Mercury speciation and other constituent data from deep sediment cores in Alviso Slough, South San Francisco Bay, California, 2012-16

Publication Date

2018-07-03

Time Period

2012-05-29

Time Period

2016-01-14

Revision

2018-07-20

Marvin-DiPasquale, M.C., Arias, M.R., Agee, J.L.,Kieu, L.H., Kakouros, E., Jaffe, B.E., and Wahl, D.B., 2018, Mercury speciation and other constituent data from deep sediment cores in Alviso Slough, South San Francisco Bay, California, 2012-16 (ver. 2.0, July 20, 2018): U.S. Geological Survey data release, https://doi.org/10.5066/F7HQ3Z3K.

Type: Citation Type: Related Primary Publication

The South Bay Salt Ponds Restoration Project (SBSPRP) is a long-term (50 year time-frame) wetland restoration effort located in multiple regions around the bay-land interface of South San Francisco Bay (SFB). It is focused on converting over 15,100 acres of former industrial salt production ponds into a mosaic of tidally flushed wetland habitat and deeper managed ponds, for wildlife habitat and flood control (www.southbayrestoration.org). One of the three main restoration areas, the ‘Alviso Complex’ in the extreme southern portion of the South Bay, is notable in that it also represents one of the most mercury (Hg) contaminated regions within the SFB. A primary freshwater input to the Alviso Complex is Alviso slough, which is the terminus of an upper watershed drainage area that includes the largest historic mercury mining district in North America (the New Almaden mining area). Thus, Alviso Slough and the surrounding former salt production ponds contain legacy Hg contamination, which may be remobilized as a result of changing hydrodynamics in the region due to SBSPRP management actions. During 2006, the first series of deep sediment cores was collected from Alviso Slough (5 from the slough thalwag and 10 from the fringing vegetated marsh) (Marvin-DiPasquale and Cox, 2007). This initial sampling was undertaken to assess how much Hg (and in what chemical form) is buried within and adjacent to Alviso Slough, with the expectation that opening up of former salt ponds to tidal flushing will both widen and deepen Alviso Slough and thus remobilize sediment and sediment associated legacy mercury. Subsequently, there were two significant management actions associated with the SBSPRP that have the potential to mobilize sediment and legacy mercury buried within Alviso Slough. The first was the breaching of Pond A6 during December 2010. The second was the construction and initial operation of an adjustable tidal control structure associated with Pond A8. The 2012 and 2016 deep sediment core data presented here builds on the previously published 2006 deep core dataset and expands our understanding of the distribution and degree of Hg contamination in deep sediments of Alviso Slough. This data is used in conjunction with bathymetric change measurements (Foxgrover and others, 2011) to provide estimates of how much mercury has been mobilized within Alviso Slough since restoration activities began.

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