Concurrent removal of Cr(III), Cu(II), and Pb(II) ions from water by multifunctional TiO2/Alg/FeNPs beads

The use of multifunctional materials for water remediation is a modern approach where adsorption phenomena and heterogeneous photocatalysis can be applied for the removal of pollutants. Since the ideal remediation system should be able to remove both organic and inorganic pollutants, a crucial aspect to consider is the knowledge of operational parameters affecting the removal process, especially when heavy metal ions are present in concoction as in real systems. Given the proven efficiency of multifunctional TiO₂/Alg/FeNPs magnetic beads for the removal of model organic pollutants, this study investigated the possibility to exploit such system also for the removal of mixed heavy metals (MHM), specifically Cr(III), Cu(II), and Pb(II) ions, under ultraviolet irradiation at a wavelength of 254 nm. After a preliminary screening on the optimal catalyst loading, operating parameters such as the initial concentration of metal ions, contact and irradiation time, and pH were investigated to optimize the removal of metal ions using response surface methodology (RSM) via Box–Behnken design. Starting from a MHM solution containing 44 ppm of each metal ion, the removal of Pb(II), Cr(III), and Cu(II) ions in the aqueous solution was nearly completed (>98.4%) for all three ions within 72 min of irradiation at almost neutral pH (pH = 6.8). The stability of TiO₂/Alg/FeNPs was confirmed by retrieving and reusing the beads in three consecutive cycles of heavy metals removal without observing significant changes in catalyst efficiency.     

Non-carcinogenic risk assessment of eight metals in the source groundwater of Shaying River Basin

Because of serious pollution of river water, people living along the Shaying River in China exploit the groundwater as a drinking water resource. Various pollutants including heavy metals have been detected in the groundwater at depths up to 200 m. To perform a non-carcinogenic risk assessment, the hazard index (HI) was determined for several metals present in the groundwater. High resolution inductively coupled plasma–mass spectrometry and inductively coupled plasma–atomic emission spectroscopy were used to measure the levels of Hg, Fe, Mn, Zn, Cd, Cr, Cu and Pb in source groundwater of eight tap water treatment plants (WTPs) during a 3-year period (2007–2009). Zn was present at the highest concentration of up to 101.2 μg l⁻¹ and Cd contributed the most (57.8%) to the HI in the WTPs, followed by Mn (14.3%) and Cr (13.1%). Both hazard quotients of individual metals and HI of total non-carcinogenic risk in each WTP were below 1.0, suggesting that the water posed negligible health risk on local residents. Temporal and spatial comparisons showed that high HIs tend to occur in low water periods (i.e., summer), and the City Pressure Station (Fuyang City) had the highest HI, followed by Yingnan Pressure Station (Yingnan Country) and Taihe WTP (Taihe Country). This study provides benchmark information useful for regulatory authorities to control the discharge of metals into the Shaying River Basin, and serves as a basis for comparison to other river systems in the world.     

Speciation and separation of Cr(VI) and Cr(III) using coprecipitation with Ni/2-Nitroso-1-naphthol-4-sulfonic acid and determination by FAAS in water and food samples

A speciation procedure for chromium(III) and chromium(VI) in the water and food samples has been established in the presented work. The procedure presented based on quantitative recoveries of Cr(III) > 95% using coprecipitation of Ni²⁺/2-Nitroso-1-naphthol-4-sulfonic acid. The total chromium was measured after reduction of Cr(VI) by concentrated H₂SO₄ and ethanol. The Cr(VI) was calculated as the difference between the total Cr content and the Cr(III) contents. The analytical variables, pH, amounts of precipitate, sample volume for optimum recoveries of Cr(III) were investigated. The influences of the some alkaline and earth alkaline ions and some transition metals on the recoveries of analyte ions were also investigated. The preconcentration factor was 50. The detection limit (3σ) of the reagent blank for chromium(III) was 1.33 μg L⁻¹. The relative standard deviations for determinations were found to be <7%, and % of relative error was calculated <6%. The method was validated by certified reference materials of tea (GBW 07605) and bush branches and leaves (GBW 0703). The procedure was successfully applied to the speciation of chromium in natural water and food samples (fish, white cheese, cow’s meat, black tea, boiled wheat).     

