Pesticides and nutrients in the Tindall aquifer Mataranka region
Details:
Title
Pesticides and nutrients in the Tindall aquifer Mataranka region,
Creator
Schult, Julia,
Northern Territory, Department of Environment and Natural Resources,
Collection
E-Publications,
E-Books,
PublicationNT,
02/2019,
Date
2019-02,
Location
Mataranka region,
Tindall,
Description
This study is the fourth in a series of baseline groundwater quality surveys in water allocation planning areas of the Top End of the Northern Territory.
The study investigated whether pesticides were present in the Mataranka region of the Tindall aquifer, and if nutrient concentrations in the aquifer were elevated.
18 bores in the Mataranka region were sampled for pesticides, nutrients and general parameters in July 2018. Six pesticides were detected during the survey with 30% of bores containing residues of at least one pesticide. With the exception of one pesticide in one sample, concentrations in all samples were several orders of magnitude below current environmental guideline values for 95% ecosystem protection.
Ammonia (NH3), nitrite (NO2) and filterable phosphorus (FRP) concentrations were very low (<0.001 mg/L) in all but one sample, while nitrate (NO3) concentrations spanned several orders of magnitude from 0.004 to 1.5 mg/L. Total filterable phosphorus (TFP) concentrations were at intermediate levels of 0.041-0.086 mg/L and total filterable nitrogen reflected the range of NO3 concentrations with concentrations of <0.010 to 1.5 mg/L.
Irrigated agricultural land use was associated with the highest levels of pesticide contamination and the highest NO3 concentrations. Elevated NO3 was also present in undeveloped non-agricultural areas in the southern part of the aquifer. There was no apparent cause to explain these high concentrations, although high NO3 in Central Australian groundwater has previously been attributed to microbial activity in termite mounds.
The total filterable phosphorus levels were relatively high compared to other regions. They occurred throughout the aquifer, indicating that they are unlikely to originate from a point source of pollution. In the absence of baseline phosphorus data prior to this study it was not possible to determine whether the observed TFP concentrations are natural.
The results of this study are similar to those in other Top End regions and do not pose a current risk to aquatic ecosystem health. Nevertheless, they act as a reminder that it is important to adhere to best practice in the storage and application of chemicals and that ongoing monitoring is required to ensure increasing impacts are detected early.,
Notes
Made available via the Publications (Legal Deposit) Act 2004 (NT).,
Table of contents
Abbreviations and Acronyms -- Summary -- 1 Introduction -- 1.1 Background and study aims -- 1.2 The Tindall Limestone Aquifer -- 1.3 Historical and current use of groundwater in the region -- 1.4 Risks to Groundwater Quality -- 1.5 Current Knowledge of Groundwater Quality -- 2 Methods -- 2.1 Site Selection -- 2.2 Water Quality Sampling -- 2.3 Historical data -- 3 Results -- 3.1 QA/QC -- 3.2 General water quality -- 3.3 Field measurements -- 3.4 Nutrients -- 3.4.1 Current nutrient levels -- 3.4.2 Effects of Land Use -- 3.4.3 Historical NO3 concentrations -- 3.5 Pesticides -- 4 Discussion -- 4.1 Nutrients -- 4.2 Pesticides -- 5 References -- Appendix A: List of analytes for pesticide/herbicide analysis -- Appendix B: Field and Nutrient Data -- Appendix C: Historical NO3 concentrations in bores of the Mataranka region -- Appendix D: Pesticide Data,