Oral Presentation NCGRT/IAH Australasian Groundwater Conference 2019

Using environmental isotopes to constrain pollutant migration pathways in an intensive agricultural area – Pampas, Argentinia (480)

Agustin Cabrera 1 , Matthew Currell 1 , Dioni Cendon 2 , Ian Cartwright 3 , Xiangyu Ma 1 , Monica T. Blarasin 4 , Adriana E. Cabrera 4 , Edel Matteoda 4 , Daniela Giacobone 4 , Veronica Lutri 4
  1. RMIT University, Melbourne, VIC, Australia
  2. Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
  3. School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC, Australia
  4. Universidad Nacional de Rio Cuarto, Rio Cuarto, Argentina

This study is examining pollutant migration in groundwater in an area of intensive agriculture - the Argentinian Pampas (Cordoba Province). Groundwater is of critical importance to the region’s communities and is facing multiple water quality threats. These include release and migration of geogenic arsenic as well as input of nutrients, herbicides and pesticides from expanding agribusiness. A multi-isotopic tracer approach is being used to better constrain groundwater flow, mixing and ground-surface water interaction in the system, with a view to assisting long-term protection of groundwater quality.

Samples for stable and radiogenic isotopes (δ2H, δ18O, 3H, 14C and 36Cl) have been collected from groundwater wells and surface water bodies used for irrigation and domestic supplies, in the Tortugas sub-basin in the central Argentinian Pampas. The samples have been analysed for a suite of agri-chemicals, including commonly applied herbicides and insecticides (Glyphosate, Atrazine, AMPA and others).

Preliminary results show significant inputs of agricultural chemicals into shallow groundwater and surface water. Additionally, certain herbicides and pesticides (e.g., 2,4-D and AMPA) were detected in some deep supply wells (>100 m) which are thought to be confined and thus isolated from input of pollutants at the surface. These data indicate that the confined aquifer may be affected by leakage and/or bypass flow via rapid pathways. Tritium, radiocarbon and other environmental isotope data will be used to refine these interpretations and improve understanding of the extent of inter-aquifer connectivity.

The preliminary results indicate that deep, confined aquifers in the region may be subject a greater degree of water quality threat than previously assumed. The study highlights the value of combining environmental isotopic data with sampling for contaminants during assessment of vulnerability to water quality threats in water supply aquifers