Heavy Metal Lability in Porewater of Highway Detention Pond Sediments in South-Eastern France in Relation to Submerged Vegetation

Abstract

Highway detention ponds can fill with sediments from runoff water loaded with trafficrelated materials. Sediment disposal is problematic and various protocols are currently studied, including phytoremediation. Here we present a preliminary study on four highway detention ponds in southern France to identify key sediment characteristics. Our objectives were to characterize metal content and physicochemical properties of the sediments and to evaluate the role of charophytes, which grow spontaneously in ponds, on metal lability. Vegetated and non-vegetated areas were compared. The lability of Mn, Cu, Zn, and Pb complexes was greater in the presence of charophytes. No variation in grain size composition was observed between non-vegetated and vegetated areas. These results may be useful to implement a phytoremediation strategy using those spontaneous charophytes. Our results suggest that local factors may impact sediment characteristics: for instance, strong gusts of wind, typical of southern France climate, may blow particles (some of them not related to traffic) in and out of detention ponds.

Trace metal extraction and biomass production by spontaneous vegetation in temporary Mediterranean stormwater highway retention ponds: Freshwater macroalgae (Chara spp.) vs. cattails (Typha spp.)

“…The difference between MRA and the three other ponds is due to a high concentration of carbonate previously reported (Triboit et al, 2010) and may also be related to the fact that the main Chara species here was C. vulgaris and not C. globularis.…”

“…Expressing metal contents in sediment per area unit of pond showed that there was a better homogeneity of values for Pb (ranging from 677 to 1261 mg m À2 ) and Zn (ranging from 6153 to 9091 mg m À2 ) than for Cd (ranging from 6 to 18 mg.m À2 ) and Cu (ranging from 1203 to 6707 mg m À2 ) in the sediments (Supplementary data 2). These results showed that whatever the technical characteristics of the ponds (Triboit et al, 2010), Pb and Zn contents retained in sediment were similar. However, higher Cd and Cu contents in sediment per area unit were found in MRA pond in which the sediment amount was higher with a higher level of mineral matter than in the other ponds.…”

“…Several studies have shown that the genus Chara was considered as hyperaccumulator of heavy metals even in unpolluted natural aquatic ecosystem (Lacerda et al, 1992). In a previous study, we showed that the lability of Cu, Zn, and Pb complexes in sediments of motorway ponds was greater in the presence of Chara meadows than without vegetation (Triboit et al, 2010). These metals and also Cd primarily originate from vehicular traffic (Gunawardana et al, 2012).…”

“…Four highway retention ponds lining the routes A7 and A54 in South-East France, named MRA, GRA, GRB and GRD were selected based on feature similarities and the location map was presented previously (Triboit et al, 2010). The first one was located near Avignon, along A7 highway, the others being located next to Salonde-Provence, along A54 highway.…”

“…Limit of detection was 0.5 mg kg À1 DW for Cd. Concentrations of Zn, Pb, Cu, Cd, Mn and Fe were measured in the sediments porewater with the Diffusive Gradients in Thin films (DGT) technique, as previously described (Triboit et al, 2010). DGT units were fully immersed at 2 cm depth below the sediment surface (6 per ponds).…”