Uptake and loss of dissolved 109Cd and 75Se in estuarine macroinvertebrates

Semaphore crabs (Heloecius cordiformis), soldier crabs (Mictyris platycheles), ghost shrimps (Trypaea australiensis), pygmy mussels (Xenostrobus securis), and polychaetes (Eunice sp.), key benthic prey items of predatory fish commonly found in estuaries throughout southeastern Australia, were exposed to dissolved (109)Cd and (75)Se for 385 h at 30 k Bq/l (uptake phase), followed by exposure to radionuclide-free water for 189 h (loss phase). The whole body uptake rates of (75)Se by pygmy mussels, semaphore crabs and soldier crabs were 1.9, 2.4 and 4.1 times higher than (109)Cd, respectively. There were no significant (P>0.05) differences between the uptake rates of (75)Se and (109)Cd for ghost shrimps and polychaetes. The uptake rates of (109)Cd and (75)Se were highest in pygmy mussels; about six times higher than in soldier crabs for (109)Cd and in polychaetes for (75)Se - the organisms with the lowest uptake rates. The loss rates of (109)Cd and (75)Se were highest in semaphore crabs; about four times higher than in polychaetes for (109)Cd and nine times higher than in ghost shrimps for (75)Se - the organisms with the lowest loss rates. The loss of (109)Cd and (75)Se in all organisms was best described by a two (i.e. short and a longer-lived) compartment model. In the short-lived, or rapidly exchanging, compartment, the biological half-lives of (75)Se (16-39 h) were about three times greater than those of (109)Cd (5-12h). In contrast, the biological half-lives of (109)Cd in the longer-lived, or slowly exchanging compartment(s), were typically greater (1370-5950 h) than those of (75)Se (161-1500 h). Semaphore crabs had the shortest biological half-lives of both radionuclides in the long-lived compartment, whereas polychaetes had the greatest biological half-life for (109)Cd (5950 h), and ghost shrimps had the greatest biological half-life for (75)Se (1500 h). This study provides the first reported data for the biological half-lives of Se in estuarine decapod crustaceans. Moreover, it emphasises the importance of determining metal(loid) accumulation and loss kinetics in keystone prey items, which consequently influences their trophic transfer potential to higher-order predators.     

Isolation and characterization of 1,2,4-trichlorobenzene mineralizing Bordetella sp. and its bioremediation potential in soil

A soil which has been polluted with chlorinated benzenes for more than 25 years was used for isolation of adapted microorganisms able to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB). A microbial community was enriched from this soil and acclimated in liquid culture under aerobic conditions using 1,2,4-TCB as a sole available carbon source. From this community, two strains were isolated and identified by comparative sequence analysis of their 16S-rRNA coding genes as members of the genus Bordetella with Bordetella sp. QJ2-5 as the highest homological strain and with Bordetella petrii as the closest related described species. The 16S-rDNA of the two isolated strains showed a similarity of 100%. These strains were able to mineralize 1,2,4-TCB within two weeks to approximately 50% in liquid culture experiments. One of these strains was reinoculated to an agricultural soil with low native 1,2,4-TCB degradation capacity to investigate its bioremediation potential. The reinoculated strain kept its biodegradation capability: (14)C-labeled 1,2,4-TCB applied to this inoculated soil was mineralized to about 40% within one month of incubation. This indicates a possible application of the isolated Bordetella sp. for bioremediation of 1,2,4-TCB contaminated sites.     

Atrazine sorption and fate in a Ultisol from humid tropical Brazil

This study combined laboratory based microcosm systems as well as field experiments to evaluate the mobility of atrazine on a Ultisol under humid tropical conditions in Brazil. Results from sorption experiments fit to the Freundlich isotherm model [K(f) 0.99 mg kg(-1)/(mg l(-1))(1/n)], and indicate a low sorption capacity for atrazine in this soil and consequently large potential for movement by leaching and runoff. Microcosm systems using (14)C-atrazine to trace the fate of the applied herbicide, showed that 0.33% of the atrazine was volatilized, 0.25% mineralized and 6.89% was recorded in the leachate. After 60 d in the microcosms, 75% of the (14)C remained in the upper 5 cm soil layer indicating atrazine or its metabolites remained close to the soil surface. In field experiments, after 60 d, only 5% of the atrazine applied was recovered in the upper soil layers. In the field experiments atrazine was detected at a depth of 50 cm indicating leaching. Simulating tropical rain in field experiments resulted in 2.1% loss of atrazine in runoff of which 0.5% was adsorbed onto transported soil particles and 1.6% was in solution. Atrazine runoff was greatest two days after herbicide application and decreased 10 fold after 15 d. The use of atrazine on Ultisols, in the humid tropics, constitutes a threat to water quality, causing surface water and ground water pollution.     

