10th U6+ Consortium of African Universities International Conference

Chromium-laden tannery effluent discharged into the Sagana River, Kirinyaga County, Kenya, exceeds the regulatory thresholds set by NEMA and the WHO, threatening aquatic biodiversity, irrigation water quality, and community health. Conventional treatment technologies remain economically prohibitive to resource-constrained Kenyan industrial settings, renewing interest in rhizofiltration using locally abundant hydrophytic macrophytes as a low-cost, ecologically congruent alternative. Colocasia esculenta (taro) and Xanthosoma sagittifolium (cocoyam), two Araceae species widely distributed along tropical riparian corridors, present compelling rhizofiltration potential owing to their extensive root architecture, tolerance to waterlogging, and prolific biomass. However, the mechanistic pathways governing chromium uptake, translocation, biotransformation, and sequestration in these species remain critically underexplored. This review synthesizes current literature on chromium speciation chemistry, sulfate–chromate transporter competition, subcellular sequestration via cell-wall binding and phytochelatin-mediated vacuolar chelation, antioxidant enzyme dynamics, and rhizospheric microbiome contributions to chromium bioavailability, drawing on comparative evidence from related Araceae and hydrophytic taxa where direct evidence is absent. Critical knowledge gaps are identified in the absence of subcellular chromium localization data for either species, unresolved bioconcentration and translocation factor behavior under authentic multi-contaminant effluent matrices, the limited characterization of the native rhizosphere microbiome's functional contribution to chromium speciation transformation, the near-complete absence of published chromium performance data for Xanthosoma sagittifolium species, and the paucity of dose-response evidence under field-realistic effluent concentration gradients. These gaps collectively establish the empirical and mechanistic foundation indispensable for validating either species as a scientifically defensible, scalable rhizofiltration phytosystem for chromium-laden industrial effluent remediation within Kenya and comparable sub-Saharan African contexts.