Fingerprinting sediment source: the example of a drainage basin in Devon, UK

In view of the many difficulties associated with the determination of the source of suspended sediment transported by a stream, the 'fingerprinting' technique which employs sediment properties to identify the source offers considerable potential. Several limitations of the technique must, however, be recognised. Results of applying this approach to identifying sediment sources within a small agricultural drainage basin in Devon UK are reported. A variety of sediment properties have been employed in order to test the consistency of the results obtained and a simple mixing model has been used to quantify the relative importance of the contributions from surface soil and channel banks.link_to_subscribed_fulltextpostprin

Comparing the rates of absorption and weight loss during a desorption test using near infrared spectroscopy

The importance of determining skin hydration has over the years prompt the development of many instruments and methods, specifically designed to assess this parameter or water contents especially in the stratum corneum, and have greatly matured to suit different anatomical sites and measure multiple attributes. Of those, Near Infrared Spectroscopy (NIRS) has gained wide interest as a precise, safe, fast and noninvasive technique for determining skin hydration due to its high sensitivity to hydrogen bonding and ability to measure the amount of water in skin directly using the intensities of overtone and combination bands of OH and HOH water bonds occurring in the NIR region, that are good indicators of the state of skin hydration. This paper reports near infrared spectrophotometric measurements using a highly sophisticated spectrophotometer in the region of 1000-2500 nm to study the water uptake and dehydration properties of skin in vitro using samples of porcine skin. Initial results of pure liquid water and skin samples have clearly displayed the prominent bands associated with water content, and desorption tests have been able to verify changes in these bands associated with water content, although a clear correlation between the rates of weight loss and absorbance loss at various hydration periods has not yet been established. These preliminary results are expected to further explain the relationship between water and skin, and its role within, in hope to aid the future development of a portable instrument based on near infrared spectroscopy that would be capable of directly measuring skin hydration and/or water content in a fast and noninvasive manner

Assessment of dam trapping efficiency from water residence time: Application to fluvial sediment transport in the Adour, Dordogne, and Garonne River basins (France)

Dam-trapping efficiency can be estimated by using the hydraulic residence time. On the regional scale, the global impact of several dams can be assessed by taking into account the spatial organization of dams along the river network. Therefore, in this study, a method is proposed to estimate the global-trapping efficiency, TEw, for any watershed containing more than one dam. This method is applied to the Adour, Dordogne, and Garonne River watersheds (southwestern France). The spatial organization of dams and its impact on TEw and on sediment yields measured at 37 TSM sampling stations over 2 years are discussed. Positive correlation between drainage areas and river sediment loads corrected from dam regulation using TEw, as well as comparisons between TEw-corrected sediment yields and sediment yields measured upstream from dams, point out the interest of the method in order to reconstitute the natural sediment yields

Earth is (mostly) flat: Apportionment of the flux of continental sediment over millennial time scales Comment

10.1130/G34846C.1Geology421e316-GLGY

Sediment and fluvial particulate carbon flux from an eroding peatland catchment

Erosion and the associated loss of carbon is a major environmental concern in many peatlands and remains difficult to accurately quantify beyond the plot scale. Erosion was measured in an upland blanket peatland catchment (0.017 km2) in northern England using Structure‐from‐Motion (SfM) photogrammetry, sediment traps and stream sediment sampling at different spatial scales. A net median topographic change of –27 mm yr–1 was recorded by SfM over the 12‐month monitoring period for the entire surveyed area (598 m2). Within the entire surveyed area there were six nested catchments where both SfM and sediment traps were used to measure erosion. Substantial amounts of peat were captured in sediment traps during summer storm events after two months of dry weather where desiccation of the peat surface occurred. The magnitude of topographic change for the six nested catchments determined by SfM (mean value: 5.3 mm, standard deviation: 5.2 mm) was very different to the areal average derived from sediment traps (mean value: –0.3 mm, standard deviation: 0.1 mm). Thus direct interpolation of peat erosion from local net topographic change into sediment yield at the catchment outlet appears problematic. Peat loss measured at the hillslope scale was not representative of that at the catchment scale. Stream sediment sampling at the outlet of the research catchment (0.017 km2) suggested that the yields of suspended sediment and particulate organic carbon were 926.3 t km–2 yr–1 and 340.9 t km–2 yr–1 respectively, with highest losses occurring during the autumn. Both freeze–thaw during winter and desiccation during long periods of dry weather in spring and summer were identified as important peat weathering processes during the study. Such weathering was a key enabler of subsequent fluvial peat loss from the catchment

Impacts of natural and human drivers on the multi-decadal morphological evolution of tidally-influenced deltas

