Heavy metal distribution in dust from elementary schools in Hermosillo,Sonora, México

The city of Hermosillo, Sonora in northern Mexico was investigated for its heavy metals content. Samples of sedimented dust in roofs from 25 elementary schools were analyzed for their contents of Ni, Cr, Zn, Cd, Co, Ba, V, Pb, Fe and Cu after digestion with nitric acid. The results of the analysis were used to determine spatial distribution and magnitude of heavy metals pollution. The results of this study reveal that heavy metals distribution is different in two areas of the city. The southern area contains higher concentrations of heavy metals than the northcentral area. The mean level of Cd in exterior dust is 5.65 mg kg⁻¹ in the southern area whereas the mean level of Cd is 2.83 mg kg⁻¹ in the northcentral area. Elevated concentrations of Zn (2012 mg kg⁻¹), Pb (101.88 mg kg⁻¹), Cr (38.13 mg kg⁻¹) and Cd (28.38 mg kg⁻¹) in roof dust were found in samples located near industrial areas. Principal component analysis (PCA) was applied to the data matrix to evaluate the analytical results and to identify the possible pollution sources of metals. PCA shows two main sources: (1) Pb, Cd, Cr and Zn are mainly derived from industrial sources, combined with traffic sources; (2) Fe, Co and Ba are mainly derived from natural sources. V and Ni are highly correlated and possibly related to fuel combustion processes. Enrichment factors were calculated, which in turn further confirms the source identification. Ba and Co are dominantly crustal. Anthropogenically added Cd, Pb, Zn and Cr show maximum enrichment relative to the upper continental crustal component. The distribution of the heavy metals in dust does not seem to be controlled only by the topography of the city, but also by the location of the emission sources.     

Real-world emission factors of fifteen carbonyl compounds measured in a Hong Kong tunnel

Real-world vehicle emissions of carbonyls were determined in summer and winter of 2003 at the Shing Mun Tunnel, Hong Kong. Fifteen carbonyl species have been analyzed in this study. The total measured carbonyls emission factors ranged from 21.7 to 68.9 mg veh⁻¹ km⁻¹ among different measurement periods, with an average of 35.8±11.9 mg veh⁻¹ km⁻¹. Higher carbonyl emissions were found to be associated with a high proportion of diesel-fueled vehicles. Total measured carbonyl emissions from Diesel-fueled Vehicle (DV, 71.5 mg veh⁻¹ km⁻¹) were about 7 times higher than those from Non-Diesel-fueled Vehicle (NDV, 10 mg veh⁻¹ km⁻¹). The five carbonyls with the largest DV emission factor were, in decreasing order, formaldehyde (38.3 mg veh⁻¹ km⁻¹), acetaldehyde (11.4 mg veh⁻¹ km⁻¹), acetone (5.3 mg veh⁻¹ km⁻¹), crotonaldehyde (5.2 mg veh⁻¹ km⁻¹) and benzaldehyde (2.0 mg veh⁻¹ km⁻¹). These five carbonyl compounds together accounted for 87% of the sum of all DV carbonyl emission factors. For NDV, the five most abundant carbonyls in NDV emission at the tunnel were, in decreasing order, formaldehyde (3.5 mg veh⁻¹ km⁻¹), acetone (1.8 mg veh⁻¹ km⁻¹), methyl ethyl ketone (1.6 mg veh⁻¹ km⁻¹), m,p-tolualdehyde (1.0 mg veh⁻¹ km⁻¹) and acetaldehyde (mg veh⁻¹ km⁻¹). They accounted for 85% of the sum of all NDV carbonyl emission factors.     

