This paper considers the modeling and forecasting of daily maximum hourly ozone concentrations in Laranjeiras, Serra, Brazil, through dynamic regression models. In order to take into account the natural skewness and heavy-tailness of the data, a linear regression model with autoregressive errors and innovations following a member of the family of scale mixture of skew-normal distributions was considered. Pollutants and meteorological variables were considered as predictors, along with some deterministic factors, namely week-days and seasons. The Oceanic Niño Index was also considered as a predictor. The estimated model was able to explain satisfactorily well the correlation structure of the ozone time series. An out-of-sample forecast study was also performed. The skew-normal and skew-t models displayed quite competitive point forecasts compared to the similar model with gaussian innovations. On the other hand, in terms of forecast intervals, the skewed models presented much better performance with more accurate prediction intervals. These findings were empirically corroborated by a forecast Monte Carlo experiment. 相似文献
In April-May 2004, the World Health Organization (WHO) implemented, with local authorities, United Nations (UN) agencies and non-governmental organisations (NGOs), an early warning system (EWS) in Darfur, West Sudan, for internally displaced persons (IDPs). The number of consultations and deaths per week for 12 health events is recorded for two age groups (less than five years and five years and above). Thresholds are used to detect potential outbreaks. Ten weeks after the introduction of the system, NGOs were covering 54 camps, and 924,281 people (IDPs and the host population). Of these 54 camps, 41 (76%) were reporting regularly under the EWS. Between 22 May and 30 July, 179,795 consultations were reported: 18.7% for acute respiratory infections; 15% for malaria; 8.4% for bloody diarrhoea; and 1% for severe acute malnutrition. The EWS is useful for detecting outbreaks and monitoring the number of consultations required to trigger actions, but not for estimating mortality. 相似文献
Sex identification has been studied in several species of crustacean decapods but only seldom was the role of multimodality investigated in a systematic fashion. Here, we analyse the effect of single/combined chemical and visual stimuli on the ability of the crayfish Procambarus clarkii to identify the sex of a conspecific during mating interactions. Our results show that crayfish respond to the offered stimuli depending on their sex. While males rely on olfaction alone for sex identification, females require the combination of olfaction and vision to do so. In the latter, chemical and visual stimuli act as non-redundant signal components that possibly enhance the female ability to discriminate potential mates in the crowded social context experienced during mating period. This is one of the few clear examples in invertebrates of non-redundancy in a bimodal communication system. 相似文献
False negative detections may bias the surveys for rare species and reduce the reliability of models based on the proportion
of occupied patches. We assessed the detectability of the Eurasian otter Lutra lutra through the standard survey method by analysing the detection history of 28 sampling stretches surveyed monthly between March
2001 and January 2003. Each survey negative for otter spraints was considered as a false negative if the otter had been recorded
in the previous and/or following month (respectively, cFN and FN). Otter marking intensity (MI) (MI=N° of spraints per kilometre)
was calculated and assumed to represent an index of its relative abundance. Spraints were found in 81.7% of all surveys. Yearly
MI ranged from 1.02 to 101.4 spraints per kilometre. In 2002, mean MI was significantly lower than in the previous year, while
no clear seasonal trend could be outlined. The minimum number of surveys required to establish the occurrence of the otter,
as estimated by a probability model, was 2.6 and was inversely related to MI. For a sub-sample of 18 sampling stretches, the
relation between the frequency of both cFN and FN and five variables of potential interest for otters was tested by means
of stepwise linear multiple regressions, yielding two highly significant models, which both included only MI as the explanatory
variable. The frequency of both FN and cFN was correlated to MI and the resulting equations used to assess the percentage
of surveys positive for otters in both years. After the correction for non-detections, otter site occupancy did not vary between
the 2 years, except for one river when applying the more conservative estimate of false negatives (cFN). Multiple visits and
the assessing of MI should become standard components of otter surveys. This approach has broad applicability and may be applied
to assess the large-scale distribution of other rare or elusive mammalian carnivores. 相似文献
Although many aspects of environmental accounting methodologies in food production have already been investigated, the application of environmental indicators in the fruit sector is still rare and no consensus can be found on the preferred method. On the contrary, widely diverging approaches have been taken to several aspects of the analyses, such as data collection, handling of scaling issues, and goal and scope definition. This paper reviews studies assessing the sustainability or environmental impacts of fruit production under different conditions and identifies aspects of fruit production that are of environmental importance. Four environmental assessment methods which may be applied to assess fruit production systems are evaluated, namely Life Cycle Assessment, Ecological Footprint Analysis, Emergy Analysis and Energy Balance. In the 22 peer-reviewed journal articles and two conference articles applying one of these methods in the fruit sector that were included in this review, a total of 26 applications of environmental impact assessment methods are described. These applications differ concerning e.g. overall objective, set of environmental issues considered, definition of system boundaries and calculation algorithms. Due to the relatively high variability in study cases and approaches, it was not possible to identify any one method as being better than the others. However, remarks on methodologies and suggestions for standardisation are given and the environmental burdens of fruit systems are highlighted. 相似文献
