Deposition of Mn from automotive combustion of methylcyclopentadienyl manganese tricarbonyl beside the major highways in the greater Toronto area, Canada

Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used in Canada since 1976 as an antiknock agent in gasoline, completely replacing Pb in 1990. An early study of much higher Mn concentrations in gasoline showed that the combustion of MMT leads to the formation of inorganic manganese oxides, especially Mn3O4. Recent emission testing by Lawrence Livermore National Laboratory for Ethyl Corp. has shown that Mn is primarily emitted as a phosphate or sulfate along with minor amounts of oxides. The main objective of this research was to analyze the deposition of Mn from MMT to the terrestrial environment beside the major highways in the greater Toronto area (GTA), Canada. The results were compared with Pb and other trace elements such as Al, Ca, Fe, Mg, Cu, Zn, Na, and the Cl ion (water extractable) to study the behavior of Mn in soil. The study area was located near major Toronto highways 401 (urban) and 400 (rural), at 43 degrees 67' N and 79 degrees 37' W (latitude and longitude) (278,560 and 47,835 cars/day), respectively. Surface soil samples (0-5 cm depth) were collected at distances up to 40 m from the roadside. Parameters evaluated included total and available Mn and other trace elements, particle size, pH, organic content, and cation exchange capacity. Based on high traffic density along 401, higher Mn deposition was expected. No significant differences were found between the 401 and 400 Barrie (E(+1)) sites, attributable to the natural background levels of Mn or its contribution by other sources such as Mn-enriched road dust or naturally occurring crustal Mn. However, the 400 King City (E(+2)) site had significantly lower Mn levels than did the other three sites, 401 and 400 Barrie. This may be explained by the types of soil along the 401 and 400 sites. The King City site along 400 was found to be higher in sand content than were the 401 sites. A higher sand content could result in higher leaching of Mn to the bottom layer of the soil. Although MMT has been used continuously for approximately 25 years in Canada, its contribution to the terrestrial environment has been very low and has not significantly increased Mn levels along the highways, as demonstrated by this study.     

Fluoride Emissions and Forest Growth

Abstract

The October 1995 court decision allowing Ethyl Corporation to offer methylcyclopentadienyl manganese tricarbonyl (MMT) for sale to refiners for introduction into unleaded gasoline as an octane enhancer is likely to result in increased fine (PM_2.5) manganese (Mn) concentrations in ambient air. Concern exists regarding possible health effects. In this paper, recent fine Mn concentrations in three monitoring networks and one U.S. Environmental Protection Agency (EPA) study of personal exposure are analyzed. One network consists mainly of rural sites in national parks in the United States, a second consists mainly of urban sites in California, and the third consists mainly of urban sites in Canada where MMT has been used for a number of years. During the late 1980s and early 1990s, mean ambient concentrations ranged from 1 ng/m³ in the mostly rural network to 3 ng/m³ in the mostly urban California network to 12 ng/m³ in the MMT-impacted Canadian network. Several lines of evidence suggested that some of the fine Mn observed in the United States during the 1986-1992 period was contributed by automobiles using leaded gasoline, for which MMT was a registered fuel additive. However, the near-disappearance of leaded gasoline has resulted in a very small portion of fine Mn being attributed to automobiles in the years since 1992.A source apportionment analysis suggested that crustal contributions to ambient fine Mn are on the order of 1-2 ng/m³ in both the United States and Canada.     

