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

Using Forensics To Identify Contamination Source

• r

‘Know what you know and then know a bit more’

J amie Robinson Principal Geochemist SKM 16th 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:

NH NH3(aq) + H (aq) + H2O(l) O(l) = NH = NH4

+(aq) + O

(aq) + OH-(aq) (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 oC 0.19% unionised. At pH 9 and 10oC 37.1% unionised.

Sources of Ammoniacal N in groundwater

Graphic: Pidwirny, M. (2004). Introduction to the Biosphere – The Nitrogen Cycle. Fundamentals of Physical Geography. http:/ / www.physicalgeography.net/ fundamentalks/ 9s.html

The Nitrogen Cycle

• NH4

+ is strongly

attached on to clays through cation exchange.

• As a result, NH4

+ is

much less mobile than nitrate (by a factor of about 4 to 5)

Natural NH4 in coastal aquifers

From: S antoro, A. E. (2010). Microbial nitrogen cycling at the saltwater-freshwater

• interface. Hydrogeology J
• urnal, 18:187-202.

Fertilizers Animal waste

Bugs cause nitrogen transformation at the saline interface

• Decreases in nitrification and coupled denitrification
• Increase in nitrate reduction to ammonium

Saltwater- freshwater transition serves as redox boundary between suboxic and oxic porewaters

Sources of GW ammonium

Source NH4

+ Range (mg/ L)

Ref

Drinking water <0.5 (UK), <1.5 (WHO)

EA, WHO

Buried organic soils <2 – 29

Roy et al. (2003)

Urban stormwater 0.1 – 3.5

Wakida and Lerner (2005)

Landfill leachate (UK) <0.1 – 2190

Robinson (1995)

Leaky sewers <0.1 – 55

Wakida and Lerner (2005)

Gasworks <0.3 – 84

JDFR (2008 – 2010),

Coal mine waters 57 – 148

Manning and Hutcheon (2004)

Deep discharges (oilfields) 108 - 1010

Manning and Hutcheon (2004)

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

At least two sources of nitrogen N and O present in nature as isotopes M icrobial reactions favour lighter isotopes (i.e.

15N

substrate) But – signatures 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

10 20 30 40 50 60 70 5 10 15 20 25 30

Nitrate 18O (per mil) Nitrate 15N

What Was Found-stable isotopes

23 22 21

20

19 18 17 16

15

14 13 12 11

10

9 8 7 6

5

4 3 2 1

• 1
• 2
• 3
• 4
• 5

M ixed – non-gasworks? (PB, 2008) Gasworks (PB, 2008) Bulk soils (S chmidt&Gleixner 2005) Cretaceous Organic shales Deep saline groundwater Rainwater ammonia (Heaton 1986) Fertiliser (Heaton 1986) Soil organic nitrogen (Heaton 1986) Animal Sewerage nitrate (Heaton 1986) Ocean nitrate (Heaton 1986) Domestic sewerage (Lindau et al 1989) Septic waste (Bleifuss et al)

Ammonium 15N

Nitrate 15N versus 18O

Nitrate Fertiliser Atmospheric Nitrates Animal & human Wastes

NH4 Fert.

Air

Soil Nitrate Explosives

A B Gasworks

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

Peat Clay/ sands Waste

Bivariate plots

S eawater / coastal rainwater “Leachate” (sump samples)

S hallow groundwater Deep saline groundwater S urface water

Is leachate really leachate??

Piper diagram

S eawater Rainfall recharge

Nitrogen Isotopes – 15N(NH4)

23 22 21

20

19 18 17 16

15

14 13 12 11

10

9 8 7 6

5

4 3 2 1

• 1
• 2
• 3
• 4
• 5

M ixed – non-gasworks? (PB, 2008) Gasworks (PB, 2008) Bulk soils (S chmidt&Gleixner 2005) Cretaceous Organic shales Deep saline groundwater Rainwater ammonia (Heaton 1986) Fertiliser (Heaton 1986) Soil organic nitrogen (Heaton 1986) Animal Sewerage nitrate (Heaton 1986) Ocean nitrate (Heaton 1986) Domestic sewerage (Lindau et al 1989) Septic waste (Bleifuss et al)

Ammonium 15N

M ain conclusions:

• Isotopic NH4 similar for leachate and natural GW.

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 Of Grazing Animals

Lead poisoning of animals. Dead horses, cows, sick 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

• establish if soil lead was

from sulphide geology or

• ther sources. Showed

lead was predominantly a

• xide/oxy-hydroxide

Bioaccessibility – more for

• xides/ oxy-hydroxides,

than sulphates.

Assessing the Risk

• Risk T
• Animal Health
• Risk T
• Crop Health
• Risk From M eat Consumption
• Risk From Egg Consumption
• Financial Risk T
• Farmer, blight
• Financial Risk T
• 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.