Parâmetros físico-químicos, teores de agroquímicos, hormônios estrógenos e metais no Rio Santo Antônio (Brasil-Argentina): ecotoxicidade e efeito na qualidade da água do Parque Nacional do Iguaçu

Abstract

The Santo Antônio River is a surface watercourse that naturally also serves as a boundary between part of the territories of Brazil and Argentina. It is one of the tributaries of the left bank of the Lower Iguaçu River, a region that houses the Iguaçu National Park, a Conservation Unit of Integral Protection renowned for its rich biodiversity. The objective of this study was to evaluate the impact of the Santo Antônio River (Brazil-Argentina) on the quality of the Iguaçu River from a physico-chemical and ecotoxicological point of view. Water and sediment samples were collected at ten points: eight along the Santo Antônio River (P1 to P8), from the source to the mouth, and two others in the Iguaçu River, one upstream (P9) and another downstream (P10) of the mouth of the Santo Antônio River. The land use data show intensive agriculture on the Brazilian side and higher frequency of forest cover in the Argentine part. In the physicochemical analysis, points P6, P7, P8 and P10 showed turbidity above the limit, while all points had biochemical demand of oxygen higher than allowed by current legislation. The concentration of estriol (E3) hormone, present at all points, varied from 10.50 μg.L-1 to 30.54 μg.L-1. The 17β-estradiol (E2) was detected only in P2. The herbicide 2,4-D was detected in quantities above the permitted at points P3, P6, P7, P8 and P9. High concentrations of aluminum and iron were detected in P8 and, excess to the limit of manganese legislation in P8 and P10. In the sediments, high concentrations of aluminum, iron, titanium, vanadium and manganese were confirmed at points P8 and P10. In addition, chromium, nickel and copper exceeded the limits legislated in several points. The toxicity results for Artemia salina showed high mortality rates at P1, P3, P4, P5, P8 and P10. However, no sample was toxic to Eisenia fetida, with leakage rates below 30%. In the test with Lithobates catesbeianus, the points P4, P6 and P7 revealed cytotoxicity and mutagenicity, whereas the points P5, P8, P9 and P10 showed only cytotoxicity. The results for the bioindicator Allium cepa indicated that the points P2, P3, P4, P5, P9 and P10 presented both cytotoxicity and mutagenicity, in addition, point P6 was identified as cytotoxic, while points P7 and P8 showed mutagenicity. Lactuca sativa did not undergo significant changes in germination. Finally, for human liver cells HuH7.5 was observed cell proliferation in P1, P2 and P8, while P9 and P10 presented cytotoxicity. The results obtained with different bioindicators indicated correlations with several physicochemical parameters and elements analyzed, as evidenced by the analysis of main components (PCA). The results show that the Santo Antônio River contributed to decrease the quality of the waters of the Iguaçu River, especially in terms of turbidity, COD, BOD, E3, of the elementary parameters and ecotoxicity for A. salina. Points P8 and P10 stood out as the most critical, presenting high concentrations of heavy metals, pesticides and hormones, besides significant toxicity in bioindicators. These results highlight the need for conservation and environmental management actions, especially in the Rio Santo Antônio basin, to reduce the impacts of water pollution from this river and the effects on the Iguaçu National Park.