Human impact on Holocene sediment dynamics in the Eastern Mediterranean – the example of the Roman harbour of Ephesus

During the past millennia, many erosion and accumulation processes have been modified by anthropogenic impact. This holds especially true for the environs of ancient settlements and their harbours along the Mediterranean coasts. Our multi‐proxy investigations in the Roman harbour and the harbour canal of Ephesus (western Turkey) reveals that humans have significantly triggered soil erosion during the last three millennia. Since the eighth century bc , and especially since the Hellenistic period, a high sedimentation rate indicates fast alluviation and delta progradation of the Küçük Menderes. Deforestation, agriculture (especially ploughing) and grazing (especially goats) were the main reasons for erosion of the river catchment area. One consequence was significant siltation of the Hellenistic/Roman harbour basin. This sediment trap archives the human impact, which was strongly enhanced from Hellenistic/Roman to Byzantine times (second/first centuries bc to the sixth/seventh centuries ad ), evidenced by high sedimentation rates, raised values of heavy metal contaminations [lead (Pb), copper (Cu)], the occurrence of fruit tree pollen and of intestinal parasites. From the middle to the end of the first millennium ad , the influence of Ephesus declined, which resulted in a decrease of human impact. Studies of several ancient settlements around the Mediterranean Sea tell a comparable story. They also confirm that during their most flourishing periods the human impact totally overprinted the climatic one. To detect the latter, geo‐bio‐archives of relatively pristine areas have to be investigated in detail. Copyright © 2016 John Wiley & Sons, Ltd.     

Extending Service Life of Household Water Filters by Mixing Metallic Iron with Sand

The use of metallic iron filters (Fe⁰ filters) has been discussed as a promising low‐cost option for safe drinking water production at household level. Filter clogging due to the volumetric expansive nature of iron corrosion has been identified as the major problem of Fe⁰ filters. Mixing Fe⁰ and sand (yielding Fe⁰/sand filters) has been proposed as a tool to extent filter service life. However, no systematic discussion rationalizing Fe⁰/sand mixtures is yet available. This communication theoretically discussed suitable Fe⁰/sand proportions for efficient filters. Results suggested that Fe⁰/sand filters should not contain more that 50 vol% Fe⁰ (25 wt% when Fe⁰ is mixed with quartz). The actual Fe⁰ percentage in a filter will depend on its intrinsic reactivity.     

Dynamics of suspended sediment transport and yield in a large agricultural catchment,southwest France

The dynamics of suspended sediment transport were monitored continuously in a large agricultural catchment in southwest France from January 2007 to March 2009. The objective of this paper is to analyse the temporal variability in suspended sediment transport and yield in that catchment. Analyses were also undertaken to assess the relationships between precipitation, discharge and suspended sediment transport, and to interpret sediment delivery processes using suspended sediment‐discharge hysteresis patterns. During the study period, we analysed 17 flood events, with high resolution suspended sediment data derived from continuous turbidity and automatic sampling. The results revealed strong seasonal, annual and inter‐annual variability in suspended sediment transport. Sediment was strongly transported during spring, when frequent flood events of high magnitude and intensity occurred. Annual sediment transport in 2007 yielded 16 614 tonnes, representing 15 t km^?2 (85% of annual load transport during floods for 16% of annual duration), while the 2008 sediment yield was 77 960 tonnes, representing 70 t km^?2 (95% of annual load transport during floods for 20% of annual duration). Analysis of the relationships between precipitation, discharge and suspended sediment transport showed that there were significant correlations between total precipitation, peak discharge, total water yield, flood intensity and sediment variables during the flood events, but no relationship with antecedent conditions. Flood events were classified in relation to suspended sediment concentration (SSC)–discharge hysteretic loops, complemented with temporal dynamics of SSC–discharge ranges during rising and falling flow. The hysteretic shapes obtained for all flood events reflected the distribution of probable sediment sources throughout the catchment. Regarding the sediment transport during all flood events, clockwise hysteretic loops represented 68% from river deposited sediments and nearby source areas, anticlockwise 29% from distant source areas, and simultaneity of SSC and discharge 3%. Copyright © 2010 John Wiley & Sons, Ltd.     

