CONTAMINAÇÃO RIBEIRINHA POR METAIS (E METALOIDES) NA FRONTEIRA BRASIL - PARAGUAI: ANÁLISE DE BIOINDICADORES E AVALIAÇÃO DE RISCOS À SAÚDE

Abstract

Population growth has led to increasing contamination of water, soil, and vegetation. In this context, plants act as effective bioindicators due to their ability to accumulate high levels of trace elements. This study evaluated the Santa Virgem River basin, located along the Brazil–Paraguay border, by quantifying the elements As, Ba, Ca, Co, Cr, Cu, K, Mg, Mn, Ni, P, S, Se, Zn, and Pb in water, soil, and plant samples, including an angiosperm from the Apiaceae family, the liverwort Dumortiera sp., and mosses, using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Water samples showed low concentrations of toxic metals, frequently below the limit of detection (LOD for As, Ba, Co, Cr, Ni, Se, and Pb), whereas phosphorus ranged from 0.20 to 2.00 mg/L, exceeding by up to 20 times the limit established by CONAMA (0.10 mg/L). Iron concentrations ranged from 0.13 to 0.36 mg/L, with occasional exceedance of the 0.30 mg/L threshold defined by operational and sensory acceptability criteria for drinking water, without association with adverse effects on human health. In soils, iron was the predominant element, ranging from 13,256 to 33,658 mg/kg, followed by macronutrients such as K, Ca, and Mg. Phosphorus concentrations were higher near the river, reaching up to 98 mg/kg, and arsenic reached 7.22 mg/kg in marginal areas. Nevertheless, the Pollution Load Index, consistently below 1, indicated the absence of significant metal pollution. Plant species exhibited distinct bioaccumulation patterns. The Apiaceae angiosperm showed moderate concentrations, with iron ranging from 1,369 to 4,529 mg/kg and manganese from 59 to 214 mg/kg, reflecting the typical behavior of vascular plants. The liverwort Dumortiera sp. exhibited substantially higher levels, with iron ranging from 16,235 to 30,054 mg/kg, manganese from 781 to 3,832 mg/kg, potassium from 2,144 to 13,010 mg/kg, phosphorus from 4,774 to 7,484 mg/kg, as well as elevated concentrations of chromium (24.6–43.5 mg/kg) and lead (8.2–15.7 mg/kg). Mosses also showed strong retention capacity, accumulating iron between 17,575 and 24,678 mg/kg, manganese between 1,090 and 1,790 mg/kg, and phosphorus close to 9,600 mg/kg, highlighting their sensitivity to environmental variations. The Biological Accumulation Coefficient confirmed that bryophytes, represented by Dumortiera sp. and mosses, accumulated elements such as iron, manganese, chromium, nickel, and lead at levels far exceeding those observed in the Apiaceae, reinforcing their role as efficient environmental bioindicators. Human health risk assessment, considering scenarios of water ingestion, accidental soil ingestion, and dust inhalation, revealed Hazard Quotients (HQ) below 1 for all potentially toxic metals, indicating negligible non-carcinogenic risk. Phosphorus represents a warning regarding agricultural inputs rather than a direct toxicological risk. Overall, the results indicate low metal contamination in the Santa Virgem River, a marked agricultural influence on nutrient levels particularly phosphorus and confirm the high efficiency of bryophytes as environmental bioindicators. These findings highlight the importance of continuous monitoring in riparian ecosystems subject to anthropogenic pressure, especially regarding nutrient inputs in agricultural areas.