Remobilization Potential Research Articles

Seasonal changes of chemical contamination in coastal waters during sediment resuspension

The potential of remobilization of pollutants is a major problem for anthropogenic ecosystems, because even when the anthropogenic source of pollution is identified and removed, pollutants stored in sediments can be released into the water column and impact pelagic communities during sediment resuspension provoked by dredging, storms or bottom trawling. The objectives of the present study were to assess the changes observed in the chemical composition of the water column following resuspension of a polluted marine sediment and the consequences for the chemical composition of adjacent marine waters according to season. For that purpose, an experimental sediment resuspension protocol was performed on four distinct occasions, spring, summer, fall and winter, and the changes in nutrients, organic contaminants and inorganic contaminants were measured after mixing sediment elutriate with lagoon waters and offshore waters sampled nearby. Significant seasonal variations in the chemical composition of the contaminated sediments were observed, with a strong accumulation of PAHs in fall, whereas minimum PAH concentrations were observed during winter. In all seasons, sediment resuspension provoked a significant enrichment in nutrients, dissolved organic carbon, and trace metal elements like Ni, Cu, and Zn in offshore waters and lagoon waters, with enrichment factors that were season and site dependent. The most pronounced changes were observed for offshore waters, especially in spring and winter, whereas the chemical composition of lagoon waters was weakly impacted by the compounds supplied by sediment resuspension.

Remobilization potential of metallic elements (Cu, Zn, As, Cd, and Pb) from amended mine soil under unsteady-state seepage conditions

Remobilization potential of metallic elements (Cu, Zn, As, Cd, and Pb) from amended mine soil under unsteady-state seepage conditions

A unified approach for including non-extractable residues (NER) of chemicals and pesticides in the assessment of persistence

All chemicals form non-extractable residues (NER) to various extents in environmental media like soil, sediment, plants and animals. NER can be quantified in environmental fate studies using isotope-labeled (such as 14C or 13C) tracer compounds. Previous NER definitions have led to a mismatch of legislation and state of knowledge in research: the residues are assumed to be either irreversibly bound degradation products or at least parts of these residues can be released. In the latter assumption, soils and sediments are a long-term source of slowly released residues. We here present a conceptual experimental and modeling approach to characterize non-extractable residues and provide guidance how they should be considered in the persistence assessment of chemicals and pesticides. Three types of NER can be experimentally discriminated: sequestered and entrapped residues (type I), containing either the parent substance or xenobiotic transformation products or both and having the potential to be released, which has indeed been observed. Type II NER are residues that are covalently bound to organic matter in soils or sediments or to biological tissue in organisms and that are considered being strongly bound with very low remobilization rates like that of humic matter degradation rates. Type III NER comprises biogenic NER (bioNER) after degradation of the xenobiotic chemical and anabolic formation of natural biomolecules like amino acids and phospholipids, and other biomass compounds. We developed the microbial turnover to biomass (MTB) model to predict the formation of bioNER based on the structural properties of chemicals. Further, we proposed an extraction sequence to obtain a matrix containing only NER. Finally, we summarized experimental methods to distinguish the three NER types. Type I NER and type II NER should be considered as potentially remobilizable residues in persistence assessment but the probability of type II release is much lower than that of type I NER, i.e., type II NER in soil are “operationally spoken” irreversibly bound and can be released only in minute amounts and at very slow rates, if at all. The potential of remobilization can be evaluated by chemical, physical and biological methods. BioNER are of no environmental concern and, therefore, can be assessed as such in persistence assessment. The general concept presented is to consider the total amount of NER minus potential bioNER as the amount of xenoNER, type I + II. If a clear differentiation of type I and type II is possible, for the calculation of half-life type I NER are considered as not degraded parent substance or transformation product(s). On the contrary, type II NER may generally be considered as (at least temporarily) removed. Providing proof for type II NER is the most critical issue in NER assessment and requires additional research. If no characterization and additional information on NER are available, it is recommended to assess the total amount as potentially remobilizable. We propose our unified approach of NER characterization and evaluation to be implemented into the persistence and environmental hazard assessment strategies for REACH chemicals and biocides, human and veterinary pharmaceuticals, and pesticides, irrespective of the different regulatory frameworks.

