Potentially toxic element accumulation of bryophyte taxa in contaminated soils at Tak Province, Thailand

Three sampling locations, Mae Sot National Forest, Pha Daeng waterfall, and agricultural land in Pha De, were representative locations in contaminated areas for determining bryophyte communities and their potentially toxic element (PTE) accumulation capacity. A total of 18 bryophyte taxa from 10 genera and 10 families were recorded. Fissidentaceae is the dominant family in the study area. Pollution load index (PLI) indicated that anthropogenic activities, particularly zinc (Zn) mining activities were key causes of PTE pollution in soils, particularly cadmium (Cd) and Zn. The order of Cd and Zn concentrations in bryophyte tissue as a function of sampling location was: agricultural area > waterfall > forest, where PTEs in bryophyte tissue were in the order Zn > Cd. Bryum coronatum showed significant Zn accumulation (>300,000 mg kg(-1)), while Philonotis thwaitessii had substantial Cd accumulation (50 mg kg(-1)). Principal component analysis (PCA) indicated that P. thwaitessii and Fissidens involutus had high correlation with Cd and Zn, which might be used as bioindicators in the Cd and Zn co-contaminated area. According to X-ray fluorescence analysis, the order of atomic percentage elemental composition in plant tissue was: Al > Fe > Pb > Cd > Zn > Cu > Ni > Cr > Mn. When taking Cd contents in phyllidium surfaces of bryophyte taxa into account, P. thwaitessii, Notothylas javanica and Splachnobryum oor-schotii may serve as phytoremediators of Cd because their percentage atomic Cd values were >10 %, and whole plant tissues had Cd concentrations exceeding 10 mg kg(-1). In light of its capacity for Cd phytoremediation and biomonitoring, P. thwaitessii may be the most suitable bryophyte taxon in the Mae Tao River Basin.