Molybdenum background and pollution levels in the Taipu River, China

Pollution of river sediments by industrial molybdenum (Mo) is a potential threat to human and ecosystem health, yet the lack of a geochemical background level for Mo has limited risk assessment. Here, we studied Mo in 25 surface sediments and 8 core sediments in the Taipu River, Yangtze River Delta region, China. We measured total Mo and Mo in acid-extractable, reducible, oxidizable and residue fractions. Results show a background Mo level of 0.35 mg/kg of natural Mo in core samples. Surface sediments are contaminated with an average Mo concentration of 0.58 mg/kg, ranging from 0.22 to 3.47 mg/kg. The highest proportion of Mo in oxidizable, of about 74%, is observed in the most contaminated samples, whereas that of deep subsurface samples is about 22%. Possible pollution sources include dyeing, textile and metal casting.