Particle concentrations and physical parameters in surface sediments and aggregates from the Portuguese continental margin

Critical erosion stress (u*cri) was determined by using an erosion chamber with controlled bottom stress to the surface sediments in the sediment-core. The u* was increased in small steps of 0.08 cms-1, until u*cri was attained for both agreggates and the undelying sediment.(Thomsen and Gust (2000) Sediment stability and characteristics of resuspended aggregates of the western European continental margin. Deep Sea Res 47/10: 1881-1897). When possible, the u* initiating bedload transport of aggregates was also recorded.The resuspended particles were collected in a polycarbonate bottle. A subsample was concentrated onto precombusted Whatman GF/F glass filters. The dry weight was subsequently determined. Based on the weight of the collected particles and the area of the core we estimated the resuspendable particle concentration. This measure was used with the measurements obtained with (3) to calculate the Total Particulate Carbon (TPC), Total Organic Carbon (TOC), and Particulate Organic Nitrogen (PON).Particles were concentrated onto precombusted Whatman GF/F glass filters and analyzed with a Euro-EA Elemental analyzer (Hekatech) standardized with acetanilide. We measured the percentages of carbon (%C), organic carbon (%OC) and organic nitrogen (%ON) (e.g. Ehrhardt and Koeve (1999) Determination of particulate organic carbon and nitrogen. In: Grassho!, K., Kremling, K., Ehrhardt, M. (Eds.), Methods of Seawater Analysis. Verlag Chemie, Weinheim, pp. 437-444.)PCB and PCN were concentrated onto precombusted Whatman GF/F glass filters and determined by AIMES GmbH using two-dimensional gas chromatography-isotope ratio mass spectrometry, after Horii et al (2005): Congener-specific carbon isotopic analysis of technical PCB and PCN mixtures using two-dimensional gas chromatography-isotope ratio mass spectrometry.Environ Sci Technol. 2005 Jun 1;39:4206-12.