Adsorption of mercury species on river sediments - effects of selected abiotic parameters

摘要

Abiotic parameters (pH, temperature, current velocity, mercury species concentration, and sediment and aqueous media composition) influence mercury species (MeHg~+, EtHg~+, PhHg~+ and inorganic Hg~(2+)) adsorption on river sediments. The highest amount of adsorbed MeHg~+ and EtHg~+ (82-93% and 85-91% for static and agitated system, respectively) occurred at pH 3-4. For PhHg~+ the maximum adsorption (90% and 95% for static and agitated systems) was located over the broad 3-10 pH range, while for Hg~(2+) (94% and 97% for static and agitated systems) it was at pH ~ 3. Temperature (4.5-60℃) influenced the adsorption rate but not the quantity. Both rate and quantity increased in the order: static < agitated ≤ stirred systems. The aqueous medium composition affected both rate and quantity. Sulfate caused the largest adsorption decrease for organomercury species (15-25% decrease); sulfide reduced Hg~(2+) adsorption about 67%. Cations at pH 5.2 reduced either the adsorption rate (Ca~(2+), Al~(3+)) or the total adsorption (Zn~(2+), Fe~(3+)). Positive correlations were found between sediment C, N, S content as well as cation exchange capacity (CEC) with mercury adsorption (R = 0.45-0.66, 0.56-0.89, 0.45-0.61 and 0.55-0.73, respectively) while negative correlations were observed with Fe and Al (R = -0.63 to -0.90 and -0.65 to -0.86, respectively).