Risk assessment and source apportionment for PAHs in wetland sediment and biomonitoring by  Alternanthera ficoidea (L.) plant

The study focuses on monitoring of PAHs pollution in East Kolkata Wetland, a Ramsar site in India using biomonitoring potential of Alternanthera ficoidea (L.) plant. Root, shoot, leaves and rhizobium of the plant are checked with respect to PAHs accumulation and translocation. Measurement of total concentration of 16 priority PAHs in that wetland sediment (85.37±3.37 µg/g) along with Benzo[a]pyrene equivalent toxicity (21.252±0.96 µg/g) indicates high carcinogenic risk based on Canadian soil quality guidelines. The APTI value of Alternanthera ficoidea (22.25±0.12>17) recognizes it as tolerant species. SEM analysis of leaf sample shows stomatal blockage by particulate matter which implies PAHs storage in it. Different parts of the plant viz root, shoot, leaves and rhizobium show different uptake and distribution pattern of PAHs (∑ PAHsleaf : 420.23±0.60 µg/g, ∑ PAHsstem : 230.83±4.87 µg/g, ∑ PAHsroot 68.45±3.17µg/g and ∑ PAHsrhizobium (68.66±4.35 µg/g). Significance of the results is arbitrated based on one-way ANOVA (p (2.7×10-5<0.5)) and F (7.77) >Fcrit (2.49)). Determination of lipid content of leaf, root and stem reconfirms it as good bioaccumulator of PAHs. The study also highlights the LMW and HMW accumulation pattern in different parts of plants and translocation of PAHs from root is also described in connection. Source apportionment analysis based on some diagnostic ratios suggests that pyrogenic activities (more specifically vehicular emissions) are the potential contributor of PAHs sources in that wetland. Bioconcentration and translocation factors supports distributional pattern of PAHs in different parts of plants and moreover revealed that both air-to-leaf and sediment-to-root transfer pathways are contributor for bioaccumulation.