Exploring phytoremediation potential for nitrocellulose-contaminated soil: a case study from Spilamberto (Modena)

The study investigates the effects of a specific soil pollutant on seed germination and plant growth, with the aim of exploring the potential of phytoremediation as a strategy to address and resolve an environmental issue. Phytoremediation utilizes the natural ability of plants to absorb, accumulate, degrade, or stabilize pollutants from soil, water, and air, and it is considered an environmentally sustainable and cost-effective technique for the remediation of contaminated sites. In this context, the study presents a case in which plants could play a key role in addressing a specific environmental problem located in the Municipality of Spilamberto (Modena). Here, historical explosive manufacturing activities have led to the contamination of a large area (approximately 50 hectares) with nitrocellulose (NC). As part of a broader strategy aimed at transforming waste into a resource (End of Waste), the project seeks to explore the accelerated biodegradation of NC in soil, promoting the release of nitrate ions and evaluating their potential use as fertilizing agents. To assess the feasibility of using plants as a strategy for managing NC-contaminated soil, the project initially aimed to investigate the effects of NC on seed germination and plant growth. The phytotoxicity of NC-contaminated soil was assessed through germination bioassays using Lepidium sativum L., while the effects on plant growth were evaluated with Lactuca sativa and Triticum aestivum, representing dicots and monocots. Three substrate concentrations were tested: 20% NC (w/w), obtained by mixing NC-contaminated soil (34% NC w/w) with standard substrate, and two additional treatments where NC had been partially degraded by Nitrosomonas sp., resulting in final concentrations of 12% (NB1) and 10% (NB2). Germination tests followed APAT guidelines, assessing seed germination (SG) and root elongation (RE), with results expressed as Germination Index (GI%). Growth tests were carried out in pots under controlled conditions. Soils containing untreated NC (20%) showed high GI values (>60%), indicating no phytotoxicity. In contrast, soils with bacterially treated NC (NB1 and NB2) showed significantly reduced GI values, particularly at higher concentrations. Interestingly, despite the reduced germination, substrates with bacterially digested NC had a positive effect on plant growth. Agronomic (biomass, allometric measures, LAI) and physiological (Dualex) analyses revealed a slight but significant (p < 0.05) increase in plant growth on NB1 substrates. These findings suggest that while bacterially treated NC may initially exhibit phytotoxic effects—possibly due to nitrate accumulation—its degradation products may later act as fertilizers, enhancing plant growth under certain conditions. This study highlights the complex interaction between NC degradation products and plant development, suggesting that, the transformation of NC-contaminated soil through microbial treatment may enhance plant growth, supporting the feasibility of phytoremediation as a strategy to manage a specific soil contamination issue.