An in situ filtration system for trace element determination in suspended particulate matter

Abstract

A system for in situ filtration of suspended particulate matter (SPM) has been developed specifically for trace element determination. Minimization of metal contamination sources was realized by careful choice of materials and designing a “closed–open–closed” electronic procedure for the soaking of the system. In order to prevent undesired pressure increase due to the filter clogging and to avoid modification of metal distribution in the different phases of SPM, a relief valve was used to keep the pumping pressure constant. The possibility to perform a sub-sampling of SPM was also taken into account to expand the analytical capabilities. Finally, the sampler was equipped with a multiparametric probe in order to carry out real-time measurements of physical parameters (temperature, salinity, fluorescence, turbidimetry) and operating conditions (flow rates, filtered volumes, energy consumption). The system has been tested and applied successfully in Antarctic coastal waters (Terra Nova Bay, Ross Sea) in the framework of the Italian Research Programme in Antarctica (PNRA). The analytical possibilities allowed by the large amount of SPM which can be collected by FIS500 (50–100 mg) include total metal concentration, solid speciation and morphological investigation by scanning electron microscopy.