Carbon Dynamics and CO₂ Fluxes in Coastal Waters and Sediments Along the Zubair Creek in Southern Iraq
Keywords:
Khor al-Zubair, carbon dioxide, total organic carbon, Alkalinity, Water quality, coastal pollution, southern Iraq, Climate change, Global Warming.Abstract
This study aimed to assess the role of Khor Al-Zubair as a carbon sink within coastal ecosystems and to understand the dynamics of carbon exchange between the atmosphere, water, and sediments under the influence of tides and industrial activities. The study was conducted at three main stations stretching from Khor Al-Zubair Port to Umm Qasr Port, with a field and laboratory monitoring program carried out over a period of 13 hours during a semi-diurnal tidal cycle. The results showed a statistically significant spatial variation in water temperature (F= 685.00, P < 0.001), which affected gas solubility and carbonate system reactions. At the same time, pH values ranged from 7.0 to 7.2, primarily influenced by tidal fluctuations (P= 0.001). Salinity also reached its highest value at Station 3 near the Arabian Gulf (52.416 ppt) and its lowest value at Station 2 (44.864 ppt), while total alkalinity ranged from 170–212 mg/L and dissolved carbon dioxide from 5.9–15.9 mg/L. Calculations of the partial pressure of carbon dioxide (pCO₂) showed high values ranging from 3,616–11,950 µatm compared to atmospheric levels (478–576 µatm), confirming that Khor Al-Zubair acts as a net source of carbon emissions rather than a carbon sink. In the sediments, the average total organic carbon (TOC) was 1.59%, with a maximum value of 4.39%, while the calcium carbonate (CaCO₃) content ranged from 7.83–26.58%, and the average total alkalinity was 428.44 mg/L, indicating that the sediments possess buffering capacity that helps limit the effects of water acidification and maintain the stability of the carbonate system. The study concludes that Khor Al-Zubair is a source of carbon dioxide emissions; however, its high alkalinity and abundance of bicarbonate and carbonate contribute to maintaining chemical equilibrium and limiting water acidification.
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