Faculty of Technical Sciences

TY - JOUR

T1 - Development of a groundwater contamination index based on the agricultural hazard and aquifer vulnerability

T2 - Application to Portugal

AU - Serra, João

AU - Cameira, Maria do Rosário

AU - Cordovil, Cláudia M.d.S.

AU - Hutchings, Nicholas J.

N1 - Publisher Copyright: © 2021 Elsevier B.V.

PY - 2021/6

Y1 - 2021/6

N2 - Reducing nitrate leaching may not result in a significant improvement of groundwater quality. The amount of nitrate reaching groundwater depends not only on the hazard related to agricultural activities but also on-site specific groundwater vulnerability. Using national databases and other compiled datasets, the agricultural hazard was calculated as the ratio of (i) the nitrate leached estimated from the N surplus, and (ii) the water surplus, a proxy of the percolating water below the root zone. By combining the hazard with a multi-parameter groundwater vulnerability, a spatially explicit groundwater contamination risk, developed for mainland Portugal, was computed for 1999 and 2009. Results show an increase from 8,800 to 82,679 ha of the territory rated with a very high contamination risk. The priority areas were successfully screened by the Index, coinciding with the current Vulnerable Zones, although additional hotspots were detected in southern Portugal. Percolation, including both irrigation activity and precipitation, was found to be a key driver for the groundwater contamination risk due to its opposite effects in the hazard and in the vulnerability. Reducing nitrogen leaching may be insufficient to reduce the risk of nitrate contamination if there is a relatively larger reduction in precipitation. This index is particularly useful when applied to contrasting situations of vulnerability and hazard, which require distinct mitigation measures to mitigate groundwater contamination.

AB - Reducing nitrate leaching may not result in a significant improvement of groundwater quality. The amount of nitrate reaching groundwater depends not only on the hazard related to agricultural activities but also on-site specific groundwater vulnerability. Using national databases and other compiled datasets, the agricultural hazard was calculated as the ratio of (i) the nitrate leached estimated from the N surplus, and (ii) the water surplus, a proxy of the percolating water below the root zone. By combining the hazard with a multi-parameter groundwater vulnerability, a spatially explicit groundwater contamination risk, developed for mainland Portugal, was computed for 1999 and 2009. Results show an increase from 8,800 to 82,679 ha of the territory rated with a very high contamination risk. The priority areas were successfully screened by the Index, coinciding with the current Vulnerable Zones, although additional hotspots were detected in southern Portugal. Percolation, including both irrigation activity and precipitation, was found to be a key driver for the groundwater contamination risk due to its opposite effects in the hazard and in the vulnerability. Reducing nitrogen leaching may be insufficient to reduce the risk of nitrate contamination if there is a relatively larger reduction in precipitation. This index is particularly useful when applied to contrasting situations of vulnerability and hazard, which require distinct mitigation measures to mitigate groundwater contamination.

KW - Agricultural contamination

KW - Gross nitrogen balance

KW - Groundwater pollution

KW - Groundwater vulnerability

KW - Nitrate leaching

KW - Risk index

UR - http://www.scopus.com/inward/record.url?scp=85100629669&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2021.145032

DO - 10.1016/j.scitotenv.2021.145032

M3 - Journal article

C2 - 33581543

AN - SCOPUS:85100629669

VL - 772

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 145032

ER -