Understanding the effects of rainfall on elephant-vegetation interactions around waterholes

The distribution of surface water affects herbivore-vegetation interactions in arid and semi-arid regions. Limited access to surface water typically results in the emergence of vegetation gradients around natural and artificial water sources. In particular, African elephants can create large-scale gradients of woody vegetation. Understanding the dynamics of these gradients is of particular importance for the conservation of other, less mobile herbivores that depend on woody vegetation in areas close to water. While rainfall is known to be a key determinant of herbivore-vegetation interactions in dry areas, we only have limited understanding on how it impacts woody vegetation gradients around waterholes. To address this problem, we developed a deterministic simulation model that describes the interplay of rainfall, elephants and woody vegetation in the vicinity of waterholes. The model is based on elephant telemetry data and the ecological conditions in Etosha National Park (ENP), Namibia. We found that decreasing amounts of rainfall led to an increased degradation of woody vegetation, which was particularly severe in areas close to water. Based on this result we conclude that low rainfall was an important driver of recently observed patterns of vegetation degradation in ENP. More generally, rainfall appears to be a key factor that determines elephant-vegetation interactions and thus dynamics of woody vegetation gradients around waterholes. Using long-term rainfall data from ENP, we also demonstrate that an increase in the number of water sources during periods of low rainfall can mitigate the destructive impact of elephants in areas close to water. However, more research is required to assess the sustainability and effectiveness of rainfall-adapted strategies of artificial water provisioning in more detail. In particular it is important to investigate potential effects on elephant population dynamics.     

臭氧和好氧生物法处理污水处理厂出水的纳米过滤浓缩液

城市污水处理厂出水的纳米过滤浓缩液较难直接生物处理。臭氧氧化该浓缩液降低DOC的速度较慢,但是可以有效地破坏该浓缩液中含苯环和有色基团的大分子有机物,显著增加小分子有机物的相对含量,从而增大其可生化降解性能。研究发现臭氧的投量为52mg/L左右时,臭氧化改善该纳米过滤浓缩液的可生化降解性能的效果最佳。     

Linking Theory and Practice for Restoration of Step-Pool Streams

Step-pools sequences are increasingly used to restore stream channels. This increase corresponds to significant advances in theory for step-pools in recent years. The need for step-pools in stream restoration arises as urban development encroaches into steep terrain in response to population pressures, as stream channels in lower-gradient areas require stabilization due to hydrological alterations associated with land-use changes, and as step-pools are recognized for their potential to enhance stream habitats. Despite an increasingly voluminous literature and great demand for restoration using step-pool sequences, however, the link between theory and practice is limited. In this article, we present four unique cases of stream restoration using step-pools, including the evolution of the approaches, the project designs, and adjustments in the system following restoration. Baxter Creek in El Cerrito, California demonstrates an early application of artificial step-pools in which natural adjustments occurred toward geomorphic stability and ecological improvement. Restoration of East Alamo Creek in a large residential development near San Ramon, California illustrates an example of step-pools increasingly used in locations where such a channel form would not naturally occur. Construction of a step-pool channel in Karnowsky Creek within the Siuslaw National Forest, Oregon overcame constraints posed by access and the type and availability of materials; the placement of logs allowed natural scouring below steps. Dry Canyon Creek on the property of the Mountains Restoration Trust in Calabasas, California afforded a somewhat experimental approach to designing step-pools, allowing observation and learning in the future. These cases demonstrate how theories and relationships developed for step-pool sequences over the past two decades have been applied in real-world settings. The lessons from these examples enable us to develop considerations useful for deriving an appropriate course of design, approval, and construction of artificial step-pool systems. They also raise additional fundamental questions concerning appropriate strategies for restoration of step-pool streams. Outstanding challenges are highlighted as opportunities for continuing theoretical work.     

Increased Frequency of Low‐Magnitude Floods in New England1

Armstrong, William H., Mathias J. Collins, and Noah P. Snyder, 2012. Increased Frequency of Low‐Magnitude Floods in New England. Journal of the American Water Resources Association (JAWRA) 48(2): 306‐320. DOI: 10.1111/j.1752‐1688.2011.00613.x Abstract: Recent studies document increasing precipitation and streamflow in the northeastern United States throughout the 20th and early 21st Centuries. Annual peak discharges have increased over this period on many New England rivers with dominantly natural streamflow – especially for smaller, more frequent floods. To better investigate high‐frequency floods (<5‐year recurrence interval), we analyze the partial duration flood series for 23 New England rivers selected for minimal human impact. The study rivers have continuous records through 2006 and an average period of record of 71 years. Twenty‐two of the 23 rivers show increasing trends in peaks over threshold per water year (POT/WY) – a direct measure of flood frequency – using the Mann‐Kendall trend test. Ten of these trends had p < 0.1. Seventeen rivers show positive trends in flood magnitude, six of which had p < 0.1. We also investigate a potential hydroclimatic shift in the region around 1970. Twenty‐two of the 23 rivers show increased POT/WY in the post‐1970 period when comparing pre‐ and post‐1970 records using the Wilcoxon rank‐sum test. More than half of these increases have p < 0.1, indicating a shift in flow regime toward more frequent flooding. Region wide, we found a median increase of one flood per year for the post‐1970 period. Because frequent floods are important channel‐forming flows, these results have implications for channel and floodplain morphology, aquatic habitat, and restoration.     

