Advanced chemical and optical sensors to reduce diffuse pollution in urban waters

Diffuse pollution represents a critical challenge for the sustainable management of aquatic environments, with a clear need for novel methods that improve analytical capacity of local, regional and international stakeholders. Typically arising from nonpoint sources across a wide geographical area, diffuse pollution is complex environmental issue to address and necessitates an integrated approach that includes improved monitoring capacity and participative community engagement. Urbanization aggravates diffuse pollution through land-use change, increased runoff events and the introduction of persistent organic and inorganic pollutants to the aquatic environment, with negative effect on water quality and consequent risks to human health. With the objective to support Agenda 2030 and develop new tools for indicator 6.3.2 and the EU’s Water Framework Directive, I explored different approaches to evaluate water quality. The first section of the thesis reports the application of optical methods to assess organic matter dynamics in surface waters (fluorescent and chromophoric organic matter fractions) and nutrients (phosphates and nitrates) concentrations. Fluorescent results were analysed using PARAFAC modelling to explore changes in organic matter content and coupled with UV-Vis spectrophotometry to investigate inorganic compounds concentrations and microbial activities across river path, exploring longitudinal dynamics of river as it moved closer to developed areas. The second section of the thesis focuses on combining spectroscopic and chromatographic methods to identify the release of six endocrine disruptor compounds (phthalic acid esters) from biodegradable plastic bags in aquatic environment. Degradation experiments were conducted in two different settings: direct solar radiation exposure and shielded conditions. 1H-NMR analysis confirmed the release of phthalates, with higher concentrations observed in the samples exposed to sunlight. The leaching rate ranged from 264–342 microgram/g plastic under light exposure to 20–167 microgram/g in dark conditions. These results indicate that the accumulation of compostable plastic wastes lead to the release of phthalic acid esters, which are further transported across aquatic environments (by tributaries and emissaries to lake, marine and oceanic waterbodies) with potential implications for ecosystem health and human exposure to these emerging contaminants. The third section of the thesis describes the development of a low-cost optical sensor for water monitoring. The sensor was an open-source prototype, offering an affordable and accessible solution for the analysis of optically active species in the visible region of the electromagnetic spectrum. In particular, the end use focused on combined application with visual colorimetric test kits employed in various citizen science campaigns promoted by FreshWater Watch. To achieve this goal, following an initial phase of setup optimization, the prototype's analytical performances in terms of reliability and sensitivity were evaluated with inter and intra-day trials. All the recorded calibration curves exhibited similar correlation coefficients, with a relative standard deviation (RSD) of 7.60%. To assess sensor consistency, ten replicate measurements of a standard solution were recorded, resulting in an RSD equal to 2.73%. Collectively, all these tests confirmed the reliability and effectiveness of this novel new sensor.