The Use of Vetiver Grass to Rehabilitate City Garbage Leachate by Isotope Techniques

摘要

The objective of this research work was to solve the impact of leachate from city garbage on the environment through to the use of vetiver grass. The experiment was conducted in the Royal Working Area at the Doi Tung Development project, Chiang Rai Province, northern Thailand during 2001-03.The city garbage was packed in circular cement blocks, 1.5m diam. And 1.5m high. Each block was covered with topsoil to a depth of 10 cm. The leachate from the garbage was drained through a pipe fixed at 120cm and trapped for analysis. The experimental design was an RCB with 5 replications, having 4 treatments in each replication. The treatments included: (i) control, (ii) vetiver grass planted on 50% of the area with the spacing of 10×10 cm, (iii) vetiver grass planted on 75% of the area with the spacing of 10 ×10 cm, (iv) vetiver grass planted on 100% of the area with 10×10cm spacing. Root distribution of the vetiver grass was studied using ~(32)P techniques. ~(32)P solution was injected into the garbage at the depths of 30,60,90,and 120 cm. The results indicated,more roots were found at 30cm depth, but clearly declined at lower depths. The ~(32)P radioactivity was detected at the edge of the block for each depth. Also observed was that the dense roots of vetiver entangled and acted as a underground dam. Treatment # 4 showed the full efficiency in trapping leachate. Moreover, vetiver could absorb more macro elements when it was older. The concentration of residual sodium carbonate (RSC) and sodium absorption ratio (SAR) were f round to be extremely high in the garbage residue, making it unsuitable for normal growth of plants. Yet, the vetiver grass was able to grow in this adverse condition-a miracle plant indeed!