(原始内容存档于2016-08-20). Nitrogen and the Hydrologic Cycle. Extension Fact Sheet. Ohio State University. [2006-10-24]. (原始内容存档于2006-09-01). The Carbon Cycle. Earth Observatory
Cl− 的高溶解度及低反應性,很適合用來研究氯循环,在大部份的研究中作為同位素的追蹤劑。 Öberg, G. The natural chlorine cycle - fitting the scattered pieces. Applied Microbiology and Biotechnology