Light history modulates antioxidant and photosynthetic responses of biofilms to both natural (light) and chemical (herbicides) stressors

In multiple stress situations, the co-occurrence of environmental and chemical factors can influence organisms’ ability to cope with toxicity. In this context, the influence of light adaptation on the response of freshwater biofilms to sudden light changes or to herbicides exposure was investigated by determining various parameters: diatom community composition, photosynthetic parameters, chlorophyll a content, antioxidant enzyme activities. Biofilms were grown in microcosms under sub-optimal, saturating, and high light intensities and showed already described characteristics of shade/light adaptation (community structure, photosynthetic adaptation, etc.). Light history modulated antioxidant and photosynthetic responses of biofilms to the stress caused by short-term exposure to sudden light changes or to herbicides. First biofilms adapted to sub-optimal light intensity (shade-adapted) were found to be more sensitive to an increase in light intensity than high-light adapted ones to a reduction in light intensity. Second, while light history influenced biofilms’ response to glyphosate, it had little influence on biofilms’ response to copper and none on its response to oxyfluorfen. Indeed glyphosate exposure led to a stronger decrease in photosynthetic efficiency of shade-adapted biofilms (EC₅₀ = 11.7 mg L⁻¹) than of high-light adapted communities (EC₅₀ = 35.6 mg L⁻¹). Copper exposure led to an activation of ascorbate peroxidase (APX) in biofilms adapted to sub-optimal and saturating light intensity while the protein content decreased in all biofilms exposed to copper. Oxyfluorfen toxicity was independent of light history provoking an increase in APX activity. In conclusion this study showed that both previous exposure to contaminants and physical habitat characteristics might influence community tolerance to disturbances strongly.     

Carrier element-free coprecipitation (CEFC) method for separation and pre-concentration of some metal ions in natural water and soil samples

A simple, rapid and sensitive separation/pre-concentration procedure for Cd(II), Cr(III), Co(II), Cu(II), Fe(III), Pb(II) and Mn(II) ions in environmental samples has been established. The present procedure is based on a combination of carrier element-free coprecipitation (CEFC) and flame atomic absorption spectrometric (FAAS) determinations of understudy trace metal ions. A cationic surfactant (N-cetyl N,N,N trimethyl ammonium bromide (CTAB)) as coprecipitant was used without adding any carrier element for coprecipitation of understudy ions. The optimum conditions for the coprecipitation process were investigated on several commonly tested experimental parameters, such as pH of the solution, amount of coprecipitant. The pre-concentration factor was found to be 10. The detection limits corresponding to three times the standard deviation of the blank (N = 20) for Cd(II), Cr(III), Co(II), Cu(II), Fe(III), Pb(II) and Mn(II) ions were found as 0.61, 16.8, 12.7, 1.36, 2.08, 4.30 and 0.22 μg L⁻¹, respectively. The present procedure was successfully applied for separation and pre-concentration of investigated ions in several liquid environmental samples. In order to support the accuracy of the method, the certified reference materials (BCR 141 R calcareous loam soil and CRM025-050 soil) were analyzed. The experimental results are in good agreement with the certified values.     

Low exposure levels of urban metals induce heterotrophic community tolerance: a microcosm validation

The biological response of periphyton chronically exposed to metals of urban origin (Cd, Ni and Zn) was investigated with a Pollution-Induced Community Tolerance (PICT) approach using a previously developed short-term toxicity test based on β-glucosidase (heterotrophic) activity. Periphyton was grown on plastic membranes immersed in indoor aquaria contaminated with metals at realistic contamination levels (0.3, 3 μg/l for Cd, 5, 50 μg/l for Ni, 20, 200 μg/l for Zn). After 3 weeks of exposure, biofilms’ parameters (dry-weight, chlorophyll a concentration, heterotrophic activity) were analyzed and tolerance acquisition of the heterotrophic communities was assessed using the toxicity test. Modifications of bacterial and eukaryotic community structure were assessed with Automated Ribosomal Intergenic Spacer Analysis (ARISA). Effects of metal exposure were observed on biofilms parameters in the Cd and Zn experiments. Tolerance levels increased for both Cd-exposed biofilms, and for the high metal treatment biofilms in the Ni and Zn experiments. Analysis of the ARISA profiles showed that metal exposure affected the structure of both bacterial and eukaryotic communities. Moreover, Cd tolerance of the Zn-exposed heterotrophic communities was evaluated, which showed that the Zn-tolerant community (high metal treatment in the Zn experiment) also became tolerant to Cd (co-tolerance). The study shows that tolerance acquisition can be detected after exposure to environmental metal concentrations using β-glucosidase activity as an endpoint in short-term toxicity tests.     

