Controls on hourly variations in urban background air pollutant concentrations

Average 21st century concentrations of urban air pollutants linked to cardiorespiratory disease are not declining, and commonly exceed legal limits. Even below such limits, health effects are being observed and may be related to transient daytime peaks in pollutant concentrations. With this in mind, we analyse >52,000 hourly urban background readings of PM₁₀ and pollutant gases throughout 2007 at a European town with legal annual average concentrations of common pollutants, but with a documented air pollution-related cardiorespiratory health problem, and demonstrate the hourly variations in PM₁₀, SO₂, NO_x, CO and O₃. Back-trajectory analysis was applied to track the arrival of exotic PM₁₀ intrusions, the main controls on air pollutants were identified, and the typical hourly pattern on ambient concentrations during 2007 was profiled. Emphasis was placed on “worst case” data (>90th percentile), when health effects are likely to be greatest. The data show marked daytime variations in pollutants result from rush-hour traffic-related pollution spikes, midday industrial SO₂ maxima, and afternoon O₃ peaks. African dust intrusions enhance PM₁₀ levels at whatever hour, whereas European PM incursions produce pronounced evening peaks due to their transport direction (across an industrial traffic corridor). Transient peak profiling moves us closer to the reality of personal outdoor exposure to inhalable pollutants in a given urban area. We argue that such an approach to monitoring data potentially offers more to air pollution health effect studies than using only 24 h or annual averages.     

Effect of drying on the desorption of diuron and terbuthylazine from natural soils

This work was initiated to study the effects of climate induced soil water status variations which can reach extreme values under natural conditions on the sorption process of hydrophobic organic compounds. Based on the classical slurry batch methodology an approach is developed that allows the fast and careful complete drying of soil suspensions (microwave technique). Classical adsorption experiments were followed by three desorption steps with and without drying cycles. Drying and re-wetting enhanced the sorption-desorption hysteresis and Freundlich adsorption coefficients increased from 5.9 to 16 and 5.2 to 21 over three drying cycles for diuron and terbuthylazine respectively. Assuming the validity of a dual stage adsorption process, model evaluation suggests that drying is as a shrinking-like process leading to conformational changes of the dominant sorbent (soil organic matter) which restrict the intra-micro-particle diffusion. Rewetting only leads to a partial recovery of the diffusional pore space.     

Nutrient ratios and the complex structure of phytoplankton communities in a highly turbid estuary of Southeast Asia

Phytoplankton diversity and abundance in estuarine systems are controlled by many factors. Salinity, turbidity, and inorganic nutrient concentrations and their respective ratios have all been proposed as principal factors that structure phytoplankton diversity and influence the emergence of potentially toxic species. Although much work has been conducted on temperate estuaries, less is known about how phytoplankton diversity is controlled in tropical, monsoonal systems that are subject to large, seasonal shifts in hydrology and to rapidly changing land use. Here, we present the results of an investigation into the factors controlling phytoplankton species composition and distribution in a tropical, monsoonal estuary (Bach Dang estuary, North Vietnam). A total of 245 taxa, 89 genera from six algal divisions were observed. Bacillariophyceae were the most diverse group contributing to 51.4 % of the microalgal assemblage, followed by Dinophyceae (29.8 %), Chlorophyceae (10.2 %), Cyanophyceae (3.7 %), Euglenophyceae (3.7 %) and Dictyochophyceae (1.2 %). The phytoplankton community was structured by inorganic nutrient ratios (DSi:DIP and DIN:DIP) as well as by salinity and turbidity. Evidence of a decrease in phytoplankton diversity concomitant with an increase in abundance and dominance of certain species (e.g., Skeletonema costatum) and the appearance of some potentially toxic species over the last two decades was also found. These changes in phytoplankton diversity are probably due to a combination of land use change resulting in changes in nutrient ratios and concentrations and global change as both rainfall and temperature have increased over the last two decades. It is therefore probable in the future that phytoplankton diversity will continue to change, potentially favoring the emergence of toxic species in this system.     