Retention and remobilization mechanisms of environmentally aged silver nanoparticles in an artificial riverbank filtration system

Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms.We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS.Single and erratic Ag breakthrough events were mainly found in 30 cm depth and Ag NP were accumulated in the upper 20 cm of the columns. Soil-aged Ag NP showed the lowest retention of only 54%. Remobilization was induced by the reduction of ionic strength and the presence of NOM in combination with mechanical forces. The presence of calcium in the aging- as well as the remobilizing media reduced the remobilization potential. Silver NP were mainly remobilized as heteroaggregates with natural colloids, while dissolution played a minor role.Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.

Lanthanum immobilization by iron and aluminum colloids

In this work, lanthanum (La) removal from aqueous solution with Al–Fe (hydr)oxides was evaluated and the precipitated materials characterized. We synthesized Al–Fe (hydr)oxides from sulfate salts in water with different La concentrations. The molar ratios of Fe/Al/La were: 500:125:0, 500:125:1, 500:125:5, 500:125:25, 500:125:125, 500:250:0, 500:250:1, 500:250:5, 500:250:25 and 500:250:125. The suspensions were aged for 90-day period, and supernatant samples were periodically collected during this time. The precipitated materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), coupled with system energy-dispersive spectroscopy (EDS). The potential for remobilization of lanthanum from the solid phases comparing the extractable La by acetic acid 0.11 mol L−1 with the total concentration (by acid dissolution with HCl/HNO3 3:1 v/v) was evaluated. All treatments reached high removal of La from contaminated water. Goethite, lepidocrocite and magnetite with structural Al were detected by XRD analysis. SEM–EDS microanalysis showed lanthanum associated with Al–Fe colloids at low La/Fe ratios, but lanthanum segregation was detected to the higher La/Fe ratio. Acetic acid extraction indicated high potential for La remobilization from precipitates, especially in the treatments with high La content. High pH in precipitation of Al–Fe (hydr)oxides provided an efficient removal of soluble lanthanum from contaminated water, but further investigation in conditions that favor the retention of the contaminant was necessary to optimize the immobilization. At high La/Fe ratios, lanthanum could be easily recovered from solid phases by 0.11 M acetic acid leaching.

Sediment-bound trace metals in Golfe-Juan Bay, northwestern Mediterranean: Distribution, availability and toxicity

The concentration, potential mobility, cation exchange capacity and toxicity of eight sediment-bound metals in Golfe-Juan Bay, France were examined. Results revealed significant spatial gradient of metal contamination along Golfe-Juan coast. The distribution and concentration of the metals appear to be influenced by the geochemical properties of the sediment, proximity to anthropogenic sources and general water circulation in the bay. The portion of trace metals found in the exchangeable, carbonate, oxidizable and reducible fractions of the sediment constitute 31%–58% of the total sediment-bound trace metal content, suggesting significant potential for remobilization of metals into the water column. Pb and Ni content of the sediment exceed the limits of the French marine sediment quality. Whole sediment extracts showed acute toxicity to marine rotifers. This study concludes that monitoring and management of sediment-bound trace metals in Golfe-Juan Bay are important so as not to underestimate their availability and risk to the marine ecosystems.

Ex situ groundwater treatment triggering the mobilization of geogenic uranium from aquifer sediments

