1

Uptake of Chemicals into Plants

by Stefan Trapp for the course 12906

Biomass on the moon? ≤ 0.21 tons

Biomass on earth?

approx. 2000 x 109 tons Plants drive global and local biochemical cycles

(water, oxygen, carbon, nutrients, energy)

> 95% plants, 0.9% fungi, 0.1 % animal (bacteria ? 1-5%?)

The cycle of matter and the origin of our soils

Danish soils have an age

of ca. 12 000 years

How plants function

Roots take up water and solutes

Stems transport water and solutes

Xylem = water pipe

Phloem = sugar pipe

Leaves transpire water

and take up gas

Fruits are sinks for phloem and xylem

2

Definition “BCF”

BCF is “bioconcentration factor”

Concentration in plants [mg/kg]

BCF = ――――――――――――――――――

Concentration in soil [mg/kg]

Take care! BCF differs for

- dry weight versus wet weight

- with uptake from air

- for roots, leaves, fruits, wood

How to determine BCF proper

Do not just take Cplant/Csoil !

.

y = 0.1744x + 23.845

R2 = 0.982

0

250

500

750

0 1000 2000 3000 4000

C soil

C p

lan

t

slope

CPlant : CSoil = BCF

intercept

= background

from air

Do not just take Cplant/Csoil !

Some measured BCF (organic compounds)

Compound Properties mean BCF Range Plant part

PAH, BaP lipophil 0.001 10-5 to 0.01 roots, leaves

TCE volatile < 10-3 < 10-3 fruits, leaves

Pesticides polar, non-

volatile

1 <1 to 10 roots, leaves,

fruits

Explosives

(TNT, RDX)

polar, non-

volatile

3 0.06 to 29 roots, leaves,

fruits

POPs (DDT,

lindane,

PCB)

lipophil 0.01 0.02 to 0.2 roots, leaves

“dioxins”

TCDD/F

lipophil 10-2 to 10-4 10-5 to 10-3 roots, leaves,

fruits

Sulfolane

(detergent)

Polar, non-

volatile

680 leaves

unit usually dw:dw

Some measured BCF (heavy metals)

Compound mean BCF max BCF

As Arsenic 0.002 0.28

Cd Cadmium 0.1 14

Hg Mercury 0.01 0.09

Ni Nickel 0.01 30

Zn Zinc 0.01 4

Cu Copper 0.01 nd

Pb Lead 0.003 nd

unit dw:dw Regression with log KOW for Conc. vegetation to Conc soil (dry wt.)

588.1log578.0log OWKBCF

BCF: Empirical regression by Travis & Arms

Easy to use

Gives good results

Old (ex-RISK)

Problem: only uptake

from soil; no air

3

Principles of plant uptake models

Soil

matrix

Soil

water

thick

Roots

xylem

water

Stem

Leaves Fruits

Air

air

diffusive

equilibrium

flux with water

fine

Roots

Kd KRW

KRW

KLA

Standard Model The standard model assumes purely physical fluxes and partitioning -

no enzymatic in/exclusion, no active transport

Roots

some facts and considerations

Some facts about roots

► We can’t see them, but they are the most important part

of the plant, i.e. most plants can survive when you

remove stem and leaves – but rarely any without roots.

► Roots make up about 50% of the mass of the plant

(in extreme cases, such as desert plants, > 90%).

► The rhizosphere has the highest metabolic capacity of

the earth (roots, bacteria, fungi).

► Average maximum rooting depth is 2.1 m for cropland,

2.9 m for forest (humid zone), 4.6 m (globe).

► Maximum observed rooting depth is 68 m (Kalahari).

The two big plant empires

Monocotyledone

(seedling with 1 leaf)

grasses, corn, onions, garlic, tulips, lilies

All cereals

Dicotyledone

(seedling with 2 leaves)

herbs, trees, vegetables

All root vegetables

Root structure

Monocotyledone Dicotyledone

Roots start at one point, no

branching; thin, long

Fractal structure, branched roots,

fine roots and thick roots.

