From Environmental Biomonitoring to Soil Fertility: Assessment of PAHs, Pesticides, and PCBs in Algae and Their Valorization as Fertilizers

Abstract

Algae and aquatic macrophytes are increasingly recognized as valuable bioresources with applications in environmental monitoring and sustainable agriculture. The present study investigates algae collected from Romanian and Bulgarian coastal areas (Stuckenia pectinata, Cladophora glomerata, Ulva Rigida, Cystoseira barbata, Microcystis) as biomonitors of organic contaminants and for the preliminary assessment of their potential for agricultural biomass reuse. The levels of selected organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs), were determined using chromatographic analytical methods in order to evaluate the contamination status of the coastal environment and the accumulation capacity of algal biomass. PAHs ranged between 0.0001 and 1.4407 μg/g dry matter. Among the organochlorine pesticides (OCPs), the highest concentration was observed for HCB in Cladophora glomerata (3.3715 μg/g dry matter), whereas among the PCBs, the highest concentration was observed for PCB52 in Cystoseira barbata (3.1265 μg/g dry matter). The structural and chemical characteristics of Cystoseira barbata were further investigated using SEM, FT-IR, and LC-MS analyses to provide a detailed characterization of its biomass composition. The structural and chemical characteristics of Cystoseira barbata were further investigated using SEM, FT-IR, and LC-MS analyses, providing a detailed characterization of the biomass composition. This characterization represents a separate descriptive component of the study and was not used to explain the agronomic responses observed with other species. The potential of Stuckenia pectinata and Cladophora glomerata biomass as soil amendments was evaluated using Allium cepa as a model plant. Twenty-four experimental units (eight treatments × three independent pots) were established. The treatment with 4 g of Stuckenia pectinata (all plant parts) produced the highest mean plant height (33 cm), corresponding to a 15.0 cm (83.3%) increase relative to the control (18 cm). Mean heights for the remaining treatments ranged from 13 to 27.5 cm. The control showed the slowest germination, while mixtures containing ~1.6% algal biomass exhibited the highest germination rate. Results are reported as treatment means (n = 3 pots). Near-infrared spectra of Allium cepa leaves revealed distinct absorbance patterns among treatments. These preliminary findings indicate that selected aquatic biomass may influence plant growth under the tested experimental conditions. However, contaminant transfer to soil and plant tissues was not assessed, and the results should therefore be interpreted as a preliminary proof-of-concept for biomass reuse rather than as evidence supporting direct agricultural or fertilizer application. Further studies are required to assess contaminant mobility, bioavailability, plant uptake, long-term agronomic performance, and regulatory compliance before practical implementation.