Manganese content of Tradescancia species exposed to automotive combustion of methylcyclopentadienyl manganese tricarbonyl in urban and rural landscapes

The purpose of this study is to assess the effect of manganese (Mn) from methylcyclopentadienyl manganese tricarbonyl (MMT) on grass (Tradescancia) species beside the major urban and rural highways in the greater Toronto area. Grass clippings were collected at distances up to 40 m from the roadside of a wooded, weakly exposed site (E+) and two unwooded, highly exposed sites (E++ and E+++) to Mn contamination. Statistical tests, including analysis of variance and correlation coefficients, were used to compare the Mn deposition on grass species with respect to distance and traffic density. A higher deposition of Mn was expected at the highly exposed sites when compared with the weakly exposed site, but a significantly higher concentration of Mn was observed at weakly exposed rural E+ site (Mn = 54.07 microg/g; dry wt) than the highly exposed urban E++ (Mn = 38.17 microg/g; dry wt) and E+++ (Mn = 35.63 microg/g; dry wt) sites. A significant correlation coefficient was found for Mn and traffic density (r2 = 0.311, p = 0.0074) at the weakly exposed site than at the highly exposed (r2 = 0.1589, p = 0.1052) urban sites. These data demonstrate that despite the continuous use of MMT in Canadian gasoline, the levels do not appear to exceed the worldwide tolerable levels (17-334 g/g; dry wt) in grass species inhabiting ecosystems next to major highways in urban regions.     

Manganese and other trace elements in urban snow near an expressway

The Mn contamination arising from the combustion of MMT (methylcyclopentadienyl manganese tricarbonyl) in unleaded gasoline was assessed using snow collected at different distances 15, 25, 125 and 150 m from an expressway (Montreal, Canada) in February 1993. The snow samples were analyzed by atomic absorption and by neutron activation for total Mn, Mg, Cu, V, Al, Zn, Fe, Na, and Ca concentrations in the soluble (<0.4 microm) and particulate fractions. ANOVA with ranked values was performed to compare element concentrations and soluble/particulate ratios among receptor sites and depths. Principal component analysis was used to describe the spatiotemporal variations of the deposition rates and the influence of meteorological factors. The average concentration of all trace elements, except Mg, Cu, and V, decreased significantly (p<0.05) from receptor sites near the road (15-25 m) to those farther away (125-150 m). The deposition rates of all metals and ions, except Cu, were highly positively correlated (tau = 0.5-0.9) with each other and inversely correlated with snowfalls. Wind frequency showed no correlation with deposition rate. The spatial trend was similar for all these elements making it difficult to distinguish Mn arising from the combustion of MMT from that due to other sources, such as road dust. Only the soluble/particulate ratio calculated for Mn seemed higher than that for the other metals, which might be explained by the particle size of Mn from MMT (0.2-0.4 microm). The present study only indicates a direct contamination of the snow by road activities and substantial deposition of trace elements near the roadway; no clear link can be established between motor vehicle emissions and the concentration of Mn in snow.     

Estimating distributions of long-term particulate matter and manganese exposures for residents of Toronto,Canada

Methylcyclopentadienyl manganese tricarbonyl (MMT), a manganese-based gasoline additive, has been used in Canadian gasoline for about 20 yr. Because MMT potentially increases manganese levels in particulate matter resulting from automotive exhausts, a population-based study conducted in Toronto, Canada assessed the levels of personal manganese exposures. Integrated 3-day particulate matter (PM_2.5) exposure measurements, obtained for 922 participant periods over the course of a year (September 1995–August 1996), were analyzed for several constituent elements, including Mn. The 922 measurements included 542 participants who provided a single 3-day observation plus 190 participants who provided two observations (in two different months). In addition to characterizing the distributions of 3-day average exposures, which can be estimated directly from the data, including the second observation for some participants enabled us to use a model-based approach to estimate the long-term (i.e. annual) exposure distributions for PM_2.5 mass and Mn. The model assumes that individuals’ 3-day average exposure measurements within a given month are lognormally distributed and that the correlation between 3-day log-scale measurements k months apart (after seasonal adjustment) depends only on the lag time, k, and not on the time of year. The approach produces a set of simulated annual exposures from which an annual distribution can be inferred using estimated correlations and monthly means and variances (log scale) as model inputs. The model appeared to perform reasonably well for the overall population distribution of PM_2.5 exposures (mean=28 μg m^-3). For example, the model predicted the 95th percentile of the annual distribution to be 62.9 μg m^-3 while the corresponding percentile estimated for the 3-day data was 86.6 μg m^-3. The assumptions of the model did not appear to hold for the overall population of Mn exposures (mean=13.1 ng m^-3). Since the population included persons who were potentially occupationally exposed to Mn (in non-vehicle-related jobs), we used responses to questionnaire items to form a subgroup consisting of non-occupationally exposed participants (671 participant periods), for which the model assumptions did appear to hold. For that subpopulation (mean=9.2 ng m^-3), the model-predicted 95th percentile of the annual Mn distribution was 16.3-ng m^-3, compared with 21.1 ng m^-3 estimated for the 3-day data.     