Fine,ultrafine and nanoparticle trace element compositions near a major freeway with a high heavy-duty diesel fraction

Trace elements and metals in the ultrafine (<0.18 μm) and accumulation (0.18–2.5 μm) particulate matter (PM) modes were measured during the winter season, next to a busy Southern California freeway with significant (∼20%) diesel traffic. Both ambient and concentrated size-segregated impactor samples were taken in order to collect enough mass for chemical analysis. Data at this location were compared to a site located 1 mile downwind of the freeway, which was reflective of urban background. The most abundant trace elements in the accumulation mode detected by inductively coupled plasma mass spectroscopy (ICPMS) were S (138 ng m⁻³), Na (129 ng m⁻³), and Fe (89 ng m⁻³) while S (35 ng m⁻³) and Fe (35 ng m⁻³) were the most abundant in the ultrafine mode. The concentrations of several trace elements, including Mg, Al, and Zn, and in particular Ca, Cu, and Pb, did not uniformly increase with size within fine PM, an indication that various roadway sources exist for these elements. Calculation of crustal enrichment factors for the two sites indicates that the freeway traffic contributed to enriched levels of ultrafine Cu, Ba, P and Fe and possibly Ca. The results of this study show that trace elements constitute a small fraction of PM mass in the nanoparticle size range, but these can and should be characterized due to their likely importance to human health.     

Removal of aqueous lead by poorly-crystalline hydroxyapatites

The use of a phosphorus amendment in altering Pb to a chemically less mobile phase is a promising strategy based on minimizing ecotoxicological risk and improving time and cost efficiency. This study evaluated crystalline and poorly-crystalline hydroxyapatite sorbents on removal of aqueous Pb in response to reaction time, solution pH, and Pb concentration. Batch experiments were conducted using a commercially-available crystalline hydroxyapatite (HA), and two poorly-crystalline hydroxyapatites synthesized from gypsum waste (CHA) and incinerated ash of poultry waste (MHA). Poorly-crystalline hydroxyapatites had greater capacity for Pb removal from a solution with a wider pH range as compared to a crystalline hydroxyapatite. The maximum sorption capacity of Pb determined by the Langmuir model was 500 mg g⁻¹ for CHA, 277 mg g⁻¹ for MHA and 145 mg g⁻¹ for HA. Removal of aqueous Pb by CHA was not dependent on solution pH, with a 98.8% reduction throughout the solution pH range of 2–9, whereas aqueous Pb removal by HA and MHA was pH-dependent with less removal in the neutral solution pH. Poorly-crystalline hydroxyapatites may provide an effective alternative to existing remediation technologies for Pb-contaminated sites.     

Mercury deposition through litterfall in an Atlantic Forest at Ilha Grande,Southeast Brazil

Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha⁻¹ y⁻¹, with leaves composing 50–84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g⁻¹, with higher concentrations during the dry season, between June and August (225 ± 17 ng g⁻¹), and lower concentrations during the rainy season (99 ± 54 ng g⁻¹). This seasonal variability was reflected in the Hg flux through litterfall, which corresponded to a Hg input to the forest floor of 122 μg m⁻² y⁻¹, with average Hg deposition of 16.5 ± 1.5 μg m⁻² month⁻¹ during and just after the dry season (June–September) and 7.0 ± 3.6 μg m⁻² month⁻¹ in the rest of the year. The variability in meteorological conditions (determining atmospheric Hg availability to foliar scavenging) may explain the pulsed pattern of Hg deposition, since litterfall temporal variability was generally unrelated with such deposition, except by a peak in litterfall production in September. Comparisons with regional data on Hg atmospheric deposition show that litterfall promotes Hg deposition at Ilha Grande two to three orders of magnitude higher than open rainfall deposition in non-industrialized areas and approximately two times higher than open rainfall deposition in industrialized areas in Rio de Janeiro State. The observed input suggests that atmospheric Hg transfer through litterfall may explain a larger fraction of the total Hg input to forest soils in Southeast Brazil than those recorded at higher latitudes.     

