturated zone processes in the Chalk aquifer. Sampling was conducted using a novel multi-level sampler during periods of water table rise over five years. The sampler allowed near continuous sampling at a vertical resolution of 0.05 m. Nitrate concentration increased as the water table seasonally recovered, with similar interannual trends with depth. The rising water table activated horizontal fractures facilitating the delivery of water elevated by up to 10 mg/L of nitrate with respect to the adjacent groundwater below. These fractures are considered to activate via piston displacement of water from the adjoining matrix. Hydrograph analysis identified sixteen events which significantly perturbed the water table within 24–48 hours of rainfall. Consistent nitrate concentrations indicate recharge through persistent fracture flow from the surface was not generally the primary driver of the rapid water table response during these events. Instead, the response was attributed to the piston displacement of porewater immediately above the water table. However, a single event in November 2012 delivered relatively dilute recharge indicating rapid persistent fracture flow following rainfall was possible to a depth of 14–15 m. Decreases in porewater nitrate concentration around fracture horizons and the dilution of many groundwater samples with respect to porewaters indicate a fresher source of water at depth. This was considered most likely to be a result of near surface water bypassing the matrix frequently because of widespread mineralisation on fracture surfaces, which retard water and solute exchange. Therefore, persistent fracture flow maybe considered a frequent process in, operating independently of the matrix, and is not necessarily event driven. This article is protected by copyright. All rights reserved.

Description: Complexes of pyrrole-2-carbaldehyde thiosemicarbazones, [(C 4 H 4 N 4 )(H)C 2 =N 3 –N 2 (H)–C 1 (=S)–N 1 H R ; R = Ph, H 2 L 1 ; Me, H 2 L 2 ; H, H 2 L 3 ] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H 2 L 1 in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(κ 2 -N 3 ,S-HL 1 ) 2 ] ( 1 ). Likewise reaction of NiCl 2 with H 2 L 2 in 1:1 molar ratio in acetonitrile in the presence of triethylamine base followed by the addition of pyridine did not yield the anticipated [Ni(κ 3 -N 4 ,N 3 ,S-L 2 )(py)] complex, moreover a bis-square-planar complex, [Ni(κ 2 -N 3 ,S-HL 2 ) 2 ] ( 2 ) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(κ 2 -N 3 ,S-HL 2 ) 2 (κ 2 -N, N-bipy)] ( 3 ). Reaction of PdCl 2 (κ 2 -P, P–PPh 2 –CH 2 –PPh 2 ) with H 2 L 3 in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(κ 3 -N 4 ,N 3 ,S–L 3 )(κ 1 -P–PPh 2 –CH 2 –P(O)Ph 2 ] ( 4 ). The ligands (HL 1 ) – and (HL 2 ) – are chelating to Ni II metal atom as anions binding through N 3 ,S-donor atoms with pendant pyrrole groups, and (L 3 ) 2– is chelating to the Pd II metal atom as dianion through N 4 ,N 3 ,S-donor atoms (pyrrole is N 4 -bonded). Fourth site in 4 is bonded to one P-donor atom of PPh 2 –CH 2 –P(O)Ph 2 , whose pendant –PPh 2 group involves auto oxidation to –P(O)PPh 2 during reaction. These complexes were characterized using analytical data, IR, NMR ( 1 H, 31 P) spectroscopy and X-ray crystallography. Complexes 1 , 2 , and 4 have square-planar arrangement, whereas complex 3 is octahedral.