4

Root surface

To take up water and

solutes, plants make ”root

hairs” of a few mm length.

These root hairs exist for

only a few hours and

increase the root surface

by factor 100 or more!

The calculated surface of 1 kg roots with 1 mm diameter is 4 m2

at a length of 1.27 km.

The true surface – due to root hairs – is 1000 m2 at a length of 10 000 km of

one single rye plant (!).

It is thus fair to assume local equilibrium between root tips and soil.

Root surface in experiments

Don't forget:

Root hairs only form in soil

or in water vapour – but

not in hydroponic solution.

Thus, many uptake

experiments in water may

lead to artefacts.

Root model mass balance

Change of mass in roots =

+uptake with water – transport to shoots

dmR/dt = CWQ – CXyQ

where

m is mass of chemical (mg)

C is concentration [mg/kg, mg/L]

Q is water flow [L/d]

index R is roots, W is water and Xy is xylem

Concentration at inflow root = concentration in soil pore water

From mass to concentration

m is chemicals’ mass (mg)

M is root mass (kg)

C is concentration (mg/kg)

C = m / M

dmR/dt = d(CR MR)/dt

The root grows – integration for C and M required (oh no ...!)

Dilution by exponential growth

Chemical mass: m = constant

Plant mass: M(t) = M(0) x e+kt

m/M = Concentration in plant: C(t) = C(0) x e-kt

0

25

50

75

100

0 24 48 72

Time

Pla

nt

mass,

co

nce

ntr

ati

on

M (kg) m/M (mg/kg)

Root model concentration

Change of concentration in roots =

+ uptake with water

– transport to shoots

– dilution by growth (rate k)

dCR/dt = CWQ/M – CXyQ/M – kCR

where

k is growth rate [d-1]

CXy is concentration in xylem = CR/KRW

CW is concentration in soil pore water

5

Partition constant Root to Water KRW

= equilibrium root to water

KRW = W + L x KOW

0.77

W ca. 0.85 log Kow

KR

W

Data by Briggs et al.

(1982) for barley

W = water content

L = lipid content

Root model solution

Mass balance: change = flux in – flux out

Set to steady-state and solve for CR

R

RW

RW CkMK

QC

M

QC

0

QCQCdt

dmXyW

Concentration: divide by plant mass M

R

XyW kCM

QC

M

QC

dt

dC

RW

RXy

K

CC

d

SoilW

K

CC

d

soil

RW

RK

C

kMK

Q

MQC

/

For high KOW (high KRW): growth dilution.

BCF > factor 100 below equilibrium

Root Model result for roots to soil (Csoil = 1 mg/kg)

0.0001

0.001

0.01

0.1

1

10

0 2 4 6 8

log Kow

C r

oo

t (m

g/k

g w

w)

T&A RCF root model

TCE

BaP

d

soil

RW

RK

C

kMK

Q

QC

0.000

0.001

0.010

0.100

1.000

PCB28

PCB52

PCB10

1

PCB13

8

PCB15

3

PCB18

0

BC

F c

arr

ot

(fre

sh w

eig

ht)

dynamic exp core equilibrium exp peel

Comparison to experimental data

Carrot

model KRW

Slow uptake velocity - factor F

QCQCFdt

dmXyW

W

RW

R C

kMK

Q

MQFC

/

1,

, WaterR

ChemR

P

PF

Mass balance: change = flux in – flux out

but with reduction factor F for slow uptake

solve for CR

7.6loglog , OWChemR KP

Default 2.2x10-9 m/s is used for the permeability water, PR,Water.

Translocation Upwards

6

Water transpiration of plants in Central Europe

1 mm = 1 L/m2

Type mm/year mm/d

Broad-leaf trees 500-800 4-5

Needle trees 300-600 2.5-4.5

Corn fields 400-500

Pasture, meadows 300-400 3-6

General rule:

About 2/3rd of precipitation (rain, snow, fog) is transpired by plants.

