TY - JOUR
T1 - On the representability of soil water samples in space and time
T2 - Impact of heterogeneous solute transport pathways underneath a sandy field
AU - Møller, Ingelise
AU - Karan, Sachin
AU - Gravesen, Peter
AU - Rosenbom, Annette Elisabeth
N1 - Publisher Copyright:
© 2022
PY - 2023/1/15
Y1 - 2023/1/15
N2 - In Europe, millions of water samples have been collected from sampling points, especially in the saturated zone to assess the water quality among others to fulfil EU water quality directives. Often water samples are collected from sampling points installed in the subsurface without knowing what the water collected represents in space and time. As such, without detailed knowledge of hydrogeological settings and fluctuations in groundwater levels, it is not possible to assess whether water collected represents a hydraulic active sediment setting or an adjacent isolated sediment body. Collecting water from the latter will hence not reveal by analysis potential contamination in the hydraulic active setting. Based on a detailed three-dimensional sedimentary facies model interpreted from geological and geophysical data combined with groundwater level measurements, this study focuses on delineating the impact of changing solute transport pathways underneath a sandy field (2 ha) exposed to bromide and pesticide applications. Hence, the analyses utilize detections in water samples of bromide, pesticides, and/or their degradation products collected through 19 years at 25 sampling points. A special focus is on the relatively high concentration, long-termed leaching of four degradation products (1,2,4-triazole, CGA108906, PPU, and desethyl-terbuthylazine) through the field. The results show that even for sand, knowledge of the hydrogeological setting and in-situ fate knowledge is imperative to assess the representability of water being sampled from both the variably-saturated and saturated zone of the soil-sediment system. Especially, the sub-horizontal layered sediments with numerous facies shifts facilitate horizontal solute transport, and fluctuations in the groundwater table seem to be decisive for, which solute transport pathways are dominating. Such detailed insights are crucial for accurately assessing sources of contaminants, leaching risk of contaminants through the variably-saturated zone, and improving monitoring procedures in the protection of the water resources and hereby the water quality of the future.
AB - In Europe, millions of water samples have been collected from sampling points, especially in the saturated zone to assess the water quality among others to fulfil EU water quality directives. Often water samples are collected from sampling points installed in the subsurface without knowing what the water collected represents in space and time. As such, without detailed knowledge of hydrogeological settings and fluctuations in groundwater levels, it is not possible to assess whether water collected represents a hydraulic active sediment setting or an adjacent isolated sediment body. Collecting water from the latter will hence not reveal by analysis potential contamination in the hydraulic active setting. Based on a detailed three-dimensional sedimentary facies model interpreted from geological and geophysical data combined with groundwater level measurements, this study focuses on delineating the impact of changing solute transport pathways underneath a sandy field (2 ha) exposed to bromide and pesticide applications. Hence, the analyses utilize detections in water samples of bromide, pesticides, and/or their degradation products collected through 19 years at 25 sampling points. A special focus is on the relatively high concentration, long-termed leaching of four degradation products (1,2,4-triazole, CGA108906, PPU, and desethyl-terbuthylazine) through the field. The results show that even for sand, knowledge of the hydrogeological setting and in-situ fate knowledge is imperative to assess the representability of water being sampled from both the variably-saturated and saturated zone of the soil-sediment system. Especially, the sub-horizontal layered sediments with numerous facies shifts facilitate horizontal solute transport, and fluctuations in the groundwater table seem to be decisive for, which solute transport pathways are dominating. Such detailed insights are crucial for accurately assessing sources of contaminants, leaching risk of contaminants through the variably-saturated zone, and improving monitoring procedures in the protection of the water resources and hereby the water quality of the future.
KW - Bromide detections
KW - Geophysical interpretation
KW - High-resolution geological model
KW - Pesticide-related detections
KW - Representative sampling
KW - Transport pathways
UR - http://www.scopus.com/inward/record.url?scp=85139364811&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2022.159039
DO - 10.1016/j.scitotenv.2022.159039
M3 - Article
C2 - 36174691
AN - SCOPUS:85139364811
SN - 0048-9697
VL - 856
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 159039
ER -