The occupation policy in the north of the state of Mato Grosso and in the state of Pará, through activities such as gold mining, pasture and subsequent agricultural activities, caused a landscape change and habitat contamination. Pesticides, for example, are on the environment as a result of their use in agriculture and mercury (Hg) is mobilized into the environment through mining, deforestation and biomass burning activities. These contaminants are highly persistent and biomagnifies at each trophic level. Chelonian, because they are long lived organisms can accumulate toxic substances for long periods, are important contamination monitors. Podocnemis unifilis, a chelonian species with wide distribution in the Amazon basin, represent an important resource for riparian and indigenous populations, with wide distribution in the Xingu River basin. This study investigated the landscape changes, contamination of pesticides and Hg in P. unifilis in the Xingu River basin. We selected locations with rivers sources or tributaries in the Xingu River basin, in the states of Mato Grosso and Pará, describing the planted area and the use of pesticides in cotton, sugarcane, corn and soybean crops, as well as deforestation and biomass burned in the historical series from the years 2005 to 2014. Between September and December 2014 fifty specimens of P. unifilis were captured for liver, muscle and adipose tissue. Were evaluated 14 active ingredients of organochlorine pesticides by gas chromatography/electron capture detector (GC/ECD), and total Hg (THg) in the tissues of P. unifilis by cold-vapor atomic absorption (CVAA) spectroscopy. It has been shown that agricultural production as well as the use of pesticides in the Xingu river basin in the state of Mato Grosso are increasing every year, and the most commonly used pesticide was Glyphosate in 2014 (8,055,248 liters). Analyzing the states separately, Glyphosate, Metamidofos, Atrazine, 2,4 D and Endosulfan were the pesticides most used in the state of Mato Grosso and, in Pará state, were Atrazine, Glyphosate, Endosulfan, Chlorpyrifos and Tebuconazole respectively. The states of Mato Grosso and Pará had a significant increase in deforestation and biomass burning between the years researched (2005-2014), especially the city of São Félix do Xingu with 17,686.20 km² deforested only in 2014 and Feliz Natal with a 272% increase in the biomass burning in the last year researched (2014). Eight pesticides were found in the tissues of P. unifilis, including isomers and metabolites (values as mean ± standard deviation): Lindane = 1.39±8.46 ng/g-1; p,p’-DDT = 20.32±24.54 ng/g-1; p,p’-DDD = 4.00±6.96 ng/g-1; p,p’-DDE = 0.95±1.15 ng/g-1; o,p’-DDT = 0.90±3.97 ng/g-1; α-Endosulfan = 3.45±17.73 ng/g-1; β-Endosulfan = 3.81±8.01 ng/g-1; and Endosulfan sulfate = 7.12±12.05 ng/g-1. THg was detected in all specimens (liver: 134.20 μg/g-1, muscle: 24.86 μg/g-1). The type of tissue influenced the concentration of pesticides and THg, and the contamination variations of P. unifilis by pesticides and THg in the tissues were not explained by the interaction between sex and the straight-line carapace length. Comparing the results with current national and international legislation for protein resources, it was verified that the specimens of P. unifilis presented concentrations of pesticides greater than the maximum residue limit for Lindane, ΣDDT and ΣEndosulfan and Hg concentration 100 times greater than the acceptable maximum. It was concluded that the crops are "agrochemical-dependent" and that specimens of P. unifilis are contaminated with organochlorine pesticides and Hg. Riparian and indigenous population of the Xingu River basin that consumes these chelonians may be gradually contaminated, with future consequences for health.
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