Incentive compatibility tests of choice experiment value elicitation questions

This paper uses laboratory experiments with induced values to address fundamental issues related to the incentive compatibility of choice experiment value elicitation questions. In particular, we compare two- versus three-option choice sets and the effect of using alternative provision rules, including one where the outcome is influenced by both participant and “regulator” votes. We find the overall proportion of choices that are inconsistent with induced preferences is rather low. However, there are more deviations from induced preferences for two-option choice sets, and for alternatives to a simple plurality vote implementation rule. A multinomial probit analysis of choices in tandem with a mixed logit welfare analysis suggests there is a statistically significant but modest degree of bias towards selecting the status quo option.     

Application and evaluation of two air quality models for particulate matter for a southeastern U.S. episode

The Models-3 Community Multiscale Air Quality (CMAQ) Modeling System and the Particulate Matter Comprehensive Air Quality Model with extensions (PMCAMx) were applied to simulate the period June 29-July 10, 1999, of the Southern Oxidants Study episode with two nested horizontal grid sizes: a coarse resolution of 32 km and a fine resolution of 8 km. The predicted spatial variations of ozone (O3), particulate matter with an aerodynamic diameter less than or equal to 2.5 microm (PM2.5), and particulate matter with an aerodynamic diameter less than or equal to 10 microm (PM10) by both models are similar in rural areas but differ from one another significantly over some urban/suburban areas in the eastern and southern United States, where PMCAMx tends to predict higher values of O3 and PM than CMAQ. Both models tend to predict O3 values that are higher than those observed. For observed O3 values above 60 ppb, O3 performance meets the U.S. Environmental Protection Agency's criteria for CMAQ with both grids and for PMCAMx with the fine grid only. It becomes unsatisfactory for PMCAMx and marginally satisfactory for CMAQ for observed O3 values above 40 ppb. Both models predict similar amounts of sulfate (SO4(2-)) and organic matter, and both predict SO4(2-) to be the largest contributor to PM2.5. PMCAMx generally predicts higher amounts of ammonium (NH4+), nitrate (NO3-), and black carbon (BC) than does CMAQ. PM performance for CMAQ is generally consistent with that of other PM models, whereas PMCAMx predicts higher concentrations of NO3-, NH4+, and BC than observed, which degrades its performance. For PM10 and PM2.5 predictions over the southeastern U.S. domain, the ranges of mean normalized gross errors (MNGEs) and mean normalized bias are 37-43% and -33-4% for CMAQ and 50-59% and 7-30% for PMCAMx. Both models predict the largest MNGEs for NO3- (98-104% for CMAQ 138-338% for PMCAMx). The inaccurate NO3- predictions by both models may be caused by the inaccuracies in the ammonia emission inventory and the uncertainties in the gas/particle partitioning under some conditions. In addition to these uncertainties, the significant PM overpredictions by PMCAMx may be attributed to the lack of wet removal for PM and a likely underprediction in the vertical mixing during the daytime.     

137Cs in the Danish Wadden Sea: contrast between tidal flats and salt marshes

The 137Cs activity of salt marsh and tidal flat sediments of the northern part of the European Wadden Sea was studied based on a comprehensive dataset of 210Pb dated cores. The 137Cs inventory of salt marsh sediments shows a major peak corresponding to the Chernobyl accident in 1986, and a minor peak located in the late 1960s interpreted as the combined effect of atmospheric testing of nuclear weapons. Emissions from the nuclear reprocessing plant Sellafield are not reflected as peaks in 137Cs activity, but may contribute to the rising 137Cs activity in the years prior to 1986. The 137Cs activity of tidal flat sediments differs from salt marsh sediment in two respects. First, the activity is much lower and, second, the major peak in the 1980s is located in the beginning instead of in the middle of the decade. The differences in 137Cs inventory between the two environments are interpreted to result from repeated cycles of deposition/resuspension and mixing on tidal flats. A simple model illustrating the consequence of mixings returns an apparent shift of major peaks in 137Cs activities backwards in time corresponding to the mixing depth divided by the deposition rate.     

Nanoplastic occurrence,transformation and toxicity: a review

Environmental Chemistry Letters - Nanoplastics are emerging contaminants of concern for living organisms and ecosystems, yet nanoplastics are difficult to extract and analyse. Once released into...     

A correlation between the fate and non-extractable residue formation of 14C-metalaxyl and enzymatic activities in soil

Extracellular, oxidative soil enzymes like monophenol oxidases and peroxidases play an important role in transformation of xenobiotics and the formation of organic matter in soil. Additionally, these enzymes may be involved in the formation of non-extractable residues (NERs) of xenobiotics during humification processes. To examine this correlation, the fate of the fungicide ¹⁴C metalaxyl in soil samples from Ultuna (Sweden) was studied. Using different soil sterilization techniques, it was possible to differentiate between free, immobilized, and abiotic (“pseudoenzyme”-like) oxidative activities. A correlation between the formation of metalaxyl NER and soil organic matter content, biotic activities, as well as extracellular phenoloxidase and peroxidase activities in the bulk soil and its particle size fractions was determined. Extracellular soil-bound enzymes were involved in NER formation (up to 8% of applied radioactivity after 92 days) of the fungicide independently from the presence of living microbes and different distributions of the NER in the soil humic subfractions.     

