Enrichments of the mantle sources beneath the Southern Volcanic Zone (Andes) by fluids and melts derived from abraded upper continental crust

Mafic basaltic-andesitic volcanic rocks from the Andean Southern Volcanic Zone (SVZ) exhibit a northward increase in crustal components in primitive arc magmas from the Central through the Transitional and Northern SVZ segments. New elemental and Sr–Nd-high-precision Pb isotope data from the Quaternary arc volcanic centres of Maipo (NSVZ) and Infernillo and Laguna del Maule (TSVZ) are argued to reflect mainly their mantle source and its melting. For the C-T-NSVZ, we identify two types of source enrichment: one, represented by Antuco in CSVZ, but also present northward along the arc, was dominated by fluids which enriched a pre-metasomatic South Atlantic depleted MORB mantle type asthenosphere. The second enrichment was by melts having the characteristics of upper continental crust (UCC), distinctly different from Chile trench sediments. We suggest that granitic rocks entered the source mantle by means of subduction erosion in response to the northward increasingly strong coupling of the converging plates. Both types of enrichment had the same Pb isotope composition in the TSVZ with no significant component derived from the subducting oceanic crust. Pb–Sr–Nd isotopes indicate a major crustal compositional change at the southern end of the NSVZ. Modelling suggests addition of around 2 % UCC for Infernillo and 5 % for Maipo.     

Stop making sense: the trials and tribulations of qualitative data analysis

An account is given of a research project with particular attention to the place of data analysis and interpretation. It shines some light into what often remains the black box of qualitative research practice, the mysterious process of generating a research narrative based on the data. The paper provides other apprentice researchers with an insight into what the data analytical experience can be like, warts and all. It raises issues to do with qualitative data analysis, the use of CAQDAS, grounded theory, the relationship between the narratives of the researcher and the researched, and about the training of qualitative researchers.     

Tree Coring as a Complement to Soil Gas Screening to Locate PCE and TCE Source Zones and Hot Spots

Preliminary risk assessment for prioritisation of site investigations requires efficient screening to reveal type and level of contamination. The screening methods, tree coring and soil gas sampling were applied and compared at two forested sites contaminated with tetrachloroethylene (PCE) or trichloroethylene (TCE) to evaluate their ability to locate source zones and contaminant hot spots. One test site represented a relatively homogeneous sandy soil and aquifer, and the second a more heterogeneous geology with both sandy and less permeable clay till layers overlying a chalk aquifer. Tree cores from different tree species were sampled and analysed, and compared to soil gas measurements and existing soil gas data. Both methods were found useful as screening tools to locate hot spots of PCE and TCE in the shallow subsurface. Tree coring was found to be particularly beneficial as a complement to soil gas sampling at sites with low permeable soils, and where contamination was located in the capillary rise or shallow groundwater. The shorter time required for tree coring reduced the costs compared to soil gas sampling, but the sensitivity and precision of tree coring were lower. However, this did not affect the feasibility of using tree coring to locate the hot spots. Moreover, a combination of the two methods can help to focus any subsequent investigations like soil or groundwater sampling. The use of tree coring to complement soil gas sampling for pre‐screening is expected to result in higher certainty for revealing hot spots and source zones at contaminated sites.     

Paleoseismology of the Gazikoy-Saros segment of the North Anatolia fault, northwestern Turkey: Comparison of the historical and paleoseismic records, implications of regional seismic hazard, and models of earthquake recurrence

We excavated five trenches across the North Anatolia fault zone (NAFZ)along the Ganos fault (Gazikoy-Saros segment), which last produced surfacerupture in 1912, near Kavakkoy where the fault enters the Gulf of Saros. The trenches exposed faulted sediments in a flood-plain environment withabundant detrital charcoal and scattered land-snail shells. Twenty-tworadiocarbon dates place constraints on the ages of the exposed sediments,which range from less than a few hundred years to about 6000 years inage. In two closely spaced trenches, we identified five discrete earthquakeevent horizons in the upper 2.5 m of stratigraphy based on abruptupward termination of shear zones, folding, fissuring, and abruptstratigraphic thickening, four of which may corresponded to historicallyrecorded large regional earthquakes. The earliest of the identified eventsoccurs below an unconformity and dates to about 4 ka B.P. The morerecent four events all occurred within the past 1000–1200 years and maycorrespond to large earthquakes in A.D. 824, ca 1354, 1509, 1766 and1912 (Ambraseys and Finkel, 1987, 1991, 1995). In another trench,we identified at least two events that have occurred during the past 500years and probably correspond to the large events of 1766 and 1912. These observations support an average return period of about 250–300years for the Gazikoy-Saros segment of the NAFZ. They also suggest thatthis segment, which is bound both to the east and west by large releasingstepovers, behaves in a quasi-periodic fashion, at least for the past severalsurface ruptures.Most of the 23 mm/yr of dextral shear between Anatolia and Europeobserved by GPS occurs on the North Anatolian fault. We use18 mm/yr and the 250–300 year recurrence rate, as determined fromour trenching and the historical record, to suggest that each of theearthquakes observed in our trenches produced several meters of slip,consistent with their inferred sizes from the extent of historical damage. Considering that Istanbul has not suffered a large nearby event in theMarmara Sea since 1766, we suggest that about 4 m of strain hasaccumulated across faults in the Marmara during these past centuries. Thisis similar to the average slip in many of the large earthquakes on the NorthAnatolian fault this century. If released seismically, this could result in anearthquake in the M 7.2–M 7.6 range, similar to the August and November,1999 earthquakes east of the Marmara Sea.     

