Behaviour and fate of urban particles in coastal waters: Settling rate, size distribution and metals contamination characterization

Abstract

The evaluation of contaminant net fluxes from the coast to the open sea requires the study of terrigeneous particles behaviour and fate. We studied the particles issued from two small coastal rivers whose waters are mixed with treated wastewater (TWW) coming from the Marseille wastewater treatment plant (WWTP) just before discharge to the Mediterranean Sea. An experimental device was developed and used to investigate particles settling rates, size distribution and metallic contamination when mixing with seawater. The particles were sampled in flood deposits of rivers and outlets during rainy periods and in the outlet water during dry periods. The flood deposits were mainly composed of 50-200 μm-sized particles, higher metals content being observed in the finest fractions. Dry period particles showed the stronger influence of wastewater inputs.

Evaluation of Discrete and Passive Sampling (Diffusive Gradients in Thin-films – DGT) Approach for the Assessment of Trace Metal Dynamics in Marine Waters – a Case Study in a Small Harbor

“…For example, while very high variability was measured for cadmium (Cd) for the first four deployment periods at sites SP1 and SP3, relatively low variability was found for the same period at site SP2. Such specific variability patterns clearly show the overall dynamics of trace metal concentrations at the study area, but also demonstrates that the discrete sampling methodology, most widely used in environmental monitoring programs and research studies, [2,3,37,38] is not ideal for (highly) dynamic aquatic systems. [39][40][41] Examining the entire 5-month period, specific trends of trace metal concentrations varied by metals and sites.…”

Spatial Distribution of Heavy Metals in the Surface Sediments of the Southern Coast of Pacitan, Indonesia

“…There is a linear correlation between heavy metal concentration and the fraction of particles, i.e., metals increased with decreasing grain size of sediments [1]. A study conducted in coastal waters of Marseille found higher concentrations of heavy metals in the finest fraction of sediments [5]. The accumulation of heavy metals in sediments also depends on hydrographic conditions such as temperature, salinity, pH and DO.…”

Characterisation of the dynamics of organic contaminants ( n -alkanes, PAHs and PCBs) in a coastal area

“…) of each fraction was governed by Stokes' law (Mantovanelli and Ridd, 2006), and the particle diameter (Ø; in m) for a given settling velocity was calculated according to Oursel et al (2014) for diameters varying from N276 to b 0.78 μm. Prior to the analysis, a small portion (10%) of the collected samples was filtered through 25-mm glass filters (Whatman GFF, 0.7 μm) for particulate organic carbon (POC) analysis.…”

“…A simple experimental device proposed by Oursel et al (2014) was setup using two identical vertical Plexiglas tubes (1 m length and 10 cm diameter), open on the top and equipped with a valve at the bottom to collect water samples. The tube was filled with 7 L of coastal seawater sampled 2 km offshore and at a 4-m depth and then acclimatised for 1 day to obtain a homogeneous temperature of the water column (close to 20°C).…”

“…Measuring 50 km in length and covering a watershed area of 523 km 2 , the Huveaune River continuously drains the highly industrialised and urbanised valleys of Marseille and through normal flow or run-off episode transport. The Jarret River has a 102-km 2 catchment area along its 21 km of watershed and passes through forests, semi-natural habitats and agricultural land area (Oursel et al, 2014). The sewage system of the city of Marseille collects sewage and moves it toward the wastewater treatment plant (WWTP), which receives on average 250,000 m 3 of water per day and has a maximum capacity of 360,000 m 3 d −1…”