Modelling of concentrations along a moving observer in an inhomogeneous plume. Biological application: model of odour-mediated insect flights

We develop a stochastic model for the time-evolution of scalar concentrations and temporal gradients in concentration experienced by observers moving within inhomogeneous plumes that are dispersing within turbulent flows. In this model, scalar concentrations and their gradients evolve jointly as a Markovian process. Underlying the model formulation is a natural generalisation of Thomson’s well mixed condition [Thomson DJ (1987) J Fluid Mech 180:529–556]. As a consequence model outputs are necessarily compatible with statistical properties of scalars observed in experiment that are used here as model input. We then use the model to examine how insects aloft within the atmospheric boundary-layer can locate odour sources by modulating their flight patterns in response to odour cues. Mechanisms underlying odour-mediated flights have been studied extensively at laboratory-scale but an understanding of these flights over landscape scales is still lacking. Insect flights are simulated by combining the stochastic model with a simple model of insect olfactory response. These simulations show the strong influence of wind speed on the distributions of the times taken by insects to locate the source. In accordance with experimental observations [Baker TC, Vickers NJ (1997) In: Insect pheromone research: new directions, pp 248–264; Mafra-Neto A, Cardé RT (1994) Nature 369:142–144], flight patterns are predicted to become straighter and shorter, and source location is predicted to become more likely as the mean wind speed increases. The most probable arrival time to the source decreases with the mean wind speed. It is shown that scale-free movement patterns arising from olfactory-driven foraging stem directly from the power-law distribution of concentration excursion times above/below a threshold level and are robust with respect to variations in Reynolds number. Flight lengths are well represented by a power law distribution in agreement with the observed patterns of foraging bumblebees [Heinrich B (1979) Oecologia 40(3):235–245].     

Copper extraction effectiveness and soil dissolution issues of EDTA-flushing of artificially contaminated soils

Ethylenediaminetetraacetic acid (EDTA) was used as a reference chelating agent in column experiments to investigate the effectiveness of chelant-enhanced flushing of soils artificially contaminated under various conditions (low/high Cu loading, and aging). The associated soil dissolution issues were of particular concern. Dissolution of indigenous Fe/Al oxides, Ca carbonates and organic matter was monitored over the course of flushing. Regardless of contamination condition, above 85% extraction efficiency could be accomplished by 10(-2) and 10(-3)M EDTA-flushing, but not 10(-4)M. The Cu extraction kinetics positively correlated to EDTA concentration but inversely to Cu loading in soils. In addition to extraction from weakly sorbed fractions, a large portion of Cu was extracted from oxide, organic matter and residual fractions, which appears to derive from soil dissolution. Cumulative dissolved amounts of Fe, Al, and Ca were found to reach as high as hundreds of mgkg(-1), which were comparable to Cu contamination. Soil organic matter, which is known to strongly interact with Fe and Al oxides, was also mobilized. The rate and extent of these soil dissolutions were also positively correlated to EDTA concentration. Therefore, the co-extraction of soil minerals and organic matter during chelant-enhanced flushing, which would alter both physical structure and chemical properties of the soils, is detrimental to future land use and deserves greater attention. The concentration of chelating agent is the most crucial factor for an effective soil flushing with minimal damage.     

Pyrolysis kinetics and residue characteristics of petrochemical industrial sludge

This study investigated the pyrolysis characteristics of sludge from wastewater treatment plants in the petrochemical industry and focused on the pyrolysis kinetics, elemental composition of residue, and volatile organic compounds (VOCs) of exhaust gas. As pyrolysis temperature increased to 773 K, the increasing rate of crude oil production tended to a stable condition. The result indicated that the optimal temperature of crude oil and water mixed production was 773 K. When pyrolysis temperature increased from 673 to 973 K, carbon, oxygen, nitrogen, and hydrogen concentrations of residue decreased and the sulfur concentration of residue increased. The concentrations of benzene, toluene,ethylbenzene, and styrene increased by the increasing pyrolysis temperature. We found that the reaction order of sludge pyrolysis was 2.5 and the activation energy of the reaction was 11.06 kJ/mol. We believe that our pyrolysis system is transitional between devolatilization and combustion.     

Autochthonous clams monitoring of Ganzirri Lake (Sicily)

Two autochthonous clams, Venerupis aurea laeta and Cerastoderma edule/glaucum, collected for a period of 1 year, from May 2007 to January 2008, were studied in the Cape Peloro lagoon. On the samples, it was evaluated the presence of pathogenic microorganisms and proteins, lipids and yield edible part were determined. It was evaluated the concentration of mineral elements (Cd, Cu, Mn, Se, Pb, Zn) and organic contaminants (∑DDT and PCBs). Salmonella is never present in any sample. Total and faecal coliform values have always been under law limits for alive bivalves mussels production and sale. Zn, Cu, Cd and Pb levels were found in clams where they are slightly lower too. Both species do not show significant changes for Mn and Se. DDT and PCBs traces were discovered in Ganzirri Lake’ samples, but in all observed cases, they were below law limits. As a result of all these observations, it is clear that, in recent years, the bivalve’s use of Ganzirri Lake does not denote toxicological risk to human health.     

