Devils Lake is a terminal lake located in northeast North Dakota. Because of its glacial origin and accumulated salts from evaporation, the lake has a high concentration of sulfate compared to the surrounding water bodies. From 1993 to 2011, Devils Lake water levels rose by ~10 m, which flooded surrounding communities and increased the chance of an overspill to the Sheyenne River. To control the flooding, the State of North Dakota constructed two outlets to pump the lake water to the river. However, the pumped water has raised concerns about of water quality degradation and potential flooding risk of the Sheyenne River. To investigate these perceived impacts, a Soil and Water Assessment Tool (SWAT) model was developed for the Sheyenne River and it was linked to a coupled SWAT and CE‐QUAL‐W2 model that was developed for Devils Lake in a previous study. While the current outlet schedule has attempted to maintain the total river discharge within the confines of a two‐year flood (36 m3/s), our simulation from 2012 to 2018 revealed that the diversion increased the Sheyenne River sulfate concentration from an average of 125 to >750 mg/L. Furthermore, a conceptual optimization model was developed with a goal of better preserving the water quality of the Sheyenne River while effectively mitigating the flooding of Devils Lake. The optimal solution provides a “win–win” outlet management that maintains the efficiency of the outlets while reducing the Sheyenne River sulfate concentration to ≤600 mg/L. 相似文献
Carbon coated monolith was prepared by sucrose solution 65 wt.% via dip-coating method. Sulfonation of incomplete carbonized carbon coated monolith was carried out in order to synthesize solid acid catalyst. The textural structure characteristics of the solid acid catalyst demonstrated a low surface area and pore volume. Palm fatty acid distillate (PFAD), a by-product of palm oil refineries, was utilized as oil source in biodiesel production. The esterification reaction subjected to different reaction conditions was performed by using the sulfonated carbon coated monolith as heterogeneous catalyst. The sulfonation process had been performed by using vapour of concentrated H2SO4 that was much easier and efficient than liquid phase sulfonation. Total acidity value of carbon coated monolith was measured for unsulfonated sample (0.5 mmol/g) and sulfonated sample (4.2 mmol/g). The effect of methanol/oil ratio, catalyst amount and reaction time were examined. The maximum methyl ester content was 89% at the optimum condition, i.e. methanol/oil molar ratio (15:1), catalyst amount (2.5 wt.% with respect to PFAD), reaction time (240 min) and temperature 80 °C. The sugar catalyst supported on the honeycomb monolith showed comparable reactivity compared with the sugar catalyst powder. However, the catalyst reusability studies showed decrease in FFA% conversion from 95.3% to 68.8% after four cycles as well as the total acidity of catalyst dropped from the value 4.2 to 3.1 mmol/g during these cycles. This might be likely due to the leaching out of SO3H group from the sulfonated carbon coated monolith surface. The leaching of active species reached a plateau state after fourth cycle. 相似文献
Rainfall interception represents the amount of water trapped in natural cover that is not drained directly to the ground. Intercepted rainfall may evaporate after a rain event, making it one of the main drivers of water balance and hydrologic regionalization. This process can be affected by factors such as climate, altitude, vegetation type, and topography. Here is a simple method of calculating rainfall interception in temperate forests using in Santa Maria Yavesia, Oaxaca, and Mexico as an illustrative study area. We used two rain gauges to measure net precipitation (Np) under the canopy at each study site and one gauge outside the canopy to obtain gross precipitation (Gp). Throughfall (Th) was indirectly measured using hemispherical photographs. Rainfall interception was obtained through a combination Th and Gp and Np. The mean rainfall interception was 50.6% in the Abies forests, 23%–40% in the coniferous‐mixed forests, and 27.4% in the broad‐leaved forests. We classified rainfall events by intensity to determine the effect of canopy structure and precipitation and found that 75% of the events were weak events, 24% were moderate events, and 1% were strong events. In addition, we found that rainfall interception was lower when the intensity of precipitation was higher. Our method can be replicated in different ecosystems worldwide as a tool for assessing the influence of rainfall interception in terms of ecological services. 相似文献
Objective: The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data.
Method: Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels.
Results: A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes.
Conclusions: The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design. 相似文献