Abstract. Dissolved CH 4 was measured in coastal waters of the southern North Sea, in two adjacent U.K. estuaries with well-defined turbidity maxima (Humber and Tyne) and in their associated river catchments, during a series of campaigns covering the period 1993-1999. In general, samples from all three environments were significantly to highly CH4 enriched relative to atmospheric air. Observed river water concentrations,-33-152 nmol L -• (940-4305% saturation) for the Humber river catchment and ---3-62 nmol L '• (86-1754% saturation) in the river Tyne, were within but toward the low end of the range of CH4 concentrations in river waters world wide. In sea waters from the outer Wash estuary (U.K. coast) and adjacent to the Dutch coast, CH4 was highly but nonlinearly correlated with salinity, consistent with strong CH 4 removal from river and/or estuarine CH4 sources influencing these locations. In transects along the Humber and Tyne estuaries, CH4 was highly negatively nonconservative, confirming the estuarine removal hypothesis. lost globally to gas exchange in estuaries, increasing previous such estimates by-8-50 %. However, as it is based on data that exclude the possibility of elevated CH 4 levels at estuarine turbidity maxima, even this revision is likely to be conservative. Detailed studies of CH4 distributions in major world estuaries would now be required in order to successfully reevaluate the CH4 budget of the coastal marine atmosphere.

The apparent transfer velocities (kw) of CH4, N2O, and SF6 were determined for gas invasion and evasion in a closed laboratory exchange tank. Tank water (pure Milli‐RO® water or artificial seawater prepared in Milli‐RO®) and/or tank air gas compositions were adjusted, with monitoring of subsequent gas transfer by gas chromatography. Derived kw was converted to “apparent k600,” the value for CO2 in freshwater at 20°C. For CH4, analytical constraints precluded estimating apparent k600 based on tank air measurements. In some experiments we added strains of live methanotrophs. In others we added chemically deactivated methanotrophs, non‐CH4 oxidizers (Vibrio), or bacterially associated surfactants, as controls. For all individual controls, apparent k600 estimated from CH4, N2O, or SF6 was indistinguishable. However, invasive estimates always exceeded evasive estimates, implying some control of gas invasion by bubbles. Estimates of apparent k600 differed significantly between methanotroph strains, possibly reflecting species‐specific surfactant release. For individual strains during gas invasion, apparent k600 estimated from CH4, N2O, or SF6 was indistinguishable, whereas during gas evasion, k600‐CH4 was significantly higher than either k600‐N2O or k600‐SF6, which were identical. Hence evasive k600‐CH4/k600‐SF6 was always significantly above unity, whereas invasive k600‐CH4/k600‐SF6 was not significantly different from unity. Similarly, k600‐CH4/k600‐SF6 for the controls and k600‐N2O/k600‐SF6 for all experiments did not differ significantly from unity. Our results are consistent with active metabolic control of CH4 exchange by added methanotrophs in the tank microlayer, giving enhancements of ∼12 ± 10% for k600‐CH4. Hence reactive trace gas fluxes determined by conventional tracer methods at sea may be in error, prompting a need for detailed study of the role of the sea surface microlayer in gas exchange.

The clearance characteristics of two sizes of hemodialyzers (0.9 m2 and 1.5 m2) from the same range of products have been studied over the dialysate flow range of 500-3,000 ml/min to establish the device's overall mass transfer resistance characteristics. The results obtained demonstrate a difference in the overall mass transfer resistance which is most marked at the commonly used dialysate flow rate of 500 ml/min. This difference suggests that the increase in size results in the introduction of flow imperfections which reduces the benefit that might be gained by the use of a larger surface area. Results established indicate a reduction in the overall mass transfer resistance with an increasing dialysate flow rate. This reduction is attributed to the presence of turbulence in the dialysate pathway at higher flow rates. The presence of such turbulence was confirmed by visual inspection of the dialyzer after the completion of the study when it was noted that the original well-ordered configuration present in a new dialyzer had been substantially disturbed. Correlation of the dialysate flow rate with overall mass transfer resistance by the use of a Wilson plots indicates a nonlinear relationship. This nonlinearity is attributed to a nonfully developed turbulent flow profile in the dialysate pathway.

The relationships between gas transfer velocity, k 600 , wind speed, wind direction, rainfall, and relative humidity were examined using measurements of SF 6 evasion from Coatenhill Reservoir, a small (0.017 km 2 ), shallow (1.9 Ϯ 0.1 m), man-made lake in northeast England characterized by predominantly low to intermediate wind speeds ϳ1-10 m s Ϫ1 . A graphical method was used to estimate the wind speed at a standard height of 10 m, U 10 , from wind speed measurements at 2 m and 3.8 m. Derived values of U 10 normalized to remove thermal stability effects (U 10

SummaryThree patients with lithium toxicity are reported, two of whom were exposed to toxic lithium levels for a prolonged period: both survived with permanent damage to basal ganglia and cerebellar connexions despite effective lowering of lithium levels by haemodialysis. Data obtained during dialysis treatment show prolonged haemodialysis to be the treatment of choice. If facilities for haemodialysis are not available or the patient presents with toxic lithium levels and miimal symptoms peritoneal dialysis will effectively lower serum lithium levels, but more slowly than haemodialysis.