Uptake and accumulation of cadmium, lead and zinc by Siam weed [Chromolaena odorata (L.) King & Robinson

The Siam weed, Chromolaena odorata (L.) King & Robinson, Family Asteraceae, was found to be a new Pb hyperaccumulator by means of field surveys on Pb soil and hydroponic studies. Plants from field collection accumulated 1377 and 4236mgkg(-1) Pb in their shoots and roots, respectively, and could tolerate soil Pb concentrations up to 100000 mgkg(-1) with a translocation factor of 7.62. Very low concentrations of Cd and Zn were found in plants collected from the field. Under nutrient solution culture condition, C. odorata from the contaminated site (CS) and from non-contaminated site (NCS) grew normally with all three metals (Pb, Cd, Zn) supplied. However, the relative growth rates of all treated plants decreased with increased metal concentrations. The percentage uptakes of Pb, Cd, and Zn by C. odorata increased with increasing metal concentrations. Pb concentration in shoots and roots reached its highest values (1772.3 and 60655.7mgkg(-1), respectively) at a Pb supply level of 10mgl(-1). While the maximum concentrations of Cd (0.5mgl(-1)) in shoots and roots of C. odorata were 102.3 and 1440.9mgkg(-1), and the highest concentrations of Zn (20mgl(-1)) were 1876.0 and 7011.8mgkg(-1), respectively. The bioaccumulation coefficients of Pb and Cd were greater than 1000. These results confirm that C. odorata is a hyperaccumulator which grows rapidly, has substantial biomass, wide distribution and has a potential for the phytoremediation of metal contaminated soils.     

Sonochemical substrate selectivity and reaction pathway of systematically substituted azo compounds

The sonochemical degradation of the systematically substituted azo compound 2,7-dihydroxy-1-phenylazonaphthaline-3,6-disulfonic acid was investigated using a frequency of 850 kHz and an acoustic input power of 61 W. All derivatives were degraded completely within 6h by the ultrasonic treatment. Trifluoromethyl substituted azo compounds exhibited 2-3-fold higher degradation rates in comparison to the reference hydrogen substituted azo compound (k=0.54 h(-1)). In contrast to enzymatic processes (azoreductase or laccase), the ultrasonic treatment for these ortho-, meta-, and para-substituted azo compound showed 1.5-50-fold higher degradation rates. Additionally the ultrasound treatment was characterized by shorter reaction times. As a result of the detection and identification of specific intermediates using LC-MS a reaction pathway of the sonochemical degradation of the analysed azo compound is proposed indicating the formation of cyclohexadienone and naphthalene quinone derivatives.     

Binding affinity of proanthocyanidin from waste Pinus radiata bark onto proline-rich bovine achilles tendon collagen type I

Binding affinity of proanthocyanidin (PA) purified from Pinus radiata bark waste onto bovine Achilles tendon collagen (type I) was studied. Adsorption of PA onto the collagen was optimized by examining pH, contact time and temperature. The adsorption was pH-dependent. The maximum adsorption capacity (Q(0)) of PA on collagen was found to be 211 mg g(-1) using the Langmuir isotherm. Comparison between two adsorbents also showed that collagen had higher adsorptivity of approximately 20% more than PVPP (polyvinyl polypyrrolidone). The high affinity between PA and collagen was further confirmed in solvent solubility experiments. The observed solvent resistance was thought to be mainly due to a hydrophobic stacking mechanism reinforced by hydrogen bonding. FT-IR spectra clearly indicated the presence of PA adsorbed on collagen. The results have interesting implications that PA can be a good protective agent for collagen against collagenase and other enzymes.     