Differences in uptake and translocation of hexavalent and trivalent chromium by two species of willows

Uptake and translocation of chromium (Cr) by two willow species was investigated. Intact pre-rooted weeping willows (Salix babylonica L.) and hankow willows (Salix matsudana Koidz) were grown hydroponically and spiked with hexavalent chromium [Cr (VI)] or trivalent chromium [Cr (III)] at 25.0 ± 0.5°C for 120 h. Removal of leaves was also performed as a treatment to quantify the effect of transpiration on uptake and translocation of either of the Cr species. Although the two willow species were able to eliminate Cr (VI) and Cr (III) from the hydroponic solution, significant differences in the removal rate for both chemical species were observed between the two willows (p < 0.05): faster removal rate for Cr (III) than Cr (VI) was detected in both willow species; hankow willows showed higher removal potential for both chemical species than weeping willows. Remarkable decreases in the removal rates for both Cr species were detected in the willows with leaves removed (p < 0.05). The results from the treatments spiked with Cr (VI) also revealed that Cr was more mobile in plant materials of hankow willows than that in weeping willows (p < 0.01), while higher translocation efficiency of Cr was observed in weeping willows than hankow willows for the Cr (III) treated (p < 0.01). However, a convincing decrease in the translocation efficiency due to the removal of leaves was only observed in the treatments spiked with Cr (VI) (p < 0.05). Substantial differences existed in the distribution of Cr species in plant materials after exposure of either of the chemical forms: roots and lower stems were the major sites for accumulation in weeping willows exposed to Cr (VI) and Cr (III), respectively; in contrast roots were the only sink in hankow willows exposed to both chemical species. The capacity of willows to assimilate both Cr species was also evaluated using detached leaves and roots of both willow species in sealed glass vessels in vivo. The results indicated that detached roots showed a more remarkable capacity to remove Cr (III) from the hydroponic solution than Cr (VI) (p < 0.01). Although detached leaves of both willow species were able to efficiently eliminate Cr (III), neither of them reduced the concentration of Cr (VI) in the solution. The results suggests that different mechanisms for uptake, assimilation and translocation of Cr (VI) and Cr (III) exist in different willow species and phytoremediation of Cr should consider this factor for the proposed target effectively.     

Genome sequencing reveals mechanisms for heavy metal resistance and polycyclic aromatic hydrocarbon degradation in Delftia lacustris strain LZ-C

Strain LZ-C, isolated from a petrochemical wastewater discharge site, was found to be resistant to heavy metals and to degrade various aromatic compounds, including naphenol, naphthalene, 2-methylnaphthalene and toluene. Data obtained from 16S rRNA gene sequencing showed that this strain was closely related to Delftia lacustris. The 5,889,360 bp genome of strain LZ-C was assembled into 239 contigs and 197 scaffolds containing 5855 predicted open reading frames (ORFs). Among these predicted ORFs, 464 were different from the type strain of Delftia. The minimal inhibitory concentrations were 4 mM, 30 µM, 2 mM and 1 mM for Cr(VI), Hg(II), Cd(II) and Pb(II), respectively. Both genome sequencing and quantitative real-time PCR data revealed that genes related to Chr, Czc and Mer family genes play important roles in heavy metal resistance in strain LZ-C. In addition, the Na⁺/H⁺ antiporter NhaA is important for adaptation to high salinity resistance (2.5 M NaCl). The complete pathways of benzene and benzoate degradation were identified through KEGG analysis. Interestingly, strain LZ-C also degrades naphthalene but lacks the key naphthalene degradation gene NahA. Thus, we propose that strain LZ-C exhibits a novel protein with a function similar to NahA. This study is the first to reveal the mechanisms of heavy metal resistance and salinity tolerance in D. lacustris and to identify a potential 2-methylnaphthalene degradation protein in this strain. Through whole-genome sequencing analysis, strain LZ-C might be a good candidate for the bioremediation of heavy metals and polycyclic aromatic hydrocarbons.

