Relations between M\"obius and coboundary polynomial

It is known that, in general, the coboundary polynomial and the M\"obius polynomial of a matroid do not determine each other. Less is known about more specific cases. In this paper, we will try to answer if it is possible that the M\"obius polynomial of a matroid, together with the M\"obius polynomial of the dual matroid, define the coboundary polynomial of the matroid. In some cases, the answer is affirmative, and we will give two constructions to determine the coboundary polynomial in these cases.Comment: 12 page

Quantifying groundwater fluxes from an aapa mire to a riverside esker formation

Water flows in peatland margins is an under-researched topic. This study examines recharge from a peatland to an esker aquifer in an aapa mire complex of northern Finland. Our objective was to study how the aapa mire margin is hydrogeologically connected to the riverside aquifer and spatial and temporal variations in the recharge of peatland water to groundwater (GW). Following geophysical studies and monitoring of the saturated zone, a GW model (MODFLOW) was used in combination with stable isotopes to quantify GW flow volumes and directions. Peatland water recharge to the sandy aquifer indicated a strong connection at the peatland–aquifer boundary. Recharge volumes from peatland to esker were high and rather constant (873 m3 d−1) and dominated esker recharge at the study site. The peat water recharging the esker boundary was rich in dissolved organic carbon (DOC). Stable isotope studies on water (δ18O, δ2H, and d-excess) from GW wells verified the recharge of DOC-rich water from peatlands to mineral soil esker. Biogeochemical analysis revealed changes from DOC to dissolved inorganic carbon in the flow pathway from peatland margin to the river Kitinen. This study highlights the importance of careful investigation of aapa mire margin areas and their potential role in regional GW recharge patterns. HIGHLIGHTS Peatland water recharge to aquifer showed connection at the peatland–aquifer boundary.; Analysis revealed changes from dissolved organic carbon to dissolved inorganic carbon in groundwater flow pathway from peatland.; Connection between an aapa mire margin and riverside esker was documented.

Spatiotemporal variability and trends in extreme temperature events in Finland over the recent decades:influence of Northern Hemisphere teleconnection patterns

Abstract Fifteen temperature indices recommended by the ETCCDI (Expert Team on Climate Change Detection and Indices) were applied to evaluate spatiotemporal variability and trends in annual intensity, frequency, and duration of extreme temperature statistics in Finland during 1961–2011. Statistically significant relationships between these high-resolution (10 km) temperature indices and seven influential Northern Hemisphere teleconnection patterns (NHTPs) for the interannual climate variability were also identified. During the study period (1961–2011), warming trends in extreme temperatures were generally manifested by statistically significant increases in cold temperature extremes rather than in the warm temperature extremes. As expected, warm days and nights became more frequent, while fewer cold days and nights occurred. The frequency of frost and icing days also decreased. Finland experienced more (less) frequent warm (cold) temperature extremes over the past few decades. Interestingly, significant lengthening in cold spells was observed over the upper part of northern Finland, while no clear changes are found in warm spells. Interannual variations in the temperature indices were significantly associated with a number of NHTPs. In general, warm temperature extremes show significant correlations with the East Atlantic and the Scandinavia patterns and cold temperature extremes with the Arctic Oscillation and the North Atlantic Oscillation patterns

Can limestone, steel slag or man-made sorption materials be used to enhance phosphate-phosphorus retention in treatment wetland for peat extraction runoff with low phosphorous concentration?

Abstract This study examined possibilities to enhance phosphorus (P) retention in wetlands using different materials that could enhance removal of phosphate P (PO₄-P) from runoff waters with fairly low P concentrations (Ptot average 80–90 μg L−1 and PO₄-P 25–30 μg L−1) typical for peat extraction runoff. The retention potential of sorption materials, that had previously shown good retention capacity was first studied in laboratory batch tests using steel slag (basic oxygen furnace slag (BOF)), Filtralite®P (high Ca and Mg clay), CFH 12 (ferrihydroxide), limestone, Phoslock® (95% bentonite clay material + 5% lanthanum) and iron gypsum in year 2010. Based on batch test results and material properties (column tests not suitable for fine clay materials such as Phoslock®), steel slag, CFH 12 and iron gypsum products were selected for column tests. The columns experiments were run for almost three months during spring 2011. Steel slag and Phoslock® were selected for further testing in situ in a treatment wetland. In the laboratory set-ups, all materials tested retained PO₄-P (70–90% in batch tests and approximately 10–80% in column experiments). However, in the field scale set-up, neither steel slag nor Phoslock® successfully retained PO₄-P. The reasons may be e.g. for steel slag, too low pH, too large grain size, and too short retention time. Also, for some set-up, the given instruction were not followed during construction works. Further studies are needed to test different particle sizes and new potential materials for retaining P in treatment wetlands with high hydraulic loading rate, low P concentration and low pH

Spatial heterogeneity of soil properties in relation to microtopography in a non-tidal rewetted coastal mire

