2006

1. Phytoremediation of high level boron contaminated soils by using Polygonum equisetiforme Sibth. & Sm. 2006 M. Serdal Sakcali*,

2. The pollution of irrigation waters by means of different toxic elements such as waste waters of industries, sewage waters and discharge waters of coal mines, geothermal plants and Boron mines create serious toxicity problems in the agricultural soils which are irrigated by these waters.

3. Phytoremediation is the use of plants to make soil contaminants non-toxic and is one form of bioremediation. The term phytoremediation generally refers to phytostabilization and phytoextraction. In phytostabilization, soil amendments and plants are used to alter the chemical and physical state of the heavy metal contaminants in the soil. In phytoextraction, plants are used to remove contaminants from the soil and are then harvested for processing.

4. Using plants for phytoremediation should possess • targeted metal(s) accumulating capability, in aerial parts preferable; • tolerance to the accumulated metal concentrations; • fast growth of the metal accumulating biomass; • ease of cultivation and harvesting. • According to Chaney et al. • metal tolerance, • hyperaccumulation are more important factors than high biomass production.

5. A recent studies of hyper accumulators for some metals (Zn, Cd, Pb, Ni, Cu, Se and Mn) has been published. There are not much information about B accumulation by plants. First hyperaccumulation studies of B were proceed on Gypsophila sphaerocephala Fenzl ex Tchi around Kirka, Eskisehir-Turkiye.

6. At this study, we want to show Polygonum equisetiforme belonging to the family Polygonaceae, well growing Balikesir region, was the best candidate as B hyperacumulator for Phytoremediation of boron contaminated soils in Bigadic, Balikesir.

7. Material and methods • Plant sources • Studying area • Water, plant and soil • Sampling • Analysis

8. 1. Plant Polygonum Equisetiforme Sibth. & Sm., was used as hyperaccumulator species, which records around Canakkale, Istanbul, Izmir, Antalya, Adana and Gaziantep regions of Turkey. P. equisetiforme was mostly distribute sea shores and waste places.

10. P. equisetiforme samples were collected on 25 November 2005 from Etibor Co., Turkey a B- mining area of Bigadic, Balikesir. This is one of the richest B mines in the world. P. equisetiforme growing on the wastewatres from the mine. P. equisetiforme growing in the open areas. P. equisetiforme growing alogside the roads polluted by the boron waste left by the trucks.

11. Water sampling Water samples were taken from waste water collecting dam and Simav creek near the mine. Çamkoy water reservoir collecting waters from boron mining areas from underground sides. Simav Creek, runing near B-minin area.

12. Analysis All samples were individually put into plastic bags and water samples into plastic bottles, which were directly brought to the laboratory for descriptions and analyses. Plant samples were carefully washed with water to remove any traces of soil and then oven-dried at 70 oC for 48 h before dry weights were measured. Samples (0.5 g) of finely ground plant material were digested with concentrated HNO3 in a microwave system (CEM). The B in the extracts was analyzed by ICP-AES (Varian-Vista model) (Nyomora et al., 1997) in at least 4 plant samples with 3 replicates. The B standard used was from Merck, Germany. Extractable B concentrations in soil were determined according to the method of Cartwright et al. (1983) by extraction with 0.01 M mannitol plus 0.01 M CaCl2 using a soil solution ratio of 1:5 and a shaking time of 16 h. The B extracted was determined by ICP-AES (Bingham, 1982).

13. Results and Discussion

14. Borates are defined by industry as any compound that contains or supplies boric oxide. A large number of minerals contain boric oxide, but three of them are the most important from a worldwide commercial standpoint are: borax, ulexite, and colemanite. These are produced in a limited number of countries, dominated by the Turkiye and United States, which together furnish about 90% of the world's borate supplies. in United States originates in the Mojave Desert of California; borax and kernite. In Turkiye most of the commercially traded ulexiteand colemanite mining in Bigadic and Emet Districts, Balikesir, andborax from Kirka, Eskisehir. Current world sources of borates.

15. Areas where high soil B are found include dry lands of South Australia, the Middle East, the west coast of Malaysia, valleys along the southern coast of Peru, the Andes foothills in northern Chile, solonchaks and solonetz soils of Russia, ferralsols of India, rendzinas in Israel, and major B2O2-7 deposits at Searles, Lake California, the highest concentrations of soil B are often concentrated in marine evaporites and in marine argillaceous sediment.