The availability of a hazard identification methodology based on early warnings is a crucial factor in the identification of emerging risks. In the present study, a specific method named Dynamic Procedure for Atypical Scenarios Identification (DyPASI) was conceived as a development of bow-tie identification techniques. The main aim of the methodology is to provide a comprehensive hazard identification of the industrial process analysed, joined to a process of continuous improvement of the results of the assessment. DyPASI is a method for the continuous systematization of information from early signals of risk related to past events. The technique provides a support to the identification and assessment of atypical potential accident scenarios related to the substances, the equipment and the site considered, capturing available early warnings or risk notions. DyPASI features as a tool to support emerging risk management process, having the potentiality to contribute to an integrated approach aimed at breaking “vicious circles”, helping to trigger a gradual process of identification and assimilation of previously unrecognised atypical scenarios. 相似文献
Chemical signature of airborne particulates and deposition dusts is subject of study since decades. Usually, three complementary composition markers are investigated, namely, (i) specific organic compounds; (ii) concentration ratios between congeners, and (iii) percent distributions of homologs. Due to its intrinsic limits (e.g., variability depending on decomposition and gas/particle equilibrium), the identification of pollution sources based on molecular signatures results overall restricted to qualitative purposes. Nevertheless, chemical fingerprints allow drawing preliminary information, suitable for successfully approaching multivariate analysis and valuing the relative importance of sources. Here, the state-of-the-art is presented about the molecular fingerprints of non-polar aliphatic, polyaromatic (PAHs, nitro-PAHs), and polar (fatty acids, organic halides, polysaccharides) compounds in emissions. Special concern was addressed to alkenes and alkanes with carbon numbers ranging from 12 to 23 and?≥?24, which displayed distinct relative abundances in petrol-derived spills and exhausts, emissions from microorganisms, high vegetation, and sediments. Long-chain alkanes associated with tobacco smoke were characterized by a peculiar iso/anteiso/normal homolog fingerprint and by n-hentriacontane percentages higher than elsewhere. Several concentration ratios of PAHs were identified as diagnostic of the type of emission, and the sources of uncertainty were elucidated. Despite extensive investigations conducted so far, the origin of uncommon molecular fingerprints, e.g., alkane/alkene relationships in deposition dusts and airborne particles, remains quite unclear. Polar organics resulted scarcely investigated for pollution apportioning purposes, though they looked as indicative of the nature of sources. Finally, the role of humans and living organisms as actual emitters of chemicals seems to need concern in the future.
Environmental Science and Pollution Research - In this study, the anthropogenic contamination in Trasimeno lake (Central Italy) was investigated using three sediment cores spanning over the last... 相似文献
- DOI: http://dx.doi.org/10.1065/espr2006.01.007
Goal, Scope and Background Amu Darya river, one of the main water resources of Uzbekistan, shows a relevant longitudinal enrichment of soluble contents
which strongly limits the human uses of its waters. Because of the low natural run-off processes, salts and pollutants are
mainly driven to the river by the return waters used for washing and irrigating the surrounding lands. The influence of return
waters on stream quality is dramatically relevant in the lower reaches of the river where almost all the flowing waters have
been previously used for the agriculture practises. To provide analytical evidence on the potential effects of return waters
on the quality of the Amu Darya river, the paper reports and comments data on salinity and metals contents of the waters flowing
in the artificial channel network of Bukhara and in the Amu Darya river, from Bukhara up to the dam forming the Tuyamuyn Hydro
Complex (THC).
Methods A total of 15 sampling sites were selected for the analytical survey: Two sites were located on the Amu Darya river downstream
from the inflow of the return waters from Bukhara, two in the river entering in the THC, and three downstream from the dam
forming the reservoir complex. The waters entering and leaving the Bukhara agricultural area were sampled in two main collectors,
while the waters flowing in the channel system were sampled in six distinct collectors. The following parameters were considered
in the survey: pH, Oxygen, Hardness, Salinity, Conductivity, P-PO4 3–, P tot, N tot, N-NO3 2–, N-NO2 –, COD, Ca2+, Mg2+, Fe,
Mn, Zn, Cr, Cu, Ni, Cd, Pb.
Results and Discussion Salt concentrations below 1000 mg/l were measured in the Amu Darya waters upstream to Bukhara. In the drainage system, salinity
exceeds the palatability limit and reaches the maximum peak of 3200 mg/l in the outflow collector. Due to dilution effects,
salinity returns to lower values (400–700 mg/l) along the Amu Darya river downstream from Bukhara; calcium and magnesium resulted
the major constituents of the overall salinity. No serious metal contaminations were detected in the waters entering and leaving
the examined channel system. Differently, the Amu Darya waters upstream to the THC showed a relevant metal contamination,
with Cr, Ni, Fe concentrations exceeding the limits for human consumption. In the downstream sites, located in the Tuyamuyn
Hydro Complex and in the Amu Darya river flowing out from this reservoir, excluding Fe, all the examined metals showed lover
concentrations and values below the normative limits.
Conclusion The direct human consumption of the lower Amu Darya waters is strongly limited by salinity and by metal contamination. Although
the salinity of the return waters from the Bukhara drainage system results in above normal limits, no corresponding increases
were measured in the Amu Darya river downstream from the return water inflow at the time of the survey. As for the metal contamination
of the Amu Darya river, the survey revealed the presence of relevant sources of metal contamination downstream from Bukhara
external to the agricultural drainage system. This contamination resulted in reduced sedimentation processes taking place
in the limnetic zones of the Amu Darya river upstream to the dam forming the Tuyamuyn Hydro Complex.
Recommendation and Outlook To fully understand the longitudinal increase of Amu Darya salinity, an evaluation of the cumulative effects of the loads
from the main agricultural areas is required, also by using mass-balance models. As for the metals, an investigation should
be addressed to identify the anthropogenic sources of contaminations present in the lower Amu Darya region and the metal loads
should be diverted. 相似文献