Using ¹⁸O/ ²H, ³H/ ³He, ⁸⁵Kr and CFCs to determine mean residence times and water origin in the Grazer and Leibnitzer Feld groundwater bodies (Austria)

Autor(en)

M. Kralik, Franz Humer, J. Fank, T. Harum, G. Klammler, D. Gooddy, J. Sueltenfuss, C. Gerber, R. Purtschert

Abstrakt

Two groundwater bodies, Grazer Feld and Leibnitzer Feld, with surface areas of 166 and 103km

² respectively are characterised for the first time by measuring the combination of δ

¹⁸O/δ

²H,

³H/

³He,

⁸⁵Kr, CFC-11, CFC-12 and hydrochemistry in 34 monitoring wells in 2009/2010. The timescales of groundwater recharge have been characterised by 131 δ

¹⁸O measurements of well and surface water sampled on a seasonal basis. Most monitoring wells show a seasonal variation or indicate variable contributions of the main river Mur (0-30%, max. 70%) and/or other rivers having their recharge areas in higher altitudes. Combined δ

¹⁸O/δ

²H-measurements indicate that 65-75% of groundwater recharge in the unusual wet year of 2009 was from precipitation in the summer based on values from the Graz meteorological station. Monitoring wells downstream of gravel pit lakes show a clear evaporation trend.A boron-nitrate differentiation plot shows more frequent boron-rich water in the more urbanised Grazer Feld and more frequent nitrate-rich water in the more agricultural used Leibnitzer Feld indicating that a some of the nitrate load in the Grazer Feld comes from urban sewer water. Several lumped parameter models based on tritium input data from Graz and monthly data from the river Mur (Spielfeld) since 1977 yield a Mean Residence Time (MRT) for the Mur-water itself between 3 and 4years in this area. Data from δ

¹⁸O,

³H/

³He measurements at the Wagna lysimeter station supports the conclusion that 90% of the groundwaters in the Grazer Feld and 73% in the Leibnitzer Feld have MRTs of <5years. Only in a few groundwaters were MRTs of 6-10 or 11-25years as a result of either a long-distance water inflow in the basins or due to longer flow path in somewhat deeper wells (>20m) with relative thicker unsaturated zones. The young MRT of groundwater from two monitoring wells in the Leibnitzer Feld was confirmed by

⁸⁵Kr-measurements. Most CFC-11 and CFC-12 concentrations in the groundwater exceed the equilibration concentrations of modern concentrations in water and are therefore unsuitable for dating purposes. An enrichment factor up to 100 compared to atmospheric equilibrium concentrations and the obvious correlation of CFC-12 with SO

₄, Na, Cl and B in the ground waters of the Grazer Feld suggest that waste water in contact with CFC-containing material above and below ground is the source for the contamination. The dominance of very young groundwater (<5years) indicates a recent origin of the contamination by nitrate and many other components observed in parts of the groundwater bodies. Rapid measures to reduce those sources are needed to mitigate against further deterioration of these waters.

Organisation(en)

Externe Organisation(en)

Umweltbundesamt, Joanneum Research Forschungsgesellschaft mbH, Natural Environment Research Council, Universität Bremen, Universität Bern

Journal

Applied Geochemistry

Band

50

Seiten

150-163

Anzahl der Seiten

14

ISSN

0883-2927

DOI

https://doi.org/10.1016/j.apgeochem.2014.04.001

Publikationsdatum

11-2014

Peer-reviewed

Ja

ÖFOS 2012

105304 Hydrologie, 104023 Umweltchemie, 104002 Analytische Chemie, 105906 Umweltgeowissenschaften

Schlagwörter

ASJC Scopus Sachgebiete

Pollution, Geochemistry and Petrology, Environmental Chemistry

Sustainable Development Goals

SDG 11 – Nachhaltige Städte und Gemeinden

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/fed59304-24c0-4a7a-b62d-c780d8bbb3ed