Renli Ma

Levels and risk assessment for humans and ecosystems of platinum-group elements in the airborne particles and road dust of some European cities

Traffic is the main source of platinum-group element (PGE) contamination in populated urban areas. There is increasing concern about the hazardous effects of these new pollutants for people and for other living organisms in these areas. Airborne and road dusts, as well as tree bark and grass samples were collected at locations in the European cities of Göteborg (Sweden), Madrid (Spain), Rome (Italy), Munich (Germany), Sheffield and London (UK). Today, in spite of the large number of parameters that can influence the airborne PGE content, the results obtained so far indicate significantly higher PGE levels at traffic sites compared with the rural or non-polluted zones that have been investigated (background levels). The average Pt content in airborne particles found in downtown Madrid, Göteborg and Rome is in the range 7.3-13.1 pg m(-3). The ring roads of these cities have values in the range 4.1-17.7 pg m(-3). In Munich, a lower Pt content was found in airborne particles (4.1 pg m(-3)). The same tendency has been noted for downtown Rh, with contents in the range 2.2-2.8 pg m(-3), and in the range 0.8-3.0 and 0.3 pg m(-3) for motorway margins in Munich. The combined results obtained using a wide-range airborne classifier (WRAC) collector and a PM-10 or virtual impactor show that Pt is associated with particles for a wide range of diameters. The smaller the particle size, the lower the Pt concentration. However, in particles <PM-10, some of the highest values correspond to the fraction <0.39 microm. Considering an average Pt content in all particles of approximately 15 pg m(-3), which is representative for all countries and environmental conditions, the tracheobronchial fraction represents approximately 10% and the alveolar fraction approximately 8% of the total particles suspended in air. However, from the environmental risk point of view, an exposure to PGEs in traffic-related ambient air is at least three orders of magnitude below the levels for which adverse health effects might theoretically occur (of approx. 100 ng m(-3)). Therefore, today inhalation exposure to PGEs from automotive catalysts does not seem to pose a direct health risk to the general population. Even though the data available today indicate no obvious health effects, there are still a number of aspects related to PGEs and catalysts that justify further research. First, continual monitoring of changes in PGE levels in air and road dust is warranted, to make sure that there is no dramatic increase from todays levels. Secondly, more detailed information on the chemical composition of the PGE-containing substances or complexes leaving the catalyst surface and the size distribution of the PGE-containing particles released during driving will facilitate a more in-depth human risk assessment.

Determination of cadmium, copper and lead in environmental samples. An evaluation of flow injection on-line sorbent extraction for flame atomic absorption spectrometry

Abstract A flow injection on-line sorbent extraction system was studied in conjunction with flame atomic absorption spectrometry to determine cadmium, copper and lead in digest solutions of solid environmental samples using octadecyl functional groups (C18) bonded silica gel as sorbent with diethylammonium-N,N-diethyldithiocarbamate (DDDC) or ammonium diethyldithiophosphate (DDPA) as complexing agent and methanol as eluent. Using DDDC as complexing agent, citric acid was used as masking agent for iron and manganese. The complexing agent DDPA selectively extracts cadmium, copper and lead at pH values 1 to 3. Using DDPA as complexing agent with citric acid at pH 1.0, the results of the analysis of five environmental standard reference materials, including coal fly ash (CRM 038), calcareous loam soil (CRM 141), lake sediment (CRM 280), river sediment (CRM 320) and estuarine sediment (CRM 277) after digestion were in good agreement with the certified values except cadmium in the river sediment with a very high iron content. With a 20-s sample loading at 8.7 ml min−1, detection limits (3σ) were 0.8, 1.4 and 10.0 μg l−1 respectively for cadmium, copper and lead.

