Kate Magee CK Associates. IPEC Houston, TX October 16, 2014

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1 Kate Magee CK Associates IPEC Houston, TX October 16, 2014

2 Metalloid Ubiquitous Elemental Minerals Soil Rivers Oceans Groundwater Food Most abundant in rocks, commonly associated with shales, deep-sea clays, iron oxides, sulfur minerals, volcanic sediments Redox Active Species 3+, 5+ are most common 1+, 2+, 3-are less common

3 Arsenate (5+) Arsenite(3+) Monomethyl- arsonic acid Monomethylarsonous acid Dimethylarsinic acid Dimethylarinous acid Hughes M F et al. Toxicol. Sci. 2011;123: Published by Oxford University Press on behalf of the Society of Toxicology 2011.

4 nt/uploads/2012/11/arsenic-skin-lesion-300x300.jpg Arsenic Toxicity Hughes M F et al. Toxicol. Sci. 2011;123: Published by Oxford University Press on behalf of the Society of Toxicology 2011.

5 Poison -Poison of Kings Medicinal - Fowler s Solution Hardening alloys Glass manufacturing Electrical device component Semiconductor Pesticides Pigments Wood preservation Forwler s Solution, Dave Ward/Flickr Dusting cotton, 1934/USDAgov/Flickr CCA wood preservatives, 2011/npic.orst.edu

6 Production tubing corrosion inhibitor (Frenier et al., 1989) Produced water (Gallup et al., 1996) Crude oils (Magawet al., 2001) ~60 ug/l (average of 26 crude samples) Gas condensate (Krupp et al., 2007) ug/l Released hydrocarbons can liberate arsenic from soils

7 Quiruvilca Mine (La Libertad Mine; ASARCO Mine), Quiruvilca District, Santiago de ChucoProvince, La Libertad Department, Peru Christian Bracke Panasqueira Mine (Couto Mineiro da Panasqueira), Panasqueira, Covilhã, Castelo Branco District, Portugal Kristalle and Crys As 2 S 3 FeAsS As 4 S 4 More than 150 arsenic-bearing minerals Arsenic has an affinity for ironand sulfur

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9 FeAsS Dissolution As 3+ (aq) Adsorption Precipitation As 5+ (aq) Desorption Immobile Mobile in Groundwater Immobile ph Iron Oxides Redox

10 pka 1 = 2.2 Arsenate (As 5+ ) H 3 AsO 4 H + + H 2 AsO 4-1 H 3 AsO 4 H 2 AsO 4 - HAsO 4 2- AsO 4 3- pka 2 = 6.97 H 2 AsO 4- H + + HAsO 4 2- Relative Abund dance pka 3 = ph HAsO 2-4 H + + AsO 3-4 pka 1 pka 2 pka 3

11 pka 1 = 9.22 Arsenite(As 3+ ) H 3 AsO 3 H + + H 2 AsO - 3 pka 2 = H 2 AsO 3- H + + HAsO 2-3 Relative Abundance 1 H 3 AsO 3 H 2 AsO 3 - HAsO 3 2- pka 3 = AsO HAsO 3 2- H + + AsO 3 3- pka 1 pka 2 pka 3

12 2 in Metal oxyhydroxidescan act as a sink and source of arsenic

13 Raven et al., 1998 Positive Surface Charge PZC Negative Surface Charge

14 Ligand Exchange Reactions (phosphate, sulfate, carbonate, silicate) Fe oxide As(V) + phosphate Fe oxide PO 4 + As(V) Reductive Dissolution Dissolution Fe 2+ (aq) + As 3+ (aq) As 5+ (aq) [As] GW Mobile

15 Arsenate more prevalent 1 H 3 AsO 4 Groundwater Oxidized Arsenic will be predominantly immobile Eh (v volts) H 3 AsO 3 H 2 AsO 4 - HAsO 4 2- AsO 4 3- [As] GW -0.5 H 2 AsO 3 - HAsO 3 2- AsO ph

16 Arsenic more likely to be mobile Arsenitemore prevalent Eh (v volts) 1 H 3 AsO 4 Sample Identification Sample 1 Sample 2 Sample 3 Sample 4 Hydrocarbon Status LNAPL Unaffected Dissolved Phase Dissolved Phase H 2 AsO Iron (III) Oxide Arsenic Speciation (1362A) Arsenic (III), mg/l HAsO Arsenic H(V), 3 AsO mg/l 3 ND H 3 ND AsO AsO 3- Inorganic Arsenic, mg/l Iron (II) Oxidation Reduction Potential Groundwater -0.5 H 2 AsO - Dissolved Oxygen, mg/l Reduced [As] GW ph HAsO 3 2- AsO 3 3-

17 Arsenic will be predominantly immobile 1 H 3 AsO 4 Orpiment, arsenopyrite, pyrite precipitate (bind arsenic) Eh (v volts) H 2 AsO 4 - HAsO 4 2- AsO 4 3- [As] GW -0.5 Sulfidic Conditions ph Reeder et al., 2006

18 EPA adopts standard of 50 ug/l 1975 Congress passed Safe Drinking Water Act Arsenic rule became effective EPA affirms standard (0.010 mg/l) EPA declares As a carcinogen EPA sets new drinking water standard (10 ug/l) Compliance date for new standard

19 National Primary Drinking Water Regulations; Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring published in Federal Register (66 FR 6976) Maximum Contaminant Level (MCL) = mg/l Enforceable Maximum Contaminant Level Goal (MCLG) = 0 mg/l Non-enforceable Applies to public water systems

20 10 ug/l Site Specific 5 ug/l 100 ug/l 10 ug/l 10/1,000/ 10,000 ug/l 10 ug/l Or Background 10/1,000 ug/l 10/50-22,000 ug/l

21 State Agency Standard (ug/l) Guidance National EPA 10 Louisiana Montana New Jersey New Mexico North Dakota Oklahoma Pennsylvania Texas Louisiana Department of Environmental Quality Montana Department of Environmental Quality NJ Department of Environmental Protection New Mexico Environmental Department North Dakota Department of Health Waste Management Oklahoma Department of Environmental Quality PA Department of Environmental Protection Texas Commission on Environmental Quality 10/50-22, echnology/recap/2003/recap%202003%20text %20Table%201.pdf EQ7_2012.pdf Site Specific 10/Background /2062NMAC-Amended2014.pdf Chapter Standards of Water Quality of the State 10/1000/10,000 er250/chap250toc.html 10/1000 ppcls.html

22 Arsenic is present in groundwater due to natural and anthropogenic sources The two major valence states of arsenic in groundwater are 3+ (arsenite) and 5+ (arsenate) mobility and toxicity differences Arsenic concentrations increase as ph increases, under postoxic conditions Arsenic immobilized under oxidizing conditions, sulfidic conditions Regulation of arsenic varies by state No valence state standards

23 Hughes et al Arsenic Exposure and Toxicology: A Historical Perspective. Toxicol. Sci. 123 (2): Raven et al Arseniteand arsenate adsorption on ferrihydrite: Kinetics, equilibrium, and adsorption envelopes. Environ. Sci. Technol. 32: Reeder et al Reviews in Mineralogy and Geochemistry. 64 (1):