The surface chemistry of pyrogenic organic carbon ( PyOM ) can be changed by a variety of abiotic and biotic oxidative and adsorption / desorption processes in the environment .Exposure of PyOM to high energy light prior to addition to soil or sediment , or while entrained in the atmosphere , may induce significant surface photooxidation , i . e . , photochemical weathering , altering its environmental reactivity .Fig . 1 The effect of PyOM additon on soil C pools ( Image by WANG Ruzhen ).