This study was performed to select plants suitable for phytoremediation as well as to develop the efficient way to purify soil contaminated with arsenic, through the research on improvement of growth and arsenic accumulation ability in Pteris multifida.

1. Twelve Pteridophyta species were cultivated in soil contaminated with heavy metals for 8 weeks. As a result, the aerial part of P. multifida showed the highest accumulation for arsenic (62.2 mg·kg-1 DW), cadmium (0.78 mg·kg-1 DW), lead (8.81 mg·kg-1 DW), and underground part showed the highest for zinc accumulation (63.57 mg·kg-1 DW). Copper accumulation ability was the highest in underground part of Pteris ensiformis, 44.4 mg·kg-1 DW and the highest in aerial part of Adiantum capillus-veneris (26.8 mg·kg-1 DW). P. multifida showed the highest accumulation ability

* A thesis for the degree of Doctor of Philosophy in February 2014.

for arsenic, and also turned ability for arsenic, and also turned out to have the accumulation ability for cadmium, copper, lead and zinc. Therefore, P. multifida was considered to be a useful phytoremediation material which is effective in purifying soil compositely contaminated with heavy metals.

2. Cultivation methods were investigated to develop the purification model of arsenic contaminated soil using P. multifida. P. multifida accumulated the most arsenic per unit area (172.42 mg·m-2 DW) due to its excellent growth and arsenic accumulation (1,289.5 mg·kg-1 DW) when planted with 20×20 cm interval. During 24 weeks of cultivation period, removal of aerial part once a year at the last day was the best in terms of arsenic accumulation. When 200 g·m-2 of citric acid was treated, the arsenic accumulation ability of P. multifida was 1,822.2 mg·kg-1 DW, improved by approximately 62.5% compared to untreated control plot (1,121.5 mg?kg-1 DW). Accumulation amount per unit area (1 m2) was also increased by 14.9%, and transfer coefficient was 0.95, moving accumulated arsenic to aerial part more quickly. Also, when P. multifida was grown under shading condition, the arsenic accumulation ability was about 1.5 times higher compared to non-shading treatment.

3. P. multifida was cultivated on compost contaminated with different concentrations of sodium arsenate [As(III)] and sodium arsenite [As(V)] for 12 weeks. Treatments of 50 and 500 mg·kg-1 arsenic showed similar growth to that of arsenic untreated control plot regardless of arsenic types, but plant height tended to decrease as concentration of arsenic increased. Arsenic accumulation ability of aerial part grown with arsenic concentrations of 50 and 500 mg·kg-1 were 802.7, 2,956.0 mg·kg-1 DW respectively in As(III) treatment and were higher than As(V) treatment (622.6, 2,841 mg·kg-1 DW). However, arsenic accumulation ability of As(V) treatment (3,883.3, 5,250.6 mg·kg-1 DW) were higher than that of As(III) treatment (3,347.8, 4,272.7 mg·kg-1 DW) when cultivated in 1,000 and 2,000 mg·kg-1 of arsenic. In the experiment of arsenic types, calcium arsenate treatment showed slightly decreased growth of P. multifida. But, growth of P. multifida cultivated in the remaining arsenic treatment was similar to untreated control plot. With only short-term cultivation of 4 weeks, aerial part of P. multifida in sodium arsenate treatment showed high arsenic accumulation of 2,289.5 mg·kg-1 DW. The arsenic accumulation (2,956.0 mg·kg-1 DW) was the highest at 12 week. On the other hand, underground part showed the highest arsenic accumulation in potassium arsenite treatment (2,470.2 mg·kg-1 DW) and calcium arsenate treatment accumulated 1,060.7 mg·kg-1 DW of arsenic.

4. Growth of P. multifida depending on arsenic types and soil pH were the best at the level of weak acid (pH 5∼6) regardless of arsenic types. As soil pH increased, the growth was generally decreased. Regardless of arsenic types and soil pH, P. multifida showed highly increased arsenic accumulation, more than 1,740 mg·kg-1 DW and 910 mg·kg-1 DW both in aerial and underground part, respectively. Arsenic accumulation ability of aerial part showed the tendency to increase as pH of soil got higher, and was the highest at pH 8 with 4,712.5 mg·kg-1 DW in As(III) treatment and 4,203.3 mg·kg-1 DW in As(V) treatment. Translocation ratio was higher than 0.5 in all treatments. Arsenic accumulation of P. multifida per plant was the most at pH 7 (3.25 mg) in As(III) treatment and at pH 7 and 8 (2.68, 2.78 mg) in As(V) treatment.

5. The growth and arsenic accumulation ability of P. multifida was improved, when fertilized with proper concentrations in any types of fertilizers. Dry weight of aerial part was the highest in 2 g·kg-1 complex fertilizer application in As(III) treatment (Na2HAsO4·7H2O, 2.2 g) and 0.5 g·kg-1 phosphate fertilizer application in As(V) treatment (NaAsO2, 1.8 g). When using 2 g·kg-1 urea, arsenic accumulation at aerial part of P. multifida in As(III) treatment was 3,048.4 mg·kg-1 DW, and was improved by 74.3% compared to control (1748.7 mg·kg-1 DW). Also in As(V) treatment, 2,996.0 mg·kg-1 DW of high arsenic accumulation was achieved in 2 g·kg-1 urea supplement. When fertilized with 2.0 g·kg-1 urea in both As(III) and As(V) treatments, arsenic accumulation of aerial part per plant was the most with 5.8, 5.1 mg, respectively.

In conclusion, P. multifida was useful for phytoremediation due to vigorous growth and arsenic accumulation ability regardless of arsenic types and concentrations as well as its various heavy metals accumulation ability. In order to purify soil contaminated with arsenic by P. multifida, the most economical and effective purification method is deemed not only to cultivate after adjusting pH of contaminated soil to 7∼8 using Ca(OH)2, and treating with 2.0 g·kg-1 urea and 200 g·m-2 citric acid, and planting with 20x20 cm of planting density under the shading condition, but also harvesting aerial part once in fall.