The relative impact of future storminess versus offshore dredging on suspended sediment concentration in a shallow coastal embayment: Rødsand lagoon,western Baltic Sea

Natural and human-induced disturbances challenge the resilience of coastal ecosystems. The relative impact of a projected increase in storm intensity versus a temporary sediment spill from the construction of the planned Fehmarnbelt Fixed Link on the suspended sediment concentrations was estimated in the shallow coastal embayment of Rødsand lagoon. The investigations were performed through a combination of field observations and numerical modeling. The numerical model was calibrated and validated with the field observations. The lagoonal response to a regional increase in wind speed showed temporarily amplified suspended particulate matter concentration (SPMC) levels (26–37%) and amplified exceedance duration above wash load (30–32%) in the entire lagoon, but especially in the shallow regions. The lagoonal response to a sediment spill outside Rødsand lagoon showed temporarily amplified SPMC levels (2–4%) and amplified exceedance duration above wash load (1–2%) in the entire lagoon, but especially in the regions in close proximity to the spill source. The regional response to increasing wind speed was thus 10-fold larger than the sediment spill where only advective sediment transport took place. This highlights the importance of the internal lagoonal processes as opposed to exterior disturbances. The study contributed to an improved understanding of the potential natural and human-induced stressors on the sediment dynamics in lagoonal ecosystems.

     

Domestic Environmental Benefits of China's Energy-Related CDM Potential

We estimate the domestic environmental and health benefits of exploiting China's energy-related CDM potential. Exploiting the CDM potential may save between 3,000 and 40,000 lives annually. Additional gains are estimated to reach upwards from 1 billion RMB annually. The key to these gains is the fact that actions and measures to reduce CO₂ emissions also reduce emissions of TSP and SO₂. In our estimate, exploiting the CDM-potential will cut SO₂-emissions by between one-half and three million tons annually. To arrive at these conclusions we synthesize a significant body of recent research on co-benefits of climate abatement in China.     

Accuracy of asymptotic series for the kinematics of high solitary waves

The accuracy of several asymptotic series expansions for wave speed and particle velocity under the crest of a solitary wave (on a fluid at rest) up to maximum height is investigated. The very accurate numerical results of Williams (1985) are the measure for our comparisons. The results are based on a scaling of calculated properties of long periodic waves to the case of solitary waves.For wave speeds the classical Boussinesq–Rayleigh expression gives good agreement up to a relative wave height of, say, 0.3. An asymptotic fourth-order expression based on Fenton (1990) can be used up to a relative wave height of 0.7, whereas the corresponding fifth-order expression is slightly less accurate.The Eulerian particle velocity profile under the wave crest is examined using a cnoidal wave expression from Fenton (1990) in the limit of the solitary wave. For low waves a `consistent' (i.e. properly truncated) fifth-order expression and an `inconsistent' ditto both coincide with Williams' results. Beginning at medium high waves, the consistent expression surprisingly exhibits oscillations in the velocity profile, and the oscillations become stronger as the wave gets higher. The inconsistent expression, however, yields the same shape as Williams' profile, but is displaced parallel to this, resulting in slightly larger velocities. For high waves also the inconsistent expression begins to differ in shape from Williams' profile, and asymptotic theory fails. Only for low waves `lowest order theory' gives acceptable results. We show analytically that for the highest wave the particle velocity profile has a horizontal tangent at the water surface; this is corroborated by Williams' numerical results.We also study the particle velocity at the wave crest as a function of wave height. It is shown that the variation has a vertical tangent for the highest wave. Two fifth-order asymptotic series for this velocity, based on the wave speed through the Bernoulli equation, show very good agreement with Williams up to a relative wave height of about 0.6.It is finally shown that it is possible to produce very accurate rational-function approximations to Williams' results for the wave speed as well as for the particle velocity at the wave crest.     

Removal of selected heavy metals from MSW fly ash by the electrodialytic process

This paper aims to assess the applicability of the electrodialytic remediation technique for the removal of zinc, lead, copper and cadmium from municipal solid waste (MSW) incinerator fly ash. A broad range of experimental conditions were studied including current densities, remediation times, use of assisting agents and cell design.

Several operational problems were identified during the electrodialytic experiments, among which are formation of precipitates, dryness of sample and partial dissolution of sample creating preferential pathways for the electric current. These problems may explain the low remediation efficiencies obtained.

Comparison between experiments showed that generally the use of Na-gluconate as assisting agent leads to better results than distilled water. Increasing the concentration of the assisting agent also results in higher removals.