Comment on “Methylcyclopentadienyl Manganese Tricarbonyl as an Antiknock: Composition and Fate of Manganese Exhaust Products”

In an article published in the August 1975, Journal of the Air Pollution Control Association entitled “Methylcyclopentadienyl Manganese Tricarbonyl as an Antiknock: Composition and Pate of Manganese Exhaust Products,” the authors conclude that, “… use of MMT in gasoline will result in no public health hazards, because of the low toxicity of manganese and because of the very low concentration of MMT that would be used in gasoline …. If all gasoline contained 0.1 g Mn/gal, the amount of airborne Mn its exhaust would contribute to urban areas would contribute to urban areas would be only 0.02-0.2 μg/m³, with a median value of 0.05 μg/m³.”     

Advances in the Analysis of Air Contaminants Comments

Abstract

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organometallic compound used as an octane improver in unleaded gasoline. The combustion of MMT leads to the formation of manganese (Mn) oxides, mainly Mn₃O₄. The objective of this study is to assess the variations over time and space of respirable (Mn_R) and total (Mn_T) Mn in the urban atmosphere and to evaluate human exposure by inhalation. Two sampling sites were selected on the island of Montreal based on their local traffic density (municipal botanical garden, C^-= 10,000–15,000 vehicles d^-1; Montreal Waterworks, C⁺= 100,000–130,000 vehicles d^-1). Air samplings were made during the day at stations located 10 m from the road using portable pumps, some of which were equipped with a cyclone. Mn_R and Mn_T and other metals were measured on Teflon filters by neutron activation. Mn exposure doses by inhalation were calculated using Monte–Carlo simulations. Mn_R and Mn_T average concentrations were significantly higher at site C⁺ (Mn_R = 0.024 µg m^-3; Mn_T = 0.050 µg m^-3) than at site C^- (Mn_R= 0.015 µg m^-3; Mn_T= 0.027 µg m^-3). Temporal profiles at sites C⁺ and site C^-were similar, with a coefficient of correlation of 0.24 for Mn_R and 0.26 for Mn_T. Trend analyses (ARIMA) also showed that the period of the week (work days vs. off days) was significantly related to Mn_R and Mn_T variations at both sites. The average exposure dose by inhalation to Mn_R and Mn_T ranged from 0.001 to 0.030 µg kg^-1 day^-1 and 0.001 to 0.05 µg kg^-1 day^-1. Mn_R and Mn_T concentrations reflected a positive relationship with traffic density. However, it remains difficult to attribute these results directly to the combustion of MMT in unleaded gasoline. On average, the Mn_R and Mn_T inhalation doses were 2 to 15 times lower than the reference dose (RfC) proposed by the U.S. Environmental Protection Agency (EPA) for the general population.     

