Temporal variations in PAH concentrations in Quercus ilex L. (holm oak) leaves in an urban area

Temporal variations of polycyclic aromatic hydrocarbon (PAH) concentrations in leaves of a Mediterranean evergreen oak, Quercus ilex L., were investigated in order to assess the suitability of this species to biomonitor PAH air contamination. Leaf samples were collected at six sites of the urban area of Naples (Italy) and at a control site in the Vesuvius National Park, in May and September 2001, and in January and May 2002. PAH extraction was conducted by sonication in dichloromethane-acetone and quantification by GC-MS. In winter, leaf total PAH concentrations showed, at all the urban sites, values 2-fold higher than in all the other samplings, reflecting the temporal trend reported for PAH air contamination in the Naples urban area. Moreover, leaf PAH concentrations showed, at all the urban sites, a decrease in May 2002 after the winter accumulation. At the control site leaf PAH concentrations showed lower values and smaller temporal variations than at the urban sites. The findings support the suitability of Q. ilex leaves to monitor temporal variations in PAH contamination. The highest winter concentrations of total PAHs were due to the medium molecular weight PAHs that increased with respect to both low and high molecular weight PAHs. The medium molecular weight PAHs showed the same temporal trend both at the urban and remote sites.     

The evolution of community water governance in Uchira, Tanzania: The implications for equality of access, sustainability and effectiveness

Community participation, ownership and cost sharing are key components of Tanzania's water policy, in common with the broad international consensus on water governance. However these policy goals are difficult to achieve, beset with paradoxes and their benefits may be overstated, both in terms of efficiency of resource management and equality of outcomes. This article draws on longitudinal ethnographic research of a village water supply in Tanzania to explore two issues: the contested nature of community ownership and the complex evolution of a ‘community‐owned’ institution. The evidence from the Uchira Water Users Association leads us to question some of the simplistic assumptions made concerning the capacity of local communities to manage service delivery and to balance equity and sustainability principles. The limitations of ‘bottom‐up’ and demand led approaches need to be recognised without discrediting their potential for challenging inequalities. The article concludes with a consideration of some of the tensions in community‐driven development, which raises some important questions about the role of the State and external agencies in setting and enforcing equity criteria in community‐managed initiatives.     

Some limitations of biological monitoring

Biological monitoring data are obtained to document changes in population abundance for resource management, to verify compliance with regulatory directives, and to assess cause and effect for research purposes. Particular statistical analyses are often not appropriate because suitable field designs are either not available or not matched a priori to the monitoring objectives. When monitoring to detect normal changes in population numbers, quantitative problems may not be as difficult as they are in detecting and assigning causation induced by a natural or man-made pollutant. Changes in biotic abundance can be caused or influenced by compensation, indirect effects, direct mortality, and interactions among environmental variables. Even though data from baseline monitoring programs should usually only be used to detect change in biotic abundance, they sometimes can be used to draw inferences about cause by correlation or to test laboratory results against a long-term historical record. Available quantitative methodologies useful in evaluating monitoring data are limited and interpretations about cause and effect are difficult.