Entanglement of Australian sea lions and New Zealand fur seals in lost fishing gear and other marine debris before and after Government and industry attempts to reduce the problem

In recent years, Australian governments and fishing industry associations have developed guiding principles aimed at reducing the impact of fishing on non-target species and the benthos and increasing community awareness of their efforts. To determine whether they reduced seal entanglement in lost fishing gear and other marine debris, we analysed Australian sea lion and New Zealand fur seal entanglement data collected from Kangaroo Island, South Australia. Contrary to our expectations, we found that entanglement rates did not decrease in recent years. The Australian sea lion entanglement rate (1.3% in 2002) and the New Zealand fur seal entanglement rate (0.9% in 2002) are the third and fourth highest reported for any seal species. Australian sea lions were most frequently entangled in monofilament gillnet that most likely originated from the shark fishery, which operates in the region where sea lions forage--south and east of Kangaroo Island. In contrast, New Zealand fur seals were most commonly entangled in loops of packing tape and trawl net fragments suspected to be from regional rock lobster and trawl fisheries. Based on recent entanglement studies, we estimate that 1478 seals die from entanglement each year in Australia. We discuss remedies such as education programs and government incentives that may reduce entanglements.     

Thermal maturity in the Central European Basin system (Schleswig-Holstein area): results of 1D basin modelling and new maturity maps

Thermal maturity information has been compiled for one of the deepest parts of the Central European Basin system, the Schleswig-Holstein area in northern Germany. New vitrinite reflectance data were obtained and old data were evaluated from a total of 31 wells. Furthermore, numerical 1D basin modelling was performed in order to interpolate/extrapolate vitrinite reflectance data to base Zechstein and base Keuper. For these two horizons, maturity maps were finally compiled revealing large differences in present-day thermal maturity within the basin. For example, vitrinite reflectance at base Zechstein ranges from greater than 4.5% in the Glueckstadt Graben to less than 1% in the northern part of the study area. Highest thermal maturity of base Keuper occurs in the West Holstein Trough and in the northern part of the Glueckstadt Graben. The timing of maturation is greatly affected by the complex tectonic evolution of the area. For six key wells distributed over the entire study area, burial and temperature histories as well as evolution of maturity were evaluated using 1D basin modelling. Deepest burial and maximum temperatures occurred either during Jurassic, Upper Cretaceous or Neogene times in these wells. Only some parts of the sedimentary package in Schleswig-Holstein show a significant increase in maturity during the Tertiary leading to additional hydrocarbon generation and entrapment.     

SARAL/AltiKa Global Statistical Assessment and Cross-Calibration with Jason-2

The CNES/ISRO mission SARAL/AltiKa was successfully launched on 25 February 2013. It reached its nominal orbit on 13 March 2013. AltiKa is the first altimeter using the Ka-band frequency. This article presents the results of the calibration and validation activities perfromed on the first year of the SARAL/AltiKa mission. The main objective of the article is to assess the SARAL/AltiKa data quality and to estimate the altimeter system performance using GDR products. To achieve this goal, we present mono-mission metrics and compare them with Jason-2 over the same period. Even if these missions do not have the same ground track, precise comparisons are still possible. They allow assessing parameter discrepancies and SSH consistency between both missions in order to detect geographically correlated biases, jumps or drifts. These results show that SARAL/AltiKa data quality is excellent: ocean data coverage is greater than 99.5%, standard deviation at cross-overs is 5.4 cm. The mission therefore fulfills the requirements of high precision altimetry and can be used (in conjunction with Jason-2) to monitor the global mean sea level, ensuring the continuity of the record over ERS/Envisat historical ground track. Possible improvements and open issues are also identified, foreseeing an even better mission performance.     