     

Column solid phase extraction of iron(III), copper(II), manganese(II) and lead(II) ions food and water samples on multi-walled carbon nanotubes

A column solid phase extraction method for preconcentration of Fe(III), Cu(II), Mn(II) and Pb(II) on multi-walled carbon nanotubes (MWNTs) has been established. The adsorption was achieved quantitatively on carbon nanotube at pH 9.0, then the retained analyte contents on the column were quantitatively eluted with 1 M HNO₃ in acetone. The effects of analytical parameters including pH of the solution, eluent type, sample volume, flow rates of eluent, matrix ions, etc. were investigated for optimization of the presented procedure. The preconcentration factor was calculated as 20. The detection limits for the understudy analyte ions were found in the range of 3.5 μg/L (Mn)–8.0 μg/L (Pb). The validation of the presented procedure was checked by the analysis of TMDA 54.4 fortified lake water and HR-1 River Sediment certified reference materials. The method was applied to the determination of analyte ions in environmental samples.     

The effects of tricentric chromium(III) propionate complex supplementation on pregnancy outcome and maternal and foetal mineral status in rat

Chromium(III) is an essential element for carbohydrate and lipid metabolism, and various chemical forms of this element are widely used as dietary supplements. Of particular interest is [Cr₃O(O₂CCH₂CH₃)₆(H₂O)₃]⁺ cation (CrProp), that has been proposed as an alternative source of Cr. However, its safety has not been studied completely. In this study we investigated the effects of CrProp supplementation on pregnancy outcome and maternal and foetal mineral status in the rat. Female Wistar rats (n = 20, 14 weeks old) were mated with males and, after successful conception were fed either AIN-93G diet supplemented with CrProp (100 mg Cr/kg diet, equals to 7.2 mg Cr/kg body mass/day) or non-supplemented diet (0.27 mg Cr/kg diet, equals to 0.02 mg Cr/kg body mass/day) for 21 days. Dams were sacrificed on 21 day of gestation, and their foetuses were examined for adverse effects. Maternal and foetal organs were analysed for minerals contents (Fe, Cu, Zn, Cr) using the AAS-method. Supplemental Cr given did not affect pregnancy outcome, litter size, body and inner organ masses, maternal blood biochemical indices. No abnormalities in gross organ morphology of foetuses were detected. Supplemental CrProp increased maternal liver and kidney Cr levels by 177% and 455%, decreased liver Cu and Zn concentrations by 9% and 12%, increased foetal liver Zn by 181%, and decreased kidney Cu level by 34%.     

Phase I trial of neoadjuvant chemoradiotherapy (CRT) with capecitabine and weekly irinotecan followed by laparoscopic total mesorectal excision (LTME) in rectal cancer patients

Summary   Background: To analyze the feasibility of capecitabine with weekly irinotecan and concurrent radiotherapy followed by laparoscopic-total mesorectal excision (LTME) in rectal cancer patients. Methods: Eligible criteria included adenocarcinoma of the rectum staged by endoscopic ultrasonography (u), spiral abdominal and pelvic CT and chest X-ray. Patients received weekly irinotecan 50 mg/m² (days 1, 8, 15, 22, 29) and capecitabine (days 1 through 5 for 5 weeks); dose level; (DL) I 250 mg/m²/bid; DL II 375 mg/m²/bid; DL III 500 mg/m²/bid, according to phase I methodology. External beam radiotherapy was delivered up to a total dose of 45 Gy in daily fractions of 1.8 Gy, 5 days a week. LTME was planned 5–7 weeks after CRT. Results: From February 2003 to February 2006, 22 patients were included. Median age was 62 (range 48 to 78). Seven pts were uT3N0 and 15 pts uT3N1. Seven patients were treated at DL I, six at DL II and nine at DL III. Grade 3 adverse events were observed in all levels. The maximum tolerated dose was reached at 375 mg/m² (DL II). Conversion rate to open surgery was 5%. Median hospital stay was 6.6 days. One month post-surgical complications were noted in five patients (23%). Median excised nodes were 11 (range 4–21). Pathological complete response was observed in two patients (9%). Conclusions: LTME after preoperative CRT with CAPIRI is feasible but severe adverse events were found in all levels despite the use of lower dose of capecitabine than previously published.     