Uranium (U) concentrations in groundwater extracted for drinking water usage from a Quaternary fluvial aquifer partly exceed the German drinking water guideline of 10μgL−1. Responsible sources and mobilization processes were unknown and gave rise to this study. Land use of the watershed is mainly agricultural leading to groundwater nitrate concentrations >50mgL−1 and a need for water treatment prior to utilization as drinking water. This is successfully accomplished by addition of nutrients triggering bacterial nitrate reduction, followed by the addition of NaOH for water softening and CO2 for pH adjustment, with subsequent reinfiltration into the aquifer. Three boreholes were drilled to obtain a total of 127 solid samples from Quaternary and underlying Tertiary sediments. Geochemistry and mineralogy were assessed using elemental analysis (CS, ICP-MS), X-ray diffraction and scanning electron microscopy to complement hydrochemical data and unravel U occurrence in the subsurface. Solid phase U fractionation was characterized by a sequential extraction procedure, U remobilization potential by a 137days column experiment. Shallow Quaternary sediments yielded low U contents <1μgg−1, higher values were found in depths of more than 20m below ground surface. Here, strata of elevated Corg and Cinorg contain up to 14μgg−1 U, mainly bound in organic and carbonate fractions. Groundwater U concentrations >10μgL−1 almost exclusively appear in this same depth range, and only in wells influenced by water treatment runoff. Results suggest that the applied water treatment approach triggers U remobilization from geogenic sources in the aquifer. The most probable mechanism is dissolution of U bearing calcite induced by CO2 application; redox reactions and pH-driven desorption appear to play a minor role in mobilization. We conclude that groundwater treatment should carefully account for unwanted hydrogeochemical side effects triggering the mobilization of geogenic trace elements such as uranium.

Staged Model of Care – the key to the best point of service in geriatrics

Background : With reference to the demographic change and the growing number of the elderly, inappropriate health care bears a great challenge for geriatric care management and especially for the health care expenditures. Inappropriate health care may refer to unnecessary medical interventions which, on the one hand, relate to unjustifiably high costs in health care systems, and on the other hand, leads to an inadequate supply of geriatric patients, with high risks of reducing their quality of life. Considering that, the need for improving individual pathways as well as the quality of an integrated geriatric care management should obtain high priority within policy developments. The Geriatric Health Care Centers (GGZ) have built up different departments in order to offer a Staged Model of Care for all geriatric patients to provide the best possible and demand-oriented care for this particular target group. The GGZ run more than 10 inpatient, part-inpatient departments and day care units for geriatric patients. Methods : In order to analyze the effectiveness of this Staged Model of Care for geriatric patients, a study was performed. The patient population includes a total number of 6120 geriatric patients (average age: 82 years, average number of diagnosis 5), who were treated in one of four different inpatient departments of the GGZ (Acute Geriatric Care Unit, Intermediate Care Unit, Medical Geriatric Care Unit and Nursing Homes) between January 2014 and December 2015. The study is based on indicators such as the average length of stay, the Barthel Index Score, the incidence of falls and pressure ulcers, staffing in full-time equivalent per patient and the therapeutic services per patient. In addition to the comparative evaluation study, a process analysis of the Comprehensive Geriatric Assessment prior to admission was conducted. Based on three documents–a process description of the different departments, the patients’ registration forms and referral criteria–three different interdisciplinary assessment teams (#1: Acute Geriatric Care Unit, #2: Intermediate & Medical Geriatric Care Unit, #3: Nursing Homes) decide on the admission of patients to a specific department. The performance of a Comprehensive Geriatric Assessment prior to admission is appropriate to ensure an adequate multidisciplinary treatment and achieve the aims of treatment. Results : The results of the study show that the indicators reflect the structure of care and the aims of treatment through the different stages of care. Within the departments Acute Geriatric Care and Intermediate Care Unit they focus on remobilization with the aim of discharging patients home or to institutions with lower care intensity. Therefore the indicators show that the average period of hospitalization is much shorter (approx. 20 days) than in long term care institutions, e.g. the Medical Geriatric Care Unit (approx. 147 days) or in Nursing Homes (approx. 635 days). In comparison to long term care units therapeutic services are provided more often to patients at the Acute Geriatric Care Unit and Intermediate Care Unit (approx. 0.7 hours/day). The indicators of staffing also demonstrate that there is no need for the attendance of physicians 24/7 in Nursing Homes. This is due to the fact that it is a residential facility where quality of life until one’s death and caregiving has priority. At the Acute Geriatric and Intermediate Care Unit the number of physicians in full-time equivalent per patient (approx. 0.12) is much higher than in Nursing Homes (approx. 0.02), because the patients’ general health condition has to be compiled first to give therapy advices and regain the patients’ independence by increasing their health literacy. Conclusions : To conclude, it can be said that the intensity of care in each stage of supply correlates with the demands and needs of geriatric patients. Therefore it provides the best point of service not only for patients but also achieves health economic advantages (e.g. usually adequate care can be offered at lower daily fees than in acute hospitals). Moreover, this Staged Model of Care allows, if necessary, the exchange of patients within the organization. A decision-tree is designed to keep high quality standards and facilitate the admission assessment for new employees. For this purpose factors of patient groups are defined in order to allocate patients more easily to different units of care (e.g. high remobilization potential as an indicator for the Acute Geriatric Care Unit etc.). However the findings show a definite need of further development towards home care concepts like ambulatory or mobile care services.

