On sensitivity analysis: Let’s use it more!

The key factors that influence the population growth rate can be identified with sensitivity analysis. Caswell presented an algorithm based on vector calculus that speeds up, and improves the practicality of the application of the sensitivity analysis, by calculating the derivatives of the explicit elements from the population Leslie matrix. Despite the usefulness of the sensitivity analysis, it is still barely applied to empirical data, partially due to requirements of high quality demographic data and failure of compatibility between time intervals of field data collection and organism’s life stage timing. This can result in the absence of a certain vital rate as a separated element in the population projection matrix, and thus intricacy in obtaining its sensitivity. In this note we call the attention for the applied value of sensitivity analysis, and also we point to a simple formula that is easily implemented in Caswell Matlab algorithm, to calculate the sensitivity of a vital rate that is not explicit as a matrix element.     

Tail loss reduces mating success in the Iberian rock-lizard,Lacerta monticola

Summary Many lizards autotomize their tails to escape when grasped by a predator. It is hypothesized that tail loss causes a reduction in social status, thereby potentially lowering their reproductive success. We experimentally induced tail loss in Lacerta monticola in a semi-natural enclosure, and show that tail loss reduced social status and mating access in males. Tailless males increased body mass more rapidly than tailed dominant males, probably due to lower aggression costs. Also, tailless females were courted less and copulated less than tailed females, supporting the hypothesis that tail loss decreases reproduction potential.Correspondence to: J. Martin     

Identification of chemical hazards for terrestrial plants in the regulatory context: Comparison of OECD and ISO guidelines

Standardized test protocols are used in the regulatory context for identifying the hazardous properties of chemicals, wastes, and contaminated materials. This paper compares the relevance of two guidelines measuring effects on terrestrial plants, the OECD TG 208 and the ISO TG 22030 and presents the scientific basis for a recent decision of the European Chemicals Agency (ECHA) under the European chemicals regulation REACH. If there are no specific phytotoxicity alerts, both guidelines are considered suitable for assessing long-term hazards, providing that a sufficient number of species is included in the OECD protocol, the recommended minimum number is six, which offer a reasonably broad selection of species to account for interspecies sensitivity. The proposed methodology, based on a combination of probabilistic assessments using Monte Carlo analysis, can be adapted for supporting similar decisions under specific regulatory processes; for example, for assessing contaminated soils or pesticides’ applications.     

PM<Subscript>10</Subscript> source apportionment in the surroundings of the San Vicente del Raspeig cement plant complex in southeastern Spain

Introduction  

The concentrations of trace metals, ionic species, and carbonaceous components in PM₁₀ (particulate matter with aerodynamic diameters smaller than 10 μm) were measured from samples collected near an industrial complex, primarily composed of cement plants, in southeastern Spain, from September 2005 to August 2006.     

Monitoring dioxins and furans in the vicinity of an old municipal waste incinerator after pronounced reductions of the atmospheric emissions

In order to get an overall picture of the environmental impact of an old municipal solid waste incinerator (MSWI) from S. Adrià del Besòs (Barcelona, Catalonia, Spain), a monitoring program addressed at determining the levels of a number of pollutants in the vicinity of the facility was initiated in 1998. In March 1999, an adaptation was carried out due to EU legislation on pollutant emissions from the stack. As a result, emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were notably reduced, and a significant (30%) decrease was found in the levels of PCDD/F in herbage samples collected in the vicinity of the MSWI. In March 2001, herbage samples were collected at the same sampling points and the PCDD/F levels measured again. The current PCDD/F concentrations range from 0.23 to 1.43 ng I-TEQ kg(-1) (dry matter), with median and mean values of 0.58 and 0.66 ng I-TEQ kg(-1) (dry matter), respectively, while in the 2000 survey the PCDD/F concentrations ranged from 0.22 to 1.20 ng I-TEQ kg(-1) (dry matter), with median and mean values of 0.57 and 0.61 ng I-TEQ kg(-1) (dry matter), respectively. Although the current PCDD/F concentrations in herbage samples are comparable to those found in recent surveys carried out in various places of Catalonia, an exhaustive evaluation of the data, including principal component analysis, indicates that other emission sources of PCDD/Fs also have a notable environmental impact on the area under direct influence of the MSWI.     