Effect of temperature on phytoextraction of hexavalent and trivalent chromium by hybrid willows

The removal of hexavalent and trivalent chromium from hydroponic solution by plants to changes in temperature was investigated. Pre-rooted hybrid willows (Salix matsudana Koidz × alba L.) were exposed to a nutrient solution spiked with potassium chromate (K₂CrO₄) or chromium chloride (CrCl₃) for 4 days. Ten different temperatures were tested ranging from 11 to 32°C. Total Cr in solutions and in plant materials were all analyzed quantitatively. The results revealed that large amounts of the applied Cr were removed from the hydroponic solution in the presence of the plants. Significantly faster removal of Cr(III) than Cr(VI) was achieved by hybrid willows from the hydroponic solutions at all temperatures (P < 0.01). The removal rates of both chemical forms of Cr by plants increased linearly with the increase of temperatures. The highest removal rate of Cr(VI) was found at 32°C with a value of 1.99 μg Cr/g day, whereas the highest value of Cr(III) was 3.55 μg Cr/g day at the same temperature. Roots were the main sink for Cr accumulation in plants at all temperatures. Translocation of both chemical forms of Cr from roots to lower stems was only found at temperatures ≥24°C. The temperature coefficient values (Q ₁₀) were 2.41 and 1.42 for Cr(VI) and Cr(III), respectively, indicating that the removal of Cr(VI) by hybrid willows was much more susceptible to changes in temperature than that of Cr(III). This information suggests that changes in temperature have a substantial influence on the uptake and accumulation of both chemical forms of Cr by plants.     

Phytoremediation of metals from fly ash through bacterial augmentation

Different combinations of four bacterial strains isolated from fly ash were used by us to study their impact on phytoextraction of metals from fly ash by Brassica juncea grown in fly ash amended with farm yard manure (50:50 w/w). Out of 11 bacterial consortia, a combination of two strains i.e. Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C7) inoculated in the rhizosphere was found to enhance Pb accumulation maximally by 278%, Mn by 75%, Zn by 163%, Cr by 226% and Ni by 414% compared to control. It is possible that these bacteria, known for N₂ fixation, solubilization of phosphorus and uptake of micronutrient, could promote the plant growth resulting in higher accumulation of metals. However, a combination of four bacteria, namely Micrococcus roseus NBRFT2 + Bacillus endophyticus NBRFT4 + Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C4) was able to increase Cd uptake maximally by 237%. Further, the translocation of metal was invariably more from root to stem than from stem to leaf which was regulated by plant transport mechanism and metal mobility. Bacteria are known to excrete protons, organic acids, enzymes and siderophores to enhance the mobilization of metals which boosted the phytoextraction of metals from fly ash.     

Ecological risk of heavy metals in sediments of the Luan River source water

Distribution and characteristics of heavy metals enrichment in sediment were surveyed including the bio-available form analyzed for assessment of the Luan River source water quality. The approaches of sediment quality guidelines (SQG), risk assessment code and Hakanson potential ecological risk index were used for the ecological risk assessment. According to SQG, The results show that in animal bodies, Hg at the sampling site of Wuliehexia was 1.39 mg/kg, Cr at Sandaohezi was 152.37 mg/kg and Cu at Hanjiaying was 178.61 mg/kg exceeding the severe effect screening level. There were 90% of sampling sites of Cr and Pb and 50% sites of Cu exceeded the lowest effect screening level. At Boluonuo and Wuliehexia, the exchangeable and carbonate fractions for above 50% of sites were at high risk levels and that for above 30% of sites at Xiahenan and Wulieheshang were also at high risk levels. Other sites were at medium risk level. Compared to soil background values of China, Hg and Cd showed very strong ecological risk, and the seven heavy metals of Hg, Cd, Cu, As, Pb, Cr, Zn at ecological risk levels were in the descending order. The results could give insight into risk assessment of environmental pollution and decision-making for water source security.     