Documentation of bioaerosol concentrations in an indoor composting facility in France

Bioaerosol concentrations were investigated in a totally indoor composting facility processing fermentable household and green wastes to assess their variability. Stationary samples were collected by filtration close to specific composting operations and then were analysed for cultivable mesophilic bacteria, thermophilic bacteria, mesophilic fungi, thermophilic fungi, endotoxins and total airborne bacteria (DAPI-staining). Indoor concentrations exceeded the background levels, between 500 and 5400 EU m(-3) for endotoxins, 10(4) and 10(6) CFU m(-3) for cultivable bacteria and generally below 10(5) CFU m(-3) for airborne cultivable fungi. No significant (p > 0.05) differences were observed between the indoor composting operations. Successive 30 minute bioaerosol samples were collected to investigate the variation of cultivable mesophilic microorganisms over the work shift. Concentrations of mesophilic bacteria and fungi varied up to 1 log unit depending on the time at which they were collected in the day. Total airborne particles, counted using an optical particle counter, were present at up to 10(8) particles m(-3) and several concentration peaks were noted. Values for total airborne bacteria were roughly 70-fold higher than cultivable bacteria. These results raise the question of the sampling strategy (duration of sampling; number of samples to be collected) used in similar studies. They provide new bioaerosol concentration data in a composting facility and suggest that the filtration sampling method might be a useful tool for exposure measurements in that occupational environment.     

Carbon and nitrogen stocks and nitrogen mineralization in organically managed soils amended with composted manures

The use of composted manures and of legumes in crop rotations may control the quality and quantity of soil organic matter and may affect nutrient retention and recycling. We studied soil organic C and N stocks and N mineralization in organically and conventionally managed dryland arable soils. We selected 13 extensive organic fields managed organically for 10 yr or more as well as adjacent fields managed conventionally. Organic farmers applied composted manures ranging from 0 to 1380 kg C ha yr and incorporated legumes in crop rotations. In contrast, conventional farmers applied fresh manures combined with slurries and/or mineral fertilizers ranging from 200 to 1900 kg C ha yr and practiced a cereal monoculture. Despite the fact that the application of organic C was similar in both farming systems, organically managed soils showed higher C and similar N content and lower bulk density than conventionally managed soils. Moreover, organic C stocks responded to the inputs of organic C in manures and to the presence of legumes only in organically managed soils. In contrast, stocks of organic N increased with the inputs of N or C in both farming systems. In organically managed soils, organic N stocks were less mineralizable than in conventional soils. However, N mineralization in organic soils was sensitive to the N fixation rates of legumes and to application rate and C/N ratio of the organic fertilizers.     

Human-mediated dispersal of aquatic invertebrates with waterproof footwear

Human-mediated dispersal has rarely been considered in wetland conservation strategies at regional scales, yet high concern exists about this aspect for (inter-)national management considering invasive species in other aquatic systems. In this context, we aim at understanding the role of human-mediated dispersal by footwear in protected wetlands with high conservation value. Zooplankton and zoobenthos were sampled in 13 shallow lakes in central Spain and, at the same time, mud attached to waders was collected and later cultured in deionized water under laboratory conditions for 4 weeks. Two-hundred and four individuals belonging to 19 invertebrate taxa were recovered after hatching; Ostracoda (84 %), Cladocera (53 %), Copepoda (30 %), Anostraca (30 %), and Notostraca (7 %) were the most frequent groups among the hatched crustaceans. NMDS and PERMANOVA analyses showed significant differences between the dispersed (via footwear) and the source active metacommunity, suggesting different dispersal abilities among the species found. Human vectors facilitate dispersal among protected lakes, which could eventuality lead to biotic homogenization and faster spread of non-indigenous species. Preservation strategies and education campaigns associated to target humans in close contact with water bodies should be imperative in conservation management of protected lakes.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0689-x) contains supplementary material, which is available to authorized users.     

Long-term disruption of growth,reproduction, and behavior after embryonic exposure of zebrafish to PAH-spiked sediment

A natural sediment spiked with three individual polycyclic aromatic hydrocarbons (PAHs; pyrene, phenanthrene and benzo[a]pyrene) was used to expose zebrafish embryos and larvae during 4 days. The total PAH concentration was 4.4 μg g^?1 which is in the range found in sediment from contaminated areas. Quantification of metabolites in the larvae after exposure confirmed the actual contamination of the larvae and indicated an active metabolism especially for pyrene and benzo[a]pyrene. After a transfer in a clean medium, the larvae were reared to adulthood and evaluated for survival, growth, reproduction, and behavior. Measured endpoints revealed a late disruption of growth (appearing at 5 months) and a trend toward a lower reproductive ability. Adults of embryos exposed to sediment spiked with PAHs displayed lethargic and/or anxiety-like behaviors. This latter behavior was also identified in offspring at larval stage. All together, these effects could have detrimental consequences on fish performances and contribution to recruitment.     