Phosphine in the marine atmosphere along a hemispheric course from China to Antarctica

The gas phosphine (PH₃) is a part of an atmospheric link of the phosphorus cycle on earth. Previous research reported the terrestrial lower tropospheric PH₃ at night in the 1 ng m⁻³ range in remote areas, with the peak of 100 ng m⁻³ in populated areas, and at daytime even lower concentrations in the pg m⁻³ range. The data of the global marine atmospheric PH₃ are still very sparse.This study presents surprisingly high concentrations of PH₃ in the order of 0.1–1 μg m⁻³ in many of 32 samples of the marine atmosphere in the latitudinal range from 30°N to 65°S (the cruise of research ship Xuelong from Shanghai Harbor, China, to Antarctica). The highest concentrations were measured near coastal areas of Eastern Asia and Western Australia. A significant correlation exists between marine atmospheric PH₃ concentration and air temperature at 22:00 (local time). PH₃ concentrations at different latitudes strongly decline with daylight intensity according to a logarithmic relationship. These surprisingly high concentrations of the readily oxidizable PH₃ in the air indicate hitherto unknown but important PH₃ emission sources in marine environment. More work is necessary to evaluate the sources of atmospheric PH₃ from marine biosphere.     

Mass levels,crustal component and trace elements in PM10 in Palermo,Italy

Results concerning the levels and elemental compositions of daily PM₁₀ samples collected at four air quality monitoring sites in Palermo (Italy) are presented. The highest mean value of PM₁₀ concentrations (46 μg m⁻³, with a peak value of 158 μg m⁻³) was recorded at the Di Blasi urban station, and the lowest at Boccadifalco station (25 μg m⁻³), considered as a sub-urban background station. Seventeen elements (Al, As, Ba, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sb, Sr, U, V, Zn) were measured by ICP-MS. Al and Fe showed the highest concentrations, indicating the significant contribution of soil and resuspended mineral particles to atmospheric PM₁₀. Ba, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V and Zn had higher concentrations at the three urban sampling sites than at the sub-urban background station. Besides soil-derived particles, an R-mode cluster analysis revealed a group of elements, Mo, Cu, Cr, Sb and Zn, probably related to non-exhaust vehicle emission, and another group, consisting of Ba, As and Ni, which seemed to be associated both with exhaust emissions from road traffic, and other combustion processes such as incinerators or domestic heating plants. The results also suggest that Sb, or the association Sb–Cu–Mo, offers a way of tracing road traffic emissions.     

Emission factors of PAHs,methoxyphenols, levoglucosan,elemental carbon and organic carbon from simulated wheat and Kentucky bluegrass stubble burns

Emission factors (EFs) of pollutants from post-harvest agricultural burning are required for predicting downwind impacts of smoke and inventorying emissions. EFs of polycyclic aromatic hydrocarbons (PAH), methoxyphenols (MP), levoglucosan (LG), elemental carbon (EC) and organic carbon (OC) from wheat and Kentucky bluegrass (KBG) stubble burning were quantified in a US EPA test burn facility. The PAH and MP EFs for combined solid+gas phases are 17±8.2 mg kg⁻¹ and 79±36 mg kg⁻¹, respectively, for wheat and 21±15 mg kg⁻¹ and 35±24 mg kg⁻¹, respectively, for KBG. LG, particulate EC and artifact-corrected OC EFs are 150±130 mg kg⁻¹, 0.35±0.16 g kg⁻¹ and 1.9±1.1 g kg⁻¹, respectively, for wheat and 350±510 mg kg⁻¹, 0.63±0.056 g kg⁻¹ and 6.9±0.85 g kg⁻¹, respectively, for KBG. Positive artifacts associated with OC sampling were evaluated and remedied with a two-filter system. EC and OC accounted for almost two-thirds of PM_2.5 mass, while LG accounted for just under 3% of the PM_2.5 mass. Since EFs of these pollutants generally decreased with increasing combustion efficiency (CE), identifying and implementing methods of increasing the CEs of burns would help reduce their emissions from agricultural field burning. PAH, OC and EC EFs are comparable to other similar studies reported in literature. MP EFs appear dependent on the stubble type and are lower than the EFs for hard and softwoods reported in literature, possibly due to the lower lignin content in wheat and KBG.     

