University at Albany doctorate student Skylar Hooler holds a gravity corer used for taking sediment samples from the lake bed on Rat Pond in Lake Clear. A research paper she wrote based on analysis of thousands of years of sediment deposits shows the impact of human industry and legislation on the metal deposits in the pond. (Provided photo)

LAKE CLEAR — After decades of human industry polluting the air, land and water with metal contamination, local water bodies have made a slow, but near-full recovery since the enactment of the Clean Air Act.

A new paper from researchers at the University at Albany tracks the last 400 years of metal deposits in a sampling of Adirondacks ponds, showing how human industry and human legislation impact the natural world.

Skylar Hooler, a doctoral student in UAlbany’s Department of Atmospheric and Environmental Sciences is the study’s first author. Her findings were published in “Environmental Pollution,” a peer-reviewed academic journal, earlier this month.

The research focused on four Adirondack ponds — Rat Pond and Black Pond in Santa Clara, Little Hope Pond in Onchiota and Challis Pond in North Hudson. The researchers used lake sediment — better known as mud — to see back in time. By drawing out long, cylindrical records from the lake bed, they could measure the concentrations of metals like lead, copper and zinc across thousands of years.

They set a pre-industrial baseline of these metals. Metals like iron, manganese, copper and zinc have high background baselines, because they’re naturally present in the bedrock. Metals like lead, arsenic or cadmium have very low baselines.

Lead and arsenic impact human health the most, Hooler said, and can cause neurological diseases. The other metals have impacts on ecosystem health.

The graphs show clear patterns in both timing and magnitude of metal contamination. For thousands of years, a baseline of naturally abundant metals like manganese, iron and zinc coast along at consistent, high levels. Metals like lead, arsenic, cadmium, nickel, cobalt, chromium and copper stayed near or at zero since they are not abundant naturally here.

Then, in the mid-1900s, as human industry ramps up, concentrations of nearly every metal spiked.

“Records displayed the onset of metal contamination between 1900 and 1940, which peaked from 1960 to 1990, aligning with previous records in the region,” according to the paper. “The signature of human activity is ubiquitous.”

The sheer concentrations of the metal deposits were shocking, Hooler said, higher than they expected.

Lead, iron, manganese and zinc rose substantially, reaching levels many times higher than their natural baselines. Arsenic, chromium, cadmium and copper also increased, moving well off the “zero” line.

The lines for iron, zinc, manganese and lead shoot up dramatically, running almost vertically along the axis tracking their prevalence. But then, toward the end of the 1900s, these lines shoot back down just as fast as regulations of emissions and pollution take hold.

Today, the graphs show most metals in the ponds have returned to near pre-industrial baseline levels, with some even hitting the “zero” line in the most recent samples.

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Pollution and politics

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Decades of acid rain from coal combustion, metal smelting and vehicle emissions had damaged local waters in many ways.

“Large-scale sampling in the 1980s found that roughly 25% of the ADK’s 3,000 lakes and ponds were too acidified to support native aquatic life,” according to the paper.

When the Clean Air Act passed in 1970 and was amended in 1990, it effectively reduced the emission of the sulfur oxides and nitrogen oxides that raised the pH of rainwater.

The acidity of water from acid rain has been reducing since the Clean Air Act. But polluted metals stored in the watershed, what the paper calls “legacy pollutants,” continued entering the waters for some time.

Hooler said if the soil is disturbed, it could remobilize these legacy pollutants and cause their levels in the lakes to spike once again. Disturbances come from things like dredging, logging, construction or fires.

Hooler said she’s enjoyed seeing the public response to the paper’s findings.

“People are taking it really as a tale of, ‘See, this is what happens when we have the legislation and we can actually made a difference and repair the ecosystem,'” Hooler said.

She said the data tells an optimistic story. Human industry caused the spike in metal pollution, and human legislation brought it back down.

“I think it just shows that we need to keep trying hard to keep good legislation in place,” she said.

Hooler grew up in Clifton Park and spent a lot of time camping at and swimming in Adirondack lakes. She always heard about the acid rain problem that plagued the lakes.

When she started studying hydrology for her master’s degree and was searching for someone to work with on her doctorate, her advisor, Aubrey Hillman, an assistant professor in Atmospheric and Environmental Sciences at UAlbany, had just started researching the history of acid rain in the Adirondacks.

