Mercury pollution may have reshaped ancient Maya waters
Ancient Maya communities used liquid mercury and cinnabar, a red pigment containing mercury, in buildings, pottery and burial sites. A new study suggests that this use may have carried a much wider environmental cost than contamination at individual archaeological locations.
Researchers examining sediments from two water bodies on the northern Yucatán Peninsula found evidence of long-lasting mercury pollution and ecological disruption. The work, reported in Science Advances, focuses on Lago Cobá and Cenote Xcach, places within the former Maya Lowlands. Its findings point to periods when mercury concentrations rose to levels considered severely harmful to aquatic life under modern sediment-safety guidance.
The study does not present ancient Maya pollution as a modern-style industrial event. Instead, it traces how repeated use of a toxic material in settlements and ceremonial contexts may have entered surrounding landscapes and persisted in aquatic environments for centuries.
Reading pollution in layers of sediment
The research team, led by Matthew Neal Waters of Auburn University, extracted sediment cores from both sites. Those cores preserve a layered record: newer material sits above older deposits, allowing researchers to reconstruct changes through time.
To establish when layers were deposited, the team used radiocarbon dating on charcoal and wood fragments. Some of the sediments were more than 2,000 years old. The researchers then measured mercury concentrations across different layers, creating a timeline of contamination rather than relying on a single modern sample.
That timing was paired with a comparison to modern sediment safety guidelines. The comparison cannot directly recreate every condition experienced by ancient organisms, but it gives a benchmark for judging whether the measured concentrations reached levels associated with harm to aquatic life.
The team also searched the cores for signs of ecological response. These included traces of algae and bacteria as well as remains of small aquatic animals preserved in the sediment. Taken together, the chemical and biological evidence allowed the researchers to compare peaks in mercury with major changes in lake and cenote ecosystems.
Two sites, two contamination histories
At Lago Cobá, mercury concentrations began increasing around A.D. 40. They peaked around A.D. 250 to 300 and returned to background levels around A.D. 520. The record indicates a substantial but time-bounded period of elevated contamination.
Cenote Xcach showed a more severe and more prolonged pattern. There, mercury levels reached concentrations considered severely harmful to aquatic life for several centuries, with a peak around A.D. 720. That longer duration is important because ecological damage is not determined only by the highest measured concentration. The length of exposure can also shape whether an ecosystem recovers, shifts into a new state or loses parts of its food web.
The periods of high contamination coincided with dramatic ecological changes identified in the sediment record. The study therefore raises the possibility that mercury was one factor in the collapse of two lake ecosystems. It does not reduce the histories of those environments or ancient communities to one cause, but it shows that a culturally valuable material could have had consequences far beyond its intended use.
Why the finding matters now
Mercury is persistent, toxic and capable of moving through ecosystems. The study adds a deep historical example to a problem usually discussed in contemporary terms, such as mining, industrial emissions and contaminated waterways. It also complicates the assumption that serious chemical pollution is exclusively a modern phenomenon.
For archaeologists and environmental scientists, the work highlights the value of looking beyond monumental sites and artifacts. Reservoirs, lakes and cenotes can retain evidence of how human choices affected local environments over long periods. Such records can reveal impacts that are not visible in architecture alone.
The findings also give new context to the extensive use of cinnabar and liquid mercury in Maya society. Their vivid color and symbolic importance may be evident in surviving objects and structures, but the sediment data point to an environmental legacy that may have extended through soils, water and aquatic life.
What the study establishes
- Mercury concentrations increased at both Lago Cobá and Cenote Xcach during periods of ancient Maya occupation.
- Lago Cobá contamination rose around A.D. 40, peaked around A.D. 250 to 300, and later returned to background levels.
- Cenote Xcach experienced more severe contamination for several centuries, peaking around A.D. 720.
- The researchers compared mercury levels with modern sediment safety guidance and examined biological evidence preserved in sediment cores.
- The results link high contamination periods with dramatic ecosystem changes, suggesting a substantial environmental cost from historical mercury use.
The central lesson is not that ancient societies anticipated modern pollution categories, but that human materials and rituals can leave ecological records lasting millennia. In the Yucatán sediments, mercury offers a chemical trace of that relationship—one that connects Maya cultural practices with the changing health of the waters around them.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
