Bridging the gap between terrestrial, riverine and limnological research: application of a model chain to a mesotrophic lake in North America

Models remain our best available tool for managing low lake dissolved oxygen concentrations, which pose a serious ecological risk. This study investigated whether process-based catchment models (INCA-N and INCA-P) could accurately drive a lake model (PROTECH), to bridge a gap between terrestrial, riverine and limnological research. INCA was calibrated over all 20 catchments of the Simcoe watershed, Canada. Daily outputs (flow, nitrogen and phosphorus concentrations) over the period 2010–2016 were selected for a common “baseline” period, and used as inputs to PROTECH, which was calibrated across the three major basins of lake Simcoe; Kempenfelt (K42), Cooks (C9), and the main basin (E51). Results showed that at catchment outflows INCA models achieved an average flow R2 of 0.8; a load R2 of 0.7 (both for TP and N-NO3), a concentration R2 of 0.4 and 0.5 (for TP and N-NO3 respectively), and an SiO2 R2 > 0.8. In each basin PROTECH achieved an R2 for both temperature and dissolved oxygen (DO) concentrations of > 0.9. Performance of N-NO3, TP and Chlorophyll-a concentrations were good (R2 values of up to 0.98, 0.92 and 0.53 respectively). Multi-stressor analyses established that most occurrences when DO dropped below the desired 7 mg/l threshold (DO7) were attributable to combinations of high temperatures and low tributary inflows. The importance of additional drivers was depth dependent, with photosynthesis being particularly important in shallower C9 and E51 basins during summer, when algae contributed sufficient O2 to the water column to inhibit DO7 events. Conversely in the deeper more strongly stratified K42 basin, greater algal growth boosted the biochemical oxygen demand, enhancing declines in DO. Lake physics explained a significant number of DO7 events in all three basins. Integrated catchment-lake modelling approaches are important in understanding lake physical and ecological processes, and the impacts of land management and future climate change

The 2010 MW 6.8 Yushu (Qinghai, China) earthquake: constraints provided by InSAR and body wave seismology

By combining observations from satellite radar, body wave seismology and optical imagery, we have determined the fault segmentation and sequence of ruptures for the 2010 Mw 6.8 Yushu (China) earthquake. We have mapped the fault trace using displacements from SAR image matching, interferometric phase and coherence, and 2.5 m SPOT-5 satellite images. Modeling the event as an elastic dislocation with three segments fitted to the fault trace suggests that the southeast and northwest segments are near vertical, with the central segment dipping 70° to the southwest; slip occurs mainly in the upper 10 km, with a maximum slip of 1.5 m at a depth of 4 km on the southeastern segment. The maximum slip in the top 1 km (i.e., near surface) is up to 1.2 m, and inferred locations of significant surface rupture are consistent with displacements from SAR image matching and field observations. The radar interferograms show rupture over a distance of almost 80 km, much larger than initial seismological and field estimates of the length of the fault. Part of this difference can be attributed to slip on the northwestern segment of the fault being due to an Mw 6.1 aftershock two hours after the main event. The remaining difference can be explained by a non-uniform slip distribution with much of the moment release occurring at depths of less than 10 km. The rupture on the central and southeastern segments of the fault in the main shock propagated at a speed of 2.5 km/s southeastward toward the town of Yushu located at the end of this segment, accounting for the considerable building damage. Strain accumulation since the last earthquake on the fault segment beyond Yushu is equivalent to an Mw 6.5 earthquake

Quantifying denitrification on a field-scale in hummocky terrain

Non-Peer ReviewedDown-slope and cross-slope curvature and elevation were used to identify nine landscape elements for a slough-focused basin in hummocky terrain near Hafford, Saskatchewan. Denitrification was measured at monthly intervals from April to October in 1986, 1987, and 1988. The measured values were interpolated to daily values using a simple soil moisture budget and a regression model relating denitrification to moisture content and air temperature. The model predicted denitrification well except in 1987, the fallow year, when the denitrification flush due to substrate availability was underestimated. Annual denitrification was higher in 1987 than in either 1986 or 1988 when wheat and canola, respectively, were grown. Low-lying and convergent elements had greater denitrification than diverging elements or those higher in the landscape. The relative abundance of the landscape elements was used to extend the denitrification predicted for the landscape elements to the whole field

Monitoring water and salt movement during a leaching irrigation using time domain reflectometry

