Phytoremediation of abandoned mine tailing ponds and hematology of cows grazing on copper-contaminated herbage in Brgy. [village]. Paco, Mankayan, Benguet [Philippines]

Mining activities in Mankayan, Benguet [Philippines] have produced abandoned mine tailing ponds with high concentration of heavy metals like copper that contaminated agricultural fields. This study characterized the surface horizon of an abandoned agricultural field, abandoned tailing pond overlaid with top soil and municipal bio waste (TP4), and abandoned tailing pond without any rehabilitation (TP3) and the changes on their properties after amendments of different levels of compost. The study also determined the phytoremediating mechanism of Paspalum conjugatum Berg. grown in various concentration of copper contaminated media amended by various levels of compost. Naturally dispersed plant propagules were also allowed to colonize (free colonization) treated plots with soil media amended with different levels of compost. The effects of copper containing herbage to the hematology of cows grazing on TP4 were also determined. Results showed that application up to 13.2 kg m-2 compost significantly improved pH and mean final OM content and caused significant reduction in exchangeable Cu in plots that utilized TP3 materials as based compared to unamended plots. Compost application of 4% (6.6 kg m-2) and 8% (13.2 kg m-2) to free colonization plots with soil materials from TP3 doubled vegetation cover from 18.33% in 0% compost application to 47.33%. On the other hand the addition of any level materials are already stable. However 5 kg m-2 compost amendment to control plots using agricultural soil significantly improved its soil final pH, but any levels of compost added did not have any significant changes on other soil properties. P. conjugatum was determined to be an effective agent only in phytostabilization due to its ability to retain copper in its roots. The plant was also able to significantly reduce exchangeable copper from 68.22 ppm in control plots with TP3 soil materials to 47.76 ppm at 6.6 kg m-2 compost application. This significant reduction of exchangeable copper was not observed in free colonization plots. The difference in results between P. conjugatum and free colonization plots shows that importance of P. conjugatum as a phytoremediating agent. It can significantly reduce copper in soil as compared to other plant species growing in the plots. It has Biological Concentration Factor (BCF) values that were greater than 1. However it has a Translocation Factor (TF) value of less than 1. Other plant species dominating the free colonization plots that can be utilized for phytostabilisation are: Cynodon dactylon, Axonopus compressus and Bidens pilosa. This differences in results between P. conjugatum and free colonization plots seemed to show the importance of P. conjugatum as a phytoremediating agent. It can significantly reduce copper in soil compared to other plant species growing in the free colonization plots. The cows grazing in TP4 were suffering from secondary copper toxicosis brought about by the continuous consumption of grasses with high levels of copper.