Chromate transport through columns packed with surfactant-modified zeolite/zero valent iron pellets

Chromate transport through columns packed with zeolite/zero valent iron (Z/ZVI) pellets, either untreated or treated with the cationic surfactant hexadecyltrimethylammonium (HDTMA), was studied at different flow rates. In the presence of sorbed HDTMA, the chromate retardation factor increased by a factor of five and the pseudo first-order rate constant for chromate reduction increased by 1.5-5 times. The increase in rate constant from the column studies was comparable to a six-fold increase in the rate constant determined in a batch study. At a fast flow rate, the apparent delay in chromate breakthrough from the HDTMA modified Z/ZVI columns was primarily caused by the increase in chromate reduction rate constant. In contrast, at a slower flow rate, the retardation in chromate transport from the HDTMA modified Z/ZVI columns mainly originated from chromate sorption onto the HDTMA modified Z/ZVI pellets. Due to dual porosity, the presence of immobile water was responsible for the earlier breakthrough of chromate in columns packed with zeolite and Z/ZVI pellets. The results from this study further confirm the role of HDTMA in enhancing sorption and reduction efficiency of contaminants in groundwater remediation.     

Enhanced phytoremediation of arsenic contaminated land

In an attempt to clean up arsenic (As) contaminated soil, the effects of phosphorus (P) fertilizer and rhizosphere microbes on arsenic accumulation by the silverback fern, Pityrogramma calomelanos, were investigated in both greenhouse and field experiments. Field experiments were conducted in Ron Phibun District, an As-contaminated area in Thailand. Soil (136-269 microg As g(-1)) was collected there and used in the greenhouse experiment. Rhizosphere microbes (bacteria and fungi) were isolated from roots of P. calomelanos growing in Ron Phibun District. The results showed that P-fertilizer significantly increased plant biomass and As accumulation of the experimental P. calomelanos. Rhizobacteria increased significantly the biomass and As content of the test plants. Thus, P-fertilizer and rhizosphere bacteria enhanced As-phytoextraction. In contrast, rhizofungi reduced significantly As concentration in plants but increased plant biomass. Therefore, rhizosphere fungi exerted their effects on phytostabilization.     

Variations in PCB concentrations between genders of six warmwater fish species in Lake Logan Martin, Alabama, USA

We collected and analyzed 955 individual fish (six species) for sexual differences in PCB bioaccumulations from a southeastern, USA reservoir. Using 2-way ANCOVAs, we found significant differences in fillet PCB concentrations between sexes for channel catfish (Ictalurus punctatus), largemouth bass (Micropterus salmoides) and spotted bass (Micropterus punctulatus). Striped bass (Morone saxatilus), black crappie (Pomoxis nigromaculatus) and freshwater drum (Aplodinotus grunniens) did not display differences between sexes in PCB concentrations. We suspect that sexual differences may be due to biological differences in reproduction, relative motility and lipid deposition. For one species (striped bass), sexual differences in PCB concentrations were inconsistent with a study in the Hudson River suggesting that sexual differences in bioaccumulations can change across ecosystems. Two species which did show sexual differences, largemouth bass and channel catfish, are often chosen as representative species (e.g., "piscivore" and "benthivore") in contaminant monitoring in many USA states indicating human consumption and risk management decisions would be improved if an equal number of male and female fish were included in composite PCBs analysis. This could reduce variability in fish PCBs data from which consumption advisories are based.     

Seasonal variations of selected herbicides and related metabolites in water, sediment, seaweed and clams in the Sacca di Goro coastal lagoon (Northern Adriatic)

This study assesses the status of Sacca di Goro coastal lagoon (Northern Adriatic, Italy) with respect to watershed pollution. Because 80% of its watershed is devoted to agriculture, plant protection products and their metabolites were found in the water column, sediments (the upper 0-15 cm layer), macroalgae (Ulva rigida) and clams (Tapes philippinarum). Five seasonal sampling campaigns were performed from May 2004 to April 2005 and concentrations measured in five stations in the lagoon and six in the watershed. Relatively high concentrations of the s-triazine - terbuthylazine -, urea herbicides - diuron - and alachlor were detected through the year mainly at stations directly influenced by the Po di Volano inflow. The concentrations of products in use follow a clear seasonal pattern with spring peaks. This pattern is also visible in the sediments as well as in biota. Among metabolites, hydroxylated compounds prevailed, often with concentrations greater than those of the parent compounds. For the most part of the year, the concentrations in biota were close to detection limits, with concentration peaks in spring.     

