Uptake of Organic Contaminants from Soil into Vegetables and Fruits - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 393

Table 9.2 Transfer of attached soil particles to leaf surfaces (Li et al. 1994 ); expressed as mg soil
g plant dw − 1

±

standard deviation

Amount of soil (mg soil g plant dw − 1 ) Plant species

Lettuce 260 ± 100

Turnip 32 ± 11

Grass 18 ± 48

Toma to 17

Broccoli 10 ± 8.1

Bean leaves 9.5

Grass (Lolium) 5.8

Wheat 4.8

Sun flowers 2.6 ± 0.9

Tobacco 2.1 ± 0.6

Soy bean 2.1

Maize 1.4

±

Cabbage 1.1 1.1

Average 28.2

Average (for fresh weight) ∗ 1.4

∗ Based on 95% water content of plants

persistent lipophilic contaminants and was contributed to soil particle attachment
(Mikes et al. 2009 ).
A default value of 10 mg soil g plant − 1 (fresh weight) for transfer of attached
soil was chosen for lettuce in the New Model Framework for dietary exposure of
children and adults (Legind and Trapp 2009 ) (for lettuce,

1kg fw L − 1 and ρ L,wet =

0.2 kg dw L − 1 , so this corresponds to 50 mg soil g plant − 1 (dry weight)).
Forgrains,1mgsoilg plant − 1 (fresh weight) transfer with attached soil particles was
assumed, due to pollution at harvest. In models predicting the exposure to radio-
nuclides, the default value for the transfer of attached soil is 5 mg soil g plant − 1
(fresh weight) (25 mg soil g plant − 1 (dry weight)) for pasture grass, and 1 mg soil
g plant − 1 (fresh weight) for other plants (Paretzke and Garland 1990 ).
In systematic experiments, Delschen et al. ( 1996 , 1999 ) investigated the uptake
and the uptake pathways of PAHs (polycyclic aromatic hydrocarbons) into vegeta-
bles and crops. They found that uptake of PAHs can both be from contaminated sites
and from the atmosphere. In some experiments, the soil was covered with fine sand
or a gas-permeable foliage. This avoided soil particle attachment, but allowed for
volatilization with subsequent adsorption to leaves. In fact, this coverage reduced the
uptake of 15 PAHs from soil almost completely, indicating soil particle attachment
to leaves as a major transfer pathway of PAHs (in particular benzo(a)pyrene and
dibenz(a,h)-anthracene) from soil to vegetables. Thus, crops with harvested parts
close to the soil surface have the highest affinity for accumulation, because soil par-
ticle attachment by rain splashing rarely affects plants with a height above 40 cm
(Dreicer et al. 1984 ;Lietal. 1994 ). No systemic uptake of PAHs via plant roots was
found. Concentrations of PAHs in peels of potato and carrots from organic farming
were generally higher than in the core of potatoes and carrots (Zohair et al. 2006 ).
The BCF for individual PAHs ranged from 0.0002 to 0.3 kg kg − 1 and decreased with

ρ L,dry =