Non-Peer ReviewedTime domain reflectometry (TDR) has become an accepted method of measuring soil water content. Laboratory results have indicated that it may also be possible to measure soil electrical conductivity (EC) using TDR. The objectives of this experiment were to investigate the utility of TDR as a field measurement of EC and to illustrate a potential application of the technique. Field research was conducted at the Saskatchewan Irrigation Development Centre on a field which has been reclaimed from salinity over the past 10 years by the installation of tile drains and a fall leaching program. To test the accuracy of bulk soil EC measurements made by TDR (ECr), EC was also measured on water samples from suction lysimeters which sampled at the same depths as the TDR waveguides and converted to a bulk soil basis (EC8). Comparisons between ECT and EC8 were made three times during the 1992 growing season (when the soil was relatively dry) and four times during the fall leaching period (when the soil was much wetter). ECr was significantly correlated (p<0.001) to EC8. However, the measurement of ECT was affected by soil moisture content and an empirical function had to be used to eliminate this source of variability. Good agreement (R2=0.93) was obtained between ECT and EC8 when this function was applied. During the leaching irrigation, water and salt movement was monitored by TDR. At most sites, a salt bulge could be clearly identified moving downward through the profile as the volume of water applied increased. With further investigation into the relationship between ECT and water content, the rapid simultaneous measurement of water content and electrical conductivity made possible by TDR should prove useful in studies of salt movement

Impacts of cover crops and crop residues on phosphorus losses in cold climates: a review

Non-Peer ReviewedThe use of plants in riparian buffers or cover crops is widely proposed as a strategy to mitigate sediment and nutrient losses from land to water. In cold climates, concerns may arise with regard to potentially elevated phosphorus (P) losses associated with freeze-thaw of plant materials. Here, we review the impacts of cover crops and crop residues on P loss in cold climates, and explore linkages between water extractable P in the plant materials and P loss in surface runoff and subsurface drainage from cropped soils. Water extractable P in plants is greatly affected by crop species and hardiness, as well as freezing regimes including both freezing temperature and the number of freeze-thaw cycles. Although controls on water extractable P in plant tissues and residues are relatively well understood, impacts on P runoff and leaching are inconsistent across studies due to the influences of soil, climate, and management factors. This review sheds light on improving winter crop cover management to minimize P losses from land to water in cold climates and points to future research needs. Specifically, more research is needed to understand interactions between soil, plant, hydrology, and management in influencing P loss, and to improve the assessment of crop contributions to P loss in field settings of cold climates. Further, the trade-offs between the concern over P and the control of sediment loss and nitrogen leaching should be acknowledged, as should the uncertainties of freezing and crop adaptability under future climate regimes

Leaching of nitrates and herbicides under low pressure (high volume) irrigation

Non-Peer ReviewedThe potential for contamination of groundwater by nitrates or pesticides from irrigated soils has not been fully evaluated. This project was initiated to monitor nitrate and herbicide leaching in a tile-drained field at SIDC in Outlook. Water samples were collected using suction lysimeters and analyzed for nitrate and four herbicides (2, 4-D, dicamba, bromoxynil and diclofop). The concentrations of nitrates at depth were maintained by the downward movement of applied andmineralized N. Trace amounts of 2, 4-D and diclofop were leached to 180 cm but bromoxynil and dicamba were not found below 60 cm depth. Dicamba and diclofop persisted longer in the soil than 2, 4-D or bromoxynil but were only present in trace amounts at the end of August

Geometrical aspects of isoscaling

The property of isoscaling in nuclear fragmentation is studied using a simple bond percolation model with ``isospin'' added as an extra degree of freedom. It is shown analytically, first, that isoscaling is expected to exist in such a simple model with the only assumption of fair sampling with homogeneous probabilities. Second, numerical percolations of hundreds of thousands of grids of different sizes and with different $N$ to $Z$ ratios confirm this prediction with remarkable agreement. It is thus concluded that isoscaling emerges from the simple assumption of fair sampling with homogeneous probabilities, a requirement which, if put in the nomenclature of the minimum information theory, translates simply into the existence of equiprobable configurations in maximum entropy states

Interleukin-1 receptor antagonist mediates toll-like receptor 3-induced inhibition of trophoblast adhesion to endometrial cells in vitro

