Nickel in Alpine Rivers Increasing Due to Cryosphere Degradation
Climate change not only reduces water reserves stored in glaciers and permafrost but may also contribute to the release of increasing amounts of solutes into high mountain rivers. Among these solutes, particular attention must be paid to heavy metals, such as nickel, which are abundant in certain rock types and are potentially toxic to aquatic organisms and human health.
A new study, the result of a collaboration between Eco Research, the Free University of Bozen-Bolzano, the Edmund Mach Foundation, and the Provincial Agency for the Environment and Climate Protection of Bolzano, analysed the spatial and temporal distribution of nickel concentrations in water samples collected between 2005 and 2023 at over 50 sites across the Adige River basin in the Province of Bolzano. Additional samples were collected seasonally between 2022 and 2023 along the Senales River, from its source to its confluence with the Adige.
The results reveal a concerning trend: in certain areas, concentrations of dissolved and bioavailable nickel have quadrupled over the last decade, frequently exceeding the environmental quality standards set by the European Union.
These findings provide important evidence of the environmental risks associated with climate change and have serious implications for water quality in Alpine rivers and other mountainous regions with similar geological and cryospheric conditions.
A B S T R A C T
Climate change and cryosphere degradation may enhance the concentrations of heavy metals in high-mountain rivers. However, the downstream export of these contaminants to lower elevations is still overlooked. In this study, we investigated the spatial and temporal patterns of dissolved and bioavailable nickel concentrations in the upper Etsch/Adige river basin (1590 km2; 54 sites) during the period of 2005–2023. Furthermore, we investigated the same concentrations seasonally (2022–2023) along a tributary (Schnals/Senales River), from the glacier origin down to the confluence with the Etsch River (13 sites). Concentrations of both nickel forms increased during the past decade by up to 4 times, yet only in river reaches draining the acidic metamorphic Ötztal Unit. Sulfide oxidation, more intense at sites featuring larger glaciers, rock glaciers, and permafrost extent in their catchment, enhanced nickel concentrations. Along the Schnals River, values were elevated in the proglacial waters (dissolved fraction up to 112 μg L–1), gradually decreased moving to lower elevations, and dropped (from 20 to 30 to 2–5 μg L–1) downstream of a large reservoir. Currently, bioavailable nickel concentrations exceed the EU environmental quality standards at 40% of the investigated sites, demonstrating sharp environmental implications that may be extended to other similar geological and cryospheric settings.