On the application of combined geoelectric weighted inversion in environmental exploration

Geophysical surveying methods are of great importance in environmental exploration. Inversion-based data processing methods are applied for the determination of geometrical and physical parameters of the target model. The use of this geoelectric inversion method is advantageous in environmental research where highly reliable information with large spatial resolution is required. The 2D combined geoelectric inversion (CGI) method performs more accurate parameter estimation than conventional 1D single inversion methods by efficiently decreasing the number of unknowns of the inverse problem (single means that data sets of individual vertical electric sounding stations are inverted separately). The quality improvement in parameter space is demonstrated by comparing the traditional 1D inversion procedure with a 2D series expansion-based inversion technique. The CGI method was further developed by weighting individual direct current geoelectric data sets automatically in order to improve inversion results. The new algorithm was named combined geoelectric weighted inversion, which extracts the solution by a special weighted least squares technique. It is shown that the new inversion methodology is applicable to resolve near-surface structures such as rapidly varying layer boundaries, laterally inhomogeneous formations and pinch-outs.     

Debris flow impact assessment caused by 14 April 2012 rainfall along the Al-Hada Highway,Kingdom of Saudi Arabia using high-resolution satellite imagery

The Al-Hada highway that descends towards the west of the city of At-Taif is a major connecting highway in the western part of the Kingdom of Saudi Arabia. It is one of the series of descending roads connecting the holy city of Makkah and the city of Jeddah with the city of At-Taif and the cities farther south along the escarpment. The length of the Al-Hada highways is about 22 km. The Al-Hada highway has been historically exposed to landslides and other geohazards since the day it was opened to public some 60 years ago. The road has been reconstructed and many slope instabilities have been remediated and the road has been expanded to two lanes in each direction. Heavy rainfalls occurred on the 14th of April 2012 in the province of At-Taif, causing huge debris flows in two places along the Al-Hada highway. As a result of that, these debris flows closed all four lanes of the highway for 2 weeks in order to remove the debris. The current research deals with mapping of all debris flows along Al-Hada highway and determining their volumes and their impact on the road. Finally, suitable solutions have been suggested to address these critical sites to minimize and/or avoid the debris flow hazards in the future.     

Earth Fissures in Wadi Najran,Kingdom of Saudi Arabia

The formation of earth fissures due to groundwater depletion has been reported in many places in North America, Europe, and Asia. Najran Basin is in the southern part of the Kingdom of Saudi Arabia, and agricultural activities and other groundwater uses have caused significant groundwater depletion there. The basin recently experienced a sudden appearance of numerous earth fissures. An interdisciplinary study consisting of an evaluation of land-use changes, and hydrological, hydrogeological, and geophysical investigations was conducted to determine the reason for the formation of the earth fissures. The hydrological analysis strongly revealed that the groundwater level is decreasing with time. Groundwater depletion would lead to the accumulation of subsurface stress, causing soil hydro-consolidation which creates the ideal condition for the formation of earth fissures. Electrical resistivity, data indicated that there are anomalies in the profiles, which are most probably due to the presence of subsurface topography, another key factor for the formation of the earth fissures.     

Extended Sediment Quality Rating for Trace Elements in Urban Waters – Case Study Klinke,Germany

The European Water Framework Directive (WFD) commits European Union member states to achieving good ecological status in all water bodies by 2015. For sediments the definition of good chemical status is based on numerical sediment quality guidelines. The aqua regia fraction is thus used for the evaluation of heavy metal concentrations in sediments. The chemical constituents in sediments responsible for mobility and toxicity are not considered generally. This article presents the combining of the sequential BCR procedure, for determining the chemical species of relevant elements, with the geoaccumulation index principle a numerical classification method for sediment quality guidelines. Using the BCR method it can be demonstrated that changes in element speciation can lead to more highly mobile species of trace elements which may affect the hazardous potential of sediments despite the “good chemical status” classification for aqua regia digestions. The Klinke stream is an urban surface water body located in Magdeburg, the state capital of Saxony‐Anhalt, Germany. Using this stream as an example it is shown that this additional information helps to describe the dynamics and discharge of the trace elements Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Pd, Cd, Sb, Ba, Pb, Bi, and U into the Elbe River from urban water bodies.     

Terrestrial radioisotopes in black shale hosted Mn-carbonate deposit (Úrkút, Hungary)

Previously, little attention has been paid to terrestrial radioisotopes (U, Th, ⁴⁰K) occurring in manganese ores, despite the fact that the biogeochemical relationship between Mn and U is versatile. Occurrence of terrestrial radioisotopes in great amounts during mining on a long-term causes significant radiation exposure. It is important to inspect black shale-hosted manganese ores from this aspect, as black shales are typically potential U-rich formations. Despite the increased radon concentration in the mine, based on the detailed major elements, trace elements and gamma spectroscopy inspection of the rock types of deposit, the U, Th enrichment was undetectable. However, the U and Th content of about average terrestrial abundance of the great ore amount may be in the background of the increased radon concentration level. This Mn-carbonate ore deposit in spite of the low U content exhibit potential radon danger for miners, which can be eliminated with intensive air change only.     

Modification of climate signals by human activities recorded in varved sediments (AD 1608–1942) of Lake Holzmaar (Germany)

Paleolimnological data from varved sediments in Lake Holzmaar (Eifel, Germany) were combined with documentary data on human activities, long-term data from the Historical Climate Database (HISKLID) for Germany and with recent monitoring data to evaluate changes in deposition that arose from climatic and human influences. The sediment data included seasonal layer thickness in an established varve chronology (1608–1942 AD), subannual chemical element counts, and multiannual organic matter data (TOC, TN, δ¹³C_org), all combined on an annual scale. Indicators for detritus deposition (lithogenic element counts and detritus layers) determined the first principal component (PC1) of the sediment data. This detritus PC1 was compared to the first PCs of the seasonal precipitation and temperature from HISKLID. While no relation was found to precipitation, the correlation with the temperature PC1 determined by spring to fall temperatures was significant. From 1608 to 1870, a positive correlation of the PCs suggests an increase of detritus deposition in the lake center with increasing non-winter temperatures. These may be linked by lake-internal sediment redeposition that increases when the periods of winter stratification become shorter and that of lake circulation longer. The detritus deposition is modulated by external detritus input depending on the intensity of erosion-conducive land use (wood pasture, wood cutting, and rotational slash-and-burn cultivation). Detritus input diminished when land use slowed down with population decrease as the consequence of plague epidemics, warfare and emigration. After 1870, forest regeneration and improving agricultural practices led to a stabilization of the catchment. Erosion and detritus deposition decreased progressively. The negative correlation of detritus deposition with the gradually increasing temperature presumably mimics a cause-effect relation, although a link with decreasing freeze–thaw action is possible. The modernization of agriculture proceeded with manuring and fertilizing, which caused an increase of lake productivity as indicated by summer blooms of diatoms with enhanced nutrient demand, increased δ¹³C_org values and sulfur concentrations. Within this well established data base we found combinations of criteria that may be used to deduce natural climatic or anthropogenic influences. The quantitative attribution of these influences remains a challenging task in paleolimnology because their interaction makes the detection of linking mechanisms difficult even at high degree of detail and the processes themselves remain debatable.