Factors influencing PM10 emissions from road pavement wear

Accelerated pavement wear is one of the major environmental disadvantages of studded tyres in northern regions and results in increased levels of PM₁₀. Measurements of PM₁₀ in a road simulator hall have been used to study the influence of pavement properties, tyre type and vehicle speed on pavement wear. The test set-up included three different pavements (one granite and two quartzite with different aggregate sizes), three different tyre types (studded, non-studded, and summer tyres) and different speeds (30–70 km h^?1). The results show that the granite pavement was more prone to PM₁₀ production compared to the quartzite pavements. Studded winter tyres yield tens of times higher PM₁₀ concentrations compared to non-studded winter tyres. Wear from summer tyres was negligible in comparison. It was also shown that wear is strongly dependent on speed; every 10 km h^?1 increase yielded an increase of the PM₁₀ concentration of 680 μg m^?3 in one of the simulator experiments.     

Speciated mercury in size-fractionated particles in Shanghai ambient air

Size-fractionated particles were collected at two sites from July 2004 to April 2006 in Shanghai. The mercury in particles was extracted and divided operationally into four species: exchangeable particulate mercury (EXPM), HCl-soluble particulate mercury (HPM), elemental particulate mercury (EPM) and residual particulate mercury. The total particulate Hg concentration during the study period ranged from 0.07 ng m^?3 to 1.45 ng m^?3 with the average 0.56 ± 0.22 ng m^?3 at site 1, while 0.20 ng m^?3–0.47 ng m^?3 with the average 0.33 ± 0.09 ng m^?3 at site 2, which is far higher than some foreign cities and comparable to some cities with heavy air pollution in China. The Hg mass content also displayed evident size distribution, with higher value in PM_1.6–3.7, somewhat higher or lower than the source profile. EXAM was only found in the summer, HPM have higher percentage in summer and fall rather than in winter and spring. The different mercury species showed different correlation to temperature, relative humidity, wind speed. HPM positively depends on temperature at both sites which implies the importance of mercury transformation on particles. In foggy days TPM increased greatly, but HPM didn't vary greatly as anticipated. Instead, RPM gained a distinguished increase. It demonstrated that aqueous reaction and complex heterogenic reactions in droplet might happen in acidic environment. The correlation of mercury with other pollutants including SO₂, NO₂, CO and PM₁₀ varies with the different mercury forms. Hybrid single-particle lagrangian integrated trajectories (HYSPLIT) model was used to back trace air mass at different representative days and results indicated that transportation from Huabei Plain will increase mercury concentration in winter and fall to some extent. The possible existing compounds and their atmospheric behavior of HPM, EPM and RPM were calculated and the compared to analyze its implication on atmospheric mercury cycle.     

Growing season methane budget of an Inner Mongolian steppe

We present a methane (CH₄) budget for the area of the Baiyinxile Livestock Farm, which comprises approximately 1/3 of the Xilin river catchment in central Inner Mongolia, P.R. China. The budget calculations comprise the contributions of natural sources and sinks as well as sources related to the main land-use in this region (non-nomadic pastoralism) during the growing season (May–September). We identified as important CH₄ sources floodplains (mean 1.55 ± 0.97 mg CH₄–C m^?2 h^?1) and domestic ruminants, which are mainly sheep in this area. Within the floodplain significant differences between investigated positions were detected, whereby only positions close-by the river or bayous emitted large amounts of CH₄ (mean up to 6.21 ± 1.83 mg CH₄–C m^?2 h^?1). Further CH₄ sources were sheepfolds (0.08–0.91 mg CH₄–C m^?2 h^?1) and pasture faeces (1.34 ± 0.22 mg CH₄–C g^?1 faeces dry weight), but they did not play a significant role for the CH₄ budget. In contrast, dung heaps were not a net source of CH₄ (0.0 ± 0.2 for an old and 0.0 ± 0.3 μg CH₄–C kg^?1 h^?1 for a new dung heap). Trace gas measurements along two landscape transects (volcano, hill slope) revealed expectedly a mean CH₄ uptake (volcano: 76.5 ± 4.3; hill: 28.3 ± 5.3 μg CH₄–C m^?2 h^?1), which is typical for the aerobic soils in this and other steppe ecosystems. The observed fluxes were rarely influenced by topography.The CH₄ emissions from the floodplain and the sheep were not compensated by the CH₄ oxidation of aerobic steppe soils and thus, this managed semi-arid grassland did not serve as a terrestrial sink, but as a source for this globally important greenhouse gas. The source strength amounted to 1.5–3.6 kg CH₄–C ha^?1 during the growing season, corresponding to 3.5–8.7 kg C ha^?1 yr^?1.     

