A simplified approach to the indirect evaluation of the chemical composition of atmospheric aerosols from PM mass concentrations

The present work shows a straightforward procedure to indirectly estimate the chemical composition at a given site only from the determination of the PM concentrations, and the classification of the days according to the main meteorological scenarios. A previous study based on the mean chemical composition associated to the main meteorological scenarios is required.This experiment has been carried out with data from two monitoring sites in the North-Western Mediterranean, one regional and one suburban background. At both sites, one-year datasets on chemical PM₁₀ composition were obtained. Based on these datasets, the mean PM₁₀ compositions according to the most relevant meteorological situations were calculated for both locations. After that, the reconstruction of the chemical composition for all the days with available PM₁₀ concentrations was completed. Subsequently, the estimated PM₁₀ composition was compared with that determined experimentally. The comparison between the rebuilt and the experimental results was very satisfactory in the case of the regional background site, and relatively replaced in the other case. Furthermore, the validation of the method at the regional background site has been conducted from the reconstruction of a 4-year data base, and subsequent comparison with the experimental chemical composition.Our results show that it is possible to attain a good approach to the chemical composition at regional background sites, where local emission sources are negligible. Conversely, when the local sources rise in importance, i.e., at a suburban background site, the approach is suitable only for those components with a more regional origin and/or those from long range transport of air masses.     

Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests

Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of mechanistic links between microbial responses to N deposition and shifts in soil organic matter (SOM) quality and quantity. We used phospholipid fatty acid (PLFA) analysis and microbial enzyme assays in soils to assess microbial community responses to long-term N additions in two distinct tropical rain forests. We used soil density fractionation and 13C nuclear magnetic resonance (NMR) spectroscopy to measure related changes in SOM pool sizes and chemical quality. Microbial biomass increased in response to N fertilization in both tropical forests and corresponded to declines in pools of low-density SOM. The chemical quality of this soil C pool reflected ecosystem-specific changes in microbial community composition. In the lower-elevation forest, there was an increase in gram-negative bacteria PLFA biomass, and there were significant losses of labile C chemical groups (O-alkyls). In contrast, the upper-elevation tropical forest had an increase in fungal PLFAs with N additions and declines in C groups associated with increased soil C storage (alkyls). The dynamics of microbial enzymatic activities with N addition provided a functional link between changes in microbial community structure and SOM chemistry. Ecosystem-specific changes in microbial community composition are likely to have far-reaching effects on soil carbon storage and cycling. This study indicates that microbial communities in N-rich tropical forests can be sensitive to added N, but we can expect significant variability in how ecosystem structure and function respond to N deposition among tropical forest types.     

African dust contributions to mean ambient PM10 mass-levels across the Mediterranean Basin

Data on mass-levels of PM₁₀ measured at regional background sites across the Mediterranean Basin, available from Airbase (European Environmental Agency) and from a few aerosol research sites, are compiled. PM₁₀ levels increase from north to south and west to east of the Basin. These variations are roughly coincident with the PM₁₀ African mineral dust load. However, when subtracting the African dust from mean PM₁₀ levels using a consistent methodology, the PM₁₀ background levels are still 5–10 μg m^?3 higher in the Eastern Basin (EMB) when compared with those in the Western (WMB), mainly due to the higher anthropogenic and sea spray loads.As regards for the seasonal trends, these are largely driven by the occurrence of African dust events, resulting in a spring-early summer maximum over the EMB, and a clear summer maximum in the WMB, although in this later region the recirculations of aged air masses play an important role. Furthermore, a marked seasonal trend is still evident when subtracting the African dust load. This is characterised by a high summer maximum (driven by low precipitation, high insolation) and a winter minimum (intense synoptic winds).Important inter-annual variations in the dust contribution are detected, more evident in the southern sites. These differences are generally associated with the occurrence of extreme dust events. Generally, the years with higher dust contributions over the EMB correspond with lower contributions over the WMB, and vice versa.The characterization of individual particles, collected in both basins during African dust events, by scanning electron microscopy reveals only slight differences between them. This fact probably reflects the high degree of mixture of mineral dust from different sources before the transport towards the receptor sites.     

