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A preliminary environmental assessment of four heavy metals (Mn, Pb, Zn and Fe) on the coast of Campeche, Mexico was carried out. Surface sediments (0–10 cm), water and plants were collected in four sites of the coastline to obtain information about the levels and spatial distribution of the selected elements. The bioconcentration factor (BCF) was calculated for plants, where the BCF of Mn (3.375–3.558) and Zn (0.291–0.888) were high for Conocarpus erectus (button mangrove) and the BCF of Fe ranged from 0.022 to 0.023 in Laguncularia racemosa (white mangrove). This study showed that a significant source of metal contamination in the coastline of Campeche could be the discharge of municipal sewage. The relationship among metals, water, sediments and plants revealed a distinct behaviour of metals transportation in the marine environment. Mangroves operated as excluder species for nonessential metals (Pb) and accumulators for essential metals (Zn). Results showed that mangroves could be employed as a phytostabiliser of heavy metals.

Laboratory and greenhouse experiments with Cyperus laxus Lam were conducted to determine the rate and extent of phytoremediation and the effect of hydrocarbons on the cytochrome P450 EROD (7-ethoxyresorufin-O-deethylase) enzymatic activity in roots. Plants were cultivated on hydrocarbon-contaminated soil (HCS) and spiked perlite. Phytoremediation was evaluated using 6.5 kg HCS (173 +/- 15 mg total petroleum hydrocarbons [TPH] g(-1) of dry soil) pots at different moisture contents; the average removal rate was 3.46-0.25 mg TPH g(-1) dry soil month(-1) and 48% was removed when moisture was kept at 60%. The aromatic hydrocarbon fraction was the mostly removed, 60%; aliphatic, 51%; and polar 24% after 24-month experiments. In unplanted pots, TPH concentration did not exhibit significant differences with respect to the initial concentration. We confirmed that the presence of hydrocarbons induced ERODactivity up to 6.5-fold. Moreover, short-term experiments (up to 13 d) with spiked perlite demonstrated that two EROD activities in roots contributed to the total detected; 60% was found in the cytosolic and 40% in the microsomal fraction. To our knowledge, this is the first work that tries to build links between the hydrocarbon-inducible character of ERODactivity in roots and the phytoremediation ability of C. laxus in highly contaminated soils.

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