Methane emissions from lakes and floodplains in Pantanal,Brazil

To evaluate the tropical wetlands contribution to the methane (CH₄) burden better, field campaigns were performed during 2004 and 2005 near the Miranda River, in five sites inside the Brazilian Pantanal region. The CH₄ fluxes were determined using the static chamber technique. Environmental variables that may affect CH₄ emissions, as the water depth, the water and air temperatures were also measured. The overall average of the 320 individual CH₄ flux measurements made between March/2004 and March/2005 was 142±314 mg CH₄ m⁻² d⁻¹, which is a value near the ones observed in other tropical flooded regions. About 47% of the fluxes measurements presented nonlinear increases in the chamber concentrations, which were assumed to be linked to CH₄ losses through bubbles. The bubble flux represented about 90% of the total CH₄ losses in the measurements and ranged from 1 to 2187 mg CH₄ m⁻² d⁻¹ with an average of 292±410 mg CH₄ m⁻² d⁻¹ (median: 153 mg CH₄ m⁻² d⁻¹). The diffusive flux ranged from 1 to 124 mg CH₄ m⁻² d⁻¹, with an average of 10±17 mg CH₄ m⁻² d⁻¹ (median: 5 mg CH₄ m⁻² d⁻¹). The fluxes from lakes were smaller than those observed in the floodplains, where the flooding was more dependent on the seasonal cycle. The diffusive flux showed a slight, but not statistically significant seasonal variation, following the seasonal variation of the flooding of the Pantanal region. A rough estimative of the total annual CH₄ emission shows that the contribution of the Pantanal is about 3.3 Tg CH₄ yr⁻¹, which represents about 3.3% of the total CH₄ emissions estimated to be originated in wetlands ecosystems. It may be a conservative estimate, which may present a large interannual variation, since it was obtained during one of the lowest flood of the Pantanal in recent years.     

Importance of wet precipitation as a removal and transport process for atmospheric water soluble carbonyls

Carbonyl compounds exist in the atmosphere as either gases or aerosols. Some of them are water soluble and known as oxidation products of biogenic and/or anthropogenic hydrocarbons. Five carbonyl compounds, glyoxal (GO), 4-oxopentanal (4-OPA), glycolaldehyde (GA), hydroxyacetone (HA) and methylglyoxal (MG) have been identified in a temporal series of 12 rain samples. The concentrations of the compounds in the samples were high at the beginning of the rain event and decreased with time to relatively low and fairly constant levels, indicating that the compounds were washed out from the atmosphere at the start of the rain event. Possibly, these compounds also existed in the cloud condensation nuclei (CCN). Wet deposition rates of the carbonyl compounds were calculated for nine samples collected during a 20 h period. The deposition rates ranged from 0 (4-OPA) to 1.2×10⁻¹ mg C m⁻² h⁻¹ (MG) with the average of 2.9×10⁻² mg C m⁻² h⁻¹. Production rates of isoprene oxidation products (GA, HA and MG) in the area surrounding the sampling site were estimated with a chemical box model. The deposition rates exceeded the production rates in most samples. This indicates that the rainfall causes a large net flux of the water soluble compounds from the atmosphere to the ground. Insoluble carbonyl compounds such as n-nonanal and n-decanal were expected to be present in the atmosphere, but were not detected in the rain during the sampling period, suggesting that an aerosol containing these insoluble compounds does not effectively act as a CCN.     