Observation and origin of organochlorine compounds and polycyclic aromatic hydrocarbons in the free troposphere over central Europe

On Zugspitze (2670 m a.s.l.), Alps, higher concentrations were observed during a winter than during a summer measurement campaign of PAHs, chlorobenzenes (43.6 vs. 2.0 pg m⁻³) and DDTs (3.7 vs. 1.2 pg m⁻³), while hexachlorocyclohexanes and PCBs were found at similar levels. The PCB, HCH and DDT levels are among the lowest ever reported from outside the Arctic. Mostly lower levels were found in samples collected in summer than in winter despite a significant boundary layer air influence, but no such influence on samples collected during the winter campaign. Boundary layer influence was quantified by Lagrangian particle dispersion model retroplume analyses. Photochemical lifetimes corresponding to k_OH < 1.5 × 10⁻¹² cm³ molec⁻¹ s⁻¹ are found for p,p′-DDT, k_OH < 0.75 × 10⁻¹² cm³ molec⁻¹ s⁻¹ for p,p′-DDE and k_OH < 1.0 × 10⁻¹² cm³ molec⁻¹ s⁻¹ for p,p′-DDD.     

Persistence of C-labeled atrazine and its residues in a field lysimeter soil after 22 years

Twenty-two years after the last application of ring-¹⁴C-labeled atrazine at customary rate (1.7 kg ha⁻¹) on an agriculturally used outdoor lysimeter, atrazine is still detectable by means of accelerated solvent extraction and LC-MS/MS analysis. Extractions of the 0-10 cm soil layer yielded 60% of the residual ¹⁴C-activity. The extracts contained atrazine (1.0 μg kg⁻¹) and 2-hydroxy-atrazine (42.5 μg kg⁻¹). Extractions of the material of the lowest layer 55-60 cm consisting of fine gravel yielded 93% of residual ¹⁴C-activity, of which 3.4 μg kg⁻¹ was detected as atrazine and 17.7 μg kg⁻¹ was 2-hydroxy-atrazine. The detection of atrazine in the lowest layer was of almost four times higher mass than in the upper soil layer. These findings highlight the fact that atrazine is unexpectedly persistent in soil. The overall persistence of atrazine in the environment might represent a potential risk for successive groundwater contamination by leaching even after 22 years of environmental exposure.     

Influence of a 1,800 MHz electromagnetic field on the EEG energy

The present study investigated the influence of electromagnetic fields (EMF), similar to that emitted by mobile phones, on brain activity. Ten women and ten men, matched for age and educational level, performed a short memory task (Wechsler test), with simultaneous Electroencephalogram (EEG) recordings at 15 scalp electrodes, both without (baseline) and with exposure to an 1,800 MHz signal. The EEG energy was found concentrated at the four basic EEG bands [α (8–13 Hz), β (14–30 Hz), δ (0–4 Hz), and θ (5–7 Hz)]. The analysis revealed that in the presence of EMF, the energy of the β band was significantly greater for females than for males at the majority of the electrodes. Since beta oscillation is associated with the shift of attention during the perception, these findings may indicate that the particular EMF (1,800 MHz signal) exerts an influence on this brain activity, which appears to be gender-related.     

Experimental investigation of the CO2 sealing efficiency of caprocks

Using a combination of experimental (petrophysical and mineralogical) methods, the effects of high-pressure CO₂ exposure on fluid transport properties and mineralogical composition of two pelitic caprocks, a limestone and a clay-rich marl lithotype have been studied. Single and multiphase permeability tests, gas breakthrough and diffusion experiments were conducted under in situ p/T conditions on cylindrical plugs (28.5 mm diameter, 10–20 mm thickness).The capillary CO₂ sealing efficiency of the initially water-saturated sample plugs was found to decrease in repetitive gas breakthrough experiments on the same sample from 0.74 to 0.41 MPa for the limestone and from 0.64 to 0.43 MPa for the marl. Helium breakthrough experiments before and after the CO₂ tests showed a decrease in capillary threshold (snap-off) pressure from 1.81 to 0.62 MPa for the limestone.Repetitive CO₂ diffusion experiments on the marlstone revealed an increase in the effective diffusion coefficient from 7.8 × 10^?11 to 1.2 × 10^?10 m².Single-phase (water) permeability coefficients derived from steady-state permeability tests ranged between 7 and 56 nano-Darcy and showed a consistent increase after each CO₂ test cycle. Effective gas permeabilities were generally one order of magnitude lower than water permeabilities and exhibit the same trend. XRD measurements performed before and after exposure to CO₂ did not reveal any distinct change in the mineral composition for both samples. Similarly, no significant changes were observed in specific surface areas (determined by BET) and pore-size distributions (determined by mercury injection porosimetry). High-pressure CO₂ sorption experiments on powdered samples revealed significant CO₂ sorption capacities of 0.27 and 0.14 mmol/g for the marlstone and the limestone, respectively.The changes in transport parameters in the absence of detectable mineral alterations may be explained by carbonate dissolution and further precipitation along a pH profile across the sample plug which would not be subject to quantitative mineral alteration.     

