Physical and chemical properties of the waters

Water quality in the Port de Barcelona (pdf)

Water quality and sediments 2019
Water quality and sediments 2018
Water quality and sediments 2017
Water quality and sediments 2016
Water quality and sediments 2015

On the coast, the continental influence modifies the characteristics of the seawater, enriching it with nutrients, increasing biological productivity and increasing the important relationship of the water column with the sea floor.  Some coastal processes are altered and modified in ports, amplifying some effects and reducing others.

Port waters receive inputs from storm water runoff, discharges from the city's sewage infrastructure spillways in rainy weather and the inflow of part of the waters of the Llobregat river. These inputs cause changes in physical characteristics (for example decreased salinity, increased suspended matter, etc.) and chemical characteristics (increased nutrients, presence of organic pollutants and heavy metals, etc.).

The sheltering of port waters fosters the gradual settling of suspended particles and organic matter on the port's sea bed. This sedimentation modifies the particle size there, with an increase in the finest materials; this is the fraction in which the main pollutants, such as heavy metals, organic compounds or organic matter, accumulate in sediments.

In winter, port waters have an excellent vertical mix of the water column. In summer, however, warming of the surface layer of the sheltered waters leads to stratification in two layers, with the upper layer hotter and more oxygenated and the lower one cooler and less oxygenated.


In general, the inner and sheltered waters are:

  • Warmer than the open waters.
  • Less salty, owing to the inflow of continental and runoff water.
  • Less dense, as they are less salty.
  • Less transparent, with more suspended solids and turbidity.

By contrast the open waters are:

  • Cooler
  • More salty
  • Denser
  • More transparent, with less suspended matter and lower turbidity


Inputs of nutrients and organic matter to the sheltered harbour waters affect the concentrations of dissolved oxygen in water, which is consumed mainly by bacteria that break down organic matter into nutrients that are available to phytoplankton and the rest of the food chain. Chlorophyll levels, which are higher in the internal waters than external ones, are an indicator of phytoplankton populations.

Port waters have higher concentrations of ammonium in the external waters, which are a clear indicator of the continental and residual origin of the inflows.

Barcelona Port Authority has been monitoring the quality of port waters for around 20 years.

The pollution gradient can be seen in the sheltered waters between the North or Port Vell area and the South area of the Prat wharf, with respect to organic contaminants and heavy metals, which is due mainly to years of polluting discharges. Pesticides like Azinphos, polycyclic aromatic hydrocarbons such as fluorene, volatile organic compounds such as toluene, or metals like mercury and nickel have been detected with varying concentrations, although these are higher in the Port Vell.

However, the gradient is reversed in open waters, with more pollution farther south, caused by the influence of the Llobregat river mouth.