Description: Reaction of 1, 9-dihydro-purine-6-thione (puSH 2 ) in presence of aqueous sodium hydroxide with PdCl 2 (PPh 3 ) 2 suspended in ethanol formed [Pd(κ 2 -N 7 ,S-puS)(PPh 3 ) 2 ] ( 1 ). Similarly, complexes [Pd(κ 2 -N 7 ,S-puS)(κ 2 -P, P-L-L)] ( 2 – 4 ) {L-L = dppm ( m = 1) ( 2 ), dppp ( m = 3) ( 3 ), dppb ( m = 4) ( 4 )} were prepared using precursors the [PdCl 2 (L-L)] {L-L = Ph 2 P–(CH 2 ) m –PPh 2 }. Reaction of puSH 2 suspended in benzene with platinic acid, H 2 PtCl 6 , in ethanol in the presence of triethylamine followed by the addition of PPh 3 yielded the complex [Pt(κ 2 -N 7 ,S-puS)(PPh 3 ) 2 ] ( 5 ). Complexes [Pt(κ 2 -N 7 ,S-puS)(κ 2 -P, P-L-L)] ( 6 – 8 ) {L-L = dppm ( 6 ), dppp ( 7 ), dppb ( 8 )} were prepared similarly. The 1, 9-dihydro-purine-6-thione acts as N 7 ,S-chelating dianion in compounds 1 – 8 . The reaction of copper(I) chloride [or copper(I) bromide] in acetonitrile with puSH 2 and the addition of PPh 3 in methanol yielded the same product, [Cu(κ 2 -N 7 ,S-puSH)(PPh 3 ) 2 ] ( 9 ), in which the halogen atoms are removed by uninegative N, S-chelating puSH – anion. However, copper(I) iodide did not lose iodide and formed the tetrahedral complex, [CuI(κ 1 -S-puSH 2 )(PPh 3 ) 2 ] ( 10 ), in which the thio ligand is neutral. These complexes were characterized with the help of elemental analysis, NMR spectroscopy ( 1 H, 31 P), and single-crystal X-ray crystallography ( 3 , 7 , 8 , 9 , and 10 ).

Description: Ruthenium(II) Complexes containing pyrimidine-2-thiolate (pymS – ) and bis(diphenylphosphanyl)alkanes [Ph 2 P–(CH 2 ) m –PPh 2 , m = 1, dppm; m = 2, dppe; m = 3, dppp; m = 4, dppb] are described. Reactions of [RuCl 2 L 2 ] (L = dppm, dppp) and [Ru 2 Cl 4 L 3 ] (L = dppb) with pyrimidine-2-thione (pymSH) in 1:2 molar ratio in dry benzene in the presence of Et 3 N base yielded the [Ru(pymS) 2 L] complexes (pymS – = pyrimidine-2-thiolate; L = dppm ( 1 ); dppp ( 3 ); dppb ( 4 )). The complex [Ru(pymS) 2 (dppe)] ( 2 ) was indirectly prepared by the reaction of [Ru(pymS) 2 (PPh 3 ) 2 ] with dppe. These complexes were characterized using analytical data, IR, 1 H, 13 C, 31 P NMR spectroscopy, and X-ray crystallography (complex 3 ). The crystal structure of the analogous complex [Ru(pyS) 2 (dppm)] ( 5 ) with the ligand pyridine-2-thiolate (pyS – ) was also described. X-ray crystallographic investigation of complex 3 has shown two four-membered chelate rings (N,S donors) and one six-membered ring (P,P donors) around the metal atom. Compound 5 provides the first example in which Ru II has three four-membered chelate rings: two made up by N,S donor ligands and one made up by P,P donor ligand. The arrangement around the metal atoms in each complex is distorted octahedral with cis : cis : tran s:P,P:N,N:S,S dispositions of the donor atoms. The 31 P NMR spectroscopic data revealed that the complexes are static in solution, except 2 , which showed the presence of more than one species.

Description: Abstract The discovery of a ~20 km wide area of bright subsurface radar reflections, interpreted as liquid water, beneath the Martian south polar layered deposits (SPLD) in data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument, and the discovery of two geologically recent potential eskers (landforms produced by subglacial melt) associated with viscous flow features in Martian mid‐latitudes, has suggested recent basal melting of Martian ice deposits may be feasible, possibly due to locally elevated geothermal heating. Locations of terrestrial subglacial lakes and major drainage axes have been successfully predicted from subglacial hydraulic potential surfaces calculated from surface topography and ice thickness. Here, we use surface topography from the Mars Orbiter Laser Altimeter and SPLD bed elevations derived from MARSIS data to calculate the subglacial hydraulic potential surface beneath the SPLD and determine whether the observed high reflectance area coincides with predicted subglacial lake locations. Given the sensitivity of terrestrial predictions of lake locations to basal topography, we derive over 1000 perturbed topographies (using noise statistics from the MARSIS data) to infer the most likely locations of possible subglacial water bodies and drainage axes. Our results show that the high reflectance area does not coincide with any substantial predicted lake locations; three nearby lake locations are robustly predicted however. We interpret this result as suggesting that the high reflectance area (assuming the interpretation as liquid is correct) is most likely a hydraulically‐isolated patch of liquid confined by the surrounding cold‐based ice, rather than a topographically‐constrained subglacial lake.