Plants are the most important element of the water budget.

Translocation upwards in the xylem

A ”standard plant” transpires 500 L

water for the production of 1 kg dry

weight biomass!

= approx. 50 L per 1 kg fresh weight

= approx. 1 L/day for 1 kg plant mass

(default value)

Definition TSCF

TSCF = ”Transpiration stream concentration factor”

[mg/L : mg/L]

If TSCF is high, good translocation upwards.

Two methods:

1) Regression to log KOW (Briggs et al., Dettenmaier et al.)

2) Calculation from root model

C_water

C_xylem TSCF

Translocation upwards in the Xylem

For translocation upwards, the chemical must cross the root and

come into the xylem.

“TSCF” = transpiration stream concentration factor = CXylem/CWater

2.44

1.78) - K (log-exp0.784 TSCF

2

OW

Briggs et al. (1982) = optimum curve

Method 1: Regression for TSCF by Briggs (1982) Method 2: Regression for TSCF by Dettenmaier (2009)

OWKTSCF

log6.211

11

Dettenmaier et al. = sigmoidal curve

7

Method 3: Calculation of TSCF with Root Model

RW

RW

RW

W

R

W

XyK

kMK

Q

QK

C

C

C

C//

RW

RXylem

K

CC Model:

Lipophilic chemicals (high log Kow) are

adsorbed in the root and not translocated

Test of TSCF-Methods

Compilation of data from literature Predicted TSCF

0

0.2

0.4

0.6

0.8

1

1.2

-2 0 2 4 6

log Kow

TS

CF

Model TSCF Briggs Dettenmaier

Modern empirical curve and theory in good agreement (for log Kow > -2).

Do not use old Briggs equation any more!

0

0.2

0.4

0.6

0.8

1

1.2

-4 -2 0 2 4 6

ca

lc. T

SC

F

log Kow

TSCF

F

RW

RW

RW

W

R

W

XyK

kMK

Q

QFK

C

C

C

C//

TSCF for very polar compounds (with factor F) All available TSCF data – help us, Bill!

Compilation of literature values by

Dettenmeier & Doucette (2009)

Sorption to wood

Kwoodlog

KWood = CWood / Cw

log KWood = – 0.27 + 0.632 log KOW

(oak)

log KWood = – 0.28 + 0.668 log KOW

(willow)

Lignin is a good sorbent

for lipophilic chemicals!

Chemicals in the Stem

Chemicals travel upwards with the water in the stem

● loss (volatilization, degradation, growth dilution)

● uptake from air

Iktdz

dC

k: overall loss rate; I: gain from air

)1()0()( // ukzukz ek

IeCzC

Stem is only considered in the Fruit Tree model

8

Uptake of contaminants into leaves and fruits

Leaves and fruits are highly exposed to air

Additionally high water flux to leaves (xylem)

plus phloem flux (sugar) to fruits

Contamination possible from soil and air

Model for uptake into leaves and fruits

+ - exchange with air

+ influx with xylem

- dilution by growth

- metabolism

Mass balance: uptake from soil and air

- phloem

Flux from roots upwards

RRR

RWR

SWS

R

R CkCKM

QCK

M

Q

dt

dC

Outflux roots is influx to (stem) leaves and fruits

R

RWL

L CKM

Q

dt

dC

low log KOW --> low KRW --> high flow upwards

outflow roots

inflow stem / leaves

Leaves – exchange with air

Stomata

Cuticle

Equilibrium between leaves and air

Leaves are plant material, like roots. But they do not hang in soil,

and not in water. Leaves hang in air.