16. Boron mines in Turkey found around Emet, Bigadic, and M. Kemalpasa regions. Mines are take places within the drainage areas of Simav and M. Kemalpasa rivers. In bigadic, drainage waters were collecting in Camkoy reservoir. However, some water from reservoir, rain water from open and inactive closed mines are flown into the Simav Creek and to the agriculture areas through irrigation water, rains and underground waters.

18. During the mining processes, boron content drainage waters, causes pollution on Simav Creek, which irrigate approx. 40,000 ha agricultural area on Balikesir, Kepsut, Susurluk and Karacabey Plains. The boron carried by the Simav Creek has over 2 ppm and threatens the fertile agricultural soils.

19. Boron have great importance for plants. However the deficiency causes some problems, excess amount of B also causes various physical and biochemical problems in plants. That is, soil containing less than 0,5 ppm boron deficiency symptoms seems. Over 2,0 ppm, B cause toxicity and consequent decrease in production and defects in the products.

20. Analyzes of soil samples from mine drenage area, shows the B contents between 6,78±0,45 and 6,96±0,95. furthermore, some samples from vineyard side have B contents 1,39±0,12 and 1,08±0,08.

21. Analyzes of Plant samples from mine drainage area, shows the B contents changes between 142,26±1,81 and 160,15±1,82. ıt shows that the B contents of plants are more than 20 times.

22. These findings agree with those of Baker & Brooks (1989), who suggested that populations of metal-tolerant, hyperaccumulating plants should be sought in naturally occurring metal-rich sites, although these plants are not ideal for phytoremediation since they are usually small and have a low biomass production. However, P. equisetiforme species from the mining area grew vigorously (nearly 80 cm canopy diameter per plant, reaching as high as 100 cm) with high biomasses. The drawbacks of species were their perennial growth habits and strong tap roots that may discourage their cultivation for phytoremediation. However this plant can serve as excellent experimental materials for molecular investigations of B hyperaccumulation mechanisms. Strains or ecotypes in strongly metal-enriched environments have usually evolved exceptionally high levels of heavy metal tolerance (Baker & Brooks, 1989; Kochian et al., 2002), as appeared to be the case in the plant species collected in the present study. Considering that more than 5 mg kg-1 of available soil B is toxic to most crop plants (Nable et al., 1997), the 277 mg kg-1 in the soil of the mining area should not have allowed anyplants to survive.

23. P. equisetiforme match the criterion of Baker et al. (2000) for a hyperaccumulator plant containing high levels of B, mainly in its upper parts. If the plant is used for phytoremediation, B-rich plant material from the remediated areas can be transported to sites requiring B fertilization. Thus the waste generated by phytoremediation may not be a problem since both deficiency and toxicity of B are present within the same provinces of Turkey, as reported by Gezgin et al. (2002). The behaviour of this species requires further testing, especially on soils with a range of lower available and total B concentrations. However, the concentration reported here will remain as a minimum concentration/criterion until further reports are available on the subject.

24. Conclusion There are many reports available describing plant species for use in the phytoremediation of metalliferous soils that contain excess amounts of Zn, Mn, Cu, Co, Pb, Al and Ni. To our knowledge, this is the first report of a plant species possessing the potential for B hyperaccumulation, especially in a region where B toxicity symptoms occur. According to Chaney et al. (1997) a hyperaccumulator plant should possess tolerance to high levels of a particular micro-element in root and shoot cells by means of vacuolar compartmentalisation and chelation and the ability to translocate an element from roots to shoots at high rates. In addition, such plants should produce high biomass (Robinson et al., 1998). In normal cases, root Zn, Cd or Ni concentrations are 10 or more times higher than shoot concentrations, but in hyperaccumulators, shoot metal concentrations in most cases exceed root levels (Chaney et al., 1997). Accordingly, the Gypsophila species reported here can be considered as hyperaccumulators because of their tolerance to high concentrations of both available and total soil B and their relatively higher (as much as 60 times) B concentrations in leaves and seeds than in roots. However, the mechanism(s) of B uptake and translocation as well as the genetic basis of B accumulation (for the isolation of genes conferring B toxicity tolerance) in Gypsophila require further investigation. The possibility of cultivation of the plant species should also be investigated for use in phytoremediation studies.