Assessment of the Lead Release from Cables Buried in Sediments into the Water Column

摘要

The study investigates the change in the water column quality in a situation where submarine communication cables cross the water bodies. In spite of precautions in technological achievements it is possible that these cables can be subjected to potential corrosion processes. This study was performed for a particular area of the St. Lawrence River. The impact of cables buried in sediments on lead speciation in the water column was shown under different conditions (anaerobic and aerobic, at different partial pressures of CO_2, presence of organic acids). Equilibrium in the water was calculated taking into account gas, water and solid phases. Programs Equilibrium and EPH from FACT were utilized in this study to calculate Eh-pH diagrams and the equilibrium in water. The main form of lead was found to be PbOH~+ (3.34x10~(-9) M/kg), the concentration of the free lead ion was two orders of magnitude lower (2.5x10~(-11) M/kg). The calculations, in which solid phases where considered, demonstrated that the water was oversaturated with respect to dolomite and iron(III) hydroxide. It was speculated that under these conditions dolomite could form a protective layer around the cable, which can delay the corrosion. Under anoxic conditions cerussite and lead sulfide precipitated. When P_(CO2) increased, the concentration of the free ion of lead increased.