As Hooler read through the literature, she noticed a large gap in the research.

In the 1980s there was a lot of research on human impacts on Adirondack water bodies, which gave researchers a large dataset. In the decades since, studies have continued, but in fewer and fewer numbers. This study was the first on this topic in a decade.

“It’s been a common belief that the impact of industry in the 1900s has disappeared,” Hooler said, “but there was a clear gap in documented research on metal recovery, so I started investigating it.

“What surprised us the most was just how slow the recovery was,” she said.

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A muddy window to the past

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Getting the samples was the most challenging part, Hooler said. They took several trips up here to get everything they needed.

Adirondack lake bed soils have high water content and are not very solid, so they did not get a lot of sample in the cores. While bodies of water sometimes have beds with clearly defined layers, she said Adirondack lake beds are really boring.

“It just looks like mud,” Hooler said.

She said they studied other lakes here, too, but didn’t get enough sediment to include. Hooler said there might be more research on these bodies of water later.

On each trip, they brought a large amount of equipment and people on the lakes and camped for several days as they worked in the hot sun. The collecting is tedious work, as it needs to be done with precise math and precise movements. The corers drop tubes into the lake bed, seal the tubes with suction and cap the samples, capturing thousands of years of sediment deposits.

Back in Albany, Hooler felt like an investigator, going through historic documents for evidence of what could cause the variations in metal disposition in the different lakes.

And she gained an appreciation for good maps.

“When I see a good map, I’m like, ‘Wow. This is really nice,'” Hooler said.

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Finding clues

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The paper reports that all the studied ponds have reached above 90% recovery to baseline metal contamination levels, which happened in just the last five years. This is the best possible outcome, Hooler said, calling it an “unprecedented milestone for the region’s environmental recovery.”

“Given the realities of continuous low-level emissions throughout the U.S. from human activities, we consider the ponds to have reached their fullest possible recovery currently,” according to the paper.

While some metals have fully returned to their pre-industrial baselines, others — like lead — probably never will. It’s still in the atmosphere, and as long as humans use airplane engines, they’ll produce lead as a byproduct.

Lead is also slower to recover, since it complexes strongly into soil, making its retention time much longer.

“This study exemplifies the resilience of lakes in the Northeast U.S. in rebounding toward natural conditions, yet it also warns of the lasting legacy of metal pollution embedded within the watershed,” according to the paper.

The different ponds first see higher levels of metals at different times. The paper hypothesizes that this is caused by “watershed disturbances” that accelerate the pollution of metal. Things like logging or major fires remove trees, increase erosion and makes it easier for metals in the watershed soil to wash into the water. This leads to higher concentrations of these metals in the lake beds during these periods of time, faster than rain or erosion alone would.

Black Pond had a massive fire in the late 1800s, causing a huge spoke in manganese and iron, which were already much higher in the pond than other tested ponds.

“At Rat (Pond), logging activity and the development of the railroad accelerated the deposition and movement of metals from soils into the water body, especially after vegetation removal and increased erosion,” according to the paper.

Clear Pond previously had the highest published concentrations of metal enrichment in the Adirondacks.

“Like Clear, both Rat and Black have been subject to multiple overlapping synergistic factors, making them highly susceptible to metal deposition,” according to the paper.

Challis Pond saw metal enrichment the earliest, which Hooler said they believe is connected to its proximity to several historical mining sites.

The construction of a railroad within a few feet of the north side of Rat Pond in 1892 and extensive logging activities around the water for decades disturbed the watershed.

In Black Pond, manganese and iron are still a little higher than they were in the 1600s — when those metals were already seen at elevated levels — because of a shorter spike after 2000, but the latest sample shows them decreasing again.

The last study of metal deposits in Adirondack lakebeds in 2004 showed recovery in Clear Pond at 77% recovery in arsenic, an 85% recovery in cadmium and a 52% recovery in lead. The paper posits that a full recovery had been hampered by ongoing pollution from the Sudbury region in the Canadian province of Ontario.

Hooler has more research on Adirondacks coming before she graduates in December.

This research was supported by the National Science Foundation with grants from the Geological Society of America Graduate Student Geoscience Research and the UAlbany Graduate Student Association.

To read a publicly accessible summary of the paper, go to tinyurl.com/musz9t54. For a full version, email skylarhooler@gmail.com or purchase it directly.