New jet-aeration system using ‘Supercavitation’

Background, aim and scope  

A newly developed fine bubble aeration system, by which air is transferred under supercavitation conditions, shows a clearly better performance than traditional, well-known aerators that rely on the jet-pump principle and its performance can be compared to oxygen transfer rates achieved in membrane and foil plate aerators.     

Survival of selected pathogens in diluted sludge of a thermophilic waste treatment plant and in NaCl-solution under aerobic and anaerobic conditions

Decimal reduction times (DRT or D-value) of Campylobacter jejuni, Salmonella enterica (formerly Salmonella choleraesuis) serovar Senftenberg, Escherichia coli, and Listeria monocytogenes were determined in two different matrices, diluted fermenter sludge (DFS) and 0.95% NaCl-solution (NaCl) at 50 degrees C, both under aerobic and anaerobic conditions. Depending on aeration, matrix composition, and the respective organism, the D-values varied between 10min and more than 15h. Generally the viability of bacteria decreased faster in DFS compared to NaCl-solution and under aerobic compared to anaerobic conditions. After 24h no viable cells could be detected in DFS, both under aerobic as well as under anaerobic conditions, whereas viable cells were still found in NaCl solutions. In both matrices the detection limits determined by means of PCR-based and classical microbiological methods were compared and pointed to lower detection limits of the latter methods. Results of the present investigation show that test organisms were far from surviving several days in DFS whereas hydraulic retention times normally used for thermophilic anaerobic digestion are in the range of 2 weeks. However, an underestimation of survival rates of the test organisms seems probable when applying aerobic standard methods.     

Risk assessment of dioxins and dioxin-like PCBs in food--comments by the German Federal Environmental Agency

Human health risk assessments for dioxins and dioxin-like PCBs (with the exception of the one by US-EPA) recommend health based exposure limits within the range of 1-4 pg WHO-TEQ/kg bw per day. As all humans are exposed to measurable levels of dioxins and related substances, the determination of the tolerated daily intake is a very significant decision and may influence limit values guiding risk reduction measures and target levels. The proposed TDI has to protect all human subpopulations. In the case of dioxin this is particularly important as the exposure of infants through breast-feeding may exceed the exposure of adults by one or two orders of magnitude. An overview of recently recommended limit values (WHO, SCF, JECFA) for PCDDs, PCDFs and dioxin-like PCBs using WHO-TEFs shows the common feature that the values were derived only from non carcinogenic endpoints. In November 2000 the Scientific Committee on Food of the European Commission published an 'Opinion of the SCF on the Risk Assessment of Dioxins and Dioxin-like PCBs in Food' [SCF, Scientific Committee on Food 2000. Opinion of the SCF on the risk assessment of dioxins and dioxin-like PCBs in food. European Commission, Brussels, Adopted on November 2000 http://europa.eu.int/comm/food/fs/sc/scf/out78_en.pdf]. On the basis of this extensive review of data and experimental results the Committee recommended a temporary tolerable weekly intake (t-TWI) of 7 pg WHO-TEQ/kg bw. Only six months later the SCF carried out a re-evaluation of its t-TWI from November 2000. The reconsideration of 'pivotal studies' led to the situation that the re-assessment is now based only on rat studies which investigated only reproductive effects only on male offspring and, in addition, three of these studies are single dose studies at gestational day 15. Applying an overall uncertainty factor of 10 to the LOAEL derived estimated human daily intakes (EHDI) the SCF concluded that 14 pg/kg bw per week should be considered as a tolerable intake for 2,3,7,8-TCDD. The SCF stated that on a body weight basis, the dioxin intake of breast-fed infants has been estimated to be one to two orders of magnitude higher than the average adult intake. Recent German data suggest that the body burden of formerly breast-fed children aged 9-11 is still about 30% higher than those of their formula-fed age-mates. As breast-feeding has measurable benefits for neurological and immunological development, formula feeding cannot be recommended as an alternative to lower dioxin intake. So the only remaining way to lower the dioxin uptake is to drastically reduce the background exposure of the general population. It is acknowledged that any recommendation of a precise number for a TDI is flawed by uncertainties and the possibility of different weight being given to the studies of relevance. The determination of the TDI has influence on all regulatory limit values that are based on the TDI value. A higher TDI lowers the level of protection for humans. It is proposed by the German Federal Environmental Agency that the TDI should be reassessed in a process transparent to the public and on the basis of all relevant endpoints from animal experiments and human epidemiology, including the assessment of cancer risks.