Abstract Over the past century, mires and peatlands have faced a wide range of degradation by artificial drainage, making them one of the most threatened ecosystems in Europe. However, restoration of drained peatlands has gained much importance over the last three decades, mostly due to the multiple ecosystem services they provide such as carbon storage, habitat provision and water flow regulation. Although there has been an increased focus on such ecosystems, spatial research on hydrophysical soil properties following rewetting in coastal mires is lacking. Therefore, the objectives of the study were to understand the spatial structures of hydrophysical properties of organic soils and spatial patterns of organic matter accumulation in relation to soil surface microtopography. Soil organic matter content (SOM) and hydraulic conductivity (Ks) of topsoils (0–28 cm), along with soil textures of the underlying mineral substrate, were investigated in a rewetted non-tidal coastal flood mire (Baltic Sea). The results indicate that the organic horizon with its relatively low Ks acts as a hydrological barrier to infiltration. Soil organic matter content (SOM), Ks and soil surface microtopography are all spatially auto-correlated within 100, 87 and 53 m, respectively. Bivariate Moran’s I revealed a positive but weak spatial correlation between SOM and Ks and a moderately strong negative spatial correlation between SOM and soil surface microtopography. A map of SOM was generated using simple kriging, which predicts higher SOM in the centre of the ecosystem, at lower elevations; and lower SOM at the edges of the study area, at higher elevations. Local depressions in the centre of the ecosystem provide a wetter and therefore more anaerobic environment, thereby decreasing carbon mineralisation rates and enabling peat accumulation. The low hydraulic conductivity of the degraded peat in the presence of lower micro-elevations in the centre of the ecosystem is likely to increase the residence time of floodwater and thus may enhance (new) peat accumulation. Thus, we conclude that, for the restoration of non-tidal coastal mires where flooding events are not as frequent, Ks and soil surface microtopography are even more important factors to consider than for tidal systems

Urban flood risk mapping using the GARP and QUEST models: A comparative study of machine learning techniques

© 2018 Elsevier B.V. Flood risk mapping and modeling is important to prevent urban flood damage. In this study, a flood risk map was produced with limited hydrological and hydraulic data using two state-of-the-art machine learning models: Genetic Algorithm Rule-Set Production (GARP) and Quick Unbiased Efficient Statistical Tree (QUEST). The flood conditioning factors used in modeling were: precipitation, slope, curve number, distance to river, distance to channel, depth to groundwater, land use, and elevation. Based on available reports and field surveys for Sari city (Iran), 113 points were identified as flooded areas (with each flooded zone assigned a value of 1). Different conditioning factors, including urban density, quality of buildings, age of buildings, population density, and socio-economic conditions, were taken into account to analyze flood vulnerability. In addition, the weight of these conditioning factors was determined based on expert knowledge and Fuzzy Analytical Network Process (FANP). An urban flood risk map was then produced using flood hazard and flood vulnerability maps. The area under the receiver-operator characteristic curve (AUC-ROC) and Kappa statistic were applied to evaluate model performance. The results demonstrated that the GARP model (AUC-ROC = 93.5%, Kappa = 0.86) had higher performance accuracy than the QUEST model (AUC-ROC = 89.2%, Kappa = 0.79). The results also indicated that distance to channel, land use, and elevation played major roles in flood hazard determination, whereas population density, quality of buildings, and urban density were the most important factors in terms of vulnerability. These findings demonstrate that machine learning models can help in flood risk mapping, especially in areas where detailed hydraulic and hydrological data are not available

Urban flood risk mapping using data-driven geospatial techniques for a flood-prone case area in Iran

10.2166/nh.2019.090Hydrology Research511127-14

Recent results from an ecohydrological study of forest species in drained tropical peatlands

Abstract Ecohydrological studies in tropical peatland have mostly focused on a small number of non-native commercial species. However, studies of native species are urgently needed as they are considered to be a possible solution in the restoration of millions of hectares of degraded tropical peatlands. We investigated peatland species on Padang Island, Indonesia, to assess their responses to changing environmental factors, particularly the high fluctuation of the water table due to intensive peatland draining. We monitored the sap-flux velocity and radial growth of six trees (four native and one non-native peatland species) in high temporal resolution using sap-flux meters and dendrometers up to seven months. Monitoring also included hydrological and micrometeorological parameters. We found that sap-flux velocity in the monitored species was mainly controlled by air vapor pressure deficits, photosynthetic active radiation, and to some extent, by wind speed and water-table depth. We also observed a species-specific correlation between daily sap-flux velocity and daily radial growth. Non-native Acacia crassicarpa had up to twice the radial growth of native species. This growth of non-native species was significantly higher at a shallow water-table depth, while native species did not show the same relationship. The interaction between water-table depth, sap-flux velocity, and radial growth in daily timescale was not straightforward, presumably because of the complex carbon-allocation mechanism in trees