State of the Bay Report 2010-Final - Anchor Environmental

In summary, elevated trace metal concentrations recorded in Saldanha Bay in 1999 were
ascribed to an accumulation of these metals in the sediments of the Bay over the preceding 20
years, much of which was re-suspended as a result of dredging operations and had settled in the
surface layers. Construction of the Marcus Island causeway and the ore jetty had contributed to this
process by reducing wave action and modifying circulation patterns prevailing in the Bay.
Subsequent monitoring has revealed a substantial overall decrease in the concentrations of metals
in the Bay, suggesting that a disturbance, like dredging which remobilises the fine sediments and resuspends
metals, can severely affect the health of the Bay and that it takes between three to six
years before the contaminated sediments are removed from the Bay by natural processes. It was
also shown that metal concentrations were elevated near the Multi-purpose Quay as a result of lead
and copper ore dust entering the environment during export activities. In addition, metal
concentrations were high (often exceeding ERL values) in the Yacht Club basin and this may be due
to the fact that this area is a depositional zone for fine grained sediments and organic matter onto
which metals adsorb.
6.4 Hydrocarbons
Poly-aromatic hydrocarbons (PAH) (also known as polynuclear- or polycyclic-aromatic
hydrocarbons) are present in significant amounts in fossil fuels (natural crude oil and coal deposits),
tar and various edible oils. They are also formed through the incomplete combustion of carboncontaining
fuels such as wood, fat and fossil fuels. PAHs are one of the most wide-spread organic
pollutants and they are of particular concern as some of the compounds have been identified as
carcinogenic for humans (Nikolaou et al. 2009). PAHs are introduced to the marine environment by
anthropogenic means (combustion of fuels) and by natural means (oil welling up or products of
biosynthesis) (Nikolaou et al. 2009). PAHs in the environment are found primarily in soil, sediment
and oily substances, as opposed to in water or air, as they are lipophilic (mix more easily with oil
than water) and the larger particles are less prone to evaporation. The highest values of PAHs
recorded in the marine environment have been in estuaries and coastal areas, and in areas with
intense vessel traffic and oil treatment (Nikolaou et al. 2009).
Samples collected in Saldanha Bay in 1999 were analysed for the presence of hydrocarbons.
No PAHs were detected in the samples. Low levels of contamination by aliphatic (straight chain)
molecules, which pose the lowest ecological risk, were detected suggesting that the main source of
contamination is the spilling and combustion of lighter fuels from fishing boats and recreational craft
(Monteiro et al. 1999).
Sediment samples were collected at five sites in the vicinity of the ore terminal and in April
2010 and tested for hydrocarbon contamination. The total petroleum hydrocarbon contamination
for all sites, with the exception of SB14, fell below the ERL value stipulated by the NOAA. The total
petroleum hydrocarbon concentration at site SB14 was equal to the ERL value. While this is not of
major concern at present, it is recommended that petroleum hydrocarbons in the vicinity of the ore
terminal continue to be monitored in future.
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 145