Chromium Distribution and Spatial Variations in the Finer Sediment Grain Size Fraction and Unfractioned Surficial Sediments on Nyanza Gulf, of Lake Victoria (East Africa)

Surficial sediments collected from the Nyanza Gulf of Lake Victoria (East Africa) were used to determine spatial concentrations of Cr and determine differences in contents of the unfractioned (whole sediment) and the finer grain size sediments, establishing any changes in Cr enrichment and potential ecological risks using sediment quality guidelines. A single pollution index was also used to evaluate level of Cr contamination. The spatial mean Cr contents in the &lt;63 µm (silt-clay) fraction were found to be significantly lower than those in the unfractioned sediments, but with a strong linear positive correlation. The study results show decreasing spatial amounts of Cr in surficial sediments of the Nyanza Gulf, when compared to a study done 20 years earlier. However, the 95% confidence limits of the overall mean Cr in unfractioned sediments exceed the threshold effect concentration (TEC), indicating the potential for Cr remobilization from sediments. In general the sediment enrichment is evidence of possible dominance of lithogenous sources of Cr in the surface lake sediments, with potential anthropogenic sources from the drainage system and nearshore urban areas. The sediments are unpolluted with respect to geoaccumulation index, and sediment enrichment factors suggest a minor to moderate enrichment of Cr in surficial sediments of three sites around the Nyanza Gulf zones and around the river mouth in the main lake.

The effect of distribution processes on the isomeric composition of hexachlorocyclohexane in a contaminated riverine system

Various factors influence the isomeric composition of hexachlorocyclohexanes which are released to the environment. Original compositions in technical mixtures may vary slightly, but higher shifts are observable for transfer processes, bioaccumulation and microbial transformation. Consequently, the isomeric composition in environmental samples is a superposition of these processes. In this study, isomeric distributions and concentrations of hexachlorocyclohexanes were analyzed in water, sediment, and soil samples of a riverine system known to be highly contaminated by hexachlorocyclohexanes. To assess desorption of hexachlorocyclohexanes from particulate matter to water, batch shaking and percolation experiments were conducted complementary. Analyzed samples exhibited total hexachlorocyclohexane concentrations of up to 2.8 µg/g in sediments and up to 21 µg/L in river water predominated by the α-isomer. Downstream hexachlorocyclohexane pattern changed toward δ-isomer domination, while overall hexachlorocyclohexane concentrations decreased. Desorption experiments supported the assumption of discrimination by preferred association of the α- and β-isomers with particulate matter, showing elevated mobilization of γ-, δ- and e-hexachlorocyclohexanes and lower mobilization of the α- and β-isomers. Soil samples of a riparian wetland exhibited elevated concentrations of hexachlorocyclohexanes exceeding 200 µg/g and predominance of α-hexachlorocyclohexanes in the top soil layer. Subjacent soil layers showed rapidly decreasing hexachlorocyclohexane concentrations and an isomeric shift toward the β-isomer. The assumed preferential mobilization of β-hexachlorocyclohexane was supported by desorption experiments. This study demonstrated firstly that transfer processes influence substantially hexachlorocyclohexane isomer distribution in the aquatic environment. Secondly, conditions of aging determine strength of association and remobilization potential of hexachlorocyclohexane residue down to an isomer-specific level.

SuMoToRI, an Ecophysiological Model to Predict Growth and Sulfur Allocation and Partitioning in Oilseed Rape (Brassica napus L.) Until the Onset of Pod Formation.