Evaluation of heavy metals in cosmetic products and their health risk assessment

Heavy metals’ contamination in cosmetic products is a serious threat. Present study was conducted to evaluate the concentrations of heavy metals (HMs) in various brands of cosmetic products with special emphasis on their health risk assessment. Five heavy metals including Cd, Cr, Fe, Ni and Pb were quantified in different brands of lotions, foundations, whitening creams, lipsticks, hair dyes and sunblock creams using atomic absorption spectrometry. Risk to the consumer’s health was determined using systemic exposure dosage (SED), margin of safety (MoS), hazard quotient (HQ), hazard index (HI) and lifetime cancer risk (LCR).On comparative basis, different brands of sunblock creams depicted highest concentration of Ni, Pb and Cr (7.99 ± 0.36, 6.37 ± 0.05 and 0.43 ± 0.01 mg/kg, respectively), whereas lipsticks had elevated levels of Fe at 12.0 ± 1.8 mg/kg, and Cd was maximum in lotions (0.26 ± 0.02 mg/kg). Multivariate analysis revealed strong associations among Cr, Ni and Pb, while Cd and Fe showed disparity in distribution and sources of contamination. MoS, HQ and HI values were within the permissible limit apart from for lotions and sunblock creams, while LCR value was higher than the permissible limit in all cosmetic products except lipsticks. Regular use of these products can cause serious threat to human health, particularly skin cancer on long time exposure. Therefore, continuous monitoring of cosmetic products, particularly with reference to HMs adulteration should be adopted to ensure the human safety and security.     

Baseline trace metals in bivalve molluscs from the Beagle Channel,Patagonia (Argentina)

In order to test the aptitude of individuals of Mytilus chilensis as biomonitors of heavy metals pollution in seawater, several samples of this mollusk together with surrounding seawater samples were collected along 170 km of the coastal area of the Beagle Channel (Tierra del Fuego, Argentina) in 2005 and 2007. The study, performed in seven locations strategically selected, involved the determination of Cd, Cr, Cu, Ni, Pb and Zn in seawaters and mollusks by atomic absorption spectrometry (AAS) and the calculation of the respective concentration factors (CFs). Obtained data were standardized and analyzed by multivariate techniques in order to establish differences between sampling sites and periods. Obtained results will be shown and the bioaccumulation ability of M. chilensis will be evaluated by comparison with results obtained for Mytilus species in different geographical marine areas. A fully discussion on the possibility of employing the results as background levels for comparative purposes in other marine waters of the world will be provided. The possible harm derived from human consumption of these mollusks will be also assessed.     

The shifts of sediment microbial community phylogenetic and functional structures during chromium (VI) reduction

The Lanzhou reach of the Yellow River, located at the upstream of Lanzhou, has been contaminated by heavy metals and polycyclic aromatic hydrocarbons over a long-time. We hypothesized that indigenous microbial communities would remediate those contaminants and some unique populations could play an important role in this process. In this study, we investigated the sediment microbial community structure and function from the Lanzhou reach. Sediment samples were collected from two nearby sites (site A and site B) in the Lanzhou reach along the Yellow River. Sediment geochemical property data showed that site A sediment samples contained significantly (p?<?0.05) higher heavy metals than site B, such as chromium (Cr), manganese (Mn), and copper (Cu). Both site A and B samples were incubated with or without hexavalent chromium (Cr (VI)) for 30 days in the laboratory, and Cr (VI) reduction was only observed in site A sediment samples. After incubation, MiSeq sequencing of 16S rRNA gene amplicons revealed that the phylogenetic composition and structure of microbial communities changed in both samples, and especially Proteobacteria, as the most abundant phylum increased from 45.1?% to 68.2?% in site A, and 50.1?% to 71.3?% in site B, respectively. Some unique OTUs and populations affiliated with Geobacter, Clostridium, Desulfosporosinus and Desulfosporosinus might be involved in Cr (VI) reduction in site A. Furthermore, GeoChip 4.0 (a comprehensive functional gene array) data showed that genes involved in carbon and nitrogen cycling and metal resistance significantly (p?<?0.05) increased in site A sediment samples. All the results indicated that indigenous sediment microbial communities might be able to remediate contaminants like Cr (VI), and this information provides possible strategies for future bioremediation of the Lanzhou reach.     