Particulate matter and manganese exposures in Toronto,Canada

Methylcyclopentadienyl manganese tricarbonyl (MMT) is a manganese-based gasoline additive used to enhance automobile performance. MMT has been used in Canadian gasoline for about 20 yr. Because of the potential for increased levels of Mn in particulate matter resulting from automotive exhausts, a large-scale population-based exposure study (∼1000 participant periods) was conducted in Toronto, Canada, to estimate the distribution of 3-day average personal exposures to particulate matter (PM_2.5 and PM₁₀) and Mn. A stratified, three-stage, two-phase probability, longitudinal sample design of the metropolitan population was employed. Residential indoor and outdoor, and ambient levels (at a fixed site and on a roof) of PM_2.5, PM₁₀, and Mn were also measured. Supplementary data on traffic counts, meteorology, MMT levels in gasoline, personal occupations, and activities (e.g. amount of vehicular usage) were collected. Overall precision (%RSD) for analysis of duplicate co-located samples ranged from 2.5 to 5.0% for particulate matter and 3.1 to 5.5% for Mn. The detection limits were 1.47 and 3.45 μg m^-3 for the PM₁₀ and PM_2.5 fractions, respectively, and 5.50 and 1.83 ng m^-3 for Mn in PM₁₀ and PM_2.5, respectively. These low detection limits permitted the reporting of concentrations for >98% of the samples. For PM₁₀, the personal particulate matter levels (median 48.5 μg m^-3) were much higher than either indoor (23.1 μg m^-3) or outdoor levels (23.6 μg m^-3). The median levels for PM_2.5 for personal, indoor, and outdoor were 28.4, 15.4 and 13.2 μg m^-3, respectively. The correlation between PM_2.5 personal exposures and indoor concentrations was high (0.79), while correlations between personal and the outdoor, fixed site and roof site were low (0.16–0.27). Indoor Mn concentration distributions (in PM_2.5 and PM₁₀), unlike particulate matter, exhibited much lower and less variable levels that the corresponding outdoor data. The median personal exposure was 8.0 ng m^-3, compared with 4.7 and 8.6 ng m^-3, respectively, for the indoor and outdoor distributions. The highest correlations occurred for personal vs indoor data (0.56) and for outdoor vs roof site data (0.66), and vs fixed site data (0.56). The concentration of Mn in particulate matter, expressed in ppm (w/w), revealed that the fixed site was the highest, followed by the roof site, outdoor, indoor, and personal. The personal and indoor data showed a statistically significant correlation (0.68) while all other correlations between personal or indoor data and outdoor or fixed-site data were quite small. The low correlations of personal and indoor levels with outdoor levels suggest that different sources in the indoor and outdoor microenvironments produce particle matter with dissimilar composition. The correlation results indicate that neither the roof- nor fixed-site concentrations can adequately predict personal particulate matter or Mn exposures.     

Regional Transport and Urban Contributions to Fine Particle Concentrations in Southeastern Canada

Abstract

The impact of various atmospheric transport directions on ambient fine particle (PM_2.5) concentrations at several sites in southeastern Canada was estimated (for May-September) using back-trajectory analysis. Three-day back trajectories (four per day) were paired with 6-hr average PM_2.5 mass concentrations measured using tapered element oscillating microbalances (TEOM). PM_2.5 concentrations at rural locations in the region were affected by nonlocal sources originating in both Canada and the United States. Comparison of sites revealed that, on average, the local contribution to total PM_2.5 in the greater Toronto area (GTA) is approximately 30–35%. At each location, average PM_2.5 concentrations under south/southwesterly flow conditions were 2–4 times higher than under the corresponding northerly flow conditions. The chemical composition of both urban and rural PM_2.5 was determined during two separate 2-week spring/summer measurement campaigns. Components identified included SO₄ ^2?, NO₃ ^?, NH₄+, black carbon and organic carbon (OC), and trace elements. Higher particle mass at the urban Toronto site was composed of a higher proportion of all components. However, black carbon, NO₃ ^?, NaCl, and trace elements were found to be the most enriched over the rural/regional background levels.     

Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO2 catalysts on the low-temperature selective catalytic reduction of NO by NH3

TiO₂-supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wet-impregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH₃ with respect to the Mn valence and lattice oxygen behavior. The surface and bulk properties of these catalysts were examined using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Catalysts prepared using lower calcination temperatures, which contained Mn⁴⁺, displayed high SCR activity at low temperatures and possessed several acid sites and active oxygen. The TPD analysis determined that the Brönsted and Lewis acid sites in the Mn/TiO₂ catalysts were important for the low-temperature SCR at 80～160 and 200～350 °C, respectively. In addition, the available lattice oxygen was important for attaining high NO to NO₂ oxidation at low temperatures.