Sulfur (S) nutrition in rapeseed (Brassica napus L.) is a major concern for this high S-demanding crop, especially in the context of soil S oligotrophy. Therefore, predicting plant growth, S plant allocation (between the plant’s compartments) and S pool partitioning (repartition of the mobile-S vs. non-mobile-S fractions) until the onset of reproductive phase could help in the diagnosis of S deficiencies during the early stages. For this purpose, a process-based model, SuMoToRI (Sulfur Model Toward Rapeseed Improvement), was developed up to the onset of pod formation. The key features rely on (i) the determination of the S requirements used for growth (structural and metabolic functions) through critical S dilution curves and (ii) the estimation of a mobile pool of S that is regenerated by daily S uptake and remobilization from senescing leaves. This study describes the functioning of the model and presents the model’s calibration and evaluation. SuMoToRI was calibrated and evaluated with independent datasets from greenhouse experiments under contrasting S supply conditions. It is run with a small number of parameters with generic values, except in the case of the radiation use efficiency, which was shown to be modulated by S supply. The model gave satisfying predictions of the dynamics of growth, S allocation between compartments and S partitioning, such as the mobile-S fraction in the leaves, which is an indicator of the remobilization potential toward growing sinks. The mechanistic features of SuMoToRI provide a process-based framework that has enabled the description of the S remobilizing process in a species characterized by senescence during the vegetative phase. We believe that this model structure could be useful for modeling S dynamics in other arable crops that have similar senescence-related characteristics.

A spatial database for landslides in northern Bavaria: A methodological approach

Landslide databases provide essential information for hazard modeling, damages on buildings and infrastructure, mitigation, and research needs. This study presents the development of a landslide database system named WISL (Würzburg Information System on Landslides), currently storing detailed landslide data for northern Bavaria, Germany, in order to enable scientific queries as well as comparisons with other regional landslide inventories. WISL is based on free open source software solutions (PostgreSQL, PostGIS) assuring good correspondence of the various softwares and to enable further extensions with specific adaptions of self-developed software. Apart from that, WISL was designed to be particularly compatible for easy communication with other databases.As a central pre-requisite for standardized, homogeneous data acquisition in the field, a customized data sheet for landslide description was compiled. This sheet also serves as an input mask for all data registration procedures in WISL. A variety of “in-database” solutions for landslide analysis provides the necessary scalability for the database, enabling operations at the local server.In its current state, WISL already enables extensive analysis and queries. This paper presents an example analysis of landslides in Oxfordian Limestones in the northeastern Franconian Alb, northern Bavaria. The results reveal widely differing landslides in terms of geometry and size. Further queries related to landslide activity classifies the majority of the landslides as currently inactive, however, they clearly possess a certain potential for remobilization. Along with some active mass movements, a significant percentage of landslides potentially endangers residential areas or infrastructure.The main aspect of future enhancements of the WISL database is related to data extensions in order to increase research possibilities, as well as to transfer the system to other regions and countries.

Combining Field and Laboratory Measurements to Determine the Erosion Risk of Cohesive Sediments Best

In contrast to non-cohesive sediments, the incipient motion of cohesive sediments is characterized by much more complex interactions between several sedimentary, biological, and chemical parameters. Thus, site-specific investigations are required to obtain information about the erosion stability of cohesive materials. This becomes even more relevant for contaminated sediments, stored in riverine sediments as a “burden of the past”, because of their remobilization potential during flood events. This article represents a twofold measuring strategy for the detection of erosion thresholds: an in situ device for determination of critical shear stresses in the field, and a laboratory approach where sediment cores are withdrawn and subsequently analyzed over depth. The combined measuring strategy was applied in the River Elbe and at selected sites of the catchment of the River Saale. The results show a great variety of erosion thresholds over depth, demonstrating the need to conduct vertical analyses, especially when addressing buried layers with contaminations. The latter is only possible in the laboratory but the in situ device revealed clear benefits in capturing the loose flocculent layer on top of the sediment that might be easily lost during sediment retrieval and transport. Consequently, it is ideal to combine both approaches for a comprehensive insight into sediment stability.