The concentration ratio between air and water is

AW

Water

Air KC

C

LAAWLW

Air

Water

Water

Leaves

Air

Leaves KKKC

C

C

C

C

C /

where KAW is the partition coefficient between air and water

(dim.less Henry's Law constant)

The concentration ratio between leaves and air is then

Because usually KAW < 1 and KLW ≈ KRW >> 1 KLA >> 1

Example calculation: Equilibrium leaf-air for benzo(a)pyrene

leaf density r = 500 kg m-3, log KOW = 6.13, KAW = 1.35 x 10-5

KLW = W + L a KOW b

= 0.8 + 0.02 x 1.22 x 1 348 962 0.95 = 16251 L/L

(to water)

KLA = KLW/KAW = 16251 / 1.35 x 10-5 = 1.2 x 109 (mg/m3 : mg/m3)

KLA/r = 1.2 x 109 (mg/m3 : mg/m3) / 500 kg/m3 = 2.4 x 106 (m3/kg)

(to air)

If CAir = 1 ng m-3 = 10-6 mg m-3

CLeaf = CAir x 2.4 x 106 m3 kg-1 = 2.4 mg kg-1 (chemical equilibrium)

9

Exchange with air

by

-gaseous deposition

through the cuticle

-gaseous exchange

through the stomata

- dry particulate deposition

- wet particulate deposition

A rough estimate for the exchange

velocity g is 1 mm/s (default value).

- Luckily, the deposition velocity vdep

of fine particles is in the same range.

Conductance versus Permeability

Take care! Typically:

Conductance g is related to gas phase concentration

)(LA

LAir

L

K

CgACgA

dt

dm

)(LW

LAir

AW

L

K

CPAC

K

PA

dt

dm

Permeability P is related to concentration in water

is equivalent, g = P / KAW

Differential equation for concentration in leaves (or fruits)

The change of mass in leaves = + translocation from roots + uptake from

air (gas and/or particles) - loss to air - growth dilution - degradation

from roots from air to air

LL kCI

dt

dCeasy to solve: linear diff. eq. of the type

LLL

LLA

LA

L

LR

RWL

L CkCMK

mLgAC

M

gAC

KM

Q

dt

dC

31000

growth &

degradation

Q: water flow L/d, M: mass kg, A: area m2, g: conductance m/d, k: rate d-1

Take care: Particle deposition and rain can be added on demand

(see script and Standard Model xls-version)

Mass Balance of Fruits

essentially identical to the mass balance in leaves

+ - exchange with air

( + spray application)

+ influx with xylem

and phloem

- dilution by growth

- metabolism

Mass balance for Fruits

The change of mass in fruits =

+ flux from xylem and phloem + uptake from air - loss to air

from roots from air to air

kCIdt

dCeasy to solve: linear diff. eq. of the type

FFF

FFA

FA

F

FR

RWF

FF CkCMK

mLgAC

M

gAC

KM

Q

dt

dC

31000

growth &

degradation

Summary: "Standard Model"

LLL

LLA

LA

L

LR

RWL

L CkCMK

mLgAC

M

gAC

KM

Q

dt

dC

31000

FFF

FFA

FA

F

FR

RWF

FF CkCMK

mLgAC

M

gAC

KM

Q

dt

dC

31000

RRWRWR CkMQKCMQCF

dt

dC ///

where index R is root, W is water, L is soil, F is fruit and A is air.

C is concentration (mg/kg), Q is water flux (L/d), M is plant mass (kg), K is

partition coefficient (L/kg or kg/kg), A is area (m2), g is conductance (m d-1)

and k is rate (d-1).

A system of coupled linear differential equations

10

A ”standard” child eats

100 to 200 mg soil a day (*)

”Pica child: 10 grams (acute effects)

How much soil do you eat?

More than you think ...

* ECETOC: 100 mg/d, MST: 200 mg/d

Direct Soil Uptake

tak for foto, Peter

Transfer to leaves with attached soil

Soil on plant surfaces

(Li et al. 1994)

[g soil/kg plant dw]

Lettuce 260

Wheat 4.8

Cabbage 1.1

Default value: 1% attached soil (wet weight) for leaves

0.1% for fruits and anything else

BCF(leafy vegetables to soil) = BCF model + 0.01 or 0.001

Changes on demand

This is an open code, and me and my team modify

as needed. Sometimes we add, or ommit

- factor F for slow uptake

- fraction at particles in air

- wet and dry particulate deposition

- wet deposition (rain)

and more

Doesn't mean that something is false:

There is no "true" standard model, it changes

with the scenario and the compound.