Description: Complexes of pyrrole-2-carbaldehyde thiosemicarbazones, [(C 4 H 4 N 4 )(H)C 2 =N 3 –N 2 (H)–C 1 (=S)–N 1 H R ; R = Ph, H 2 L 1 ; Me, H 2 L 2 ; H, H 2 L 3 ] with nickel(II) and palladium(II) are described. The reaction of nickel(II) acetate with H 2 L 1 in methanol in 1:1 molar ratio yielded a complex of composition, [Ni(κ 2 -N 3 ,S-HL 1 ) 2 ] ( 1 ). Likewise reaction of NiCl 2 with H 2 L 2 in 1:1 molar ratio in acetonitrile in the presence of triethylamine base followed by the addition of pyridine did not yield the anticipated [Ni(κ 3 -N 4 ,N 3 ,S-L 2 )(py)] complex, moreover a bis-square-planar complex, [Ni(κ 2 -N 3 ,S-HL 2 ) 2 ] ( 2 ) was formed. However, in the presence of bipyridine (bipy), it yielded the addition product, [Ni(κ 2 -N 3 ,S-HL 2 ) 2 (κ 2 -N, N-bipy)] ( 3 ). Reaction of PdCl 2 (κ 2 -P, P–PPh 2 –CH 2 –PPh 2 ) with H 2 L 3 in toluene in the presence of triethylamine has yielded a complex of stoichiometry, [Pd(κ 3 -N 4 ,N 3 ,S–L 3 )(κ 1 -P–PPh 2 –CH 2 –P(O)Ph 2 ] ( 4 ). The ligands (HL 1 ) – and (HL 2 ) – are chelating to Ni II metal atom as anions binding through N 3 ,S-donor atoms with pendant pyrrole groups, and (L 3 ) 2– is chelating to the Pd II metal atom as dianion through N 4 ,N 3 ,S-donor atoms (pyrrole is N 4 -bonded). Fourth site in 4 is bonded to one P-donor atom of PPh 2 –CH 2 –P(O)Ph 2 , whose pendant –PPh 2 group involves auto oxidation to –P(O)PPh 2 during reaction. These complexes were characterized using analytical data, IR, NMR ( 1 H, 31 P) spectroscopy and X-ray crystallography. Complexes 1 , 2 , and 4 have square-planar arrangement, whereas complex 3 is octahedral.

Description: The long-term success of the geological storage of CO2 is dependent on the integrity of the sealing horizons, yet there is a paucity of data on permeability, permeability anisotropy, and factors that affect them. Using samples from an ongoing field trial for CO2 sequestration, this paper presents measured vertical (kv) and horizontal (kh) permeabilities across a range of effective pressures. Petrological and petrophysical analyses highlight what are the dominant controls on permeability. The Krechba field in Algeria is one of the largest CO2 storage projects currently running with over 3M tonnes of CO2 injected since 2004. Experimental samples of the caprock and underlying storage domain were recovered from the base of the succession. Caprock permeability ranges from 10−23 to 10−19 m2. Permeability decreases with decreasing porosity and pore throat radius and increasing clay mineral content. Primary depositional heterogeneous distribution of clay minerals produced contrasting layers of relatively low and high permeability resulting in extreme kh/kv ratios of up to 50,000. Samples with the same porosity, mean pore throat size and clay mineral content can have kh/kv differing by 〉4 orders of magnitude. The data was used to model permeability using the Yang-Aplin model. Accuracy of the predicted permeabilites was found to reflect the measured permeability anisotropy. The results highlight that lateral migration of CO2 will be significant and that the caprock succession at Krechba should provide a good seal, even with decreasing effective pressure during injection, in the absence of significant modification by deformation and/or reaction with the CO2-rich fluids.