HEAVY METAL ABSORPTION PROPERTIES IN

FRAXINUS EXCELSIOR AND PLATANUS ORIENTALIS

IN CONDITIONS OF YEREVAN, ARMENIA

Lilit Khachatryan PhD student, junior researcher lilit.khachatryan@cens.am

Center for Ecological - Noosphere Studies NAS RA www.cens.am

I N T R O D U C T I O N

Urban trees deliver multiple ecosystem services in modern cities. They

moderate the effect of urban heat island and hence help combat climate

change. They reduce urban noise and radiation level, improve the

quality of urban environmental compartments: air, soil, water and

finally - the well-being and health conditions of citizens. One of major

ecosystem services delivered by urban trees is absorption and

accumulation of different environmental pollutants and heavy metals

in particular. Different tree species have different heavy metal

absorption and accumulation properties depending on anatomic,

physiological and biochemical peculiarities. The research goal was

studying the heavy metal absorption potential in two tree species

Fraxinus excelsior and Platanus orientalis involved in Yerevan green

infrastructure. This research was implemented in 2015 and 2016.

R E S U L T S

C O N C L U S I O N S • F. excelsior is more resistant to Yerevan conditions than P. orientalis

• According to chemical analysis of leaves, the studied tree species

absorb the highest concentrations of 3 out of 5 studied heavy metals: Hg,

Ni, Mo

• P. orientalis best absorbs Hg, Ni, Mo, whereas F. excelsior has better

Cu and Zn absorption properties.

R E F E R E N C E S 1. Doganlar Z.B, Doganlar O. et al. Heavy metal pollution and physiological changes in the leaves

of some shrub, palm and tree species in urban areas of Adana, Turkey / Chemical Speciation and

Bioavailability, Vol. 26, №4, 2014, 65-78.

2. Khachatryan L.R., Hovhannisyan H.A. Seasonal variations of heavy metal contents in leaves of

Platanus orientalis growing in Yerevan, Armenia / Ecology and Safety, Vol. 10, 2016, 295-302.

3. Patel K.S., Sharma R., Dahariya N.S., Yadav A. et al. Heavy metal contamination of tree leaves

/ American Journal of Analytical Chemistry, 6, 2015, 687-693.

4. Whitlow T.H., Bassuk N.L. Ecophysiology of urban trees and their management – The North

American experience / Hort Science, Vol. 23(3), June 1988, 542-546.

A C K N O W L E D G E M E N T My cordial gratitude to the Biochemistry Department CENS, SUMFOREST team and all those who

devotedly assist and inspire me in my research.

b. Sampling and analysis

AAS AAnalyst-800 PE US

Central Analytical Laboratory CENS

Hg Ni Mo Cu Zn

Position of 9 selected sampling locations

in Yerevan

R E S E A R C H M E T H O D S

a. Visual observations Alekseev’s tree condition

assessment scale

I class – normal

II class – weakened

III class – severely weakened

IV class – drying

V class – dried

• visual injuries of assimilatory

apparatus of the trees,

• the amount of dead branches,

• crown and trunk deformation etc.

a) V i s u a l o b s e r v a t i o n d a t a

33.3 11.1

44.4

55.5

22.3 33.4

0%

20%

40%

60%

80%

100%

2015 2016

III

II

I

Fig. 1. Ash trees: Visual observation data for 2015

and 2016

55.5

11.1

44.5

66.6

33.3

0%

20%

40%

60%

80%

100%

2015 2016

IV

III

II

Fig. 2. Plane trees: Visual observation data for 2015 and 2016

According to visual observation data for 2015 and 2016, almost half of ash trees was found

weakened (II class). The share of trees in normal condition was 33.3% in 2015 reducing to

11.1% in 2016, while that of severely weakened trees (III class) made 22.3% in 2015 increasing

to 33.4% in 2016 (Fig. 1). No specimens in normal condition were found in plane trees. Over

50% of the trees in 2015 and 11% in 2016 were assessed as weakened (II class). In 2016 vs.

2015 the quantity of severely weakened and drying specimens got dramatically increased (Fig.

2). Visual assessment data have indicated that F. excelsior is morе resistant to Yerevan

conditions than P. orientalis.

b) C h e m i c a l d a t a

According to averaged data for leaf

chemical analysis, the studied tree species

absorb higher concentrations of 3 out of 5

studied heavy metals: Hg, Ni, Mo. P.

orientalis absorbs Hg, Ni, Mo more

intesively than F. excelsior, while the

latter has better Cu and Zn absorption

potential (Fig. 3, 4). In both tree species

the averaged concentrations of Hg

exceeded the upper threshold of accepted

normal concentrations by 6.3-8 and toxic

concentrations – by 1.6-2 times (Fig. 5).

The averaged concentrations of Ni and

Mo exceeded the upper threshold of the

accepted normal concentrations by 1.4-2.3

and 1.3-1.9 times, respectively (Fig. 6).

0 3 6 9 12 15 18 21

Ni

Mo

Cu

Zn

C (mg/kg)

P. orientalis

F. excelsior

Fig. 3. Averaged and aggregated data on heavy metal absorption

properties of ash and plane trees for 2015 and 2016

0.064 0.065 0.066 0.067 0.068 0.069

F. excelsior

P. orientalis

C (mg/kg)

Fig. 4. Averaged and aggregated data on Hg absorption

properties of ash and plane trees for 2015 and 2016

0

0.5

1

1.5

2

2.5

F. excelsior P. orientalis F. excelsior P. orientalis

2015 2016

C (

mg/

kg)

MoNiNormal concentration

Fig. 6. Averaged concentrations of Mo and Ni in leaves of ash and plane trees for

2015 and 2016

Fig. 5. Averaged concentrations of Hg in leaves of ash and plane trees for 2015

and 2016

0

0.02

0.04

0.06

0.08

0.1

F. excelsior P. orientalis F. excelsior P. orientalis

2015 2016

C (

mg/

kg)

Hg

Toxic concentration

Normal concentration

These data were obtained in the frames of a PhD research, after completion of which a relevant

database will be produced to be then used in Yerevan greening projects.

S T U D Y S I T E

• Total area: 227 sq. km

• Green area: 67.5 sq. km

• Relief: strongly dissected

• Climate: sharply continental

• Annual precipitation: 250-370mm

• Population: 1.074 million people

• Share of industries: 42% Yerevan

R E S E A R C H M A T E R I A L

Platanus orientalis L. Fraxinus excelsior L.

Native species

One of most widespread trees

Ecologically tolerant to local

climatic conditions

Research materials for this research were leaves of ash and plane trees.