Left photo: ARDEC senior researcher during field planting of Ipil (Intsia bijuga). Right photo: Field measurement of field planted Molave (Vitex paviflora)

The Agroforestry Research, Development and Extension Center (ARDEC) is conducting a study on the potential of six forest tree species such as Molave (Vitex paviflora Juss), Narra (Pterocarpus indicus Willd), Ipil (Instia bijuga (Colebr.) O. Ktze.), Bani (Pongomia pinnata (L.) Merr), Nato (Palaquium luzoniense (F. Vill.) Vidal) and Balayong (Cassia nodosa) in the phytostabilization of a mercury (Hg) contaminated area in Puerto Princesa City, Palawan. The experiment is particularly being implemented in the abandoned mining site of Palawan Quicksilver Mines Inc. (PQMI), a former mercury-ore-producing mining company which operated from 1953 to 1976 in Barangay Sta. Lourdes.

The study uses phytostabilization strategy, a phytoremediation which aims at reducing the mobility of contaminants in the soil through plant accumulation in roots and leaf tissues therefore, minimizing leaching of contaminants to groundwater.

The implementation of the study started on February 2019 in collaboration with the Mines and Geosciences Bureau (MGB). The general purpose of the study is to generate technology that can help immobilize soil-Hg contaminants in the area.

The field-planting in observation plots was conducted on October 2019 during the wet season. Initial data gathered for the growth performance of planted forest tree species showed 90 to 94 percent mean survival rate for all species. However, only Narra and Molave show promising mean growth increment in terms of height and diameter.

The plant-tissue and rhizospheric soil sample collection and analysis which are the major requirements to determine the capability of a planted test plant for phytostabilization are scheduled in October 2020. Scientifically, the positive growth performance does not speak for the potential of the planted test-plants in phytostabilization of Hg-contaminated area. Other parameters such as soil, total Hg and plants total accumulated Hg are needed to determine the potential of the test-plants for phytostabilization.

Phytostabilization using forest trees has been suggested as a cost-efficient, socially acceptable, sustainable, and ecologically-sound solution to remediate heavy metal-contaminated areas. It is ideal to use forest trees in phytostabilization because they produce high biomass that serves as storage for contaminants being absorbed, and provide aesthetic value  to the area. Rodrigo Real, ARDEC