Bio-ecological effects of 4-nonylphenol on the soil-plant system

Aims: Nonylphenols are emerging pollutants with known adverse effects on aquatic ecosystems, especially on animals, where they act as endocrine disruptors and cancer promoters. Less known are the effects on terrestrial ecosystems, with contradictory reports about soil microorganisms and plants, largely dependent upon the tested doses and model organisms. In this framework, the present research aims at evaluating the effects of 4-nonylphenol on the soil-plant system, under realistic exposure conditions, focusing on targets at different levels of complexity, from biological to ecological responses. Methods: The acute to chronic effects of different 4-nonylphenol soil contaminations were evaluated, in microcosms, on biochemical, physiological and morphological traits of Lactuca sativa leaves, as well as on soil microbial activity. Results: A variable susceptibility of leaf traits to 4-nonylphenol was observed, with mostly acute responses over few days from exposure, and the induction of compensatory mechanisms, including the increase in chlorophyll concentrations in the healthy parts of the leaves. Microbial communities, instead, show a high resistance toward 4-nonylphenol, attributable to the high organic matter content of the employed soil, which may modulate the pollutant bioavailability. Conclusions: Findings shed light on the complex interactions of 4-nonylphenol with the soil-plant system, where its toxicity can be substantially dependent upon the characteristics of the receiving system. From a practical point of view, the maintenance of high soil organic matter contents appears to be crucial in buffering ecosystems from 4-nonylphenol contamination and in preserving their functionality.