First evidence for covalent linkage of acidic metabolites of metalaxyl and DDT as non-extractable pesticide residues in soil and sediment

Soils and sediments are a major sink for lipophilic organic pollutants. The remobilization potential of non-extractable residues is an important aspect of the environmental risk assessment and is directly linked to the binding modes of xenobiotics to macromolecular geopolymers. For instance, weak binding will favour rapid release of toxic metabolites, whereas strong binding will favour release in the long run. So far there is few strong evidence on the precise nature and strength of pollutant binding to organic matter. We used 1,1,1-trichloro-2,2-bis(chlorophenyl)ethane (DDT) contaminated sediment and metalaxyl spiked microbial active soil for alkaline hydrolysis reaction with 18O-sodium hydroxide (Na18OH). Gas chromatography–mass spectrometry analyses showed 2 Da shifts in molecule ions of 2,2-bis(chlorophenyl)acetic acid methylester (DDA-methylester) and additionally in fragment ions of 18O-metalaxyl indicating monolabeled derivatives of both pesticide metabolites.18O-labeling of the carboxyl moiety during hydrolysis proved the cleavage of the metabolites from organic macromolecules. This is the first concrete evidence for stable ester linkage of acidic metabolites of DDT and metalaxyl in soil and sediment matrices.

Remobilization of sterically stabilized silver nanoparticles from farmland soils determined by column leaching

SummaryThe increasing application of silver (Ag)‐engineered nanoparticles (ENP) will enhance their release to the aquatic and terrestrial environments. Hence, the retention potential of the sterically stabilized Ag ENP (AgNM‐300k, Organisation for Economic Cooperation and Development (OECD)) standard material was tested in a sandy Cambisol and in a clay‐ and silt‐rich Luvisol. In addition, the remobilization potential of the same soils spiked with AgNM‐300k was investigated in columns after 3 and 92 days of incubation. The AgNM‐300k dispersion and the soil solutions were examined with dynamic light scattering (DLS). Inductively coupled plasma optical emission spectroscopy (ICP‐OES) and inductively coupled plasma mass spectrometry (ICP‐MS) were used to analyse soils and soil solutions subjected to different digestion and extraction techniques (aqua regia, nitric acid (HNO3) and EDTA (ethylenediamninetetraacetate)). The 24‐hour batch test showed a 10‐fold greater retention coefficient for AgNM‐300k in the silt‐ and clay‐rich Luvisol than in the sandy Cambisol. In addition, all applied extraction techniques indicate a greater potential for mobility of Ag ENP for the sandy Cambisol. However, a small release from the column of AgHNO3 (measured Ag content in the fraction &lt; 0.45 µm after HNO3 digestion) was observed after 3 as well as after 92 days of incubation for both soils. The largest amount of Ag was released from the Cambisol during the first percolation step (water:soil ratio = 1 l kg−1) after the soil was incubated for 3 days. This AgHNO3 release corresponded to approximately 1% of the total amount of Ag in the soil column. The correlation obtained between released AgHNO3 and AlHNO3 suggests that even the Ag released at small concentrations is associated with soil colloids. Thus, hetero‐aggregation is a potentially important process controlling retention.

Impoundments Increase Potential for Phosphorus Retention and Remobilization in an Urban Stream

Weirs are conventional structures that control water level and velocity in streams to facilitate water resource management. Despite many weirs built in streams, there is little information how weirs change hydrology regime and how that translates to sediment and phosphorus (P) responses. This study evaluated the influence of weirs on P retention and mobilization in an urban tributary of the Han River in Korea. Total P concentrations in sediments upstream of weirs were higher than the downstream site, mainly due to the increase of potentially available fractions (labile P and aluminum- and iron-bound P) (p < 0.05). Equilibrium phosphorus concentrations (EPCo) were lower than soluble reactive phosphorus (SRP) concentrations of stream waters, but there was an increasing trend of sediment EPCo upstream of weirs compared to the downstream site (p < 0.001) indicating a greater potential for P release upstream of weirs. Sediment core incubation showed that SRP release rates upstream of weirs were higher than the downstream site under anoxic conditions of the water column (p < 0.01), but not under oxic conditions. SRP release rates under anoxic conditions were greater than that measured under oxic conditions. Un-neutral pH and increased temperature could also enhance SRP release rates upstream of weirs. We conclude that weirs can increase P retention within stream sediments and potentially promote significant P releases into waters, which in turn cause eutrophication.