Default Data for Fruits and Leaves

Fruits Leaves Unit

Mass M 1 1 kgww

Area A 1 5 m2

Density r 1000 500 to

1000

kgww m-3

Water stream Q 0.02 to 0.2 1 L d-1

Lipid content L 0.02 0.02 kg kgww-1

Water content W 0.15 0.8 L kg-1

Conductance g 86.4 86.4 m d-1

Deposition velocity

from air

vdep 86.4 86.4 m d-1

Growth rate k 0.035 0.035 d-1

Time to harvest t 60 60 d

Attached soil R 0.001 0.01 kg/kg

Standard Model in excel

http://homepage.env.dtu.dk/stt/

-2 0 2 4 6

1

-3

-7

0.0001

0.001

0.01

0.1

1

10

100

1000

C Leaves

log Kow

log Kaw

1

-1

-3

-5

-7

-9

partitioning

air-water

Accumulation in leaves: polar, non-volatile compounds

(such as pesticides, detergents, pharmaceuticals)

Uptake from soil into leaves

calculated with the Fruit Tree Model

11

Uptake from soil into fruits

-2 0 2 4 6

1

-3

-7

0.0001

0.001

0.01

0.1

1

10

C Fruit

log Kow

log Kaw

1

-1

-3

-5

-7

-9

Accumulation in fruits: less than in leaves, but same

type (polar and non-volatile) of compounds

1 -1 -3 -5 -7 -9

-2

2

6

0.0001

0.001

0.01

0.1

1

10

C Fruits

log Kaw

log Kow

-2

0

2

4

6

Uptake into fruits from air

“the usual candidates”: semivolatile lipophilic organic

compounds such as PCB, DDT, PAH, PCDD/F

Crop specific models Application of the Standard Model

The "Standard Model" is the easiest way to calculate the dynamic

system soil-plant-air in a "correct way". That's why it is rather

popular. It is used by

● EU Chemical risk assessment (TGD, REACH)

● CLEA Contaminated Land Exposure Assessment (UK)

● Csoil (NL)

● RISK (USA)

and also

● Teaching at DTU

● Teaching here and now ☺

Limitations of the Standard Model

The "Standard Model" is only applicable

● for neutral organic compounds

● for exponentially growing plants

● for steady state

Thus it is difficult to simulate real scenarios.

It is more a "generic" model.

More realistic scenarios can be simulated using the "dynamic

cascade model" (more tomorrow).

Do you have any questions?

12

Application of the Standard Model:

Can we do Urban Gardening?

Exercise: Health Risks of Urban Gardening

Question

Which pollutants do you think are of relevance for

Urban Gardening in Copenhagen ?

Example compound

Benzo[a]pyrene very potent carcinogenic (lung cancer)

unit risk (air) 1.2 ng/m3 = 1 cancer in 10 000 persons

Polycyclic aromatic hydrocarbon PAH

log Kow 6.13

KAW (Henry’s law constant) 1.39x10-5 L/L

Emissions from all kind of fires (heating, traffic, industry)

Concentrations in air 0.1 ng/m3 to > 10 ng/m3

Copenhagen center (HC Andersen Bvd) 0.34 ng/m3 (average)

Concentrations in soil 0.05 mg/kg to > 3 mg/kg

Copenhagen 0.084 to 2.1 mg/kg

Legal standards for BaP water, air, soil and food

Compound (Ground-)

Water

Air Soil Food

Benzo(a)

pyren

10 ng/L 1 ng/m3

0.3 to

3 mg/kg

1 to 10

ug/kg

comment Sum PAH BaP only

quality and

intervention

much

higher than

water…

Legal standards for soil and air were derived without considering

uptake into food from these compartments.

13

Problem

► few measurements of garden soil, no legal standards

for home-grown food

► uncertainty at authorities + precautionary principle

→ forbudt!

