Metal accumulation by plants growing in China: Capacity, synergy, and moderator effects

Plant accumulation of heavy metals (HMs) has become a global concern, however, the bio-accumulation distributions, their inter-correlations, and relationships with influencing factors remain unknown at the national scale in China. Here, we investigate the bio-accumulation capacity, as indicated as bio-concentration factors (BCFs), for chromium (Cr), cadmium (Cd), lead (Pb), copper (Cu), and Zinc (Zn) across plants growing on China (span 22 provinces) and their relationships, based on national meta-analysis of 46 publications (210 species, and 66 families). Results showed that: (1) Plants show diverse capacity of HM accumulation. About 20.6% of the plant tissue cases indicates strong phytoremediation ability for HMs (i.e., Ln BCF > 0), including 38.5% of Cd, 28.5% of Cr, 11.9% of Cu, 7.6% of Pb, and 16.6% of Zn. The families with the greatest numbers of published strong HMs phytoremediation cases are Poaceae, Asteraceae, and Brassicaceae. (2) The capacity to uptake and accumulation one of these HMs is significantly correlated with the ability to absorb the others (p <.001) for both all plants and organs but differ in strength and degree of correlations. The synergistic effect of the accumulation of these metals is more stable in stems than other parts. Leaves and roots differ significantly in metal co-accumulating strengths and enrichment patterns. (3) Experimental factors affect the HM bio-accumulation processes and bio-mediated mechanisms and responsible for substantial heterogeneous in phytoremediation effectiveness. These findings suggest that the use of plant as a soil pollution indicator and phytoremediation technique, synergistic strategies of bio-accumulation as ecological indicators and bio-mediated mechanisms for phytoremediation of polymetallic contaminated areas, with considering sensitivity of influencing factors, might have a crucial effect on the eco-service, eco-environment, and land management and could reduce material hazards by increasing bio-accumulation efficiency, or could reduce human health risk by decreasing potential intake of HMs. We argue that this meta-analysis would aid the assessment of the strength of general HM risks, the evaluation of regional soil contamination hazards and consequences, and the configuration of plant species and traits efficiently for phytoremediation potential.