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Diffuse pollution of groundwater in urban areas. David Lerner, Nigel Tait and Brenda Chisala Catchment Science Centre University of Sheffield. …and thanks to our funders, NERC, EPSRC, EA. With thanks to Mike Rivett, Yuesuo Yang, Mike Barrett and other colleagues. Outline. The message:

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Diffuse pollution of groundwater in urban areas

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Diffuse pollution of groundwater in urban areas l.jpg

Diffuse pollution of groundwater in urban areas

David Lerner, Nigel Tait and Brenda Chisala

Catchment Science CentreUniversity of Sheffield

…and thanks to our funders, NERC, EPSRC, EA

With thanks to Mike Rivett, Yuesuo Yang, Mike Barrett and other colleagues


Outline l.jpg

Outline

  • The message:

    • Multiple urban sources ≡ diffuse pollution

  • Outline:

    • Urban recharge

    • Urban groundwater pollution

    • Nitrate loads in Nottingham

    • Organic sources and risks

    • Summary


Urban pathways for precipitation l.jpg

Precipitation

Evapo-transpiration

Evaporation

Roofs

Surface runoff

Storm sewers

Directrecharge

Sewer leakage

Roofsoakaways

Infiltrationsystems

Urban pathways for precipitation

Urban recharge

Lerner, 2002, Hydrogeology Journal, 10, 143-152


Urban supply pathways l.jpg

Consumptiveuse

Importedwater supply

Sewers

Localgroundwater

Irrigationexcess

Septictanks

Mainsleakage

Sewer leakage

Urban supply pathways

Urban recharge

Lerner, 2002, Hydrogeology Journal, 10, 143-152


Water supply and rainfall to selected cities l.jpg

Water supply and rainfall to selected cities

Urban recharge


Urban recharge nottingham l.jpg

Urban recharge, Nottingham

Urban recharge

Yang et al. 1999, Environmental Geology, 38, 183-198


Chlorinated solvents in urban groundwater l.jpg

Chlorinated solvents in urban groundwater

Urban groundwater pollution

Rivett et al. 1990, Journal of Hydrology, 113, 307-323

Burston et al. 1993, Journal of Hydrology, 149, 137-161


Sewage in groundwater meadows nottingham l.jpg

Sewage in groundwater, Meadows, Nottingham

Urban groundwater pollution

  • Meadows, like all UK urban areas, is fully sewered

Barrett et al. 1999. Water Research. 33(14), 3083-3097


Road salt in groundwater l.jpg

Road salt in groundwater

Urban groundwater pollution

Howard & Haynes, 1993 Geoscience Canada,20, 1-8Howard & Beck, 1993 JCH, 12, 245-268


N in nottingham groundwater l.jpg

N in Nottingham groundwater

Urban groundwater pollution


Nottingham case study l.jpg

Sheffield

Meadows

Nottingham

Nottingham case study

Nitrate loads in Nottingham


Hydrogeological map of nottingham l.jpg

1

0

0

N

Groundwater level

0

1

8

0

2

150

4

0

1

0

River

9

0

Multi-levelsampler

1

1

0

3

1

Mercia Mudstone

0

7

Triassic Sandstone

Meadows

0

6

0

5

L. Magnesian Lst.

0

4

20

Glacial drift

Alluvium

0

3

Nottingham

2

0

1

0

0

1

0

2

0

Km

Hydrogeological map of Nottingham

Nitrate loads in Nottingham


Recharge rates from solutes l.jpg

Cl:N:SO4

Cl:N:SO4

Cl:N:SO4

Recharge rates from solutes

Sewers

WaterMains

Rain

Cl:N:SO4

Nitrate loads in Nottingham


Process for estimating recharge and loads l.jpg

No

Conceptual aquifer model

Calibratedheads?

Yes

Groundwater flow model

TOTALRECHARGE

START

Transport models for Cl, SO4, N

Calibratedconcentrations?

Yes

No

Change flowmodel?