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.     

Structure of Mn-Zr mixed oxides catalysts and their catalytic performance in the gas-phase oxidation of chlorocarbons

The catalytic activity and selectivity of manganese zirconia mixed oxides were evaluated for the oxidation of two common chlorinated pollutants found in waste streams, namely 1,2-dichloroethane (DCE) and trichloroethylene (TCE). Mixed oxides with varying Mn-Zr content were prepared by coprecipitation via nitrates, and subsequent calcination at 600 degrees C for 4 h in air. These catalysts were characterised by means of several techniques such as atomic emission spectrometry, N2 adsorption-desorption, powder X-ray diffraction, temperature-programmed desorption of ammonia, pyridine adsorption followed by diffuse reflectance infrared spectroscopy and temperature-programmed reduction with hydrogen. The active catalytic behaviour of Mn-Zr mixed oxides was ascribed to a substantial surface acidity combined with readily accessible active oxygen species. Hence, the mixed oxide with 40 mol% manganese content was found to be an optimum catalyst for the combustion of both chlorocarbons with a T50 value around 305 and 315 degrees C for DCE and TCE oxidation, respectively. The major oxidation products were carbon dioxide, hydrogen chloride and chlorine. It was observed that the formation of both CO2 and Cl2 was promoted with Mn loading.     

Combination of ozonation with conventional aerobic oxidation for distillery wastewater treatment

Laboratory-scale experiments were conducted in order to investigate the effect of ozone as pre-aerobic treatment and post-aerobic treatment for the treatment of the distillery wastewater. The degradation of the pollutants present in distillery spent wash was carried out by ozonation, aerobic biological degradation processes alone and by using the combinations of these two processes to investigate the synergism between the two modes of wastewater treatment and with the aim of reducing the overall treatment costs. Pollutant removal efficiency was followed by means of global parameters directly related to the concentration of organic compounds in those effluents: chemical oxygen demand (COD) and the color removal efficiency in terms of absorbance of the sample at 254 nm. Ozone was found to be effective in bringing down the COD (up to 27%) during the pretreatment step itself. In the combined process, pretreatment of the effluent led to enhanced rates of subsequent biological oxidation step, almost 2.5 times increase in the initial oxidation rate has been observed. Post-aerobic treatment with ozone led to further removal of COD along with the complete discoloration of the effluent. The integrated process (ozone-aerobic oxidation-ozone) achieved approximately 79% COD reduction along with discoloration of the effluent sample as compared to 34.9% COD reduction for non-ozonated sample, over a similar treatment period.     

Heavy metal-rich wastes sequester in mineral phases through a glass-ceramic process

Certain sludges generated by industry are rich in contaminating elements and are a major environmental problem. In this study, we determine the ability of these contaminating elements to be incorporated into a glass-matrix and in various mineral phases after a crystallization process. The contaminating elements studied were obtained from sewage sludges (SS) and galvanic sludges (GS), our raw materials. The sludge samples were taken from urban wastewater treatment plant in Catalonia (NE Spain) with high levels of phosphorus oxide (P(2)O(5)). In silica glasses, P(2)O(5) acts as a network former. We determined the chemical composition of both the SS and GS, as well as their thermal behaviour by differential thermal analysis and thermal gravimetric analysis (DTA-TG) to obtain their melting curves. The vitreous transition temperature of the obtained glass was established by dilatometer technique at 725 degrees C. The DTA-TG curve of the glass obtained has an exothermal wide peak at 860 degrees C corresponding to crystallization of the two phases: a spinel phase and a phosphate phase. A second exothermal wide peak at 960 degrees C was attributed to the crystallization of aluminium pyroxene, anorthite and fluor-apatite, with two exothermal phenomena attributed to the evolution of these phases. An exothermal peak at 1100 degrees C was attributed to gehlenite crystallization. Scanning electron microscope observations and energy-dispersed X-ray spectroscopy microanalyses of glass-ceramic showed that the contaminating elements were concentrated in the spinel phases, which are the first phases to crystallize during the cooling of glass. Finally, the spinel structure permits the incorporation of all the contaminating elements into it.     