Aeolian to shallow-marine shelf architecture off a major desert since the Late Pleistocene (northern Mauritania)

Continental shelves off major desert regions are not expected to host substantial amounts of sediments due to long-lasting and unfocused material supply and a high re-mobilization potential of aeolian material. This study, in contrast, demonstrates that significant volumes of sediments have accumulated on the northern Mauritanian shelf under the arid climate conditions and prevail over consecutive climatic cycles.Eight late Pleistocene to Holocene depositional units, each formed under contrasting depositional conditions, are identified in high-resolution seismo-acoustic data and dated sediment cores. These are: (1) a highly differentiated Pleistocene paleo-landscape older than the past climatic cycle, (2) a continental dune complex (MIS-4), (3) a thick regressive shallow-water clinoform (late MIS-3), (4) a regressive to lowstand shore deposit (latest MIS-3), and (5) a local transgressive cover (LGM to deglacial). Additionally, (6) an open-shelf highstand cover, (7) an outer-shelf highstand wedge and (8) mid-shelf mud depocenters have formed during the Holocene sea-level highstand.The common local offshore formation and preservation of confined stratigraphic units, in particular from during MIS-3, mark the interplay of: a) episodes of pronounced arid climatic conditions resulting in enhanced aeolian and coastal sediment input, b) shelf current patterns focusing sediment deposition locally, and c) early post-depositional sediment stabilization providing protection against erosion. Prominent internal surfaces at 63 and 115m modern water depths indicate widespread and intense erosional activity during late MIS-3 regression and MIS-2 lowstand to post-LGM transgression, hosting coarse shell sands and gravels from beach and shoreface paleo-environments. The reasons for the high preservation potential of confined stratigraphic units are: a) carbonaceous cementation, b) sediment composition (massive widespread shore-related gravel and shell beds with subtle minor admixtures of cohesive material), and c) morphological protection (inside seafloor depressions and behind sheltering relief).

Post-Integration Silencing of piggyBac Transposable Elements in Aedes aegypti

The piggyBac transposon, originating in the genome of the Lepidoptera Trichoplusia ni, has a broad host range, making it useful for the development of a number of transposon-based functional genomic technologies including gene vectors, enhancer-, gene- and protein-traps. While capable of being used as a vector for the creation of transgenic insects and insect cell lines, piggyBac has very limited mobility once integrated into the genome of the yellow fever mosquito, Aedes aegypti. A transgenic Aedes aegypti cell line (AagPB8) was created containing three integrated piggyBac elements and the remobilization potential of the elements was tested. The integrated piggyBac elements in AagPB8 were transpositionally silent in the presence of functional transposase, which was shown to be capable of catalyzing the movement of plasmid-borne piggyBac elements in the same cells. The structural integrity of one of the integrated elements along with the quality of element-flanking DNA, which is known to influence transposition rates, were tested in D. melanogaster. The element was found to be structurally intact, capable of transposition and excision in the soma and germ-line of Drosophila melanogaster, and in a DNA sequence context highly conducive to element movement in Drosophila melanogaster. These data show that transpositional silencing of integrated piggyBac elements in the genome of Aedes aegypti appears to be a function of higher scale genome organization or perhaps epigenetic factors, and not due to structural defects or suboptimal integration sites.

