Declining bacteria, lead, and sulphate, and rising pH and oxygen in the lower Mississippi River

Various air and water pollution issues in the US were confronted in the last 60 years using national policy legislation, notably the Clean Water Act and the Clean Air Act. I examine changes in the concentrations of bacteria, oxygen, lead, and sulphate at the terminus of the Mississippi River before and after these pollution abatement efforts. Microbial concentrations increased or were stable from 1909 to 1980 but decreased about 3 orders of magnitude after the 1970s, while the average oxygen content increased. A large decline in lead concentration occurred after the 1960s, along with a less dramatic decline in sulphate concentrations. The pH of the river dropped to a low of 5.8 in 1965 as sulfur dioxide emissions peaked and averaged 8.2 in 2019 after emissions declined. Decades of efforts at a national scale created water quality improvements and are an example for addressing new and existing water quality challenges.

Automated summary

This study focuses on various air and water pollution issues confronted by the US over the past 60 years, with a particular emphasis on changes in bacteria, dissolved oxygen, lead, and sulfate concentrations at the terminus of the Mississippi River before and after the implementation of the Clean Water Act and the Clean Air Act. The research findings indicate significant improvements in water quality under these pollution abatement efforts.