The biogeochemical cycling of chlorine

Abstract

Chlorine has important roles in the Earth's systems. In different forms, it helps balance the charge and osmotic potential of cells, provides energy for microorganisms, mobilizes metals in geologic fluids, alters the salinity of waters, and degrades atmospheric ozone. Despite this importance, there has not been a comprehensive summary of chlorine's geobiology. Here, we unite different areas of recent research to describe a biogeochemical cycle for chlorine. Chlorine enters the biosphere through volcanism and weathering of rocks and is sequestered by subduction and the formation of evaporite sediments from inland seas. In the biosphere, chlorine is converted between solid, dissolved, and gaseous states and in oxidation states ranging from −1 to +7, with the soluble, reduced chloride ion as its most common form. Living organisms and chemical reactions change chlorine's form through oxidation and reduction and the addition and removal of chlorine from organic molecules. Chlorine can be transported through the atmosphere, and the highest oxidation states of chlorine are produced by reactions between sunlight and trace chlorine gases. Partial oxidation of chlorine occurs across the biosphere and creates reactive chlorine species that contribute to the oxidative stress experienced by living cells. A unified view of this chlorine cycle demonstrates connections between chlorine biology, chemistry, and geology that affect life on the Earth.

Low-dimensional lateral heterojunctions made of hexagonal boron nitride and carbon materials as efficient electrocatalysts for the chlorine evolution reaction: a study of DFT and machine learning

“…The chlorine cycle is a crucial component of biogeochemical cycles, exerting substantial inuence on both climate and ecosystems. 1,2 An integral part of this cycle involves chlorinated organic compounds (Cl org ), commonly utilized in chemical production elds such as the fabrication of energetic materials. [3][4][5][6] This process, however, invariably results in the generation of signicant volumes of chlorine-laden wastewater.…”

Whole genome sequence and 16S rRNA gene amplicon metagenomics of enhanced in-situ reductive dechlorination at a tetrachloroethene-contaminated superfund site

“…The copyright holder for this preprint this version posted June 24, 2024. ; https://doi.org/10.1101/2024.06. 20.599892 doi: bioRxiv preprint -4 -Organohalides (OHs), including VC, are produced during natural biogeochemical processes and microbial transformations of chlorinated solvents contribute to the global Cl cycle [4,5,6].…”

“…-4 -Organohalides (OHs), including VC, are produced during natural biogeochemical processes and microbial transformations of chlorinated solvents contribute to the global Cl cycle [4,5,6].…”

Chlorine Distribution in Soil and Vegetation in Boreal Habitats along a Moisture Gradient from Upland Forest to Lake Margin Wetlands

“…Chloride (Cl – ), the predominant form of chlorine (Cl) in nature, was previously considered nonreactive in terrestrial ecosystems but this view has changed. − Extensive natural chlorination of organic matter has been observed in many terrestrial ecosystems. − Experiments with radioactive Cl ( 36 Cl) as a tracer have confirmed natural chlorination rates corresponding to as much as 50–300% of the annual wet deposition of Cl in several types of soils without plant roots, , and substantially higher organic matter chlorination rates with active roots present . The variation of soil Cl at large and coarse spatial scales has been correlated to atmospheric Cl – deposition and soil organic matter content. ,,, At local scales, other factors may be more important, but detailed Cl distribution among local topography causing gradients in soil wetness, nutrient flux, and biogeochemical cycling in the landscape have rarely been assessed.…”

“…Chloride (Cl – ), the predominant form of chlorine (Cl) in nature, was previously considered nonreactive in terrestrial ecosystems but this view has changed. 1 − 3 Extensive natural chlorination of organic matter has been observed in many terrestrial ecosystems. 4 − 7 Experiments with radioactive Cl ( 36 Cl) as a tracer have confirmed natural chlorination rates corresponding to as much as 50–300% of the annual wet deposition of Cl in several types of soils without plant roots, 8 , 9 and substantially higher organic matter chlorination rates with active roots present.…”