FACTORS CONTROLLING MERCURY EVASION FROM SURFACE WATER DURING ESTUARINE MIXING, BERRY'S CREEK, NEW JERSEY

This study assesses the effects of freshwater-saltwater mixing in a tidal marsh on the formation and flux of dissolved gaseous mercury (DGM) to the atmosphere, as well as speciation changes during mixing, through intensive real-time measurements of gaseous mercury evasion and water sample analysis. Initial sampling was conducted in Berry's Creek, a tidal tributary to the Hackensack River in northern New Jersey with freshwater conditions in the upper reach and brackish conditions near the confluence with the Hackensack River. Berry's Creek was historically subjected to extensive discharges of mercury from the Ventron-Velsicol mercury processing site, which is listed on the USEPA National Priorities List (NPL).

Gaseous mercury evasion was measured in the field using a flux chamber and atomic absorption (Mercury Instruments UT-3000). During preliminary sampling in August 2005, mercury flux rates were moderately low under freshwater conditions (~ 50 ng/m2/hr), increased dramatically to a peak of over 1000 ng/m2/hr during the onset of the flood tide, and rapidly declined to lower levels by high tide (~50-100 ng/m2/hr). Salinity during the sampling period ranged from 0 to 5 ppt. Water samples were collected at low tide, mid-tide and high tide and analyzed using ion chromatography and inductively coupled plasma mass spectrometry (ICP-MS) for major anions and cations, and atomic fluorescence spectroscopy for total aqueous mercury and DGM concentrations. Dissolved organic carbon (DOC) was measured using a Shimadzu TOC analyzer, and DOC quality characteristics were determined through absorption and fluorescence scans. Total suspended sediments were determined by filtration and weighing. Mercury flux rates may be correlated with changes in dissolved ions, DOC quality or quantity, or total suspended sediments.