title: Impact of intensive horticulture practices on groundwater content of nitrates, sodium, potassium, and pesticides.
abstract: A monitoring program of nitrate, nitrite, potassium, sodium, and pesticides was carried out in water samples from an intensive horticulture area in a vulnerable zone from north of Portugal. Eight collecting points were selected and water-analyzed in five sampling campaigns, during 1 year. Chemometric techniques, such as cluster analysis, principal component analysis (PCA), and discriminant analysis, were used in order to understand the impact of intensive horticulture practices on dug and drilled wells groundwater and to study variations in the hydrochemistry of groundwater. PCA performed on pesticide data matrix yielded seven significant PCs explaining 77.67% of the data variance. Although PCA rendered considerable data reduction, it could not clearly group and distinguish the sample types. However, a visible differentiation between the water samples was obtained. Cluster and discriminant analysis grouped the eight collecting points into three clusters of similar characteristics pertaining to water contamination, indicating that it is necessary to improve the use of water, fertilizers, and pesticides. Inorganic fertilizers such as potassium nitrate were suspected to be the most important factors for nitrate contamination since highly significant Pearson correlation (r = 0.691, P < 0.01) was obtained between groundwater nitrate and potassium contents. Water from dug wells is especially prone to contamination from the grower and their closer neighbor's practices. Water from drilled wells is also contaminated from distant practices.
authors.affiliation: REQUIMTE/Departamento de Ciências Químicas, Laboratório de Bromatologia e Hidrologia da Faculdade de Farmácia da Universidade do Porto, Porto, Portugal.
authors.forename: Armindo
authors.initials: A
authors.lastname: Melo
authors.forename: Edgar
authors.initials: E
authors.lastname: Pinto
authors.forename: Ana
authors.initials: A
authors.lastname: Aguiar
authors.forename: Catarina
authors.initials: C
authors.lastname: Mansilha
authors.forename: Olívia
authors.initials: O
authors.lastname: Pinho
authors.forename: Isabel M P L V O
authors.initials: IM
authors.lastname: Ferreira
mesh_terms: D000383:Agriculture / Q000379:methods*; D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis*; D010575:Pesticides / Q000032:analysis*; D011174:Portugal; D011188:Potassium / Q000032:analysis*; D012964:Sodium / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D009566:Nitrates; D010575:Pesticides; D014874:Water Pollutants, Chemical; D012964:Sodium; D011188:Potassium