Influence of Suspended Clay Minerals and Humic Matter on the Solid Phase Extraction Efficiency of Selected Pesticides from Water

The purpose of this investigation was to determine the influence of humic acids (HA) and Ca-montmorillonite (CaM) on the solid-phase extraction (SPE) efficiency of atrazine, alachlor and α-cypermethrin from water samples at various pH-values. The nature and intensity of binding of the studied pesticides to CaM were determined by X-ray diffraction analysis and termogravimetric analysis (TGA) test. The studied pesticides eluted from discs were analysed by thin-layer chromatography (TLC). The effects of CaM and humic acid were generally pH-dependent and acted independently in extraction efficiency influence. Lower recovery of pesticides was observed at higher pH values when CaM was ≥0.1 g and was attributed to greater dispersion of clay, increased surface area and subsequent adsorption. Concentrations of dissolved organic carbon (DOC) in humic acid had less effect on the extraction efficiency when water was at pH 8 compared to water at pH 2, which was probably due to greater nonpolar interactions of the pesticides to the charge-neutralized humic acid molecule.     

Nutritional status as an indicator of impending food stress*

Famine early warning systems benefit from a variety of indicators which together signal the initial stages of food stress for particular population groups. Anthropometry has been used as an indicator in early warning systems, but there are inherent problems in its use which should be understood. Using data from Turkana pastoralists of northwest Kenya, this paper discusses the problems of: time lag between food shortages and changes in body size and composition; use of reference points; accurate age assessment; and establishment of baseline data. Diet composition data are suggested to be an additional nutrition-oriented indicator of impending food stress and one in which problems associated with anthropometry are not inherent. Both measures may be useful in monitoring a population, but their strengths and weaknesses should be appreciated.     

Investigating environmental migration and other rural drought adaptation strategies in Baja California Sur,Mexico

Regional Environmental Change - This paper explores the relationship between specific household traits (region of residence, head of household occupation, financial diversity, female level of...     

Understanding Human–Landscape Interactions in the “Anthropocene”

This article summarizes the primary outcomes of an interdisciplinary workshop in 2010, sponsored by the U.S. National Science Foundation, focused on developing key questions and integrative themes for advancing the science of human–landscape systems. The workshop was a response to a grand challenge identified recently by the U.S. National Research Council (2010a)—“How will Earth’s surface evolve in the “Anthropocene?”—suggesting that new theories and methodological approaches are needed to tackle increasingly complex human–landscape interactions in the new era. A new science of human–landscape systems recognizes the interdependence of hydro-geomorphological, ecological, and human processes and functions. Advances within a range of disciplines spanning the physical, biological, and social sciences are therefore needed to contribute toward interdisciplinary research that lies at the heart of the science. Four integrative research themes were identified—thresholds/tipping points, time scales and time lags, spatial scales and boundaries, and feedback loops—serving as potential focal points around which theory can be built for human–landscape systems. Implementing the integrative themes requires that the research communities: (1) establish common metrics to describe and quantify human, biological, and geomorphological systems; (2) develop new ways to integrate diverse data and methods; and (3) focus on synthesis, generalization, and meta-analyses, as individual case studies continue to accumulate. Challenges to meeting these needs center on effective communication and collaboration across diverse disciplines spanning the natural and social scientific divide. Creating venues and mechanisms for sustained focused interdisciplinary collaborations, such as synthesis centers, becomes extraordinarily important for advancing the science.     

Analysis of ambient,precipitation-weighted,and lake sulfate concentrations in the Adirondack region of New York

AbstractIt is well known that many ecosystems in the eastern United States, including the Adirondack Mountain region of New York, are particularly sensitive to acidic deposition because the soils and lakes in the region tend to have low values of base saturation and acid neutralizing capacity, respectively [e.g. Environ Sci Policy, 1 (1998), 185]. To facilitate tracking the impacts of anthropogenic emissions on air quality, acidic deposition, and surface water quality, the National Atmospheric Deposition Program, New York State Department of Environmental Conservation, and Adirondack Lake Survey Corporation have been monitoring ambient sulfur dioxide and aerosol sulfate levels, and anion and cation concentrations in wet deposition and lake water over the past few decades. In this paper, we discuss the seasonality and year-to-year variability, and illustrate some of the complexities in estimating temporal trends in these data. The periods of analysis extended through 2000, beginning in 1991 for the ambient air quality data, 1978 for the wet deposition data, and 1982 for the lake water quality data. While the lake water SO4(2-) concentrations appear to be decreasing gradually, the air concentration data appear to have changed abruptly in the 1990s and the precipitation-weighted concentrations exhibited both gradual and sharp decreases during the same period.     

A theoretical integration of leader emergence and leadership effectiveness: Over,under, and congruent emergence

There is a long and rich history of research on the concept of leader emergence. Much of this research positions leader emergence alongside leadership effectiveness as an epiphenomenal criterion in leadership research. Although this view has enhanced our understanding of factors that influence leader emergence and leadership effectiveness individually, our understanding of the potential alignment or misalignment of these concepts remains opaque. Following from this, we are left with unanswered questions concerning how, why, and under what conditions do the right or wrong leaders emerge or fail to emerge. Theory that develops insights into these questions is needed to advance our understanding of leadership and to cope with challenges of identifying and developing effective leaders and maximizing leadership potential in organizations. By integrating theories of leader emergence and leadership effectiveness—and considering their implications jointly—we provide a conceptual basis for identifying and understanding a more complete range of leader emergence than has been suggested in the literature. Importantly, our theoretical frame explains how our leader emergence types—over-emergence, under-emergence, congruent emergence, and congruent non-emergence—are differentially associated with a common set of factors. In doing so, we illuminate tradeoffs that might accompany different interventions intended to enhance leadership in organizations.