Utilization of membrane filtration for preconcentration and determination of Cu(II) and Pb(II) in food,water and geological samples by atomic absorption spectrometry

A method for separation–preconcentration of Cu(II) and Pb(III) ions by membrane filtration has been presented. The analyte ions were collected on acetate membrane filter as their 1-2-pyridylazo 2-naphthol (PAN) complexes. The analytes were determined by flame atomic absorption spectrometry. The analytical parameters including pH, eluent type, sample volume, amount of PAN, etc. were examined in order to gain quantitative recoveries of analyte ions. The effects of foreign ions on the recoveries of analyte ions were also investigated. The detection limits by three sigma were found to be 1.2 and 3.5 μg L⁻¹ for Cu(II) and Pb(II), respectively. The preconcentration factor was 60 for Cu(II) and 20 for Pb(II). The validation of the presented procedure was checked by the analysis of certified reference materials. The optimized method was successfully applied to food, water and geological samples with good results.     

Potential of coffee husk biomass waste for the adsorption of Pb(II) ion from aqueous solutions

The uptake of Pb(II) from the aqueous solution by Coffee Husk Biomass Waste (CHBW) as a green low cost solid phase adsorbent was critically studied. The chemical composition and the surface morphology of the CHBW were determined and fully characterized by FESEM-EDX. In batch mode, the effect of various analytical parameters e.g. adsorbent dose, contact time and analyte concentration on lead(II) ions retention by the biomass CHBW was performed. The adsorption equilibrium of Pb(II) ions was achieved after 60 min with very high percentage 98%, and an adsorption capacity of 19.02 mg/g lead towards the adsorbent was determined. Sorption kinetics data was fitted well with pseudo-second-order model with good correlation coefficient (R² = 1) and (q_e,cal) 19.23 mg/g, (eq_e,exp) 19.07 mg/g. The sorption isotherm fitted better with the Freundlich model (R² is close to the unity). The Langmuir gives maximum adsorption capacity (q_max) of Pb(II) was 37.04 mg/g. These results indicated that, the coffee husk is an efficient, sustainable, and low-cost adsorbent for Pb(II) uptake from wastewater.     

Alterations of valve closing behavior in juvenile Catarina scallops (Argopecten ventricosus Sowerby, 1842) exposed to toxic metals

We conducted an evaluation of alterations produced in the valve closing speed of juvenile Argopecten ventricosus (Catarina scallop) exposed to the metals cadmium, chromium and lead, because of the connection of this response to the state of health of the mollusk. Bioassays were conducted with 50 juveniles (length 3 ± 0.5 cm) exposed to 0.02, 0.1, 0.2 mg Cd l⁻¹; 0.1, 0.5, 1.0 mg Cr l⁻¹; 0.04, 0.2, 0.4 mg Pb l⁻¹ and 0.8 and 1.6 mg Cd + Cr + Pb l⁻¹ for 480 h. The average valve closing speed at the end of the experiment was under 1 s in the control group, from 2 to 3.6 s in the bioassays with cadmium, from 1.4 to 3.4 s with chromium, from 3 to 12 s with lead, and from 12 to 15 s with the metal mixtures. It was found that there are significant differences between the values recorded in assays with metals and the control (P < 0.05). The retardation of valve closing in the organisms exposed to toxic substances is probably caused by damage to the sensory cilia located on the edge of the mantle.