Atmospheric distribution of polycyclic aromatic hydrocarbons and deposition to Galveston Bay,Texas, USA

Estimates of the atmospheric deposition to Galveston Bay of polycyclic aromatic hydrocarbons (PAHs) are made using precipitation and meteorological data that were collected continuously from 2 February 1995 to 6 August 1996 at Seabrook, TX, USA. Particulate and vapor phase PAHs in ambient air and particulate and dissolved phases in rain samples were collected and analyzed. More than 95% of atmospheric PAHs were in the vapor phase and about 73% of PAHs in the rain were in the dissolved phase. Phenanthrene and napthalene were the dominant compounds in air vapor and rain dissolved phases, respectively, while 5 and 6 ring PAH were predominant in the particulate phase of both air and rain samples. Total PAH concentrations ranged from 4 to 161 ng m⁻³ in air samples and from 50 to 312 ng l⁻¹ in rain samples. Temporal variability in total PAH air concentrations were observed, with lower concentrations in the spring and fall (4–34 ng m ⁻³) compared to the summer and winter (37–161 ng m⁻³). PAHs in the air near Galveston Bay are derived from both combustion and petroleum vaporization. Gas exchange from the atmosphere to the surface water is estimated to be the major deposition process for PAHs (1211 μg m^{− 2} yr^{− 1}), relative to wet deposition (130 μg m⁻² yr^{− 1}) and dry deposition (99 μg m⁻² yr^{− 1}). Annual deposition of PAHs directly to Galveston Bay from the atmosphere is estimated as 2  t yr⁻¹.     

Effect of natural compounds on reducing formaldehyde emission from plywood

The effects of natural compounds on reducing formaldehyde emission from plywood were investigated. Urea, catechin and vanillin were examined as the natural formaldehyde reducers. The microemission cell, with an internal volume of 35 ml, the maximum exposed test surface area of 177 cm² and an air purge flow rate of 50 ml min⁻¹, was used to measure specific emission rate (SER). In the case of no reducer treatment, formaldehyde emission from plywood was fast and SERs were 4.4 mg m⁻² h⁻¹ at 30 °C and 15 mg m⁻² h⁻¹ at 60 °C. When this plywood was treated with the natural compounds, the SERs of formaldehyde were decreased at all temperatures. In the case of urea treatment, the SERs of formaldehyde decreased to 0.30 mg m⁻² h⁻¹ at 30 °C and 0.65 mg m⁻² h⁻¹ at 60 °C. When the urea treatment was applied to the inside of kitchen cabinet (made from plywood; 270 cm wide, 60 cm deep, 250 cm high), the concentration of formaldehyde was reduced substantially from 1600 to 130 μg m⁻³. The reducing effect of formaldehyde continued during the observation period (6 months), with a mean concentration of 100 μg m⁻³. Reducers in the plywood would react with released formaldehyde. Application of natural compounds such as urea, catechin and vanillin could provide a simple and effective approach for suppressing formaldehyde emission from plywood.     

Natural radioactivity levels in soil samples from some areas of Himachal Pradesh,India using γ-ray spectrometry

²²⁶Ra, ²³²Th and ⁴⁰K analysis has been carried out in soil samples collected from some areas of Himachal Pradesh, India using γ-ray spectrometry. The measured activity in soil ranges from 42.09 to 79.63 Bq kg⁻¹, 52.83 to 105.81 Bq kg⁻¹ and 95.33 to 160.30 Bq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K with the mean values of 57.34, 82.22 and 135.75 Bq kg⁻¹, respectively. The measured activity concentration of ²²⁶Ra and ²³²Th in soil samples collected from these areas is higher and for ⁴⁰K is lower than the world average. The radium equivalent activity in all the soil samples is lower than the safe limit set in the OECD report (370 Bq kg⁻¹). The value of the external exposure dose has been determined from the content of these radionuclides in soil. It has been observed that on the average, the outdoor terrestrial gamma air absorbed dose rate is about 83.28 nGy h⁻¹. The study yields an annual effective dose in the range of 0.07–0.13 mSv. The average value of annual effective dose lies in the global range of outdoor radiation exposure given in United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) [(2000). Effects and risks of ionizing radiations. UN, NY]. The activity concentration of ²³⁸U has also been determined using fission track technique and the values range from 3.26 to 7.71 mg kg⁻¹ with a mean value of 4.38 mg kg⁻¹.     