Environmental impact assessment of radionuclide and metal contamination at the former U site at Kadji Sai, Kyrgyzstan

During 1949–1967, a U mine, a coal-fired thermal power plant and a processing plant for the extraction of U from the produced ash were operated at the Kadji Sai U mining site in Tonsk district, Issyk-Kul County, Kyrgyzstan. The Kadji Sai U legacy site represents a source of contamination of the local environment by naturally occurring radionuclides and associated trace elements. To assess the environmental impact of radionuclides and trace metals at the site, field expeditions were performed in 2007 and 2008 by the Joint collaboration between Norway, Kazakhstan, Kyrgyzstan, Tajikistan (JNKKT) project and the NATO SfP RESCA project. In addition to in situ gamma and Rn dose rate measurements, sampling included at site fractionation of water and sampling of water, fish, sediment, soils and vegetation. The concentrations of radionuclides and trace metals in water from Issyk-Kul Lake were in general low, but surprisingly high for As. Uptake of U and As was also observed in fish from the lake with maximum bioconcentration factors for liver of 1.6 and 75, respectively. The concentrations of U in water within the Kadji Sai area varied from 0.01 to 0.05 mg/L, except for downstream from the mining area where U reached a factor of 10 higher, 0.2 mg/L. Uranium concentrations in the drinking water of Kadji Sai village were about the level recommended by the WHO for drinking water. The 234U/238U activity ratio reflected equilibrium conditions in the mining pond, but far from equilibrium outside this area (reaching 2.3 for an artesian well). Uranium, As and Ni were mainly present as low molecular mass (LMM, less than 10 kDa) species in all samples, indicating that these elemental species are mobile and potentially bioavailable.The soils from the mining sites were enriched in U, As and trace metals. Hot spots with elevated radioactivity levels were easily detected in Kadji Sai and radioactive particles were observed. The presence of particles carrying significant amount of radioactivity and toxic trace elements may represent a hazard during strong wind events (wind erosion). Based on sequential extractions, most of the elements were strongly associated with mineral matter, except for U and As having a relatively high remobilization potential. Low Kd was obtained for U (3.5 × 102 L/kg d.w.), intermediate Kds (∼3 × 103 L/kg d.w.) were obtained for 226Ra, As and Ni, while a high Kd (2.2 × 105 L/kg d.w.) were obtained for Pb. The accumulation of metals in fish gills reflected the LMM species in the Issyk-Kul water, and did not show any bioaccumulation. The muscle Hg concentrations in all fish species were low and did not represent any health risk even for groups at risk.Total gamma and Rn dose rate to man amounted to about 12 mSv/y, while the highest calculated dose rate for non-human species based on the ERICA Assessment Tool were obtained in terrestrial plants (164 μGy/h) due to the Ra exposure. The results obtained showed that radiation doses to resident public at all of the investigated sites in the Kadji Sai area were in general relatively low. Low radiological risk and no detrimental health impact on resident public can be expected at these sites. However, exposure to Rn and Tn in the living environment can be further reduced by implementing simple countermeasures such as ventilation of dwelling cellars. More focus in the Kadji Sai area should probably be put on trace elements, especially the As uptake in fish in Lake Issyk-Kul.

Mapping the degree of decomposition and thaw remobilization potential of soil organic matter in discontinuous permafrost terrain

Soil organic matter (SOM) stored in permafrost terrain is a key component in the global carbon cycle, but its composition and lability are largely unknown. We characterize and assess the degree of decomposition of SOM at nine sites representing major land‐cover and soil types (including peat deposits) in an area of discontinuous permafrost in the European Russian Arctic. We analyze the elemental and stable isotopic composition of bulk SOM, and the degree of humification and elemental composition of humic acids (HA). The degree of decomposition is low in the O‐horizons of mineral soils and peat deposits. In the permafrost free non‐peatland soils there is enrichment of13C and 15N, and decrease in bulk C/N ratios indicating more decomposed material with depth. Spectral characterization of HA indicates low humification in O‐horizons and peat deposits, but increase in humification in the deeper soil horizons of non‐peatland soils, and in mineral horizons underlying peat deposits. GIS based maps indicate that less decomposed OM characteristic of the O‐horizon and permafrost peat deposits constitute the bulk of landscape SOM (&gt;70% of landscape soil C). We conclude, however, that permafrost has not been the key environmental factor controlling the current degree of decomposition of SOM in this landscape due to relatively recent permafrost aggradation. In this century, active layer deepening will mainly affect SOM with a relatively high degree of decomposition in deeper mineral soil horizons. Additionally, thawing permafrost in peat plateaus may cause rapid remobilization of less decomposed SOM through thermokarst expansion.