Copper and pesticide residues in mediterranean soils: a case study of four crops in Zadar County, Croatia

Abstract This study investigated copper accumulation and pesticide residue patterns in agricultural soils under four cropping systems (stone fruit, olive, grapevine and potato) in Zadar County, Croatia. Soil samples were taken before and after the growing season. Copper concentrations were determined by ICP-MS after microwave digestion. A total of 453 pesticide-active compounds were analyzed using available standards by LC–MS/MS and GC–MS/MS after a modified QuEChERS extraction. The highest copper concentration was found in stone fruit soils (34 mg kg −1 ) and the lowest in vineyards (25.9 mg kg −1 ). After the growing season, there was a significant increase in copper concentration in stone fruit ( p = 0.020) and vineyard soils ( p = 0.018), with individual values reaching 290 mg kg −1 . Alarmingly, 30% of the samples from olive groves exceeded the critical copper limit of 100 mg kg −1 . Copper levels increased after the season in up to 90% of the plots, indicating widespread accumulation. Pesticide residues varied by crop and season. The fungicide boscalid was prevalent in vineyard soils before the season, but decreased after, while fludioxonil, tebuconazole and fluopyram increased. Difenoconazole was present in all crop soils, most prevalent in potatoes. Insecticides such as omethoate, thiamethoxam and chlorpyrifos were found in all locations, with thiamethoxam increasing in potato soils despite its legal ban. Pendimethalin was the most widely used herbicide. These results show considerable crop- and season-specific contamination patterns and emphasize the need for sustainable pesticide use, soil monitoring, and targeted strategies to protect soil and ecological integrity in Mediterranean agroecosystems.