Increase Font Size Decrease Font Size

Assessment of Marine Pollution in Sediments from the Caspian Sea

Introduction

IAEA-MESL collaborated with the Caspian Environment Programme (CEP) on a GEF-UNDP International Waters project to investigate the marine pollution in the Caspian Sea. CEP has five Littoral States: Azerbaijan, Federation of Russia, Islamic Republic of Iran, Kazakhstan and Turkmenistan.

The main sources of pollution to the Caspian Sea have generally been considered to be offshore oil production and land-based sources, notably the Volga River. The presence of oil in the Caspian Sea region has been known since ancient times and the oil reserves were amongst the first to be exploited in the world. Baku was a centre for oil production at the turn of the 20th century and developed further development during the era of the Soviet Union. Exploration and exploitation, especially of offshore reserves, has blossomed since the break up of the Soviet Union. Public opinion polls in the region have highlighted concerns about the oil and gas industry as a source of pollution to the environment of the Caspian Sea. Oil production areas cover vast areas of the coastal zone, particularly along the south coast of the Apsheron Peninsula in Azerbaijan.

Figure 1 & Figure 2Oil derricks and scrapped vessels in Baku Harbour, Azerbaijan
(Photograph by SJ de Mora)

Sampling and Analyses

Separate missions were undertaken in Azerbaijan, Federation of Russia, Islamic Republic of Iran and Kazakhstan No permission was given to sample in Turkmenistan. Altogether 105 surface sediment samples were collected using a Van Veen grab from October 2000 to September 2001. The following contaminants were measured: metals, aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides (lindane, DDT, etc.), and polychlorinated biphenyls (PCBs), together with other parameters such as grain size distribution, total organic carbon (TOC), carbonate content, and hexane extractable organic matter (EOM).

Figure 3 R/V Mammed Suleymanov, the ship used for sample collection in Azerbaijan
(Photograph by SJ de Mora)

Characteristics of the Sediments

Fine material (mud/silt/clay), with a larger surface to volume (or weight) ratio, has a greater potential to scavenge and retain both inorganic and organic pollutants from the water column than relatively coarse sandy sediment. Locations where fine-grain material deposit are likely to exhibit elevated concentrations of pollutants. For example, the content of Co and Pb correlate with that of Al, a marker of fine-grain material of terrigenous origin. As wind induced mixing in the shallow northern waters winnows out the fine-grain material, pollutants discharged into this region are not likely to accumulate in the immediate vicinity and thus are exported.

Mercury

The mercury content was low in the northern sector of the Caspian Sea where sediments were relatively coarse or composed mostly of carbonates.

The mercury concentrations were high at many sites in Azerbaijan, and the Hg content exceeded the NOAA ERL value of 0.15 µg g-1. In particular, the sediments to the south of Baku Bay were notably polluted.

Copper

Concentrations were low in the northern part of the Caspian Sea. The Cu content exceeded the NOAA ERL, 34 µg g-1, value at several locations in Azerbaijan and Iran. A hot spot was also evident in Kazakhstan.

The Kura River seems to be an important source of Cu locally. This pollution most likely is derived from either mining activities in the catchment area, but agricultural sources may play a minor role.

Total DDTs

The NOAA Effects Range Low (ERL) for total DDTs (ie, DDT and the breakdown products of DDE and DDD) is 1600 pg g-1. The concentrations of DDT-related compounds surpassed this quality standard at a number of locations, especially in Azerbaijan and Iran.

The Kura River showed a strong signal, with the maximum concentration of total DDTs near the river mouth (13400 pg g-1). The lowest concentrations were found in the North Caspian Sea, particularly in the north-eastern shallow area of Kazakhstan.

DDT degrades only slowly to DDE and DDD in the environment. Relatively high proportions of DDT would indicate recent influxes and, by implication, ongoing DDT usage throughout the region. As shown below, the distribution of DDT, DDD and DDE demonstrated that DDT contamination is a contemporary and ubiquitous issue in the Caspian Sea.

Conclusions: Organic Pollutants

Conclusions: Heavy Metals

Generally, the concentrations of heavy metals co-varied with those of aluminium, reflecting the influences of terrigenous inputs and grain size.

References