New research just released discusses a lower pH (toward the acidic) depth zone in the water column of the Chesapeake Bay. That's a concern because the Bay's fresh/brackish waters don't have the same buffering capacity as full salinity seawater.
Acid zone in Chesapeake Bay identified
What was discovered:
"In their research, [Wei-Jun] Cai and his colleagues discovered a "pH minimum zone" that occurs at a depth of approximately 10-15 meters (~30-50 feet) in the Chesapeake Bay. The pH in this zone is roughly 7.4, nearly 10 times higher in acidity (or a unit lower in pH) than what is found in surface waters, which have an average pH of 8.2. ... This zone is suspected to be due to a combination of factors, most importantly, from acids produced when bottom water rich in toxic hydrogen sulfide gets mixed upward. The team reported the findings in a paper in Nature Communications on August 28, 2017."
What's causing it:
"As Cai analyzed the data from these cruises and another in April 2015, he noticed that the Bay's pH seemed to reach a minimum at depths between 10-15 meters. To explain this, Cai built a biogeochemical model to simulate the way oxygen is consumed and inorganic carbon and acids are produced to match the observations measured in the Chesapeake Bay. Using direct hydrogen sulfide measurements collected in the bottom waters by Luther, Cai calculated how much acid would need to be produced to explain this minimum zone."
What's (currently) controlling it:
"The team's research shows that currently the dissolving of living shells and non-living aragonite and calcite minerals has provided a self-regulating mechanism to buffer or prevent the Chesapeake Bay's bottom waters from becoming acidic."
Interesting, as well as concerning.
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