Characteristics of vertical profiles and sources of PM2.5, PM10 and carbonaceous species in Beijing

In August 2003 during the anticipated month of the 2008 Beijing Summer Olympic Games, we simultaneously collected PM₁₀ and PM_2.5 samples at 8, 100, 200 and 325 m heights up a meteorological tower and in an urban and a suburban site in Beijing. The samples were analysed for organic carbon (OC) and elemental carbon (EC) contents. Particulate matter (PM) and carbonaceous species pollution in the Beijing region were serious and widespread with 86% of PM_2.5 samples exceeding the daily National Ambient Air Quality Standard of the USA (65 μg m⁻³) and the overall daily average PM₁₀ concentrations of the three surface sites exceeding the Class II National Air Quality Standard of China (150 μg m⁻³). The maximum daily PM_2.5 and PM₁₀ concentrations reached 178.7 and 368.1 μg m⁻³, respectively, while those of OC and EC reached 22.2 and 9.1 μg m⁻³ in PM_2.5 and 30.0 and 13.0 μg m⁻³ in PM₁₀, respectively. PM, especially PM_2.5, OC and EC showed complex vertical distributions and distinct layered structures up the meteorological tower with elevated levels extending to the 100, 200 and 300 m heights. Meteorological evidence suggested that there exist fine atmospheric layers over urban Beijing. These layers were featured by strong temperature inversions close to the surface (<50 m) and more stable conditions aloft. They enhanced the accumulation of pollutants and probably caused the complex vertical distributions of PM and carbonaceous species over urban Beijing. The built-up of PM was accompanied by transport of industrial emissions from the southwest direction of the city. Emissions from road traffic and construction activities as well as secondary organic carbon (SOC) are important sources of PM. High OC/EC ratios (range of 1.8–5.1 for PM_2.5 and 2.0–4.3 for PM₁₀) were found, especially in the higher levels of the meteorological tower suggesting there were substantial productions of SOC in summer Beijing. SOC is estimated to account for at least 33.8% and 28.1% of OC in PM_2.5 and PM₁₀, respectively, with higher percentages at the higher levels of the tower.     

Characterization of emissions from portable household combustion devices: particle size distributions,emission rates and factors,and potential exposures

A series of source tests were conducted to characterize emissions of particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), and total hydrocarbon (THC ) from five types of portable combustion devices. Tested combustion devices included a kerosene lamp, an oil lamp, a kerosene space heater, a portable gas range, and four unscented candles. All tests were conducted either in a well-mixed chamber or a well-mixed room, which enables us to determine emission rates and emission factors using a single-compartment mass balance model. Particle mass concentrations and number concentrations were measured using a nephelometric particle monitor and an eight-channel optical particle counter, respectively. Real-time CO concentrations were measured with an electrochemical sensor CO monitor. CO₂, CH₄, and THC were measured using a GC-FID technique. The results indicate that all particles emitted during steady burning in each of the tested devices were smaller than 1.0 μm in diameter with the vast majority in the range between 0.1 and 0.3 μm. The PM mass emission rates and emission factors for the tested devices ranged from 5.6±0.1 to 142.3±40.8 mg h⁻¹ and from 0.35±0.06 to 9.04±4.0 mg g⁻¹, respectively. The CO emission rates and emission factors ranged from 4.7±3.0 to 226.7±100 mg h⁻¹ and from 0.25±0.12 to 1.56±0.7 mg g⁻¹, respectively. The CO₂ emission rates and emission factors ranged from 5500±700 to 210,000±90,000 mg h⁻¹ and from 387±45 to 1689±640 mg g⁻¹, respectively. The contributions of CH₄ and THC to emission inventories are expected to be insignificant due both to the small emission factors and to the relatively small quantity of fuel consumed by these portable devices. An exposure scenario analysis indicates that every-day use of the kerosene lamp in a village house can generate fine PM exposures easily exceeding the US promulgated NAAQS for PM_2.5.     