Implications: Recently, various Mn catalysts have been evaluated as SCR catalysts. However, there have been no studies on the relationship of adsorption and desorption properties and behavior of lattice oxygen according to the valence state for manganese oxides (MnO_x). Therefore, in this study, the catalysts were prepared by the wet-impregnation method at different calcination temperatures in order to show the difference of manganese oxidation state. These catalysts were then characterized using various physicochemical techniques, including BET, XRD, TPR, and TPD, to understand the structure, oxidation state, redox properties, and adsorption and desorption properties of the Mn/TiO₂ catalysts.     

Dry atmospheric inputs of trace metals at the Mediterranean coast of Israel (SE Mediterranean): sources and fluxes

This study presents the first detailed data on aerosol concentrations of trace metals (Cd, Pb, Cu, Zn, Cr, Mn, Fe and Al) at the SE Mediterranean coast of Israel, and assesses their sources and fluxes. Aerosol samples were collected at two sampling stations (Tel-Shikmona and Maagan Michael) along the coast between 1994 and 1997. Two broad categories of aerosol trace metal sources were defined; anthropogenic (Cd, Cu, Pb and Zn) and naturally derived elements (Al, Fe, Mn and Cr). The extent of the anthropogenic contribution was estimated by the degree of enrichment of these elements compared to the average crustal composition (EF_crust). High values (median >100) were calculated for Cd, Pb and Zn, minor values for Cu and relatively low values (<10) for Fe, Mn and Cr. The crustal-derived elements exhibited a statistically significant seasonal pattern of higher concentrations during spring and autumn (e.g. Al concentrations in some cases during these periods were observed to be in excess of 1500 ng m⁻³). In the eastern Mediterranean basin crustal-dominated elements are enriched by 2–3 times while others (Cd and Pb) are comparable to the northwestern Mediterranean. The Pb : Cd ratios of ∼150 are higher than in coastal European sites (60–116) or emission materials (∼50). It is speculated that these differences are attributed mainly to the mixing of crustal material with local and European emissions. At present, it is impossible to quantify the latter two fractions. Back trajectory analysis and the subsequent categorization of two main aerosol populations, ‘European’ and ‘North Africa–Arabian’, exhibited a significantly different geochemical imprint on the aerosol chemical composition. ‘European’-derived air masses indicated significantly higher EF_crust values for Cd and Pb due to the greater anthropogenic character of the aerosol population, with a dilution by crustal material of this population leading to comparatively lower EF_crust values associated with the North African–Arabian air masses.     

Trace elements exposure influences proximate body composition and antioxidant enzyme activities of the species tilapia and catfish in Burullus Lake—Egypt: human risk assessment for the consumers

The trace elements concentration in the fish estimates the contamination degree in the aquatic environment. These toxic trace elements are transported into the human through the consumption of polluted fish. This study estimated the effect of Cd, Hg, Pb, As, and Al on tilapia species and catfish Clarias gariepinus (six for each species of fish) inhabiting Burullus Lake—Egypt 30° 33′–31° 08′ E and 30° 22′–31° 35′ N. The highest Pb concentrations recorded in the muscle of C. gariepinus 2.29 ± 0.29 μg/g while S. galilaeus was estimated the lowest Hg concentration of 0.54 ± 0.02 μg/g which indicated the presence of contaminants exceeded the limits permitted by FAO/WHO and EC. The maximum mean carbohydrate, lipid, and protein recorded in O. niloticus 18.66, 16.33, and 58.16 mg/g, respectively; moisture in O. aureus 67.33%; and ash 16.41% in O. niloticus. The lowest amount of carbohydrate was recorded in the T. zillii 14.1 mg/g, lipid, and ash in C. gariepinus 11.65 mg/g and 3.375%, respectively. Protein and moisture in the S. galilaeus were 53.75 mg/g and 60.75%, respectively. The results recorded a marked insignificant (P > 0.05) decrease in CAT, GR, and GPx activity in O. niloticus. GSH and SOD activity was an insignificant (P > 0.05) decrease in C. gariepinus. The results concluded that the trace elements concentrations exceed the maximum permissible limits recommended in fish samples set by Egypt, FAO, WHO, and EC. The estimated weekly intake of all elements through consumption of studied fish species inhabiting Burullus Lake by a child (15 kg) in Egypt is well above the PTWI recommended by FAO/WHO, whereas it is well below the PTWI for human consumption by young people (40 kg) and adult person (70 kg), at least in respect of residual levels of studied elements excluding Cd and Hg. Thus, for consumer protection, these fish species are unsafe and have hazardous effects for children, and about youth and adult consumption, caution must be taken to consider individuals eating significant amounts of fish.