Analytical solution for Joule–Thomson cooling during CO2 geo-sequestration in depleted oil and gas reservoirs

Mathematical tools are needed to screen out sites where Joule–Thomson cooling is a prohibitive factor for CO₂ geo-sequestration and to design approaches to mitigate the effect. In this paper, a simple analytical solution is developed by invoking steady-state flow and constant thermophysical properties. The analytical solution allows fast evaluation of spatiotemporal temperature fields, resulting from constant-rate CO₂ injection. The applicability of the analytical solution is demonstrated by comparison with non-isothermal simulation results from the reservoir simulator TOUGH2. Analysis confirms that for an injection rate of 3 kg s^?1 (0.1 MT yr^?1) into moderately warm (>40 °C) and permeable formations (>10^?14 m² (10 mD)), JTC is unlikely to be a problem for initial reservoir pressures as low as 2 MPa (290 psi).     

Metallothionein levels in Algerian mice (Mus spretus) exposed to elemental pollution: an ecophysiological approach

The potential use of metallothioneins (MTs) as biomarkers of trace metal contamination was evaluated for the first time in the Algerian mouse (Mus spretus). Mice were collected seasonally in an abandoned mining area (Aljustrel) and in a reference area, both located in southern Portugal. MT levels were quantified in liver and kidney by differential pulse polarography and hepatic elemental concentrations (Mn, Fe, Cu, Zn, Se) were determined by particle-induced X-ray emission. Hepatic iron and selenium concentrations were elevated in mice from Aljustrel mine when compared to reference animals. MTs levels were averagely higher in mice from Aljustrel than those originated from the reference area. A season-dependent significant effect was found on the hepatic and renal MT concentrations, characterized by higher levels in winter and lower in autumn. In contaminated mice positive relationship between liver elemental contents (Cu in autumn and Fe in winter) and MTs were found. The seasonal variation of MT suggests that probably physiological and environmental factors could influence hepatic and renal MT induction. Results seem to imply that some environmental disturbance occur in the vicinity of the Aljustrel mine. Therefore, for the management purposes MT levels should be followed in liver of M. spretus, especially in winter. Furthermore, other physiological factors that could influence MT expression and turnover in Algerian mouse should also be monitored.     

Hydrolysed wool: a novel chelating agent for metal chelant-assisted phytoextraction from soil

Phytoextraction has revealed great potential, however it is limited by the fact that plants need time and nutrient supply and have a limited metal uptake capacity. Although the use of synthetic chelators, such as EDTA, enhances heavy metal extraction, it also produces the negative side effects of high phytotoxicity, as well as leaching of essential metals. The aim of this research was to investigate the application of wool, in mobilising metals and in improving the phytoextraction of metals-contaminated soil. We performed column experiments with 14 d and 7 d partially hydrolysed wool as chelating agent on a silty-loamy sand agricultural soil. In the column experiment the 14 d wool hydrolysate mobilised 68% of Cu in soil, whereas in the case of Cd it mobilised 5.5%. The model plant selected for the phytoextraction experiments was tobacco (Nicotiana tabacum). The plant uptake of Cd and Cu, assisted by the application of 6.6 g kg(-1) wool hydrolysate was increased by 30% in comparison to the control plants. The application of 13.3 g kg(-1) wool hydrolysate enhanced the Cu uptake by up to 850%. Moreover, high leaching probability frequently observed when applying chelating agents, such as EDTA or ethylene diamine disuccinate (EDDS), were not detected. The use of hydrolysed wool therefore merits further investigation.     

Haematology, genotoxicity, enzymatic activity and histopathology as biomarkers of metal pollution in the shrew Crocidura russula

Haematological (WBC, RBC, Hgb and Hct) and genotoxicity (MNT) parameters, hepatic enzymatic activities (GST, GPx and GR), and a histopathological evaluation of liver, kidneys and gonads were assessed as general biomarkers of metal pollution in the shrew Crocidura russula inhabiting a pyrite mining area. Specimens exposed to metals presented a few significant alterations when compared with reference animals: GST activity decreased; micronuclei increased; and evident liver alterations related to metal exposure were observed. On the basis of all the parameters studied, age was an important factor that partly explained the observed variation, whereas sex was the least important factor. Significant correlations were also found between heavy metal concentrations and biomarkers evaluated, demonstrating the great influence of these metals in the metabolic alterations. To the best of our knowledge, these data constitute the first measurements of a battery of biomarkers in shrews from a mine site and are among the few available for insectivorous mammals.     

Revisiting e-waste management practices in selected African countries

ABSTRACT

African countries are among the prime destinations of electronic waste (e-waste) also called Waste of Electrical and Electronic Equipment (WEEE), and have been challenged with the management of its environmental and health impacts. This paper was carried out to understand the e-waste sector and policy responses in selected African countries. Data for the study were generated from sources; such as policy documents, legislations and literature. Findings show that the import of WEEE is on rising in Africa while landfill and incineration continued to be widely used handling approaches. Countries studied lack WEEE specific national policies and stringent policy instruments to enforce proper collection and recycling systems. Despite the start-ups in emerging recycling operations, a major gap is that informal e-waste actors dominate the e-waste chain from collection to material extraction and refurbish activities through rudimentary tools that cannot detect toxic elements. Tackling the problem demands integrated multi-actor interventions with multiple stakeholders to reduce WEEE inflow on one hand, and ramping up safe recycling capacity on the other hand.