No

Yes

De-convolute

RECHARGESLOADS

Process for estimating recharge and loads

Nitrate loads in Nottingham


Time and space division of 4 mass balance models l.jpg

20 km N-S

16 km W-E

standard spacing 500m

1 layer

MODFLOW &MT3Din Visual MODFLOW

River Leen

River Trent

Time and space division of 4 mass balance models

Nitrate loads in Nottingham


N loads to nottingham groundwater l.jpg

N loads to Nottingham groundwater

  • 1990s urban load 21 kg/ha/y

  • Comparable to intensive arable load

  • Where from?

Nitrate loads in Nottingham


Urban fertilisers l.jpg

Urban fertilisers

Nitrate loads in Nottingham

Wakida & Lerner, 2005, Water Research, 29 3-16


Leaking sewers l.jpg

Leaking sewers

Nitrate loads in Nottingham


Septic tank systems l.jpg

Septic tank systems

Nitrate loads in Nottingham

Wakida & Lerner, 2005, Water Research, 29 3-16


Housing and house building l.jpg

Housing and house building

Nitrate loads in Nottingham


Industrial use and spillage l.jpg

Industrial use and spillage

Nitrate loads in Nottingham


Ammonium plume from rexco l.jpg

2000

mg/l

N

150

1800

Farm

Borehole

T4

Field Well

1600

100

Factory

Monitoring

Ponds

BH

T3

1400

T2

14

Former

Abstraction

Coking

BH

Plant

50

Yard Well

Drain

Groundwater

Lagoon

head

1200

Former Colliery

Pit Head

Large Lagoon

Ammonium

Spoil Heap

concentration

10

1000

200

400

600

800

1000

1200

1400

1600

1800

1

Ammonium plume from Rexco

Nitrate loads in Nottingham


Landfills l.jpg

Landfills

  • NH4 in leachate up to 1500 mg/l

  • >10 000 closed landfills in UK, mostly unlined

  • Loads up to 4000 kg N/ha/y

Nitrate loads in Nottingham


N loads in nottingham l.jpg

N loads in Nottingham

Nitrate loads in Nottingham

Wakida & Lerner, 2005, Water Research, 29 3-16


Organic sources and risks l.jpg

Organic sources and risks

  • Density of sources

    • National

    • Nottingham

  • Risks from urban sources

    • Nottingham

  • Loads

Organic sources


Chlorinated solvent industry database tait et al 2004 l.jpg

Chlorinated solvent industry database Tait et al. 2004


Density of chlorinated solvent users l.jpg

Sheffield

Nottingham

London

Density of chlorinated solvent users

Densityscale:sites/km2

  • 75 000 current sites

  • London - 2,500 dry cleaning outlets

Organic sources

Tait et al. 2004, SOTTE 319, 77-98


Nottingham point or diffuse sources l.jpg

Potential TCE sources in Nottingham

1991

Unconfined aquifer

How dense a pattern to become diffuse pollution?

Potential TCE sources

Nottingham: point or diffuse sources?

Organic sources


Risk analysis for urban groundwater l.jpg

Sources

Pathways

Receptor

Risk analysis for urban groundwater

Organic sources


Bos the model components l.jpg

Groundwater

flow model

Catchment zone tool

Landuse analysis

Databases

Pollution risk model

BOS: the model components

GUI

Organic sources

Tait et al., 2004, Environmental Modelling and Software, 19, 1111-1124


The catchment zone model l.jpg

Stochastic MODPATH

1 particle per node

Monte Carlo simulations

E.g., recharge, permeability

Frequency of arrival givesprobability of node in capture zone

The catchment zone model

Organic sources


Landuse gis l.jpg

Landuse GIS

Organic sources


Specific industry databases l.jpg

Specific industry databases

Organic sources


New unconfined catchment l.jpg

New unconfined catchment

Raw predicted catchment

Probability contoured catchmentwith industries

Confined

Unconfined

Organic sources

New borehole

Industries

Existing borehole


The pollution risk component l.jpg

The pollution risk component

Organic sources

  • Monte Carlo analysis


Predicted concentrations l.jpg

Predicted concentrations

Organic sources


Validation l.jpg

Validation

  • Risk models are rarely validated

  • Construct and believe

  • Attempted validation against field data

    • 2 wells14 (not independent)