STUDY QUESTION Is interleukin-1 receptor antagonist (IL-1RA) involved in the toll-like receptor 3 (TLR 3)-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro? SUMMARY ANSWER IL-1RA mediates the TLR 3-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro. WHAT IS KNOWN ALREADY It is well documented that endometrial TLR 3 activation leads to impairment of trophoblast binding to endometrial cells in vitro. IL-1RA is known as an anti-implantation factor, as its injection significantly reduced implantation rates in mice by an effect on endometrial receptivity. STUDY DESIGN, SIZE, DURATION Poly I:C was used as a TLR3 specific ligand and endometrial cells were either treated or not with Poly I:C (treated versus control) in vitro. IL-1RA was applied to block IL-1 signal transduction. IL-1RA was knocked down by Accell Human IL1RN siRNA. Flagellin was used to stimulate TLR 5. SP600125 (JNK) was applied to inhibit the mitogen-activated protein kinases (MAPK) pathway. BAY11 -7082 was used to inhibit the nuclear factor-κB (NF-κB) pathway. The experiments were performed in three replicates on three separate days. PARTICIPANTS/MATERIALS, SETTING, METHODS An in vitro assay was developed using RL95-2 (an endometrial cell line) and JAr (a trophoblast cell line) cells. Initially, the production of IL-1RA in RL95-2 cells in response to TLR 3 activation was measured. To determine whether the TLR 3-induced inhibition of trophoblast binding was mediated through IL-1RA: (i) we evaluated the effect of IL-1RA on the attachment of trophoblast cells to endometrial cells; (ii) we knocked down TLR3-induced IL-1RA gene expression by IL-1RA Small interfering RNA (siRNA) and evaluated trophoblast attachment to endometrial cells. Finally, to clarify through which pathway TLR 3-induced inhibition of trophoblast binding occurs: (i) activation of NF-κB and MAPK was detected by transfecting the cells with secreted placental alkaline phosphatase reporter plasmids bearing promoter sequences for each transcription factor; (ii) the inhibitors for NF-κB and MAPK were used to block signaling; (iii) it was then investigated whether addition of these inhibitors could restore the TLR 3-induced impairment of trophoblast attachment to the endometrial cells. MAIN RESULTS AND THE ROLE OF CHANCE Our results showed that addition of polyinosinic:polycytidylic acid (Poly I:C) to RL95-2 cells significantly increased the production of IL-1RA (P < 0.05). Addition of human recombinant IL-1RA to RL95-2 cells remarkably decreased the adhesion rate of trophoblast cells to endometrial cells (P < 0.05). In addition, suppression of TLR3-induced IL-1RA gene expression in RL95-2 cells significantly restored trophoblast cells attachment to endometrial cells in the presence of Poly I:C (P < 0.05). Only TLR3 and not TLR5 induced MAPK activation (P < 0.05). TLR3 ligation did not affect NF-κB activation. Of NF-kB and MAPK inhibitors, only MAPK's inhibitor could achieve restoration of spheroid adhesion to endometrial cells (P < 0.05). LIMITATIONS, REASONS FOR CAUTION This study has been only done in vitro. Future in vivo studies will confirm our data. WIDER IMPLICATIONS OF THE FINDINGS The findings of this study have a potential clinical application in introducing IL-1RA as one of the diagnostic infertility markers in the endometrium, which can affect the process of embryo adhesion at the time of implantation. Moreover, based on the novel data obtained in the current study, blocking and regulating the MAPK pathway by its inhibitors can be used as a new strategy to prevent and treat virus-induced infertility cases in ART techniques. STUDY FUNDING/COMPETING INTEREST This study was partially funded by a Marie Curie IIF-253948 grant to I.C. and was partially funded by the author's institutions. The authors have no conflict of interest to declare

Combined impacts of future land-use and climate stressors on water resources and quality in groundwater and surface waterbodies of the upper Thames river basin, UK

It is widely acknowledged that waterbodies are becoming increasingly affected by a wide range of drivers of change arising from human activity. To illustrate how this can be quantified a linked modelling approach was applied in the Thames river basin in southern UK. Changes to river flows, water temperature, river and reservoir quality were predicted under three contrasting future “storylines”; one an extension of present day rates of economic development, the others representing more extreme and less sustainable visions. Modelling revealed that lower baseflow conditions will arise under all storylines. For the less extreme storyline river water quality is likely to deteriorate but reservoir quality will improve slightly. The two more extreme futures could not be supported by current management strategies to meet water demand. To satisfy these scenarios, transfer of river water from outside the Thames river basin would be necessary. Consequently, some improvement over present day water quality in the river may be seen, and for most indicators conditions would be better than in the less extreme storyline. However, because phosphorus concentrations will rise, the invoked changes in water demand management would not be of a form suitable to prevent a marked deterioration in reservoir water quality

Special fast diffusion with slow asymptotics. Entropy method and flow on a Riemannian manifold

We consider the asymptotic behaviour of positive solutions $u(t,x)$ of the fast diffusion equation $u_t=\Delta (u^{m}/m)={\rm div} (u^{m-1}\nabla u)$ posed for x\in\RR^d, $t>0$, with a precise value for the exponent $m=(d-4)/(d-2)$. The space dimension is $d\ge 3$ so that $m<1$, and even $m=-1$ for $d=3$. This case had been left open in the general study \cite{BBDGV} since it requires quite different functional analytic methods, due in particular to the absence of a spectral gap for the operator generating the linearized evolution. The linearization of this flow is interpreted here as the heat flow of the Laplace-Beltrami operator of a suitable Riemannian Manifold (\RR^d,{\bf g}), with a metric ${\bf g}$ which is conformal to the standard \RR^d metric. Studying the pointwise heat kernel behaviour allows to prove {suitable Gagliardo-Nirenberg} inequalities associated to the generator. Such inequalities in turn allow to study the nonlinear evolution as well, and to determine its asymptotics, which is identical to the one satisfied by the linearization. In terms of the rescaled representation, which is a nonlinear Fokker--Planck equation, the convergence rate turns out to be polynomial in time. This result is in contrast with the known exponential decay of such representation for all other values of $m$.Comment: 37 page