Phytoremediation Test for Arsenics Pollution Control in Contaminated Industrial Soil in Porto Marghera

摘要

A field test to evaluate the suitability of phytoremediation to cope with the presence of arsenic (As) in an industrial area located in Porto Marghera (Venice Lagoon, Italy) is under study. The polluted area is an artificial island, 41 ha broad, built using different materials, including industrial by-products. Part of the soil top layer (0-2 m) is affected by the presence of As, representing a potential concern to the underneath water table. Both the phytostabilisation potential using rapid-growth trees (poplars and willows) and the phytoextraction efficiency of the hyperaccumulator fern Pteris vittata are investigated. Tests are carried on an experimental 40x80 m2 field, half planted with trees, 1/4 with fern and Va used as control. Two clones of Populus deltoides (Dvina, Lena), one of P.x canadensis (Neva), two of Salix matsudana (S76-005 and S76-008), and one of Salix alba (SI64-017) were planted in the experimental area, 1600-sq-m, in a randomized block design with four replications at a density of Short Rotation Coppice (6000 plants/ha). The phytostabilisation affected by two-year-old salicaceae is evaluated as As-leaching reduction from the topsoil to the water table, as a consequence of the rain water infiltration reduction caused by the intensive transpiration activity of the trees, which ranged between 2 and 2.2 mm day~(-1). With this purpose, the water balance of the experimental area and the As content in groundwater are measured and compared with a neighbouring control area vegetated with indigenous weeds. Results indicated that clones of Populus deltoids and canadensis were more suitable than clones of salix in controlling water leakage to the water table. Organic matter in the soil sample taken around populus clones was also higher (2.5%) than in other samples (1.5%). The different clones are also evaluated for other useful characteristics relevant to As control, as accumulation capacity of As in leaves and wood and rate of growth, in order to select the best fitted clone for this specific environment. Results show that the populus clone Neva was the most acclimated to this environment showing highest growth rates and the best physiological performance.An Italian ecotype of the fern Pteris vittata was found in the Venice region, and approximately 100 plants were propagated and planted in the experimental area. Fern plants confirmed their high ability to accumulate As (about 400 ug Kg~(-1) d.m. in old leaves and 200 μg Kg~(-1) d.m ) in the aboveground plant organs. Plants showed, however, a reduced biomass accumulation compared to the same plants grown in a clean soil nearby.