     

Analytical methods and validation for determining trace elements in red wines

The objective of this work is to quantify As, Hg, Cd, Ni and Pb in Portuguese red wines. First, the methods for the quantification of trace elements in red wines were validated. Several pre-treatments were compared, namely a pre-digestion process with HNO₃, a pre-oxidation step with H₂O₂, and a spiking step of wine samples with a known concentration of the trace elements analyzed. Except for As, it was determined that the quantification of the trace elements does not require a pre-digestion process with HNO₃. For all of the trace elements analyzed, a pre-oxidation step with H₂O₂ may enable an accurate quantification. The techniques chosen for the quantification of trace elements were hydride generation atomic absorption spectrometry (HGAAS) for As and Hg, electrothermal atomic absorption spectrometry (ETAAS) for Cd, and flame atomic absorption spectrometry (FAAS) for Ni and Pb. In the second stage of this work, 25 Portuguese red wines spanning all of the red wine-producing regions were analyzed for all of the five trace elements referred to above. Only Cd and Pb have shown concentrations above the limit values defined by the “Organization Internationale de la Vigne et du Vin.” The Target Hazard Quotient (THQ) equation was used to determine in which wine-producing regions that wine consumption can be a problem for public health in terms of the concentrations of the five trace elements analyzed. THQ values have indicated that for the universe of the 25 red wines analyzed no region produces wines that can pose problems for public health, when the Portuguese red wine standard consumption is considered.     

Major and trace elements in soils in the Central Pyrenees: high altitude soils as a cumulative record of background atmospheric contamination over SW Europe

Background, aim, and scope  

High mountain soils constitute a long-term cumulative record of atmospherically deposited trace elements from both natural and anthropogenic sources. The main aims of this study were to determine the level of major and trace metals (Al, Ti, Mn, Fe, and Zr) of lithologic origin and airborne contaminating trace elements (Ni, Cu, Zn, As, Cd, and Pb) in soils in the Central Pyrenees as an indication of background contamination over SW Europe, to establish whether there is a spatial pattern of accumulation of trace elements in soils as a function of altitude, and to examine whether altitude-related physicochemical properties of soils affect the accumulation of major metals and trace elements.     

Source origin of trace elements in PM from regional background,urban and industrial sites of Spain

