Global Corrections to Reference Irradiance Spectra for Non-Clear-Sky Conditions

Abstract

Photochemical reactions in surface waters play important roles in element cycling and in the removal of organic contaminants, among other processes. A central environmental variable affecting photochemical processes in surface waters is the incoming solar irradiance, as this initiates these processes. However, clear-sky incident irradiance spectra are often used when evaluating the fate of aquatic contaminants, leading to an overestimation of contaminant decay rates due to photochemical transformation. In this work, incident irradiance satellite data were used to develop global-scale non-clear-sky correction factors for commonly used reference irradiance spectra. Non-clear-sky conditions can decrease incident irradiance by over 90% depending on the geographic location and time of the year, with latitudes above 40°N being most heavily affected by seasons. The impact of non-clear-sky conditions on contaminant half-lives was illustrated in a case study of triclosan in lake Greifensee, which showed a 39% increase in the triclosan half-life over the course of a year under non-clear-sky conditions. A global annual average correction factor of 0.76 was determined as an approximate way to account for non-clear-sky conditions. The correction factors are developed at monthly and seasonal resolutions for every location on the globe between 70°N and 60°S at a 4 km spatial resolution and can be used by researchers, practitioners, and regulators who need improved estimates of incident irradiance.

Formulation Controls the Potential Neuromuscular Toxicity of Polyethylene Photoproducts in Developing Zebrafish

“…Photoproduced leachates were generated in an Atlas XLS+ solar simulator equipped with a long-arc Xe lamp and daylight filter (Ametek Inc.) maintained at ∼30 °C using aluminum plates interfaced to a recirculating chiller. Relative to yearly averaged, clear sky natural sunlight at 40°N, 56 simulated sunlight was 3fold greater (Table S1). These irradiation conditions are comparable to those used by Walsh et al, 13 in which notable differences in chemical composition between leachates were reported.…”