Microalgae, such as Parachlorella kessleri, have significant potential for environmental remediation, especially in removing heavy metals like zinc from water. This study investigates how P. kessleri, isolated from a polluted river in Argentina, can remediate zinc. Using atomic force microscopy (AFM), the research examined the interactions between Zn particles and cells grown with different nitrogen sources—nitrate or ammonium. The results showed that cells grown with nitrate produced extracellular polymeric substances (EPS), while those grown with ammonium did not. Raman spectroscopy revealed distinct metabolic responses based on the nitrogen source, with nitrate-grown cells showing altered profiles after zinc exposure. Zinc exposure also changed the surface roughness and nanomechanical properties of the cells, particularly in those producing EPS. AFM force spectroscopy experiments then confirmed strong Zn binding to EPS in nitrate-grown cells, while interactions were weaker in ammonium-grown cells that lacked EPS. Overall, our results elucidate the critical role of EPS in Zn removal by P. kessleri cells and show that Zn remediation is mediated by EPS adsorption. This study underscores the significance of regulating nitrogen sources to stimulate EPS production, offering insights that are essential for subsequent bioremediation applications.

The widespread and extensive use of pesticides in European crop production to reduce losses from weeds, diseases, and insects may have serious consequences on the ecosystem and human health. This study aimed to identify 20 active substances of high health risk, based on their detection frequency within and across the environmental matrices (soil, crop, water, and sediment) and to identify their associated hazardous effects. A sampling campaign was conducted across 10 case study sites in Europe and 1 in Argentina and included conventional and organic farming systems. In 31% of cases, the detected substances were found at a higher concentration in the soil than in the corresponding crops, 93% of the compounds were fungicides, and the remainder were insecticides. 43% of the substances, 57% of which were insecticides, were detected only in soil. There was a clear relationship between soils and crops in terms of contamination, but not between water and sediment. Portuguese soil (wine grapes) had the highest number of substances (12) with average concentrations (AC) varying between 1 and 162 μg/kg, followed by French (11 substances in wine grapes) (1≤AC≤64 μg/kg) and Spanish soils (9 substances in vegetables) (3≤AC≤59 μg/kg). The crops corresponding to these soils contained a relatively high number of detected substances and several in high average concentrations (AC). The risk quotient was consistently higher for conventional farms than for organic farms. For the soils from conventional farms, 5 active substances (chlorpyrifos, glyphosate, boscalid, difenoconazole, lambda-cyhalothrin, and one metabolite: AMPA) were considered high risk. For water samples, 2 substances (dieldrin and terbuthylazine) found were high risk, and for sediment, there were 3 substances (metalaxyl-M, spiroxamine, and lambda-cyhalothrin). There were 6 substances detected in crops that are suspected to cause human health effects. Uncontaminated soil is a prerequisite for the adoption of sustainable alternatives to pesticides. Efforts are needed to elucidate the unknown effects of mixtures, including biocides and banned compounds in addition to the substances used in agriculture.