Despite their significant role in source apportionment analysis, studies dedicated to the identification of tracer elements of emission sources of atmospheric particulate matter based on air quality data are relatively scarce. The studies describing tracer elements of specific sources currently available in the literature mostly focus on emissions from traffic or large-scale combustion processes (e.g. power plants), but not on specific industrial processes. Furthermore, marker elements are not usually determined at receptor sites, but during emission. In our study, trace element concentrations in PM₁₀ and PM_2.5 were determined at 33 monitoring stations in Spain throughout the period 1995–2006. Industrial emissions from different forms of metallurgy (steel, stainless steel, copper, zinc), ceramic and petrochemical industries were evaluated. Results obtained at sites with no significant industrial development allowed us to define usual concentration ranges for a number of trace elements in rural and urban background environments. At industrial and traffic hotspots, average trace metal concentrations were highest, exceeding rural background levels by even one order of magnitude in the cases of Cr, Mn, Cu, Zn, As, Sn, W, V, Ni, Cs and Pb. Steel production emissions were linked to high levels of Cr, Mn, Ni, Zn, Mo, Cd, Se and Sn (and probably Pb). Copper metallurgy areas showed high levels of As, Bi, Ga and Cu. Zinc metallurgy was characterised by high levels of Zn and Cd. Glazed ceramic production areas were linked to high levels of Zn, As, Se, Zr, Cs, Tl, Li, Co and Pb. High levels of Ni and V (in association) were tracers of petrochemical plants and/or fuel-oil combustion. At one site under the influence of heavy vessel traffic these elements could be considered tracers (although not exclusively) of shipping emissions. Levels of Zn–Ba and Cu–Sb were relatively high in urban areas when compared with industrialised regions due to tyre and brake abrasion, respectively.     

Trace element contaminants in mineral fertilizers used in Iran

The application of mineral fertilizers which have contaminants of trace elements may impose concern regarding the entry and toxic accumulation of these elements in agro-ecosystems. In this study, 57 mineral fertilizers (nitrogen, potassium, phosphate, and compound fertilizers) distributed in Iran were analyzed for their contents of Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, and Fe. The results revealed that the contents of these trace elements varied considerably depending on the type of the element and the fertilizer. Among these elements, Fe displayed the highest average content, whereas Cd showed the lowest. Generally, the trace element contents in P-containing fertilizers were higher than those in nitrogen and potassium fertilizers. The mean values of trace elements (mg kg^?1) in P-containing fertilizers were 4.0 (Cd), 5.5 (Co), 35.7 (Cr), 24.4 (Cu), 272 (Mn), 14.3 (Ni), 6.0 (Pb), 226 (Zn), and 2532 (Fe). Comparing trace element contents to limit values set by the German Fertilizer Ordinance showed that the mean contents of potentially toxic trace elements, such as Cd and Pb, were lower than their limit values in all groups of fertilizers. On the other hand, while a number of fertilizers contained a high content of some essential trace elements, particularly Fe, they were not labeled as such.     

Total element concentration and chemical fractionation in airborne particulate matter from Santiago,Chile

Total element determination and chemical fractionation were carried out in airborne particulate matter (PM₁₀) from the Cerrillos monitoring station in Santiago, Chile, sampled in July (winter), 1997–2003.Element concentration in the period under study (1997–2003) was statistically analyzed through cluster analysis in order to identify groups of elements having similar behavior along time. Elements such as Cd, Cu, Pb, Ni, As and Mg show a clear decrease in concentration with time. On the contrary, chromium increases its concentration almost linearly during the period.In order to estimate whether the presence of a certain element in PM₁₀ matrix is mainly due to anthropogenic or natural processes, the enrichment factor of each element was determined.According to their behavior in the sequential extraction procedure, the elements were grouped by multivariate analysis in three clusters: (a) those mobile elements (Pb, Cd, Zn, Mn, Cu and As) which are weakly bound to the matrix (fractions 1 and 2) (b) those elements (V, Ti, and Cr) mainly bound to carbonates and oxides (fraction 3) and (c) the most immobile elements (Ni, Mo, Ca, Mg, Ba and Al), mainly bound to silicates and organic matter (fraction 4). A source of great concern is the fact that elements of such high toxicity as Pb, Cd and As are highly concentrated in both mobile fractions, indicating that these elements have a direct impact on the environment and on the health of the exposed population.     