    • 7 contaminantsmeasurements

  • Also national MTBE observations (not shown)

Organic sources


Validation38 l.jpg

13/14 predictions within a factor of 2

Validation

Organic sources

bql = below quantification limit


Predicted pce concentrations l.jpg

50%ile log(CPCE), 2005

Borehole

Simulation

Location

Study

Area

Predicted PCE concentrations

Organic sources

Tait et al., submitted, Environmental Modelling and Software


Risks from leaking sewers l.jpg

Risks from leaking sewers

  • Nottingham sewer network

  • Stochastic distribution of leaks

    • Related to sewer age

  • Total leakage ≡ 10 mm/y

  • Amended pollution risk model

    • Bacterial sorption and die-off

Organic sources


Chlorinated solvent load in birmingham aquifer l.jpg

Tame

Aquifer

Valley

boundary

Borehole and catchment

Unconfined

Birmingham Fault

aquifer

Confined

aquifer

Industrial area

0

4 km

Chlorinated solvent load in Birmingham aquifer

Assume:

  • Steady state

  • Boreholes are pumping representative concentrations of TCE, PCE, etc

1 from Rivett et al. 2005 QJEGH 38, 337-250

Organic sources


Reminder of the story l.jpg

Reminder of the story

  • Urban recharge

    • plenty in cities

  • Urban groundwater pollution

    • N, organics, sewage, salt, etc

  • Nitrate loads in Nottingham

    • 21 kg/ha/yr from contaminated land, sewers, mains

  • Organic sources and risks

    • Many sources, significant risks

  • The message:

    • Multiple urban sources ≡ diffuse pollution

Summary


Selected nottingham references l.jpg

Selected Nottingham references

M.H. Barrett, K.M. Hiscock, S. Pedley, D.N. Lerner, J.H. Tellam and M.J. French, 1999. Marker species for identifying urban groundwater recharge sources – a review and case study in Nottingham UK. Water Research. 33(14), 3083-3097.

Y. Yang, D.N. Lerner, M.H. Barrett, and J.H. Tellam, 1999. Quantification of groundwater recharge in the city of Nottingham, UK. Environmental Geology, 38(3), 183-198.

D.N. Lerner, 2002. Identifying and quantifying urban recharge: a review. Hydrogeology Journal, 10(1), 143-152.

D.N. Lerner, 2003. Estimating urban loads of nitrogen to groundwater. Journal of the Chartered Institution of Water and Environmental Management. 17(4), 239-244.

N. G. Tait, R. M. Davison, J. J. Whittaker, S.A. Leharne and D. N. Lerner, 2004. Borehole Optimisation System (BOS) - A GIS based risk analysis tool for optimising the use of urban groundwater. Environmental Modelling and Software, 19, 1111-1124.

F.T. Wakida & D.N. Lerner, 2005. Non-agricultural sources of groundwater nitrates: a review and case study. Water Research, 39, 3-16.

F.T. Wakida & D.N. Lerner, 2006. Potential nitrate leaching to groundwater from house building. Hydrological Processes, 20(9):2077-2081.

B.N. Chisala, N.G. Tait and D.N. Lerner,in press . Evaluating the risk of methyl tertiary- butyl ether (MTBE) to urban groundwater at city scale: Nottingham case study. Journal of Contaminant Hydrology, December 2005.

N. G. Tait, R. M. Davison, S. A. Leharne and D. N. Lerner. Borehole Optimisation System (BOS) - Assessing the Potential Value of Urban Groundwater in Nottingham. Submitted, January 2006.

Also papers led by R Taylor, K Powell and S Trowsdale.

Summary


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