Elucidating the function of ejaculate expulsion and consumption after copulation by female Euxesta bilimeki

Postcopulatory processes can influence male reproductive success in several animal species. Females can use different mechanisms to bias male paternity after copulation. One of such mechanisms consists in expelling all or part of the ejaculate after copulation. Euxesta bilimeki is an Ulidiid fly whose females not only frequently expel ejaculates after mating but also consume the ejaculate after expulsion. In order to understand the significance of these behaviors we examined video recordings of courtship, copulatory, and postcopulatory behaviours. The presence of sperm in female storage organs was confirmed after mating with males of different sizes and was correlated with duration of courtship, copulation, and the period from the end of copulation to ejaculate expulsion. The effect of ejaculate consumption on female fitness (fecundity and longevity) was compared among females held under different dietary treatments: a rich diet consisting of protein, sugar and water, an intermediate diet composed of sugar and water, a poor diet of only water and females that were completely deprived of food and water. All of the observed females expelled ejaculates after mating. The probability of storing sperm in the two spermathecae and the ventral receptacle was correlated with interactions between the duration of all behaviours examined and male size. Except for starved females, who lived longer when allowed to consume ejaculates, ejaculate consumption had no effect on fitness. Results suggest that females can bias sperm storage according to male mating effort, while the consumed ejaculate had some nutritional value only evident when females were completely starved.     

Determining patterns of variability in ecological communities: time lag analysis revisited

All ecological communities experience change over time. One method to quantify temporal variation in the patterns of relative abundance of communities is time lag analysis (TLA). It uses a distance-based approach to study temporal community dynamics by regressing community dissimilarity over increasing time lags (one-unit lags, two-unit lags, three-unit lags). Here, we suggest some modifications to the method and revaluate its potential for detecting patterns of community change. We apply Hellinger distance based TLA to artificial data simulating communities with different levels of directional and stochastic dynamics and analyse their effects on the slope and its statistical significance. We conclude that statistical significance of the TLA slope (obtained by a Monte Carlo permutation procedure) is a valid criterion to discriminate between (i) communities with directional change in species composition, regardless whether it is caused by directional abundance change of the species or by stochastic change according to a Markov process, and (ii) communities that are composed of species with population sizes oscillating around a constant mean or communities whose species abundances are governed by a white noise process. TLA slopes range between 0.02 and 0.25, depending on the proportions of species with different dynamics; higher proportions of species with constant means imply shallower slopes; and higher proportions of species with stochastic dynamics or directional change imply steeper slopes. These values are broadly in line with TLA slopes from real world data. Caution must be exercised when TLA is used for the comparison of community time series with different lengths since the slope depends on time series length and tends to decrease non-linearly with it.     

Factors driving mortality and growth at treeline: a 30-year experiment of 92 000 conifers

Understanding the interplay between environmental factors contributing to treeline formation and how these factors influence different life stages remains a major research challenge. We used an afforestation experiment including 92 000 trees to investigate the spatial and temporal dynamics of tree mortality and growth at treeline in the Swiss Alps. Seedlings of three high-elevation conifer species (Larix decidua, Pinus mugo ssp. uncinata, and Pinus cembra) were systematically planted along an altitudinal gradient at and above the current treeline (2075 to 2230 m above sea level [a.s.l.]) in 1975 and closely monitored during the following 30 years. We used decision-tree models and generalized additive models to identify patterns in mortality and growth along gradients in elevation, snow duration, wind speed, and solar radiation, and to quantify interactions between the different variables. For all three species, snowmelt date was always the most important environmental factor influencing mortality, and elevation was always the most important factor for growth over the entire period studied. Individuals of all species survived at the highest point of the afforestation for more than 30 years, although mortality was greater above 2160 m a.s.l., 50-100 m above the current treeline. Optimal conditions for height growth differed from those for survival in all three species: early snowmelt (ca. day of year 125-140 [where day 1 is 1 January]) yielded lowest mortality rates, but relatively later snowmelt (ca. day 145-150) yielded highest growth rates. Although snowmelt and elevation were important throughout all life stages of the trees, the importance of radiation decreased over time and that of wind speed increased. Our findings provide experimental evidence that tree survival and height growth require different environmental conditions and that even small changes in the duration of snow cover, in addition to changes in temperature, can strongly impact tree survival and growth patterns at treeline. Further, our results show that the relative importance of different environmental variables for tree seedlings changes during the juvenile phase as they grow taller.