Occurrence of current use pesticides in bumblebees and environmental matrices under different land uses scenarios in the Southeast Pampas, Argentina

Abstract

Bees (Apidae) are crucial in global biodiversity, ecosystems stability and crops production. In the last years, they have been threatened by several factors, such as agricultural intensification and excessive use of pesticides. In Argentina, the native bumblebee, Bombus pauloensis, is one of the most prevalent species of the genus, and could be useful for pollution biomonitoring. The aim of this study is to assess the impact of land use on the levels of Current Use Pesticides (CUPs) in workers and drones of B. pauloensis, flowers and soil from foraging sites near Mar del Plata City. Sampling sites included a conventional agriculture area (A1), an ornamental plants field next to an municipal waste landfill (A2), natural reserve with agroecological agriculture (A3) and urban area (A4), and were carried out during application (P1) and post-application (P2) periods of pesticides. 50 compounds were assessed by QUECHERS-LC-MS/MS. The highest pesticides levels were found in A1 for flowers and soils and general higher levels during P1 was seen in flowers. Ten compounds were detected in flowers, four in soil and one in bumblebees. The ?CUPs in flowers during P1 were found to be 10,70 (A1), 4,93 (A2), 1,55 (A3) and 3,07 ng/g (A4), while in P2 were 6,72 (A1),1,77 (A2), 4,83 (A3) and 127,57 ng/g (A4). Soils showed ?CUPs levels of 3,00 (A1) and 0,9 ng/g (A3) during P1 (no detections in A2 and A4), while in P2 were 34,50 (A1), 5,13 (A2), 1,67 (A3) and 1,47 ng/g (A4). Metolachlor, Azoxystrobin, Imidacloprid cooccurred in flowers and soil. In flowers, Chlorpyrifos predominated (100% of samples(s.)) with a maximum of 7,90 ng/g (A1-P1) and a minimum of 0.67 ng/g (A3-P2), followed by Azoxystrobin (50% of s.) with a maximum of 0,69 ng/g (A1-P1). Curiously, Atrazine and Flurochloridone were found in A3 during P1, and remarkably, Cypermethrin was identified in A4 (P2) at 123,77ng/g. In soil, Azoxystrobin prevailed (37.5% of s.) with a maximum of 1,67 ng/g (A3-P2). However, in bumblebees only Dimethoate was found in workers from A2 (P2), thus further research is necessary to re-evaluate pesticides impacts on this pollinator. The pesticide pattern seen in all matrices and periods highlights the impacts that conventional agriculture could have on bumblebee’s habitat, which represents a key pollinator for many plant species in the area. To our knowledge, this work represents the first analysis of CUPs bioaccumulation in wild bees and related environmental matrices in Argentina.