Know what you know and then know a bit more J amie Robinson - PowerPoint PPT Presentation

Using Forensics To Identify Contamination Source or ‘Know what you know and then know a bit more’ J amie Robinson Principal Geochemist SKM 16 th Feb 2012

How It All Started ’ It was all about ammonium in groundwater and the cost of cleaning it up.

Quick Bit of Chemistry Ammonia is colourless gas, strongly alkaline, dissolves in water: + (aq) + O (aq) + OH - (aq) NH 3 (aq) + H NH (aq) + H 2 O(l) O(l) = NH = NH 4 (aq) Free ammonia is highly toxic to aquatic life. The percentage of unionised form related to the pH and temperature: At pH 7 and 10 o C 0.19% unionised. At pH 9 and 10 o C 37.1% unionised.

Sources of Ammoniacal N in groundwater • NH 4 + is strongly The Nitrogen Cycle attached on to clays through cation exchange. + is • As a result, NH 4 much less mobile than nitrate (by a factor of about 4 to 5) Graphic: Pidwirny, M. (2004). Introduction to the Biosphere – The Nitrogen Cycle. Fundamentals of Physical Geography. http:/ / www.physicalgeography.net/ fundamentalks/ 9s.html

Natural NH4 in coastal aquifers Bugs cause nitrogen transformation at the saline interface • Decreases in nitrification and coupled denitrification • Increase in nitrate reduction to ammonium Animal waste Saltwater- Fertilizers freshwater transition serves as redox boundary between suboxic and oxic porewaters From: S antoro, A. E. (2010). Microbial nitrogen cycling at the saltwater-freshwater interface. Hydrogeology J ournal , 18:187-202.

Sources of GW ammonium + Range (mg/ L) Source NH 4 Ref EA, WHO Drinking water <0.5 (UK), <1.5 (WHO) Roy et al. (2003) Buried organic soils <2 – 29 Wakida and Lerner (2005) Urban stormwater 0.1 – 3.5 Robinson (1995) Landfill leachate (UK) <0.1 – 2190 Wakida and Lerner (2005) Leaky sewers <0.1 – 55 JDFR (2008 – 2010), Gasworks <0.3 – 84 Manning and Hutcheon (2004) Coal mine waters 57 – 148 Manning and Hutcheon (2004) Deep discharges (oilfields) 108 - 1010

Case Study Investigated ammonium within groundwater at a former gasworks site in South East England. Alluvial deposits, including peat, overlying terrace sands and gravels. A large river and sewage treatment works bound the site. Remediation of soil undertaken costing £Ms, validation showed ammonium in groundwater was not degrading. Regulators insisted ammonium was treated.

Investigation Design Two underground water bodies – perched water and underlying gravel aquifer. Chemical analysis to distinguish source included: Stable isotopes (nitrogen and oxygen), Seawater indicators (bromide and boron), Sewer/sewage indicators (e-coli, Kjeldahl nitrogen)* and Major ion analysis . *Organic nitrogen forms ammonium through ammoniafication or mineralisation .

Case Study: Piper Diagram Seawater Rain water

Case Study: Bivariant Plot Increasing chloride: increasing ammonium, saline intrusion/ marine sediments Increasing ammonium, no chloride change – gasworks.

Case Study: Isotopic Analysis N and O present in nature as isotopes M icrobial reactions favour lighter isotopes (i.e. � � 15 N substrate) At least two sources of But – signatures nitrogen exist.

Case Study : Conclusions The following conclusions are drawn from the study: The groundwater quality was being impacted by more than one source; There is more than one source of ammonium in the groundwater at the site; In addition to gasworks source there is likely to be a source from saline intrusion, the sewage works and shallow alluvial sediments.