Detection and characterization of zinc- and cadmium-binding proteins in Escherichia coli by gel electrophoresis and laser ablation-inductively coupled plasma-mass spectrometry ☆

Metals bound to proteins play key roles in structure stabilization, catalysis, and metal transport in cells, but metals may also be toxic. As a consequence, cells have developed mechanisms to control metal concentrations through binding to proteins. We have used a hyphenated strategy linking gel electrophoresis with laser ablation-inductively coupled plasma-mass spectrometry in order to detect, map, and quantify metal-binding proteins synthesized in Escherichia coli under zinc- and cadmium-stress conditions. We report the development of a powerful analytical method suitable for detection and characterization of metalloproteins in complex, unfractionated bacterial cell extracts. The approach was validated by using an E. coli strain overexpressing the cyanobacterial metallothionein protein SmtA. We observed induction of SmtA synthesis by zinc and binding of both zinc and cadmium cations by this protein. A profile of zinc- and cadmium-binding proteins was obtained from E. coli cytoplasmic fractions. Analysis of induction patterns and metal contents demonstrated the presence of proteins with high metal content which, on further study, should lead to the identification of novel metal-binding proteins.

Selective flow injection sorbent extraction for determination of cadmium, copper and lead in biological and environmental samples by graphite furnace atomic absorption spectrometry

Abstract A flow injection sorbent extraction system was developed for determination of trace and ultratrace cadmium, copper and lead in biological and environmental standard reference materials by graphite furnace atomic absorption spectrometry (GFAAS). Using ammonium diethyldithiophosphate (DDPA) as complexing agent with citrate as masking agent at pH 2, the analytes were selectively preconcentrated with effective removal of the matrixes including the salt matrix in saline water and the other high-content heavy metals in digested biological and geological samples. The two-second eluate containing most of the analyte complexes was collected for the GFAAS measurement. All analytical results obtained were in good agreement with the certified values. Enrichment factors of 12, 13 and 13 compared with 20 μl direct injection of aqueous solution and detection limits (3σ) of 0.003, 0.05 and 0.04 μg l −1 for cadmium, copper and lead respectively, could be obtained with 20-s sample loading at 8.7 ml min −1 for sorbent extraction and 20 μl eluate injection for peak area measurement. The relative standard deviation at 0.1 μg l −1 cadmium, 1 μg l −1 copper or 3 μg l −1 lead was around 2%.

Expression of the PitA phosphate/metal transporter of Escherichia coli is responsive to zinc and inorganic phosphate levels

Escherichia coli possesses two major systems for inorganic phosphate (P(i)) uptake. The Pst system (pstSCAB) is inducible by low phosphate concentrations whereas the low-affinity transporter (pitA) has been described as constitutively expressed. PitA catalyses transport of metal [Mg(II), Ca(II)]-phosphate complexes, and mutations in pitA confer Zn(II) resistance. Here we report that pitA transcription is not constitutive; activity of a single-copy pitA-lacZ transcriptional fusion (monolysogen) was maximal at high extracellular Zn(II) (150 microM), in the absence of added P(i), and in a well-defined pitA mutant strain. Intracellular zinc levels were unaffected by adding Zn(II) to the medium for both the wild-type and mutant strains. However, in the wild-type strain, Mg levels (per gram of dry biomass) fell by eightfold in cells grown with added Zn(II) and by 20-fold when Zn(II) and P(i) were added to cultures. Mutation of pitA reduced the effects of external Zn(II) and phosphate levels on Mg pools, consistent with competition or inhibition by Zn(II) of PitA. The mechanism of pitA regulation by extracellular Zn(II) and P(i) is unknown but appears not to involve Fur or other well-characterized regulators.

Flow injection sorbent extraction with dialkyldithiophosphates as chelating agent for the determination of cadmium, copper and lead by flame atomic absorption spectrometry

Abstract Using octadecyl functional groups (C 18 ) bonded to silica gel as sorbent and methanol as eluent, the flow injection sorbent extraction features of dialkyldithiophosphates (RO) 2 P(S)S − as the chelating agent for cadmium, copper and lead was investigated in respect of the effects of pH, alkyl substituent group, reagent concentration and masking agent, with flame atomic absorption spectrometric detection. The elements are quantitatively extracted with the short-alkyl-chain reagents (R up to propyl) in acidic medium. The extractability decreases with the number of carbon atoms in the alkyl groups of the reagents and with the reagent concentration when the alkyl groups are larger than butyl, but masking agents increase the extractability. An explanation proposed for this effect is the formation of polynuclear chelates. Diethyldithiophosphate can be used for the selective determination of cadmium, copper and lead in digested solid environmental samples. With 20 s sample loading at 8.7 ml min −1 , the enhancement factors are 35 for cadmium and copper or 26 for lead; the detection limits (3σ) are 0.8, 1.4 and 10.0 μg 1 −1 for cadmium, copper and lead, respectively.