City of Copenhagen does currently not allow gardening of food crops

on contaminated soil - and that is the whole city area!

but the citizens of Copenhagen do it!

Which advice can we give urban gardeners in

Copenhagen?

Exercise 1

open file

”Standard Plant Uptake model 2013 empty.xls”

and

1) Predict uptake of BaP from soil and air into plant

with Copenhagen data,

2) calculate dietary intake with garden plants and

3) estimate associated health risks

Step 1: Enter substance data for

benzo(a)pyrene in Copenhagen city

► Open file “Standard Plant Uptake Model 2013 empty”

- enter these data for benzo(a)pyrene cells A3 .. C10

Source:

Rippen G., Handbuch

Umweltchemikalien

Air: HC Andersen Boulvd.

soil: clean soil;

water; legal standard

Result: Predicted concentrations in (garden) plant

see cells A21 .. C28 and Figure 1

Result of step 1: Predicted concentrations of

benzo(a)pyrene in plants from Copenhagen City

Now we know the concentrations in air, food, soil ...

but is this dangerous?

It depends on how much of this is eaten.

Who eats what?

Consumption data of average Danish are available for children and adults

Average Consumption in Denmark

Data for average Danish women are default in the model

plus Air inhalation: 10.7 and 11.3 m3/d Soil ingestion 0.1 and 0.05 g/d

bodyweight child 35 kg and woman 67 kg

900500

205127 109

7348

12

1

10

100

1000

10000

Wat

er (g

/d)

Milk

(g/d

)

Bre

ad &

Cer

eals

(g/d

)

Tree

frui

ts (g

/d)

Mea

t (g/

d)

Potato

es (g

/d)

Veget

able

s (g

/d)

Fish (g

/d)

g/d

child woman

14

Step 2: Enter consumption data of an urban

gardener in Copenhagen

Data for average Danish women are default in the model

but how much eats a typical gardener from his own garden in Copenhagen?

I doubt that it’s more than 10% - or? Ingestion of soil I chose 50 mg/d.

Divide numbers for roots, leaves and fruits by factor 10 (cells B33 to B35)

Consumption data

Water 1.4 L/d

Air 11.3 m3/d

Soil 5.00E-05 kg/d

Roots 0.043 kg/d

Leaves 0.019 kg/d

Fruits (corn) 0.137 kg/d

Bodyweight 67 kg

Consumption data

Water 1.4 L/d

Air 11.3 m3/d

Soil 5.00E-05 kg/d

Roots 0.0043 kg/d

Leaves 0.0019 kg/d

Fruits (corn) 0.0137 kg/d

Bodyweight 67 kg

Before: all diet (default) After: diet from urban garden (10%)

Result of step 2: Calculated dietary intake

Predicted human exposure (daily uptake) of benzo(a)pyrene

including gardening in Copenhagen City cells A37 to E44

”Garden all” is via soil, roots, leaves and fruits.

It is more BaP than from water or from air ... but how toxic is it?

Dosis facit venum

“All substances are

poisons:

there is none which is not

a poison. Only the right

dose differentiates a

poison from a remedy.”

Paracelsus (1493-1541)

German physician and father of

modern toxicology.

“The amount makes the toxicity”

How toxic are PAH and benzo(a)pyrene?

0

25

50

75

100

0 2 4 6 8 10 12

Concentration

Eff

ec

t

Effect (threshold) (linear)

Dose-response relationships - Unit Risk

toxic without

threshold

linear

toxic with

threshold

sigmoid

Levels below the threshold are non-toxic sigmoid dose-effect curve.

Some effects (cancer, gentoxicity) do not have a threshold

– the risk of effect decreases linearly and we use Unit Risk

Common measures of health risk

ADI: Acceptable daily intake – no effect below the ADI

“Unit risk”: Linear slope, victims per million per lifetime.

for stochastic risks (e.g. cancer).

Target: not more than 1 victim per 1 000 000

inhabitants per lifetime for each chemical

is "virtually safe".

