Determination of polybrominated diphenyl ethers in soil and sediment from an electronic waste recycling facility

In this study samples of ten species of fish were analyzed for concentrations of organochlorine pesticides, PCBs and heavy metals (Pb, Cd, and Cu). Fish were captured using electric fishing on ten sites along the Dr?me river (Rh?ne-Alpes region). Quantitative determination of the organochlorine and PCBs compounds was performed by gas chromatography-electron-capture detection (GC-ECD). The concentrations of heavy metals were determined by atomic absorption spectrophotometry. Samples contained detectable concentrations of lindane, PCBs, and heavy metals but at concentrations below the maximum residue limit (MRL). Non-parametric statistical analysis was performed to distinguish groups of sites with different levels of contamination. PCBs concentrations increased along the river with four groups of sites significantly different from each other. Cadmium concentrations were below the MRL. Lead contamination showed two groups significantly different and a repartition similar to PCBs. Copper contamination was correlated with the localization of vineyards. We assessed the potential effects of contamination the otter (Lutra lutra). The concentrations of all pollutants analyzed in fish sampled in this study are lower than the threshold values described in literature. The Dr?me river is relatively unpolluted river, and the establishment of otter populations should not be affected by pollution.     

Effects of leachate recirculation on biogas production from landfill co-disposal of municipal solid waste,sewage sludge and marine sediment

Leachate recirculation is an emerging technology associated with the management of landfill. The impact of leachate recirculation on the co-disposal of three major wastes (municipal solid waste, sewage sludge and sediment dredgings) was investigated using a laboratory column study. Chemical parameters (pH, COD, ammoniacal-N, total-P) and gas production (total gas volume, production rates and concentrations of CH4 and CO2) were monitored for 11 weeks. Leachate recirculation reduced waste-stabilization time and was effective in enhancing gas production and improving leachate quality, especially in terms of COD. The results also indicated that leachate recirculation could maximize the efficiency and waste volume reduction rate of landfill sites.     

Copper tolerance,uptake and accumulation by Phragmites australis

Copper (Cu) uptake and accumulation of five populations of Phragmites australis growing in two mine sites (Parys Mountain, Wales, UK and Plombières, Belgium) contaminated with Cu and three 'clean' sites (Felixstowe, UK; Wisbech, UK and Mai Po, Hong Kong) were studied under field and glasshouse conditions. Cu tolerances in these populations of seedlings raised from seeds collected from the above five sites were also studied under glasshouse conditions. Although concentrations of Cu in the plant tissues (leaves, stems, rhizomes and roots) of P. australis and the associated soils from the Cu-contaminated sites were significantly higher than those of the plant tissues and the soils collected in the clean sites, small differences were found between the two Cu-contaminated populations and the three clean populations when seedlings were grown in 0.1 and 0.5 microg ml(-1) Cu treatment solutions. In general, different populations of seedlings showed similar growth responses, metal uptake and indices of Cu tolerance when cultured in the same Cu treatment solution for 3 weeks. There was insufficient evidence to support the hypothesis that the Cu-contaminated populations have evolved to Cu-tolerant ecotypes.     

Chemical speciation and extractability of Zn,Cu and Cd in two contrasting biosolids-amended clay soils

An incubation experiment was conducted to study the chemical speciation and extractability of three heavy metals in two contrasting biosolids-amended clay soils. One was a paddy soil of pH 7.8 and the other was a red soil of pH 4.7 collected from a fallow field. Anaerobically digested biosolids were mixed with each of the two soils at three rates: 20, 40 and 60 g kg(-1) soil (DM basis), and unamended controls were also prepared. The biosolids-amended and control soils were incubated at 70% of water holding capacity at 25 degrees C for 50 days. Separate subsamples were extracted with three single extractants and a three-step sequential extraction procedure representing acetic acid (HOAc)-soluble, reducible and oxidisable fractions to investigate the extractability and speciation of the heavy metals. As would be expected, there were good relationships between biosolids application rate and metal concentrations in the biosolids-amended soils. The three heavy metals had different extractabilities and chemical speciation in the two biosolids-amended soils. Ethylene diamine tetraacetic acid extracted more Cu, Zn and Cd than did the other two single extractants. The oxidisable fraction was the major fraction for Cu in both biosolids-amended soils and the HOAc-soluble and reducible fractions accounted for most of the Zn. In contrast, Cd was present mainly in the reducible fraction. The results are discussed in relation to the mobility and bioavailability of the metals in polluted soils.     

The role of arbuscular mycorrhiza in zinc uptake by red clover growing in a calcareous soil spiked with various quantities of zinc

Three pot experiments were conducted to investigate the role of arbuscular mycorrhiza (AM) in Zn uptake by red clover. Plants inoculated with Glomus mosseae and uninoculated controls were grown in a sterile calcareous soil in 'Plexiglas' (Acrylic) containers with two nylon net partitions (30 microm mesh) to separate the central root zone from the two outer hyphal zones. The effects of mycorrhiza on plant growth and Zn uptake changed dramatically with increasing Zn addition level (range 0-1200 mg kg(-1)) in the root zone. With Zn addition levels <300 mg kg(-1), added Zn did not affect plant yield and above the critical level plant yield gradually decreased but was always higher for mycorrhizal than for controls. Below the critical Zn application rate (50 mg kg(-1)), Zn uptake was enhanced while above this level Zn translocation to the shoots decreased. At all Zn addition levels, mycorrhizal colonization increased Zn absorption and accumulation in the roots, and this may help to explain the alleviation of Zn toxicity at high Zn application rates. As expected, AM colonization enhanced P nutrition and hence yield at all added Zn levels studied. Efforts were made to obtain direct evidence for hyphal contribution to Zn uptake by applying both Zn to the hyphal growth zone and additional P to the root zone to avoid the 'growth dilution effect'. The data demonstrate that mycorrhizal hyphae could absorb Zn directly from the soil and then transfer it to the plant roots. The hyphal contribution to Zn uptake by the host plant reached its maximum value at the Zn addition level of 50 mg kg(-1), in which Zn uptake via the extramatrical hyphae comprised 22% of total uptake, thus confirming the critical Zn application level found previously.     