Temporal variability in particle-associated pesticide exposure in a temporarily open estuary, Western Cape, South Africa

This study assesses the risk of current-use pesticides in a temporarily open estuary in South Africa by developing probabilistic risk estimates. Particle-associated pesticides (chlorpyrifos, prothiofos, cypermethrin, fenvalerate, endosulfan and p,p-DDE) and physicochemical parameters (salinity, temperature, flow, and total organic content (TOC)) were measured in the Lourens River estuary (Western Cape) twice a month over a period of two years and equilibrium partitioning theory was applied to calculate concentrations of pesticides in the water. The 90th percentile concentrations of pesticides associated to suspended particles and the calculated concentrations in water were 34.0microg kg(-1) and 0.15microg l(-1) for prothiofos, 19.6microg kg(-1) and 0.45microg l(-1) for chlorpyrifos and 18.6microg kg(-1) and 0.16microg l(-1) for endosulfan. Highest average concentrations were found around the summer season due to higher application rates and as a result of the low flow during this season. Species sensitivity distribution indicated a 1.5-2.8 times higher toxicity (hazardous concentration HC5) for marine organisms compared to freshwater organisms. The calculated concentrations in the water exceeded all threshold values suggested by international water guidelines. Chlorpyrifos and endosulfan posed the highest acute risk to the Lourens River estuary. No sufficient toxicity data and threshold values were found for prothiofos.     

Effect of pre-treatment and supporting media on Ni(II), Cu(II), Al(III) and Fe(III) sorption by plant root material

In this work Paspalum notatum root material was used to elucidate the influence of acid leaching pre-treatment and of sorption medium on metal adsorption. Ground P. notatum root was leached with 0.14M HNO(3). Leached root material (LRM) and non-leached root material (NLRM) were employed to flow sorption of Ni(II), Cu(II), Al(III) and Fe(III) in 0.5M CH(3)COONH(4) medium at pH 6.5. For LRM the sorption was also studied in 0.5M KNO(3) medium. The acid pre-treatment increased the sorption capacity (SC) for all ions studied. For the KNO(3) medium, Cu(II) and Fe(III) sorption was higher than in CH(3)COONH(4) and the type of the Ni(II) isotherm's model changed. The Freundlich model was the most representative isotherm model to describe metallic ions sorption. The (1)H NMR spectra showed differences between LRM and NLRM and the acid-basic potentiometric titration elucidated that acid-leaching procedure affected the root material sorption sites once only two predominant sorption sites were found for LRM (phenolic and amine, both able cations sorption) and five sorption sites (two carboxylic, amine and two phenolic) were founded for NLRM.     

Leaded electronic waste is a possible source material for lead-contaminated jewelry

Highly leaded jewelry, often imported from China, remains widely available in the United States. Leaded electronic waste is exported from the United States to several Asian countries where solder is recovered and circuit boards are stripped of parts in small workshops. To assess whether electronic waste is being recycled into the jewelry, lead, tin and copper content of highly leaded jewelry samples were determined by atomic absorption spectrometry. Sixteen jewelry items previously determined to contain 20-80% lead by weight were analyzed. Samples were digested in nitric acid for analysis of lead and copper, and in aqua regia for analysis of tin. Six samples contained significant amounts of tin, from 20.8% to 29.9% by weight. In addition, copper was a significant minor component of five of these samples (up to 4% by weight). Copper (present at 10-40% by weight in circuit boards) was shown to rapidly move into heated lead-tin solder. The combined lead-tin-copper content of these six items ranges from 93.5% to 100%, suggestive of a solder-based source material. These results are consistent with the hypothesis that recycled circuit board solders are being used to produce some of the heavily leaded imported jewelry sold in the United States. Should this hypothesis be substantiated, it suggests that environmental policies to protect children's health must address both proper recycling of source materials as well as restrictions of the lead content in consumer goods.