Effects of aqueous stable fullerene nanocrystals (nC60) on Daphnia magna: Evaluation of sub-lethal reproductive responses and accumulation

Concerns exist regarding the inadvertent release of engineered nanomaterials into natural systems, and the possible negative ecosystem response that may occur. Understanding sub-lethal effects may be particularly important to determining ecosystem responses as current levels of nanomaterial release are low compared to levels projected for the future. In this work, the sub-lethal effects and bioaccumulation of water stable, nanocrystalline fullerenes as C₆₀, (termed nC₆₀) were studied in Daphnia magna, a globally distributed, parthenogenetic zooplankton. Sub-lethal concentrations were first determined for both mature mother (LD₅₀ = 0.4 mg L⁻¹) and neonate (gestating) daphnids (0.2 mg L⁻¹) in standard 48 h exposure tests. Subsequent experiments focused on the accumulation and effects (at temperatures of 18–28 °C) of nC₆₀, during the D. magna reproductive cycle. The results demonstrate that upon sub-lethal exposure, the mortality rates of gestating daphnids increased with time and developmental stage. The maturation of daughter daphnids was negatively impacted. The mother daphnids were unable to reproduce again after exposure during pregnancy, and differential bioaccumulation occurred as a function of lipid content in the daphnia with the highest accumulation level of 7000 mg kg⁻¹ wet weight. Taken together, these results not only describe the accumulation and sub-lethal effects of nC₆₀ on exposed daphnia, but also highlight the importance of sub-lethal exposure scenarios, which are critical to fully understanding the potential impact of fullerenes and other engineered nanoscale materials on natural systems.     

Nitrous oxide emissions from mineral and organic soils of a Norway spruce stand in South–West Germany

Due to the high temporal and spatial variability of N₂O fluxes, estimates of N₂O emission from temperate forest ecosystems are still highly uncertain, particularly at larger scales. Although highest N₂O emissions with up to 7.0 kg N ha⁻¹ yr⁻¹ were mainly reported for soils affected by stagnant water, most of the reported gas flux measurements were performed at forest sites with well-aerated soils yielding mostly to low mean annual emission rates less than 1.0 kg N ha⁻¹ yr⁻¹. This study compares N₂O fluxes from upland (Cambisols) and temporally water-logged (Gleysols, Histosols) soils of the Central Black Forest (South-West Germany) over a period of 2 yr. Mean annual N₂O fluxes from investigated soils ranged between 0.2 and 3.9 kg N ha⁻¹ yr⁻¹. The fluxes showed a large variability between the different soil types. Emissions could be clearly ranked in the following order: Cambisols (0.26–0.75 kg N ha⁻¹ yr⁻¹)<Gleysols (1.37–2.68 kg N ha⁻¹ yr⁻¹)<Histosol (3.66–3.95 kg N ha⁻¹ yr⁻¹). Although the Cambisols cover two-thirds of the investigated area, only about half of the overall N₂O is emitted from this soil type. Therefore, regional or national N₂O fluxes from temperate forest soils are underestimated if soils characterised by intermediate aeration conditions are disregarded.     

Preparation of controlled nano-MgO and investigation of its bactericidal properties

Nano-MgO is a good bactericide but with strong alkalinity in water due to its rapid hydrolysis. To control its hydrolysis rate and keep its bactericidal properties, we synthesized nano-MgO microspheres using chitosan–alginate system in this study. The synthesized nano-MgO release-controlled microspheres (nMgO-RCM) were with 0.98–1.20 mm of particle sizes. Also, their embedding ratio and loading percentage was 63.52% and 12.27%, respectively. Based on the characterization results, nano-MgO was only observed on surface of the nMgO-RCM. Its release rate from the nMgO-RCM could be controlled by the chitosan–alginate system, and the observed rate constant (k_obs) increased from 0.0289 h⁻¹ to 0.0358 h⁻¹ with the increment of the dosage from 10 mg L⁻¹ to 80 mg L⁻¹. Furthermore, the nMgO-RCM could maintain pH value lower than 8.5 and colony counts less than 20 CFU mL⁻¹ for at least 120 h.     

