Li et al. ran a simulation to analyze pH trends in the Chesapeake Bay between 1951 and 2010, revealing a complex web of factors that altered the bay’s pH over that 60-year period.
Nutrient runoff into the Chesapeake Bay increased between 1950 and 1980 before dropping in the 1990s, thanks primarily to decreased atmospheric deposition of nitrogen and to upgrades in wastewater treatment systems. Agricultural lime application and intensified chemical weathering, which also decrease acidity, became more common over the study period. In contrast, coal mining, drainage from which can increase water acidity, declined over the study period. Weather played a role as well: Typical spring rainfall, as well as particularly wet decades such as the 1970s, pushed the upper bay freshwater plume farther into the middle of the bay and increased the area’s pH.
The researchers examined all these factors and found that overall, the upper bay generally became more alkaline over time but that deeper waters in the middle and lower bay became more acidic. No long-term trend in the pH of the surface waters of the middle and lower bay was observed, as the effects of river alkalinization and ocean acidification mixed and essentially canceled each other out.
They found that river alkalinization had twice the effect on the Chesapeake Bay’s long-term pH trends compared with ocean acidification. Both processes played a greater role than coastal eutrophication did.
I guess the science isn't settled.
The Wombat has Rule 5 Sunday: Surf’s Up up and garnering clicks at The Other McCain.
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