Pyrite oxidation enhances nutrient release into freshwater on the Barton Peninsula, Maritime Antarctica

Pyrite oxidation coupled with rock weathering occurs on the Barton Peninsula and is likely to be accelerated by progressive glacial melting, which exposes more bedrock to weathering. King George Island (KGI), with a surface area of 1250 km², is the largest of the South Shetland Islands (SSI) and is located about 120 km north of the Antarctic Peninsula. The study area, the Barton Peninsula, forms the southwestern part of KGI and is the second-largest ice-free area on the island, with an approximate surface area of 12 km². The Barton Peninsula is predominantly composed of volcanic and plutonic rocks; volcanic rocks make up most of the peninsula and the sampling area, with compositions ranging from basaltic andesite to andesite. In the northern part of the peninsula, strongly weathered paragneiss displays a distinct rusty coloration caused by pyrite oxidation and is enriched within many of the volcanic rocks (Balci and Gunes, 2024). A series of oxidation experiments using pyrite-bearing and non-pyrite-bearing rocks was conducted, and the results were integrated with water geochemistry as well as the mineralogical and elemental compositions of freshwater, sediments, and rocks to evaluate the influence of pyrite oxidation on surface waters of the peninsula. Acid-production potential analyses show that andesitic rocks exposed at the northern tip of the peninsula have the highest values, ranging from 51.25 to 78.1 kg H₂SO₄ per ton of rock. The pH of the experimental media remained acidic even after 240 days of andesite-water interaction. Consistently, the highest releases of Ca (average 1.2 ppm), Mg (1.34 ppm), Mn (0.056 ppm), K (0.074 ppm), and Fe (0.092 ppm) were observed from pyrite-bearing andesitic rocks, whereas the highest releases of P and N were associated with basaltic andesite. Oxidation of andesitic rocks also released elevated concentrations of Zn and Cu. In agreement with the experimental data, freshwaters with low pH (3.7–4.2), high sulfate (46–92 mg/L), and high Fe (0.8–16.5 mg/L) occur at the northern tip of the peninsula. In contrast to neutral waters, these acidic waters exhibit the highest concentrations of cations (e.g., K, Na, Si, and Ca) and anions (e.g., SO₄²⁻). This indicates that pyrite oxidation coupled with enhanced silicate weathering acts as a powerful natural fertilizer on the peninsula and is likely to increasingly regulate microbial and ecosystem productivity in the future as global warming drives progressive glacial melting.

Keywords: Maritime Antarctica, Pyrite, Nutrients, Oxidation,

References:

Balci and Gunes, 2024 Generation and geochemical characteristics of acid rock drainage (ARD) in Barton Peninsula, King George Island (KGI), maritime, Antarctica, Vol.954 Science of The Total Environment.