Distribution, availability, and sources of trace metals in different particle size fractions of urban soils in Hong Kong: Implications for assessing the risk to human health

The concentration and loading distribution of trace metals (Cu, Zn, Pb, Co, Ni, Cr, and Mn) and major elements (Al, Ca, Fe, and Mg) in different particle size fractions (2000-280, 280-100, 100-50, 50-10, 10-2, and <2 μm) of surface soils from highly urbanized areas in Hong Kong were studied. The enrichment of Pb, Cu, and Zn in the urban soils was strongly influenced by anthropogenic activities, and Pb accumulated in fine particles was mainly derived from past vehicular emissions as shown by Pb isotopic signatures. Trace metals primarily accumulated in clay, fine silt, and very fine sand fractions, and might pose potential health risks via the inhalation of resuspended soil particles in the air (PM₁₀ or PM_2.5), and ingestion of adhered soils through the hand-to-mouth pathway. The mobility, bioavailability, and human bioaccessibility of Pb and Zn in bulk soils correlated significantly with metal concentrations in fine silt and/or very fine sand fractions.     

Annual input fluxes and source identification of trace elements in atmospheric deposition in Shanxi Basin: the largest coal base in China

Industrialization and urbanization have led to a great deterioration of air quality and provoked some serious environmental concerns. One hundred and five samples of atmospheric deposition were analyzed for their concentrations of 13 trace elements (As, Cd, Cu, Fe, Al, Co, Cr, Hg, Mn, Mo, Pb, Se, and Zn) in Shanxi Basin, which includes six isolate basins. The input fluxes of the trace elements in atmospheric deposition were observed and evaluated. Geostatistical analysis (EF, PCA, and CA ) were conducted to determine the spatial distribution, possible sources, and enrichment degrees of trace elements in atmospheric deposition. Fe/Al and K/Al also contribute to identify the sources of atmospheric deposition. The distribution of trace elements in atmospheric deposition was proved to be geographically restricted. The results show that As, Cd, Pb, Zn, and Se mainly come from coal combustion. Fe, Cu, Mn, Hg, and Co originate mainly from interactions between local polluted soils and blowing dust from other places, while the main source of Al, Cr, and Mo are the soil parent materials without pollution. This work provides baseline information to develop policies to control and reduce trace elements, especially toxic elements, from atmospheric deposition. Some exploratory analytical methods applied in this work are also worth considering in similar researches.     

Mobility of heavy metals from polluted sediments of a semi-enclosed basin: in situ benthic chamber experiments in Taranto’s Mar Piccolo (Ionian Sea,Southern Italy)

In situ benthic flux experiments were conducted at two stations in the Mar Piccolo of Taranto (Italy), one of the most industrialised and contaminated coastal areas of the Mediterranean. Sediments of the two stations are notably different in their trace metal content, with a station closer to a Navy harbour showing higher mean concentrations of almost all investigated metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn). Conversely, both stations are characterised by significant Hg contamination, compared to the local baseline. Results of a sequential extraction scheme on surface sediments suggest a relatively scarce mobility of the examined metals (Zn > Ni > Cr > As > Cu > Pb). A Hg-specific extraction procedure showed that most of the element (93.1 %) occurs in a fraction comprising Hg bound to Fe/Mn oxi-hydroxides. Reduction of these oxides may affect Hg remobilisation and redistribution. Porewater profiles of dissolved trace metals were quite similar in the two sites, although significant differences could be observed for Al, Cu, Fe and Hg. The highest diffusive fluxes were observed for As, Fe and Mn. Mobility rates of several trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) were directly measured at the sediment–water interface. Results from benthic in situ incubation experiments showed increasing dissolved metal concentrations with time, resulting in higher fluxes for Cu, Fe, Hg, V and Zn in the most contaminated site. Conversely, fluxes of Mn, Ni and Pb were comparable between the two stations. The estimated flux of Hg (97 μg m^?2 day^?1) was the highest observed among similar experiments conducted in other highly contaminated Mediterranean coastal environments. Benthic fluxes could be partially explained by considering rates of organic matter remineralisation, dissolution of Fe/Mn oxy-hydroxides and metal speciation in sediments. Seasonal and spatial variation of biogeochemical parameters can influence metal remobilisation in the Mar Piccolo area. In particular, metals could be promptly remobilised as a consequence of oxygen depletion, posing a serious concern for the widespread fishing and mussel farming activities in the area.