A stochastic analysis of pollutant movement in groundwater

A procedure is presented that expresses pollutant movement in groundwater as a probability distribution. Probability is introduced into the pollutant movement solution process by using the Turning Bands Method (TBM), a spectral analysis model. The TBM generates a selected number of spatially-varying, correlated hydraulic conductivity fields, all of which have the same descriptive statistics, i.e., mean, standard deviation and correlation function. A groundwater flow-mass transport model developed by the Illinois State Water Survey is used to predict pollution concentration as a function of space and time for a specified groundwater contamination event. The groundwater flow-mass transport model develops a set of pollution movement estimates, one for each hydraulic conductivity field generated by the TBM. These realizations of pollutant movement are described first as frequency distributions and eventually as cumulative exceedance probability distributions;This procedure is applied to a documented field situation at the Idaho National Engineering Laboratory (INEL). Disposal of tritium in low-level radioactive and chemical wastes from the Idaho Chemical Processing Plant (ICPP) into the Snake River Plain aquifer through a deep injection well was recorded from 1976 through 1982. The movement of the tritium plume has been observed at several monitoring sites. TBM and groundwater flow-mass transport model parameters are determined in a calibration process with the recorded INEL data. One hundred realizations of a tritium disposal event during 1979 and 1980 at the INEL are used to generate cumulative exceedance probabilities of time of arrival and tritium concentration versus duration of exposure at an observation well downstream of the ICPP injection well;The observed cumulative exceedance probability distributions of time of arrival and conditional and marginal cumulative exceedance probability distributions of each tritium concentration and duration of exposure are fitted to the Pearson Type III distribution. A logit transformation is used to obtain a simple mathematical equation representing the joint cumulative exceedance probability distribution of tritium concentration and duration of exposure. Finally, the pertinence of these types of probability results to toxicity studies and benefit-cost analysis is discussed

Farmers’ perception of the effects of soil and water conservation structures on crop production: The case of Bokole watershed, Southern Ethiopia

Level soil bunds (LSB) and stone bunds (SB) have been widely implemented in Bokole watershed with World Food Programme (WFP) support since 2000-2001. However, the performance of structures against the target has not been studied. This study assessed farmers’ opinion on the effect of soil and water conservation (SWC) structures, particularly level soil bunds and stone bunds, in improving agricultural crop production. A household survey was carried out by stratified random sampling. Twenty-seven percent of the farmers who adopted SWC structure (29 households from the upper watershed and 62 households from the lower watershed) were randomly selected and interviewed. Three group  discussions were also conducted. Based on their own indicators, a high proportion of those interviewed (79.3% in the upper and 87.1% in the lower watershed) had a positive opinion about LSB and SB on their cropland, in relation to its role in improving soil fertility and crop  production. Ninety-three percent of interviewed farmers in both the upper watershed and the lower watershed perceived a change in crop yield within two years after implementation of structures. There is a need for awareness creation and for monitoring the correct management of existing soil and water conservation structures, to ensure that they function as intended, and to improve their efficiency. This can reduce the problem of a ‘decrease’ or ‘fluctuation’ in crop yield. Key words: Crop yield, non-terraced, soil bunds, stone bund, water erosion

Soil organic carbon and associated soil properties in Enset (Ensete ventricosum Welw. Cheesman)-based homegardens in Ethiopia

Enset (Ensete ventricosum Welw. Cheesman)-based homegardens have long been practiced as central elements of agricultural land management and food security in south and southwest Ethiopia. In contrast to the homegardens’ biodiversity and role in food security, soil quality has received little attention. Objective of this study was to assess soil quality parameters in typical homegardens in comparison with adjacent croplands, both under continuous management for >30 years. The study was undertaken at high (2200–2330 masl), mid (1799–1849 masl), and low (1349–1381 masl) elevation in the central Omo-Gibe basin, southwest Ethiopia. Through interviews of 49 randomly selected farm households, and soil sampling at six paired sites at high and mid elevations, and five paired sites of low elevation, we found that homegardens received the majority of household waste and manure and were less frequently tilled. By contrast, some, but not all, croplands occasionally received inorganic fertilizer. Homegarden soil had significantly greater (P < 0.05) soil organic carbon (SOC) concentrations than croplands. At 0–20 cm depth, SOC concentrations in homegardens (22.4–26.4 mg

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG2000cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems

Benefits, limitations and sustainability of soil and water conservation structures in Omo-Gibe basin, Southwest Ethiopia