Effect ≈ exposure x toxicity

Health risks due to uptake of PAH

Unit risk for oral ingestion: BaP as marker for all PAH

1 cancer case per million for 0.06 to 0.5 ng per kg bodyweight and day

for lifelong exposure = 6 x 10-8 mg/kg bw/d

or 67.3 kg x 0.06 ng/kg bw/d = 4 ng/day for 1 cancer/million

Unit risk for inhalation of PAH (BaP):

87 x 10-6 per ng/m3 (read: 87 cases per million at 1 ng/m3)

= 1.15 x 10-8 mg/m3 for 1 cancer case (lifelong)

= more toxic than with oral uptake. Don’t ask me why!

Source: SCENHIR EU expert group, unit risk of PAH (sum of all),

”virtually safe dose”.

15

Step 3: Enter Unit Risk of benzo(a)pyrene

► Into “Standard Plant Uptake Model 2013 empty” -

enter these data (cells B19 and B20):

Unit Risk

oral 6.00E-08 mg/kg bw/d

inhalation 1.20E-08 mg/m3

Result step 3: health risks from gardening in

Copenhagen (benzo(a)pyrene only)

Predicted disease in the unit per million for lifelong exposure

See cells B50 to B52

Inhalation of BaP via air leads to 28 diseases per million

inhabitants (lifetime). Gardening is 6.4.

Conclusion: Better gardening than jogging ?

Check your results (and find mistakes)

by use of the file

”Standard Plant Uptake model 2013 BaP

Copenhagen NEW.xls“

Step 4 Sensitivity analysis - uptake from air or soil?

Set C soil = 0

Little change. For the scenario we used (rather clean soil), most uptake

into garden plants is from air (3/4th).

How is that when we have polluted soil?

Sensitivity analysis - contaminated soil

Set C soil = 2.1 mg/kg (7fold legal standard)

For rather high polluted soil (7 times above legal standard), uptake of BaP

via gardening is twice as dangerous as inhalation via air.

Conclusion: exchange of polluted soil pays off.

Sensitivity analysis - legal standards

Set C soil = 0.3 mg/kg, air at 1 ng/m3, water at 10 ng/L

With environment at legal standard, air is the main source of disease.

Risk of disease is above 1 : 100 000 or 1:1000000 (not ”virtually safe”).

16

A dilemma: The legal standard for BaP in soil

In 2006, the Danish soil quality standard for BaP was raised from 0.1

mg/kg to 0.3 mg/kg (3 mg/kg as intervention value).

The arguments:

1) Germany and other countries also have so high standards

2) a strict toxicological assessment would lead to a lower standard

(0.01 mg/kg). But the background concentration in DK is 0.05 to 0.1

mg/kg.

3) a legal standard that declares the whole country to ”giftgrunde”

(contaminated site) does not help.

And that’s true … or? and as we learned, air is the main problem in

the city

Results from measurements in Copenhagen gardens

Marlies and Mette, master project since autumn 2012

Samples from 3 gardens in

- Bispebjerg (North-west of city)

- KU Life vegetable plot (Center)

- Strandlyst allotment gardens (Amager)

Measurements of soil, carrots, potatoes, green kale (grønkål)

on heavy metals (As, Cd, Cr, Cu, Ni, Pb, Zn).

Preliminary results only - don't distribute, please!

Compound Cadmium Cd

Use Germany 1977

Now ruled out!

tons

per

year

%

of

use

Colours (red, yellow) 720 30

metal industry 480 20

in plastic (PVC) 432 18

batteries 360 15

others 408 17

Cd is the beautiful yellow of post cars and

Van Gogh.

Chronic tox: kidney, liver, bone and blood

damage. Cancer (?)

High toxicity to humans

ADI 0.36 ug/kg bw/d (EFSA 2011)

soil quality standard 0.5 mg/kg,

intervention value 5 mg/kg.