Development of a reference artificial sediment for chemical testing adapted to the MELA sediment contact assay

Most persistent organic pollutants, due to their hydrophobic properties, accumulate in aquatic sediments and represent a high risk for sediment quality. To assess the toxicity of hydrophobic pollutants, a novel approach was recently proposed as an alternative to replace, refine and reduce animal experimentation: the medaka embryo–larval sediment contact assay (MELAc). This assay is performed with Japanese medaka embryos incubated on a natural sediment spiked with the compound being tested. With the aim of improving this assay, our study developed a reference exposure protocol with an artificial sediment specifically designed to limit natural sediment composition uncertainties and preparation variability. The optimum composition of the new artificial sediment was tested using a model polycyclic aromatic hydrocarbon (PAH), fluoranthene. The sediment was then validated with two other model PAHs, benz[a]anthracene and benzo[a]pyrene. Various developmental end points were recorded, including survival, embryonic heartbeat, hatching delay, hatching success, larval biometry and abnormalities. The final artificial sediment composition was set at 2.5 % dry weight (dw) Sphagnum peat, 5 % dw kaolin clay and 92.5 % dw silica of 0.2- to 0.5-mm grain size. In contrast with natural sediments, the chemical components of this artificial matrix are fully defined and readily identifiable. It is totally safe for fish embryos and presents relatively high sorption capacities for hydrophobic compounds. Studies with other hydrophobic and metallic contaminants and mixtures should be performed to further validate this artificial sediment.     

Chronic dietary exposure to pyrolytic and petrogenic mixtures of PAHs causes physiological disruption in zebrafish - part I: Survival and growth

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades leading to high concentrations in sediments of contaminated areas. To evaluate the consequences of long-term chronic exposure to PAHs, zebrafish were exposed, from their first meal at 5 days post fertilisation until they became reproducing adults, to diets spiked with three PAH fractions at three environmentally relevant concentrations with the medium concentration being in the range of 4.6–6.7 μg g^?1 for total quantified PAHs including the 16 US-EPA indicator PAHs and alkylated derivatives. The fractions used were representative of PAHs of pyrolytic (PY) origin or of two different oils of differing compositions, a heavy fuel (HO) and a light crude oil (LO). Fish growth was inhibited by all PAH fractions and the effects were sex specific: as determined with 9-month-old adults, exposure to the highest PY inhibited growth of females; exposure to the highest HO and LO inhibited growth of males; also, the highest HO dramatically reduced survival. Morphological analysis indicated a disruption of jaw growth in larvae and malformations in adults. Intestinal and pancreatic enzyme activities were abnormal in 2-month-old exposed fish. These effects may contribute to poor growth. Finally, our results indicate that PAH mixtures of different compositions, representative of situations encountered in the wild, can promote lethal and sublethal effects which are likely to be detrimental for fish recruitment.     

Criminalization of “galamsey” and livelihoods in Ghana: Limits and consequences

The fact that the artisanal and small-scale mining (ASM) sector in Ghana is driven largely by poverty means that the sector is a major source of livelihood for people in mining communities across the country. However, given the various social and environmental problems associated with the ASM sector, there is now an emerging consensus that the formalization of the sector would not only allow for these associated problems to be addressed but also ensures that the sector contributes to sustainable development and safeguard the livelihood of local communities. While a large body of extant literature has examined the challenges and opportunities facing the process of formalization, the question of the criminalization of the sector and its consequences for local livelihood has received only limited attention. Drawing from primary data collected during fieldwork in Ghana, this study examined the livelihood implications of the ban on galamsey in the Tarkwa-Nsuaem Municipality in South-Western Ghana from the perspectives of local communities and other key stakeholders. The study reveals that the ban on galamsey has imposed significant socio-economic hardships on the people and appears to be entrenching poverty rather than sustainable development. The study considers the theoretical and practical implications of the findings for sustainable livelihood enhancement in developing countries.