Dry deposition and foliar leaching of mercury and selected trace elements in deciduous forest throughfall

The estimated annual throughfall deposition flux of Hg in a northern mixed-hardwood forest in the Lake Huron Watershed was 10.5±1.0 μg m⁻² compared to an annual precipitation Hg flux of 8.7±0.5 μg m⁻² (June 1996–June 1997). The source of this additional Hg in throughfall is often attributed to wash-off of dry deposition, but foliar leaching of Hg may also be important. To determine the influence of both dry deposition and foliar leaching of Hg and other elements in throughfall, we measured a suite of trace elements (Hg, Al, Mg, V, Mn, Cu, Zn, As, Rb, Sr, Cd, Ba, La, Ce, and Pb) in throughfall, precipitation, and ambient air samples from a northern mixed-hardwood forest. Based on a multiple linear regression model, dry deposition had the most important influence on Hg, Al, La, Ce, V, As, Cu, Zn, Cd, and Pb fluxes while foliar leaching strongly influenced Mg, Mn, Rb, Sr, and Ba fluxes in net throughfall. The Hg dry deposition flux was estimated using gaseous and aerosol Hg measurements and modeled deposition velocities. The calculated dry deposition flux (∼12–14 μg m⁻²) of Hg to the canopy indicated that atmospheric deposition of Hg could easily account for all of the Hg deposited in net throughfall (1.9±0.1 μg m⁻²). Although there is a large uncertainty associated with these techniques, the modeling estimates indicate that atmospheric Hg may account for all of the Hg deposited in litterfall (11.4±2.8 μg m⁻²).     

Decadal reductions of traffic emissions on a transit route in Austria – results of the Tauerntunnel experiment 1997

Real-world emissions of a traffic fleet on a transit route in Austria were determined in the Tauerntunnel experiment in October 1997. The total number of vehicles and the average speed was nearly the same on both measuring days (465 vehicles 30 min⁻¹ and 76 km h⁻¹ on the workday, 477 and 78 km h⁻¹ on Sunday). The average workday fleet contained 17.6% heavy-duty vehicles (HDV) and the average Sunday fleet 2.8% HDV resulting in up to four times higher emission rates per vehicle per km on the workday than on Sunday for most of the regulated components (CO₂, CO, NO_x, SO₂, and particulate matter-PM10). Emission rates of NMVOC accounted for 200 mg vehicle⁻¹ km⁻¹ on both days. The relative contributions of light-duty vehicles (LDV) and HDV to the total emissions indicated that aldehydes, BTEX (benzene, toluene, ethylbenzene, xylenes), and alkanes are mainly produced by LDV, while HDV dominated emissions of CO, NO_x, SO₂, and PM10. Emissions of NO_x caused by HDV were 16,100 mg vehicle⁻¹ km⁻¹ (as NO₂). Produced by LDV they were much lower at 360 mg vehicle⁻¹ km⁻¹. Comparing the emission rates to the results that were obtained by the 1988 experiment at the same place significant changes in the emission levels of hydrocarbons and CO, which accounted 1997 to only 10% of the levels in 1988, were noticed. However, the decrease of PM has been modest leading to values of 80 and 60% of the levels in 1988 on the workday and on Sunday, respectively. Emission rates of NO_x determined on the workday in 1997 were 3130 mg vehicle⁻¹ km⁻¹ and even higher than in 1988 (2630 mg vehicle⁻¹ km⁻¹), presumable due to the increase of the HD-traffic.