A comparative study on characterization of textile wastewaters (untreated and treated) toxicity by chemical and biological tests

Toxicity of textile wastewaters (untreated and treated) and their ingredient chemicals was quantified in terms of their chemical characteristics, fish (Gambusia affinis) mortality and end point growth responses of duckweed (Lemna aequinoctialis) in short-term bioassays. Other parameters of fish bioassay were erythrocyte morphology and its counts. Despite of a definite correlation between data of biological tests (LC/EC(50) values) with that of chemical tests, biological tests were found to be relatively more sensitive to both wastewaters and ingredient chemicals. Amongst all the examined parameters of test organisms, fish RBCs (morphology and counts) sensitivity to pollutants in the wastewaters was usually maximum and therefore, their study should be included in the routine fish bioassay. Other advantage of biological test such as on Lemna is even detection of eutrophic potential of wastewaters, as noted at their higher dilutions. The ingredient chemicals (major) contributing maximum toxicity to textile dye wastewater were, acids (HCl and H(2)SO(4)), alkali (Na(2)O SiO(2)), salt (NaNO(2)) and heavy metal (Cu), whereas dyes (4) were relatively less toxic.     

Accumulation and partitioning of heavy metals in mangroves: a synthesis of field-based studies

We report the findings of a comparative analysis examining patterns of accumulation and partitioning of the heavy metals copper (Cu), lead (Pb) and zinc (Zn) in mangroves from available field-based studies to date, employing both species level analyses and a phylogenetic approach. Despite mangroves being a taxonomically diverse group, metal accumulation and partitioning for all metals examined were broadly similar across genera and families. Patterns of metal accumulation were also similar regardless of whether species were classified as salt secreting or non-secreting. Metals were accumulated in roots to concentrations similar to those of adjacent sediments with root bio-concentration factors (BCF; ratio of root metal to sediment metal concentration) of 1< or =. Root BCFs were constant across the exposure range for all metals. Metal concentrations in leaves were half that of roots or lower. Essential metals (Cu and Zn; translocation factors (TF; ratio of leaf metal to root metal concentration) of 0.52 and 0.53, and leaf BCFs of 0.47 and 0.51, respectively) showed greater mobility than non-essential metals (Pb; TF of 0.31 and leaf BCF of 0.11). Leaf BCFs for the essential metals Cu and Zn decreased as environmental concentrations increased. The non-essential metal Pb was excluded from leaf tissue regardless of environmental concentrations. Thus mangroves as a group tend to operate as excluder species for non-essential metals and regulators of essential metals. For phytoremediation initiatives, mangrove ecosystems are perhaps best employed as phytostabilisers, potentially aiding in the retention of toxic metals and thereby reducing transport to adjacent estuarine and marine systems.     

Kinetic and adsorption study of acid dye removal using activated carbon

The adsorption of three acid dyes, Acid Red 97, Acid Orange 61 and Acid Brown 425 onto activated carbon was studied for the removal of acid dyes from aqueous solutions at room temperature (25 degrees C). The adsorption of each dye with respect to contact time was then measured to provide information about the adsorption characteristics of activated carbon. The rates of adsorption were found to conform to the pseudo-second-order kinetics with a good correlation. The experimental isotherms obtained, except for Acid Orange 61 studied in mixture, were of the S-type in terms of the classification of Giles and co-workers. The best fit of the adsorption isotherm data was obtained using the Freundlich model. When a comparative study was made of the results obtained with single and mixed dyes, it can be seen that some of them affect others and modify their behavior in the adsorption process. The results indicate that activated carbon could be employed for the removal of dyes from wastewater.