Flow injection sorbent extraction with dialkyldithiophosphates as chelating agent for nickel, cobalt and manganese determination by atomic absorption spectrometry

Using octadecyl functional group (C18) bonded silica gel as sorbent and methanol or ethanol as eluent, the extractability of nickel, cobalt and manganese with diethyl-, di-n-propyl-, di-2-propyl-, di-n-butyl-, di-isobutyl-, di-2-butyl-, di-n-pentyl- and di-n-hexyldithiophosphates, (RO)2P(S)S−, was investigated in respect of the effects of pH, alkyl substituent group, reagent concentration and masking agent by flame atomic absorption spectrometry. The extractability increases with the chain length of the substituent groups in the reagents and is quantitative for alkyl groups larger than butyl at pH ca. 3. At a high concentration of di-n-pentyldithiophosphate, the metals are selectively extracted from coexisting cadmium, copper, lead and iron. As an analytical demonstration, di-n-pentyldithiophosphate was used for the determination of ultra-trace concentrations of nickel in two certified reference saline water samples (sea water and estuarine water) by graphite furnace atomic absorption spectrometry. Results were in good agreement with the certified values. The detection limit (3σ) of peak area measurement was 0.07 μg l−1 with an enrichment factor of 10 for nickel with 20-s sample loading at 8.7 ml min−1 and 20-μl eluate injection.

Airborne emission of enriched uranium at Tokai-mura, Japan.

A new strategy for characterisation of airborne uranium contamination based on elemental/isotopic analysis of tree bark is described. Bark samples collected at Tokai-mura (Japan) were subjected to high sensitivity ICP mass spectrometric analysis; for control purposes, samples from the remote Yakushima island (Southern Japan) and central Tokyo were also analysed. The uranium contents of tree bark for Tokyo and Yakushima were of similar magnitude to that at Tokai-mura (U, 0.01-1.0 microg/g - all samples), however, there were marked differences in isotope ratio values between the sites. Whereas natural uranium isotope ratio values (235U/238U, 0.0072) were observed for Yakushima and Tokyo, non-natural and natural signatures (235U/238U, 0.00697-0.01448) were realised at Tokai-mura. These findings are consistent with the release of enriched uranium at Tokai-mura.

Flow injection sorbent extraction with dialkyldithiophosphates as chelating agent for the determination of zinc by flame atomic absorption spectrometry

Abstract Dialkyldithiophosphates, (RO) 2 P(S)S − , were used as the complexing agent for flow injection on-line sorbent extraction for the determination of zinc by flame atomic absorption spectrometry. The extractability with diethyl-, di- n -propyl-, di-2-propyl-, di- n -butyl-, di-isobutyl-, di-sec.-butyl-, di- n -pentyl- and di- n -hexyldithiophosphates was compared in respect of the effects of pH, alkyl group, masking agent and reagent concentration. Di-sec.-butyldithiophosphate (0.5%, m/v) at pH 3 with 0.1 M citrate as a masking agent for iron, was used for the determination of zinc in a number of certified biological and environmental reference materials from the Community Bureau of Reference (BCR). All analytical results were in good agreement with the certified values. The detection limit (3σ) of peak height measurement, using a flow spoiler in the spray chamber, was 0.5 μg l −1 with an enhancement factor of 35 for a 20-s sample loading at 8.7 ml min −1 .

Evaluation of the analytical performance of flow injection—Flame atomic absorption spectrometry

Analytical performance of flow injection—flame atomic absorption spectrometry was evaluated in terms of precision and sensitivity. For direct aqueous-solution introduction and alcoholic-eluate introduction after on-line sorbent extraction, the influence of the interfacing parameters was investigated, including the nebulizer uptake rate, sample-introduced flow rate and coupling tube length. High sensitivity could be achieved by the exploitation of the synergetic effect of both sample pumping and aspirating processes. A low nebulizer uptake rate combined with a high flow rate of the introduced sample zone produced the optimum precision better than 2% for peak-height measurements, the optimum rates being dependent on the nebulization characteristics of the solvent used. Precision and sensitivity deteriorate with increasing length of the coupling tube.