HPLC pigment analysis of marine phytoplankton during a red tide occurrence in Tolo Harbour,Hong Kong

A red tide was detected in the inner parts of Tolo Harbour, Hong Kong, in November 2000. Water samples were collected from a fixed station at the centre of the red tide patch for microscopic analysis of phytoplankton community composition and high performance liquid chromatography (HPLC) analysis of phytoplankton pigments. At the peak of the red tide on 24 November 2000, phytoplankton was dominated by the dinoflagellate Scrippsiella trochoidea. The red tide began to decline at the end of November and, by 1 December 2000, the phytoplankton was dominated by diatoms. Chlorophylls and carotenoids in water samples were analysed using HPLC pigment separation technique. Dinoflagellates were indicated by the signature pigment peridinin. Significant correlation (r=0.999) was found between the peridinin concentration and dinoflagellate density. A decrease in peridinin and an increase in fucoxanthin, a major carotenoid in diatoms, marked the shift in phytoplankton composition at the end of the red tide. HPLC analysis also revealed the occurrence of minor phytoplankton groups that are difficult to identify by light microscopy. Red tide monitoring and study of red tide dynamics in Hong Kong have been based on cell counting and spectrophotometric or fluorometric measurement of chlorophyll a. HPLC pigment analysis provides an effective alternative for investigating phytoplankton dynamics during red tide and other algal blooms.     

Enhanced uptake of As, Zn, and Cu by Vetiveria zizanioides and Zea mays using chelating agents

Vetiveria zizaniodes (vetiver) is commonly known for its effectiveness in soil and sediment erosion control. It can tolerate to extreme soil conditions and produce a high biomass even growing in contaminated areas. Zea mays (maize) can also produce a very high biomass with a fast growth rate and possesses some degree of metal tolerance. A greenhouse study was conducted to investigate the feasibility of using vetiver and maize for remediation of arsenic (As)-, zinc (Zn-), and copper (Cu)-amended soils and evaluate the effects of chelating agents on metal uptake by these plants. Vetiver had a better growth (dry weight yield of root and shoot) than maize under different treatment conditions. The effects of different chelating agents on As, Zn, and Cu extraction from soil to soil solution were studied. Among the nine chelating agents used, it was noted that 20 mmol NTA could maximize As and Zn bioavailability, while 20 mmol HEIDA could maximize Cu bioavailability in the soil solution. The surge time in maximizing metal uptake ranged from 16 to 20 days which indicated that timing on plant harvest was an important factor in enhanced metal accumulation. In general, vetiver was a more suitable plant species than maize in terms of phytoextraction of metals from metal-contaminated soil. Application of NTA in As-amended soil and HEIDA in Cu-amended soil at the rate of 20 mmol kg(-1) increased 3-4-fold of As and Cu in shoot of both plants, whereas application of NTA (20 mmol kg(-1)) increased 37- and 1.5-fold of Zn accumulation in shoot of vetiver and maize, respectively. The potential environmental risk of metal mobility caused by chelating agents used for phytoextraction should not be overlooked.     

Performance of different microalgal species in removing nickel and zinc from industrial wastewater

A series of batch experiments was conducted to compare the ability of 11 microalgal species of the same cell density in removing nickel (Ni) and zinc (Zn) from synthetic wastewater. These included Chlorella vulgaris (commercially available), Chlorella sorokiniana and Scenedesmus quadricauda (isolates from polluted water of Wuhan, China), and eight different isolates from Hong Kong. The Wuhan isolate of Scenedesmus removed most Ni, probably due to its large biomass. Nickel concentration was reduced from an initial 30 to 0.9 mg/l after 5 min (97% Ni removal), and further declined to 0.4 mg/l after 90 min of treatment. In wastewater containing 30 mg/l Ni and 30 mg/l Zn, more than 98%, Ni and Zn were removed simultaneously at the end of 5 min treatment, indicating that the presence of Zn in wastewater did not affect Ni removal by this Scenedesmus isolate. The second most effective species for Ni removal was an isolate, tentatively identified as Chlorella miniata, Ni concentration was reduced to 10 mg/l after 90 min, and was only slightly interfered by the presence of Zn. In terms of metal removal per unit biomass or unit surface area of algal cells, C. miniata was the best species in removing Ni and Zn. At the other extreme, one Hong Kong isolate (Synechocystis sp.) did not remove any Ni and only achieved 40% Zn removal. Performance of the other isolates was comparable with the commercial C. vulgaris, less than 50% Ni was removed after 5 h of treatment and Ni removal was significantly reduced by the presence of Zn. All algae tested were found to be viable, showing these 11 species could tolerate a mixture of 30 mg/l Ni and 30 mg/l Zn in wastewater.