Presentation for 14th European Seminar on Geography of Water

REMOVAL OF PESTICIDES IN TREATMENT MICROCOSM WETLANDS: HEXACHLOROBENZENE EXAMPLE

SIRLE TRESTIP

University of Tartu

Cagliari 2011

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Table of contents Wetlands Constructed Wetlands Pesticides Hexachlorobenzene example Aim of the work Materials and methods Results and discussion Conclusion

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Wetlands One of the most biological productive

ecosystems on the planet An area of land that is seasonally or

permanently waterlogged 

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Constructed Wetlands

Cheap to operate and maintain Remove effectively contaminants without the addition of

expensive chemicals or extra energy requirements.  Aesthetically pleasing Can provide habitat for many aquatic and terrestrial

species Designed to mimic natural wetlands, but optimize the

biological and physical properties in order to maximize efficiency. 

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Pesticides

Group of artificially synthesized substances

Used for enhancing agricultural production Insecticides, herbicides, fungicides European soil – 320,000 tons per year France, Italy, Germany, Spain, Portugal –

80% of pesticides in Europe

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Hexachlorobenzene (HCB)

One of 12th banned POPs Used mostly as a fungicide Highly volatile and very persistent in

environnment High toxity and potentiality to accumulate

through food chain Found all over the world: air, soil,

sediments, water, biota, human tissues Still used as an intemrediate in some

countries

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HCB example: aim of the work

To study the effect of removal of HCB from treatment microcosm

To clarify the impact of different macrophytes (Typha and Phragmites) on different concentration of HCB (high-HCB and low-HCB) in microcosm wetland

To analyze the effects of some environmental factors on HCB biodegradation (like temperature, pH, TN, DOC, etc.)

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Material and Methods Plant rhizomes collected in February 2011 Two different plant species (Typha and

Phragmites) Selected strongest plants (9+9) Two different concentrations: high – 300 mg/kg

and low – 15 mg/kg Together with control 8 parallel testings Taking 5 times water samples and 3 times soil

samples Weekly measurements of water parameters

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Wetland microcosm

Gravel (40 cm) Mesh Contaminated

soil (180 cm) Mesh Gravel (40 cm) Water (70 cm) Plant in the

middle

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Results and DiscussionEnvironmental parameters

No reliable similarity between water parameters and presence or absence of plants

pH increase from 7.4 to 7.9 at the end of the experiment

Temperature increase from 17°C to 19°C at the end of the experient

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Results and DiscussionHCB concentration in water

High-HCB: dramatic decrease after four weeks At the end of the experiment only 16% - 26% remained

from the initial concentration Low-HCB: HCB concentration decreased, in the end of

the experiment 14% - 38% from the initial.

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Results and DiscussionHCB concentration in soil

No lag-phase Most of the HCB was removed in first two weeks Low-HCB control increasing – mistake of sampling?? At the end of the experiment the average remained HCB

concentration 2% from the initial.

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Results and DiscussionPlant biomass

Typha grew better than Phragmites, but Phragmites was weaker already in the beginnig of the experiment

In the end of the experiment new Typha shoots Plants suffered under stress: plant grow was

limited also in treatments without HCB Stress was probably caused due to drastic

environmental change

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IN THE ENDIN THE MIDDLE

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Further study and recomendations

New outdoor experiment mimicing realistic manipulations of constructed wetland

Mesocosms instead of microcosms Wetland soil and more plant species HCB concentration in plants (above-ground and

belowe-ground) To identify the microbial communities (real-time

PCR) Start sampling in earlier stage for finding out lag-

phase.

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Conclusion Wetland microcosms were effective in

removal of HCB: from soil ~ 90% and from water 70% of initial concentrations were removed.

Plants played role in removal of HCB There was no significant difference

between plant species to the removal of HCB

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THANK YOU FOR LISTENING!

QUESTIONS?