A multispecies assessment of wildlife impacts on local community livelihoods

Conflicts between the interests of agriculture and wildlife conservation are a major threat to biodiversity and human well-being globally. Addressing such conflicts requires a thorough understanding of the impacts associated with living alongside protected wildlife. Despite this, most studies reporting on human–wildlife impacts and the strategies used to mitigate them focus on a single species, thus oversimplifying often complex systems of human–wildlife interactions. We sought to characterize the spatiotemporal patterns of impacts by multiple co-occurring species on agricultural livelihoods in the eastern Okavango Delta Panhandle in northern Botswana through the use of a database of 3264 wildlife-incident reports recorded from 2009 to 2015 by the Department of Wildlife and National Parks. Eight species (African elephants [Loxodonta africana], hippopotamuses [Hippopotamus amphibious], lions [Panthera leo], cheetah [Acinonyx jubatus], African wild dogs [Lycaon pictus], hyenas [Crocuta crocuta], leopards [Panthera pardus], and crocodiles [Crocodylus niloticus]) appeared on incident reports, of which 56.5% were attributed to elephants. Most species were associated with only 1 type of damage (i.e., either crop damage or livestock loss). Carnivores were primarily implicated in incident reports related to livestock loss, particularly toward the end of the dry season (May–October). In contrast, herbivores were associated with crop-loss incidents during the wet season (November–April). Our results illustrate how local communities can face distinct livelihood challenges from different species at different times of the year. Such a multispecies assessment has important implications for the design of conservation interventions aimed at addressing the costs of living with wildlife and thereby mitigation of the underlying conservation conflict. Our spatiotemporal, multispecies approach is widely applicable to other regions where sustainable and long-term solutions to conservation conflicts are needed for local communities and biodiversity.     

Attachment of oysters to natural substrata by biologically induced marine carbonate cement

Oysters live permanently immobilised by cementation of the left valve to a hard substrate. The contact zone between oysters and natural substrata has been analysed using SEM imaging, electron dispersive X-ray microanalysis, electron backscatter diffraction and Raman spectroscopy and reveals the influence of both biogenic and non-biogenic processes in oyster cementation. Original adhesion is brought about by secretion of an organic component that acts as a nucleating surface onto which crystals precipitate. These crystals have a random orientation and are composed of high Mg calcite. This suggests that the crystals nucleating on the glue substrate are outwith the biological control experienced by the shell biomineralisation process and are formed by inorganic precipitation from seawater. It is proposed that oysters do not control or secrete crystalline cement. Instead, they adhere by secretion of an organic film onto which crystals precipitate from seawater.     

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human–ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society. Integrated international and long-term collaborative studies covering research gaps will reduce uncertainties and promote further understanding of the nitrogen cycle in various ecosystems.     

Anniston community health survey: Follow-up and dioxin analyses (ACHS-II)—methods

High serum concentrations of polychlorinated biphenyls (PCBs) have been reported previously among residents of Anniston, Alabama, where a PCB production facility was located in the past. As the second of two cross-sectional studies of these Anniston residents, the Anniston Community Health Survey: Follow-Up and Dioxin Analyses (ACHS-II) will yield repeated measurements to be used to evaluate changes over time in ortho-PCB concentrations and selected health indicators in study participants. Dioxins, non-ortho PCBs, other chemicals, heavy metals, and a variety of additional clinical tests not previously measured in the original ACHS cohort will be examined in ACHS-II. The follow-up study also incorporates a questionnaire with extended sections on diet and occupational history for a more comprehensive assessment of possible exposure sources. Data collection for ACHS-II from 359 eligible participants took place in 2014, 7 to 9 years after ACHS.