Different types of soil and water conservation (SWC) structures were introduced to Ethiopia during the last four decades for abating water erosion and sustaining agricultural productivity. This study aimed to determine benefits, limitations and sustainability of SWC structures in the Toni and Bokole watersheds of the Omo Gibe basin. A household survey was conducted on a total of 201 households, which were selected by employing a multistage sampling procedure that covered six rural kebeles.1 Moreover, six focus group discussions were conducted. The results revealed that more than 80% of respondents in Bokole watershed and all respondents in Toni watershed experienced moderate to severe soil erosion. Farmers were selective in accepting and implementing SWC structures depending on the local land characteristics. Stone bunds were widely implemented in Bokole watershed where rock fragments are abundant and Fanya juuand soil bunds were widely practiced in Toni watershed where rock fragments are not available. Owing to labor intensiveness of the SWC structures, more than 82% of respondents in Bokole and 54% in Toni perceived that labor shortage was a challenge for construction and maintenance. More than 74% of the adopter farmers were also concerned about the loss of cultivable land due to the construction of SWC structures. Number of cattle owned (p < 0.05) and having administrative responsibility in the kebele (p < 0.1) significantly and negatively influenced construction of the SWC structures in Bokole watershed. Runoff overtopping, livestock trampling and cultivation practices were mentioned as the causes of damages for the SWC structures in both watersheds. In Bokole watershed, 92% of the respondents indicated that they repaired the broken SWC structures to sustain their benefits. But 62% of respondents in Toni watershed did not repair. The effort of repairing the SWC structures was significantly (p < 0.05) and negatively influenced by farmland area in Bokole watershed and by education level in Toni watershed. The respondents’ preferences of SWC structures, rate of adoption, willingness to repair and factors affecting adoption and repairing were slightly different in Bokole watershed when compared with Toni watershed. Thus, we concluded that effective implementation and sustainability of SWC structures should critically consider the land users’ socio-economic and environmental intricacy

Towards sustainable watershed-based landscape restoration in degraded drylands: Perceived benefits and innovative pathways learnt from project-based interventions in Ethiopia

Land degradation is one of the contemporary environmental challenges affecting regions inhabited by over one-third of the global population. In response to land degradation, restoration of degraded landscapes through area closure has been implemented through government and bilateral organizations for the last three decades in Ethiopia. Objectives of this study were to: i) explore the effects of landscape restoration on vegetation cover; ii) identify the perceived benefits to local communities; and 3) synthesize the lessons learnt on communities’ willingness to sustain the restored landscapes. The study was conducted in project-supported restoration areas including the Dimitu and Kelisa watersheds representing the central rift valley dry lands and the Gola Gagura watershed representing the eastern dry land areas around Dire Dawa. The temporal changes in land use and land cover due to area closure integrated with physical and biological soil and water conservation measures were detected using GIS/Remote sensing techniques. Moreover, eighty-eight rural households were interviewed. The results of the study revealed that landscape restoration activities such as area closure integrated with physical soil and water conservation, and planting of trees and shrubs contributed to the significant changes in land covers of the watersheds in 3–5 years. Hence, barren lands were reduced by 35–100% while there were significant increases in forest lands (15%), woody grasslands (247–785%), and bushlands (78–140%). More than 90% of the respondents in the Dimitu and Gola Gagura watersheds verified that the landscape restoration activities improved vegetation cover and ecosystem services, reduced erosion, and increased incomes. A great majority of farm households (63–100%) expressed their willingness to contribute to different forms of landscape restoration interventions. Encroachment of livestock to closed area, shortage of finance, and the growing number of wild animals in closed area were the perceived challenges. Proper planning and implementation of integrated interventions, creating local watershed user associations, ensuring appropriate benefit-sharing and implementing innovative pathways to reconcile the tradeoffs could be considered to scale up interventions and address potential conflicts of interest

Efficacy and safety of exenatide once weekly versus metformin, pioglitazone, and sitagliptin used as monotherapy in drug-naive patients with type 2 diabetes (DURATION-4): a 26-week double-blind study

OBJECTIVE: To test the safety and efficacy of exenatide once weekly (EQW) compared with metformin (MET), pioglitazone (PIO), and sitagliptin (SITA) over 26 weeks, in suboptimally treated (diet and exercise) drug-naive patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Patients were randomized to subcutaneous (SC) EQW 2.0 mg + oral placebo (n = 248), MET 2,000 mg/day + SC placebo (n = 246), PIO 45 mg/day + SC placebo (n = 163), or SITA 100 mg/day + SC placebo (n = 163) for 26 weeks. MET and PIO therapies were increased to maximum-tolerated dosages. Injections with EQW or placebo were administered weekly, while oral medication or placebo was administered daily. RESULTS: Baseline characteristics were as follows: 59% men, 67% Caucasian, mean age 54 years, HbA(1c) 8.5%, fasting serum glucose 9.9 mmol/L, body weight 87.0 kg, and diabetes duration 2.7 years. HbA(1c) reductions (%) at 26 weeks (least-squares means) with EQW versus MET, PIO, and SITA were -1.53 vs. -1.48 (P = 0.620), -1.63 (P = 0.328), and -1.15 (P < 0.001), respectively. Weight changes (kg) were -2.0 vs. -2.0 (P = 0.892), +1.5 (P < 0.001), and -0.8 (P < 0.001), respectively. Common adverse events were as follows: EQW, nausea (11.3%) and diarrhea (10.9%); MET, diarrhea (12.6%) and headache (12.2%); PIO, nasopharyngitis (8.6%) and headache (8.0%); and SIT, nasopharyngitis (9.8%) and headache (9.2%). Minor (confirmed) hypoglycemia was rarely reported. No major hypoglycemia occurred. CONCLUSIONS: EQW was noninferior to MET but not PIO and superior to SITA with regard to HbA(1c) reduction at 26 weeks. Of the agents studied, EQW and MET provided similar improvements in glycemic control along with the benefit of weight reduction and no increased risk of hypoglycemia