What Happened Next • Client happy • Paid to understand if they could discharge liability regarding NH4 at other site in UK; • Study limited by available wells; • Came to a conclusion that there was a signature for stable N isotope in NH4. • Also invested in examining forensics of tar – more later

Ammonium � 15 N A 10 -5 15 20 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 What Was Found-stable isotopes Gasworks (PB, 2008) M ixed – non-gasworks ? (PB, 2008) Bulk soils (S chmidt&Gleixner 2005) Domestic sewerage Cretaceous Organic shales (Lindau et al 1989) Deep saline groundwater Soil organic nitrogen (Heaton 1986) Rainwater ammonia (Heaton 1986) Septic waste (Bleifuss et al) Animal Sewerage nitrate (Heaton 1986) Fertiliser (Heaton 1986) Ocean nitrate (Heaton 1986) B Gasworks Nitrate � 15 N versus � 18 O Nitrate � 18 O (per mil) 10 20 30 40 50 60 70 0 Air 0 NH4 Fert. Fertiliser Nitrate Nitrates Atmospheric 5 10 Wastes Animal & human Soil Nitrate Nitrate � 15 N 15 Explosives 20 25 30

Case Study Investigated ammonium associated with cellulose landfill site. Client paying substantial amount to pump ammonium from site for treatment. Landfill located in an area where natural salinity can be high and therefore investigated the source of the salinity and ammonium. The intention was to show that the ammonium was a natural phenomena and therefore treatment did not need to continue.

Hydrogeology Waste Clay/ sands Peat

Bivariate plots Deep saline groundwater “Leachate” (sump samples) eawater / rainwater coastal S Is leachate really leachate?? S hallow groundwater S urface water

Piper diagram Rainfall recharge S eawater

Ammonium � 15 N 10 -5 15 20 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 Nitrogen Isotopes – � 15 N (NH4) Gasworks (PB, 2008) M ixed – non-gasworks ? (PB, 2008) Bulk soils (S chmidt&Gleixner 2005) Domestic sewerage Cretaceous Organic shales (Lindau et al 1989) Deep saline groundwater Soil organic nitrogen (Heaton 1986) Rainwater ammonia (Heaton 1986) Septic waste (Bleifuss et al) Animal Sewerage nitrate (Heaton 1986) Fertiliser (Heaton 1986) Ocean nitrate (Heaton 1986) • Isotopic NH4 similar for leachate and natural GW. M ain conclusions:

Conclusions • Sufficient evidence to show at least a proportion of the ammonium was natural; • Disposal of the ammonium not required. • Saved client significant money every year

Lead Poisoning Lead poisoning of animals. Of Grazing Dead horses, cows, sick Animals sheep and sick puppy • Portable XRF to delineate areas, targeting soil and grass analysis. • Former mining areas (UK) • Water Pipeline (Oz) • Lead more bioaccessible depending upon its geochemistry • Lead high acute death of animals

SEM Study of Soil Scanning Electron M icroscopy used to examine the form of the lead. T o establish if soil lead was from sulphide geology or other sources. Showed lead was predominantly a oxide/oxy-hydroxide Bioaccessibility – more for oxides/ oxy-hydroxides, than sulphates.

Assessing the Risk • Risk T o Animal Health • Risk T o Crop Health • Risk From M eat Consumption • Risk From Egg Consumption • Financial Risk T o Farmer, blight • Financial Risk T o M ine Owner So quite a lot to consider!

Animal Health Risk Assessment

Not Just An Isolated Occurrence

Hydrocarbon Forensics • Classic work involved Exxon Valdiz: • M assive clean up, after a number of years tar ball appeared on beach • Using isopreniod work (pristane phytane) • Showed tar was naturally occuring and not related to the spill. • Pyrogenic and petrogenic tars • Currently use speciation of P AHs as a good way of distinguishing

Pyrogenic, Petrogenic & Phytogenic

Pyrogenic Process Forensics • It is apparent that different process at former gasworks could cause different tar chemistries; • Important to understand as history often incomplete and in some cases non –existent; • Forensic tool to update CSM based on tar chemistry to predict what processes operated; • Also implications for apportioning liability

Forensic Analysis of Coal Tar Working with Russell Thomas in PB, Bristol and as an external examiner of Strathclyde University, developed characteristic of coal tar source using P AH pairs and new GC/ GC TOF (3D) .

Conclusions • Forensic studies can help to identify and distinguish sources of potential contaminants; • This can help to understand potential liability in some cases and reduce costs for disposal; • Forensic analysis is not a panacea and is a line of evidence supporting other investigative work.