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Currently, knowledge about the dissolution kinetics of silicate minerals under seawater conditions in general and about feldspar minerals specifically is lacking, even though feldspars are the most common minerals in the earth’s crust. Consequently, global geochemical cycles of elements and isotopes overlook the potential effects of silicate dissolution in seawater and its contribution to mass balances. The aim of the present study is to quantify the effect of salinity on albite dissolution kinetics under seawater conditions and the possible impact of salinity on Sr concentrations and isotopic compositions in seawater. A series of albite dissolution experiments with synthetic NaCl solutions (0.0001–1 molal) at pH 5 and 25 °C were conducted using multi-point batch experiments (MPBEs). Above the Na concentration threshold (0.01 molal), the albite dissolution rate was found to increase with the NaCl concentration and with the ionic strength. Based on the present study and previous experimental studies, a combined model that describes the effects of pH, Na concentration and ionic strength on the albite dissolution rate was developed. The proposed model suggests that albite dissolution under natural seawater conditions is mainly controlled by the effect of ionic strength. Considering that seawater solutions are under far-from-equilibrium conditions, the dissolution rate of albite is more than order of magnitude faster in seawater than in the continental, abiotic environment. Hence, the potential of silicate dissolution in seawater to contribute elements to the oceans is significant. In addition, a MPBE was conducted with a Bancroft, Ontario, Canada albite sample using synthetic seawater (SSW). Based on the changes in Si, Al, Sr, Ca and 87Sr/86Sr with time in this experiment, it is suggested that the relative dissolution rates of albite and apatite inclusions in the albite sample control the Sr concentrations and isotopic compositions. The estimated contribution of Sr release due to feldspar dissolution in seawater under far-from-equilibrium conditions is 2.67∙108 mol y−1. This result is significant if considering other forms of Al-Si mineral dissolution on the ocean floor.

Actinometers are physical or chemical systems that can be employed to determine photon fluxes. Chemical actinometers are photochemical systems with known quantum yields that can be employed to determine accurate photon fluxes for specific photochemical reactions. This review explores in detail several practical chemical actinometers (ferrioxalate, iodide-iodate, uranyl oxalate, nitrate, uridine, hydrogen peroxide and several actinometers for the vacuum ultraviolet). Each actinometer is described with recommended conditions for its use.

Ultraviolet (UV) disinfection efficiency by low-pressure (LP) mercury lamp depends on the UV fluence (dose): the product of incident irradiance (fluence rate) and exposure time, with correction factors. Time–dose reciprocity may not always apply, as higher UV–LP inactivation of E. coli was obtained at a higher irradiance over shorter exposure time, for the same UV fluence. Disinfection by UV LEDs is limited by low radiant flux compared to mercury LP lamps. Our goal was to determine the UV-LED time–dose reciprocity of E. coli for four different central LED wavelengths (265, 275, 285 and 295 nm) under different fluence rates. Inactivation kinetics determined at UV-LED265 was not affected by the fluence rate or exposure time for a given UV fluence. In contrast, UV-LED275, UV-LED285, and UV-LED295 led to higher inactivation at low fluence rate coupled to high exposure time, for the same UV fluence. The intracellular damage mechanisms for each LED central wavelength were determined by using the bioreporters RecA as an indicator of bacterial DNA damage and SoxS as an indicator of oxidative stress. For 265 nm, higher DNA damage was observed, whereas for 285 and 295 nm, higher oxidative stress (possibly due to reactive oxygen species [ROS] damage) was observed. ROS inactivation of E. coli was predicted to be more effective when keeping the ROS concentration low but allowing longer exposure, for a given UV fluence.