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News — ALBANY, N.Y. (April 24, 2025) — A new study published by researchers at the University at Albany has presented the first documented evidence that Adirondack surface waters made a near full recovery from metal pollution since the enactment of the Clean Air Act.

Originally passed in 1963 and amended in subsequent decades, the Clean Air Act was one of the first major pieces of environmental legislation in the U.S., intended to reduce and control air pollution nationwide.

The Adirondack Park was a prime target for the legislation, with decades of acid rain damage impacting the region’s lakes, forests and fish populations.

By analyzing historical data and newly collected sediment samples, the UAlbany study found a greater than 90 percent reduction in metal contamination across four ponds in the Adirondacks over the last five decades.

Findings were published in Environmental Pollution this month.

"The Adirondacks have been a special place to me since I moved to the region when I was 10 years old. As a kid, I learned about the devastating effects acid rain had on the lakes, rivers and wildlife," said Skylar Hooler, a doctoral student in UAlbany’s Department of Atmospheric and Environmental Sciences and the study’s first author.

"During my first year of graduate school, I began reviewing the literature and was surprised to find that most recent studies evaluating recovery from metal pollution in the Adirondacks were more than a decade old. I immediately saw an opportunity to revisit this and document how well these ecosystems have recovered since the implementation of the Clean Air Act."

Analyzing Mud Pollution

To conduct the research, Hooler partnered with Aubrey Hillman, an assistant professor in whose research focuses on using lake sediments (mud) to study past climate change and human activities.

Hillman co-leads the in UAlbany’s ETEC research and development complex. The lab is equipped with instrumentation to collect and analyze natural materials, including lake sediment and coral. These samples offer clues about the Earth’s past climate conditions and how it relates to present or future climate trends.

Sky Hooler and Aubrey Hillman stand in front of a pond in the Adirondacks.Sky Hooler (left) and Aubrey Hillman stand in front of Black Pond, located within the Paul Smith's College Visitor Interpretive Center.“Collecting a sediment core is like taking a layered history book from the bottom of a lake,” Hooler said. “Each layer of sediment represents a moment in time. We use specialized coring tools to extract these long, cylindrical records from the lake bed. The goal is to preserve the layers in the exact order they were deposited, so we get an uninterrupted timeline of environmental change that can stretch back thousands of years.”

Using sediment cores collected from the four Adirondack ponds, Hooler and the research team were able to measure the concentrations of metals like lead, copper and zinc across thousands of years.

The sediment cores offered a window into pre-industrial baseline conditions, allowing the researchers to assess the extent of pollution and the success of subsequent recovery efforts, including the Clean Air Act.

“Site selection was strategic,” said Hooler. “First, we had to ensure the lakes were on land we could legally access. Then, we prioritized lakes with similar hydrology and a consistent watershed-to-lake area ratio to allow for better comparisons. Finally, we looked at historical land-use impacts. Some lakes experienced extensive logging, others fire, and some were relatively undisturbed, so we could better understand how these factors influence both contamination and recovery.”

Future Research in the Adirondacks

While the Clean Air Act was clearly a major driver of reduced pollution, Hooler believes that the recovery in Adirondack lakes was largely shaped by interactions between reduced emissions and local watershed processes.

“Many lakes show peak metal deposition between 1970 and 1990, which aligns with the phased implementation of the Clean Air Act and its amendments,” Hooler said. “However, recovery also reflects local factors, like proximity to pollution sources and prevailing wind patterns. So, while the Clean Air Act laid the foundation, the response in each lake depended on its specific environment.”

While the metal pollution project is mostly complete, Hooler’s work in the Adirondacks is ongoing. She’s currently investigating other forms of pollution, such as microplastics, and leading a larger project examining ecological regime shifts across several lakes in the region.

An ecological regime shift happens when something pushes the system too far, like pollution, climate change or even overfishing.

“This new study focuses on changes in ecological productivity, nutrient cycling and trophic status, driven by human activity over the last few centuries. Unlike the metal data, the results here point to more concerning trends that suggest lasting impacts on the ecosystem.”

Other collaborators on the metal pollution study included Sumar Hart, an Atmospheric and Environmental Sciences graduate researcher at UAlbany and William Kenney of the University of Florida’s Land Use and Environmental Change Institute.