Enhanced degradation of polycyclic aromatic hydrocarbons by biodegradation combined with a modified Fenton reaction

A study has been conducted to enhance degradation of a mixture of polycyclic aromatic hydrocarbons (PAHs) by combining biodegradation with hydrogen peroxide oxidation in a former manufactured gas plant (MGP) soil. An active bacterial consortium enriched from the MGP surface soil (0-2 m) biodegraded more than 90% of PAHs including 2-, 3-, and 4-ring hydrocarbons in a model soil. The consortium was also able to transform about 50% of 4- and 5-ring hydrocarbons in the MGP soil. As a chemical oxidant, Fenton's reagent (H2O2 + Fe2+) was very efficient in the destruction of a mixture of PAHs (i.e., naphthalene (NAP), fluorene (FLU), phenanthrene (PHE), anthracene (ANT), pyrene (PYR), chrysene (CHR), and benzo(a)pyrene (BaP)) in the model soil; noticeably, 84.5% and 96.7% of initial PYR and BaP were degraded, respectively. In the MGP soil, the same treatment destroyed more than 80% of 2- and 3-ring hydrocarbons and 20-40% of 4- and 5-ring compounds. However, the low pH requirement (pH 2-3) for optimum Fenton reaction made the process incompatible with biological treatment and posed potential hazards to the soil ecosystem where the reagent was used. In order to overcome such limitation, a modified Fenton-type reaction was performed at near neutral pH by using ferric ions and chelating agents such as catechol and gallic acid. By the combined treatment of the modified Fenton reaction and biodegradation, more than 98% of 2- or 3-ring hydrocarbons and between 70% and 85% of 4- or 5-ring compounds were degraded in the MGP soil, while maintaining its pH about 6-6.5.     

Effect of operational parameters on the removal of particulate chemical oxygen demand in the activated sludge process.

The removal of particulate material in the aeration basin of the activated sludge process is mainly attributed to bioflocculation and hydrolysis of particulate substrate. The bioflocculation process in the aeration tank of the activated sludge process occurs only under favorable conditions in the system, and several common operational parameters affect its performance. The principal objective of this research was to observe the effect of mixed liquor suspended solids, solids retention time (SRT), and extracellular polymer substances on the removal of particulate substrate by bioflocculation. A first-order particulate removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand. Based on the results presented in this investigation, a mixed liquor concentration of approximately 2200 mg/L, an SRT of at least 3 days, and a contact time of 30 minutes are needed for relatively complete removal of the particulate substrate in a plug-flow reactor.     

Long-term efficiency of catalytic converters operating in Mexico City

A 1999 ordinance by the Government of Mexico City bans 1993 model-year vehicles from on-road operation if their catalytic converters are not replaced with new ones. To validate the benefits of this action, we examined three issues related to exhaust emissions of vehicles equipped with catalytic converters. After selecting representative fleets of in-use vehicles, a comparison between emissions and catalyst efficiency in cars with two categories of exhaust emission limits was carried out. For that purpose, two fleets were selected, each made up of 10 vehicles run under similar conditions. A third, larger fleet with emissions control systems was used to evaluate and simulate real-world conditions of vehicles in a controlled laboratory. Finally, the aging effect on the catalytic converter was studied on vehicles run for 100,000 km, replacing their old emission control devices for new ones. The 1991-1992 model-year vehicles showed a high percentage of compliance with the corresponding emissions standard (90%) in comparison with 1993 model-year and later vehicles (Tier 0). However, NOx emissions were higher for the newer vehicles. Fifty percent of the 1991-1992 model-year vehicles evaluated under the official inspection/maintenance (I/M) procedure did not meet the regulated emissions standard when the results were compared with those of the U.S. Federal Test Procedure FTP-75. Our results suggest that the replacement of old catalytic converters with new ones will have little effect on decreasing polluting emissions because these vehicles were in very bad mechanical condition. Results of catalytic activity as a function of mileage indicated inefficient catalyst performance for the fleets tested. All pollutant conversions were below 90% efficiency, and they deteriorated by an average of 30% after the vehicles were run for 100,000 km.