Optimal mitigation strategies with negative emission technologies and carbon sinks under uncertainty

In recent years a body of literature has arisen on the topic of how to compose the optimal portfolio of mitigation options. The focus has been mainly on options involving shifts from high- to low- or even negative-carbon technologies. Natural sinks play an important role in any attempt to stabilize atmospheric CO₂ and usually enter as a constant term in the overall carbon budget. In this paper, we introduce natural sinks to the carbon management problem and analyze the implications for negative emission technology deployment and the overall mitigation strategy. Amongst other sensitivity analyses, we also investigate the impact of uncertainty in the carbon sink, which we find to raise the importance of negative emissions in the mitigation portfolio significantly lowering the cost of the policy mix.     

Suitability of Existing Numerical Model Codes and Thermodynamic Databases for the Prognosis of Calcite Dissolution Processes in Near-Surface Sediments Due to a CO2 Leakage Investigated by Column Experiments

Among the risks of CO₂ storage is the potential of CO₂ leakage into overlaying formations and near-surface potable aquifers. Through a leakage, the CO₂ can intrude into protected groundwater resources, which can lead to groundwater acidification followed by potential mobilisation of heavy metals and other trace metals through mineral dissolution or ion exchange processes. The prediction of pH buffer reactions in the formations overlaying a CO₂ storage site is essential for assessing the impact of CO₂ leakages in terms of trace metal mobilisation. For buffering the pH-value, calcite dissolution is one of the most important mechanisms. Although calcite dissolution has been studied for decades, experiments conducted under elevated CO₂ partial pressures are rare. Here, the first study for column experiments is presented applying CO₂ partial pressures from 6 to 43 bars and realising a near-natural flow regime. Geochemical calculations of calcite dissolution kinetics were conducted using PHREEQC together with different thermodynamic databases. Applying calcite surface areas, which were previously acquired by N₂-BET or calculated based on grain diameters, respectively, to the rate laws according to Plummer et al. (Am J Sci 278:179–216, doi:10.2475/ajs.278.2.179, 1978) or Palandri and Kharaka (US Geol Surv Open file Rep 2004–1068:71, 2004) in the numerical simulations led to an overestimation of the calcite dissolution rate by up to three orders of magnitude compared to the results of the column experiments. Only reduction of the calcite surface area in the simulations as a fitting procedure allowed reproducing the experimental results. A reason may be that the diffusion boundary layer (DBL), which depends on the groundwater flow velocity and develops at the calcite grain surface separating it from the bulk of the solution, has to be regarded: The DBL leads to a decrease in the calcite dissolution rate under natural laminar flow conditions compared to turbulent mixing in traditional batch experiments. However, varying the rate constants by three orders of magnitudes in a field scale PHREEQC model simulating a CO₂ leakage produced minor variations in the pH buffering through calcite dissolution. This justifies the use of equilibrium models when calculating the calcite dissolution in CO₂ leakage scenarios for porous aquifers and slow or moderate groundwater flow velocities. However, the selection of the thermodynamic database has an impact on the dissolved calcium concentration, leading to an uncertainty in the simulation results. The resulting uncertainty, which applies also to the calculated propagation of an aquifer zone depleted in calcite through dissolution, seems negligible for shallow aquifers of approximately 60 m depth, but amounts to 35 % of the calcium concentration for aquifers at a depth of approximately 400 m.     

Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)

Deltas contain sedimentary records that are not only indicative of water‐level changes, but also particularly sensitive to earthquake shaking typically resulting in soft‐sediment‐deformation structures. The Kürk lacustrine delta lies at the south‐western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re‐evaluates water‐level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic‐reflection profiles and side‐scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water‐level changes provides a temporal framework for the depositional record. In addition to the common soft‐sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake‐induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (¹³⁷Cs and ²¹⁰Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X‐ray imagery, X‐ray diffraction, loss‐on‐ignition, grain‐size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post‐seismic sediment reworking of earthquake‐triggered landslides.