Cadmium target value ug/kg

Vegetables 100

Potato 60

Fruit 30

source: LS Pedersen 2001, to be confirmed

Compound Lead Pb

Long history of human use. DK ruled lead

out in 2000. Lead drinking water pipes

may be a source in old houses.

Chronic tox: Children: slowed cognitive

development, reduced growth. Cancer?

High toxicity to humans

ADI 0.5 ug/kg bw/d (EFSA 2011). soil

quality standard 40 mg/kg, intervention

value 400 mg/kg.

Lead was highest 1960 to 1980 in

city centers (London, Berlin) and

leads to reduced intelligence - the

true reason for the punk wave?

Lead (Petersen

et al. 2001)

target mg/kg limit value

mg/kg fw

Vegetables 100 200

Leafy

vegetables

200 500

Green kale 500 1 000

Potato - 100

Fruits 100 -

Compound lead Pb

After ban of leaded fuel, exposure declined. Nowadays uptake in plants

mostly from air (own result).

Top figure: measured

conc. of lead in air, Paris.

Airparif 2008

Lower figure: measured

and simulated conc. of

lead in wheat and maize,

near Paris. Uptake from air

82% (1999) to 30% (2003)

Legind et al. 2012. 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1998 2000 2002 2004 2006 2008

Le

ad

mg

/kg

Year

Simulated

Measured

with green waste

with manure

0

1

10

100

1000

Cd Cu Ni Pb

So

il c

on

c m

g/k

g

Bisp soil mg/kg

KU Life

STRA

Legal quality target

Legal intervention value

Average total conc. in soil at the three garden sites

Luckily, we have low (Bisp), medium (KU Life) and high concentration

STRA in garden soil - ideal for studies.

17

Result: Comparison Cd in potatoes

KH gardens 2012 vs to DK average 2005

I didn't find many measurements of heavy metals in vegetables in DK.

Here a comparison to data from 2005, 83 potatoes from different Danish

regions. Legal standard at 100 ug/kg.

Result: Comparison Cd in corn products all DK 2005

and vegetables KH gardens 2012

Legal standard 30 to 60 ug/kg

% of acceptable daily intake ADI from carrots if you eat average

amounts of root vegetables, and all is carrots this garden.

Lead=Pb is at detection limit, values are below that.

In DK average Cd uptake with food: 71% (17 ug/d) of ADI (24 ug/d).

% of acceptable daily intake from kale if you eat average amounts of

leaf vegetables, and all is green kale from this garden.

Lead=Pb is at detection limit, values are below that.

Direct soil ingestion of lead Pb

In risk assessment of contaminated sites, we assume that each child eats

100 mg soil per day directly, and each adult 50 mg/d

(ECETOC values, MST times 2).

According to our findings, this could provide trouble with lead intake of kids.

Pb Csoil

mg/kg

child

ug/d

woman

ug/d

child

ug/kg

bw/d

woman

ug/kg

bw/d

ADI

ug/kg

bw/d

Bisp 12.4 1.2 0.6 0.0 0.0 0.5

KU Life 100.7 10.1 5.0 0.3 0.1 0.5

Stra 584.0 58.4 29.2 1.7 0.4 0.5

Direct soil uptake of lead (in Strandlyst) was the only violation of ADI we

found so far. Consider that there are also other sources than gardening!

First conclusion Urban Gardening

- We can indeed find elevated concentrations in plants from gardens

with polluted soils or air (both from air and soil uptake)

- The amount of consumption is relevant for the risk.

- Fruits and vegetables from the market are not less polluted (why ?)

- So far we found no real reason why vegetables from urban gardening

in KH should not be consumed in reasonable amounts.

- Attached soil and soil ingestion (Pb) provides the largest risk !

- Highly polluted soil (lead, Amager Strandlyst) is better not gardened.

But who measures the soil? Why does government not do these

investigations and protects the citizens? Why do DTU students need

to do this?

We must of course be careful before we come to a robust conclusion.

There might be more that we haven't looked at.

Do not distribute this, it's preliminary!

18

End of part 1. Any questions?