Enhanced multi-metal extraction with EDDS of deficient and excess dosages under the influence of dissolved and soil organic matter

This study investigated the influence of dissolved and soil organic matter on metal extraction from an artificially contaminated soil. With high concentration of DOM, the extraction of Cu, Zn and Pb was enhanced by forming additional metal-EDDS complexes under EDDS deficiency. However, the enhancement of metal extraction under EDDS excess was probably due to the soil structure being disrupted owing to humic acid enhanced Al and Fe dissolution, which induced more metals dissolving from the soils. Fulvic acid was found to enhance metal extraction to a greater extent compared with humic acid because of its high content of the carboxylic functional group. Cu extraction from the soil with high organic matter content using EDDS was the lowest due to the high binding affinity of Cu to SOM, whereas Zn extraction became the highest because of a preference for EDDS to extract Zn due to the high stability constant of ZnEDDS.     

Public Discourses of Climate Change in Hong Kong

The changing political environment in Hong Kong is likely to accelerate the transition in environmental policy discourse. Opportunities for critical public involvement are increasing and new environmental discourses are emerging. Yet, previous social surveys did not explore the range of these discourses and few focused on climate change. The paper outlines the public discourses of climate change in Hong Kong. Using Q-methodology, four distinctive discourses were identified, namely Pure Environmentalism, Political Pragmatism, Popular Optimism, and Fair Rationalism. While the first one is climate-centric, the other three are political or social in nature and do not indicate a clear or coherent climate orientation. This suggests that the climate change concern of the Hong Kong public is not tightly embedded into a coherent narrative of social and institutional transformation. Effective climate change governance and policies require strengthening the link between such concern and the public desires for social and institutional transformation. Bringing together the ongoing social movements and environmental campaigns will be instrumental to nurture an active climate citizenry.     

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid

The combination of zero-valent iron (Fe⁰) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe⁰ or IOCS alone, the Fe⁰-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe⁰ and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage.     

Long-term drivers of persistence and colonization dynamics in spatially structured amphibian populations

Many organisms live in networks of local populations connected by dispersing individuals, called spatially structured populations (SSPs), where the long-term persistence of the entire network is determined by the balance between 2 processes acting at the scale of local populations: extinction and colonization. When multiple threats act on an SSP, a comparison of the different factors determining local extinctions and colonizations is essential to plan sound conservation actions. We assessed the drivers of long-term population dynamics of multiple amphibian species at the regional scale. We used dynamic occupancy models within a Bayesian framework to identify the factors determining persistence and colonization of local populations. Because connectivity among patches is fundamental to SSPs dynamics, we considered 2 measures of connectivity acting on each focal patch: incidence of the focal species and incidence of invasive crayfish. We used meta-analysis to summarize the effect of different drivers at the community level. Persistence and colonization of local populations were jointly determined by factors acting at different scales. Persistence probability was positively related to the area and the permanence of wetlands, whereas it was negatively related to occurrence of fish. Colonization probability was highest in semipermanent wetlands and in sites with a high incidence of the focal species in nearby sites, whereas it showed a negative relationship with the incidence of invasive crayfish in the landscape. By analyzing long-term data on amphibian population dynamics, we found a strong effect of some classic features commonly used in SSP studies, such as patch area and focal species incidence. The presence of an invasive non-native species at the landscape scale emerged as one of the strongest drivers of colonization dynamics, suggesting that studies on SSPs should consider different connectivity measures more frequently, such as the incidence of predators, especially when dealing with biological invasions.     

Optimal strategies for best management practice placement in a synthetic watershed

It is significant to arrange suitable design and placement of best management practices (BMPs) for reaching the aim that can not only satisfy environmental quality standards, but also decrease the total cost of BMPs. This study applied WinVAST model to predict watershed responses. The objective of this work was to discuss both the economic costs and benefits of BMPs and the control efficiency of discharge and pollutant exports, and to create some suitable standards for the optimal BMPs placement strategies. It is significant to find an optimal number and location of BMPs. In the case study herein, the number of BMPs including a detention pond and a grassy swale would be better to be given by four. The number of BMPs should also be determined by the environmental standards. Moreover, the result shows that the optimal location of BMPs placement is in the downstream area near the outlet and on the mainstream of the catchment. When the BMPs are set in these regions, it cannot only reduce the peak flow and peak pollutant exports, but also have slow time to peak watershed responses.     

Nutrients and suspended solids in dry weather and storm flows from a tropical catchment with various proportions of rural and urban land use

The results of an investigation characterizing the nutrients and suspended solids contained in stormwater from Kranji Catchment in Singapore are reported in this paper. Stormwater samples were collected from 4 locations and analyzed for the following eleven analytes: TOC, DOC, TN, TDN, NH₄⁺, NO₂⁻ + NO₃⁻ (NO_x), TP, TDP, OP, SiO₂ and TSS. Stormwater was sampled from catchments with various proportions of rural and urban land use, including forested areas, grassed areas, agricultural and residential and commercial areas. The event mean concentrations (EMCs) of nutrients and TSS from sampling stations which have agricultural land use activities upstream were found to be higher. Comparison of site EMCs (SMCs) with published data showed that the SMCs of the nutrients and TSS are generally higher than SMCs reported for forested areas but lower than published SMCs for urban areas. Positive correlations (p < 5%) were found between loading and peak flow at locations most impacted by ubanisation or agricultural activities. Correlation between loading and rainfall variables was less distinct. EMC was found to correlate less with rainfall and flow variables compared to pollutant loading. Unlike loading, no consistent pattern exists linking EMC to any particular storm or flow variable in any of the catchments. Lastly, positive correlations were obtained between the particulate forms of nitrogen and phosphorus and TSS.