Avaliação físico-química e ecotoxicológica de solos contaminados por resíduos sólidos urbanos no semiárido brasileiro

Abstract

The improper disposal of municipal solid waste (MSW) in open dumps is a source of environmental degradation, with the potential to alter the physical and chemical properties of the soil and generate ecotoxicological effects on terrestrial organisms. The objective of this study was to evaluate soil contamination at the active landfill in the municipality of Crateús, Ceará, through the integration of physical-chemical analyses and ecotoxicological tests with seeds. Soil samples were collected at five points, three inside the landfill (P1, P2, and P3) and two outside (P4 and P5), 500 m and 2 km away, respectively. The samples were characterized in terms of pH, moisture, actual density, electrical conductivity, and particle size, following EMBRAPA methodologies. The ecotoxicological assessment was performed in accordance with ISO 11269-2, using seeds of Lactuca sativa and Allium cepa, maintained at 80% water retention capacity, a temperature of 23 ± 2 °C, and a 12-hour photoperiod. The pH values ranged from 7.7 to 8.9, characterizing alkaline soils, while moisture content was low (0.3 to 8.4%). Soil analysis in the landfill area revealed strong compaction, with actual density varying between 2.52 and 2.69 g·cm⁻³, and a predominance of the sand fraction, which decreases in the inner points. Ecotoxicological tests indicated that this contamination severely compromises plant development, especially Lactuca sativa, which showed a drastic reduction in germination (less than 50% at point P3) and a statistically significant delay in stem and leaf growth. A spatial gradient was observed: the closer to the disposal area (points P1, P2, and P3), the greater the phytotoxic effects, while distance from the contaminating source allows for attenuation of these impacts. In addition, the reduction in fresh and dry mass suggests that leachates and contaminants present in the soil cause physiological stress, interfering with water absorption and tissue production. It is concluded that the association between physicochemical parameters and biological responses evidenced the presence of phytotoxicity in landfill soils, demonstrating the effectiveness of the integrated approach for ecological risk assessment.