The world's deltas are at risk of being drowned due to rising relative sea levels as a result of climate change, decreasing supplies of fluvial sediment, and human responses to these changes. This paper analyses how delta morphology evolves over multi-decadal timescales under environmental change using a process-based model. Model simulations over 10^2 years are used to explore the influence of three key classes of environmental change, both individually and in combination: (i) varying combinations of fluvial water and sediment discharges; (ii) varying rates of relative sea-level rise; and (iii) selected human interventions within the delta, comprising polder-dykes and cross-dams. The results indicate that tidal asymmetry and rate of sediment supply together affect residual flows and delta morphodynamics (indicated by sub-aerial delta area, rates of progradation and aggradation). When individual drivers of change act in combination, delta building processes such as the distribution of sediment flux, aggradation, and progradation are disrupted by the presence of isolated polder-dykes or cross-dams. This suggests that such interventions, unless undertaken at a very large scale, can lead to unsustainable delta building processes. Our findings can inform management choices in real-world tidally-influenced deltas, while the methodology can provide insights into other dynamic morphological systems

Quantifying sheet wash erosion rates in a mountainous semi-arid basin using environmental radionuclides and a stream power model

Erosion rates and processes define how mountainous landscapes evolve. This study determines the range of erosion rates in a semi-arid landscape over decadal time spans and defines the dominant processes controlling variability in erosion rates. The varying topography and climatic regimes of the Xiying Basin (Qilian Shan Mountains, China) enables us to examine the relative roles of sheet wash versus rainsplash and the influence vegetation on soil erosion and deposition. Soil erosion rates since 1954 were determined using 137Cs along 21 transects at 4 sites with varying gradient, rainfall, and vegetation cover. The mean 137Cs derived soil erosion rate ~0.42 mm/a, consistent with the catchment level erosion rate derived from total sediment yield for a 44 year record. However, there is considerable variability in 137Cs erosion rates both between transects and along transects. Perhaps reflecting variation not only in the effectiveness of individual processes but also in their relative roles. We compare the 137Cs-derived erosion rates with 1-D models for sediment flux that incorporate sheet wash and rainsplash processes, testing them over a previously untested 60 year timescale. The variability in 137Cs erosion rates along transects is best replicated by sheet wash dominated simulations, suggesting that this is the dominant erosion process in this semi-arid landscape. The functional form of the sheetwash model can also explain our observations that 137Cs erosion rates decrease with upslope length (i.e. distance down slope) while its variability increases. However, sparsely vegetated sites, located in slightly drier locations, have higher erosion rates, and are not as accurately modeled as densely vegetated sites, suggesting that patchiness of vegetation introduces fine scale variability in erosion rates on these slopes

Student Experiences in an Online First-Year Seminar Paired with Remedial Mathematics

Educational research has explored the influence of first-year seminars, online course delivery, and developmental coursework on first-year student success, yet there is limited research on how these educational components intersect. A collective case study approach was used to explore the experiences of students enrolled in an online first-year seminar that was paired with a developmental mathematics course. Students reported different motivating factors and expectations for enrolling in the course, yet all expressed a desire to improve their academic performance and confidence. These results help to inform how delivery of an online FYS can support the goals of students and institutions

A herbivore that manipulates plant defence

Phytopathogens and herbivores induce plant defences. Whereas there is evidence that some pathogens suppress these defences by interfering with signalling pathways involved in the defence, such evidence is scarce for herbivores. We found that the invasive spider mite Tetranychus evansi suppresses the induction of the salicylic acid and jasmonic acid signalling routes involved in induced plant defences in tomato. This was reflected in the levels of inducible defence compounds, such as proteinase inhibitors, which in mite-infested plants were reduced to even lower levels than the constitutive levels in herbivore-free plants. Additionally, the spider mite suppressed the release of inducible volatiles, which are implicated in plant defence. Consequently, the mites performed much better on previously attacked plants than on non-attacked plants. These findings provide a new perspective on plant–herbivore interactions, plant protection and plant resistance to invasive species

Teaching for the transition: The Canadian PGY-1 neurosurgery \u27rookie camp\u27

Background: Transitioning from medical school to residency is difficult and stressful, necessitating innovation in easing this transition. In response, a Canadian neurosurgical Rookie Camp was designed and implemented to foster acquisition of technical, cognitive and behavioral skills among incoming Canadian post graduate year one (PGY-1) neurosurgery residents. Methods: The inaugural Rookie Camp was held in July 2012 in Halifax. The curriculum was developed based on a national needs-assessment and consisted of a pre-course manual, 7 case-based stations, 4 procedural skills stations and 2 group discussions. The content was clinically focused, used a variety of teaching methods, and addressed multiple CanMEDS competencies. Evaluation included participant and faculty surveys and a pre-course, post-course, and 3-month retention knowledge test. Results: 17 of 23 PGY-1 Canadian neurosurgical residents participated in the Camp. All agreed the course content was relevant for PGY-1 training and the experience prepared them for residency. All participants would recommend the course to future neurosurgical residents. A statistically significant improvement was observed in knowledge related to course content (F(2,32) = 7.572, p\u3c0.002). There were no significant differences between post-test and retention-test scores at three months. Conclusion: The inaugural Canadian Neurosurgery Rookie Camp for PGY-1 residents was successfully delivered, with engagement from participants, training programs, the Canadian Neurosurgical Society, and the Royal College. In addition to providing fundamental knowledge, which was shown to be retained, the course eased junior residents\u27 transition to residency by fostering camaraderie and socialization within the specialty