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981.
Ou LT Thomas JE Allen LH Vu JC Dickson DW 《Journal of environmental science and health. Part. B》2007,42(1):15-20
A field experiment was conducted to compare two plastic mulches and two application rates on surface emissions and subsurface distribution of methyl bromide (MBr) in field beds in Florida. Within 30 minutes after injection of MBr to 30 cm depth, MBr had diffused upward to soil surface in all beds covered with polyethylene film (PE) or virtually impermeable film (VIF) and applied at a high rate (392 kg/ha) and a low rate (196 kg/ha). Due to the highly permeable nature of PE, within 30 minutes after injection, MBr volatilized from the bed surfaces of the two PE-covered beds into the atmosphere. The amount of volatilization was greater for the high rate-treatment bed. On the other hand, volatilization of MBr from the bed surfaces of the two VIF-covered beds were negligible. Volatilization losses occurred from the edges of all the beds covered with PE or VIF and were greater from the high rate-treatment beds. Initial vertical diffusion of MBr in the subsurface of the beds covered with PE or VIF was mainly upward, as large concentrations of MBr were detected from near bed surfaces to 20 cm depth in these beds 30 minutes after injection and little or no MBr was found at 40 cm depth. The two VIF-covered beds exhibited greater MBr concentrations and longer resident times in the root zone (0.5-40 cm depth) than corresponding PE-covered beds. Concentrations of MBr in the root zone of the high rate-treatment beds were 3.6-6.1 times larger than the low rate-treatment beds during the first days after application. In conclusion, VIF promoted retention of MBr in the root zone and, if volatilization loss from bed edges can be blocked, volatilization loss from VIF-covered beds should be negligible. 相似文献
982.
Shinichi Nakagawa Joseph R. Waas Masamine Miyazaki 《Behavioral ecology and sociobiology》2001,50(2):180-188
Researchers investigating social recognition typically measure only behavioural responses during discrimination tests - physiological changes have been largely ignored. We examined whether little blue penguin chicks (Eudyptula minor) could distinguish siblings from other chicks using auditory cues, by measuring behavioural and heart rate changes during playback experiments. Chicks were exposed to five treatments: the begging calls of siblings, neighbouring chicks and unfamiliar chicks, and two controls (heterospecific begging calls and music). We also determined if chicks developed distinctive begging calls, by using F-ratios to quantify inter- versus intra-individual variability in a range of acoustic parameters, and applying a discriminant-function analysis. Inter-individual variation was greater for pitch than for temporal or amplitude parameters, suggesting that call pitch may be important for individual recognition. The discriminant-function analysis showed each chick's calls were distinctive and could act as a vocal signature. Treatments did not instigate different behavioural responses. However, chick heart rates during playback of sibling calls were significantly higher than those recorded during stranger, but not neighbour, playback. A simple recognition system based on familiarity may allow this plesiomorphic and loosely colonial penguin to gain at least some of the benefits associated with more advanced sibling recognition systems (some highly colonial seabirds discriminate siblings from neighbouring chicks). Heart rate could be a useful measure of social recognition abilities, particularly in species where changes in behaviour are not always evident or are difficult to observe. 相似文献
983.
Circulation and Stream Plume Modeling in Conesus Lake 总被引:1,自引:0,他引:1
Yan Li Anthony Vodacek Nina Raqueño Robert Kremens Alfred J. Garrett Isidro Bosch Joseph C. Makarewicz Theodore W. Lewis 《Environmental Modeling and Assessment》2008,13(2):275-289
A three-dimensional hydrodynamic model that includes the effect of drag from macrophytes was applied to Conesus Lake to study
the seasonal circulation and thermal structure during spring and early summer. Local weather conditions and stream flow data
were used to drive the model. The drag coefficient for macrophytes was calculated as a function of leaf density. In general,
the model results show good agreements with the observations, including vertical temperature profiles measured at two locations
and average surface temperature derived from calibrated thermal imagery for large-scale simulations of the entire lake. Additional
high-resolution simulations were carried out to understand water circulation and transport of sediment and model-generated
tracer during hydrometeorological events at stream mouths for two experimental sites. The model results show that the plume
development at stream mouths during storm events in Conesus Lake are site-dependent and may either be current- or wind-driven.
The results also show a significant effect from the presence of macrophytes on sediment deposition near stream mouths. 相似文献
984.
Trace metal dynamics in fishes from the southwest coast of India 总被引:1,自引:0,他引:1
George Rejomon Maheswari Nair Thresiamma Joseph 《Environmental monitoring and assessment》2010,167(1-4):243-255
The concentration of Fe, Co, Ni, Cu, Zn, Cd, and Pb in the muscle tissue of marine fishes like Lates calcarifer, Nemipterus japonicus, Caranx melampygus, Rastrelliger kanagurta, and Cyanoglossus macrostomus was estimated from samples collected in the continental shelf waters off Kochi and Mangalore on southwest coast of India. Species-specific and spatially heterogeneous patterns of tissue metals loads were apparent within the pelagic and demersal fish species for the two regions. The concentration ranges of Fe (541.60 to 649.60 ppm), Ni (12.12 to 13.92 ppm), and Cu (3.09 to 3.62 ppm) were higher in the demersal species C. melampygus, whereas Co (9.10 to 11.80 ppm) and Zn (79.30 to 84.30 ppm) were higher in the pelagic species L. calcarifer and Cd (4.35 to 6.38 ppm) were higher in the demersal species N. japonicus, possibly due to enhanced bioavailability of these metals from ecological processes associated with upwelling during the summer monsoon. The fish species showed a great capacity to accumulate metals, with highest bioaccumulation for the essential element iron and lowest bioaccumulation for the non-essential element lead. Among the demersal species, C. melampygus and N. japonicus had high concentration factors for the metals Fe (280,268 to 322,808), Ni (88,252 to 96,891), Cu (2,351 to 2,600), and Cd (29,637 to 32,404). In contrast, the pelagic species L. calcarifer and R. kanagurta had high concentration factors for the metals Zn (40,812 to 46,892), Co (280,285 to 423,037), and Pb (854 to 1,404). 相似文献
985.
Annie J. Morris Joseph J. Donovan Michael Strager 《Environmental Modeling and Assessment》2009,14(1):73-84
Streamflow values are commonly synthesized for locations where flow measurement stations are lacking or where only intermittent
measurements are available. In an Appalachian Mountains dataset comprised of 29 watersheds, the most appropriate among geomorphic,
geologic, and hydrogeologic datasets were selected for use in prediction of streamflow at watershed scale. A statistical model
was developed using principal components analysis (PCA) and cluster analysis (CA) for. Using CA on variables derived from
the PCA, an optimum set of variables was derived for predicting streamflow. Results indicate there are two categories of watersheds
in the study area. The first is strongly correlated with climatic variables (precipitation, temperature, elevation, and groundwater
recharge). The second is strongly correlated with two geomorphic variables (watershed slope and percentage of forested area).
The spatial distribution of cluster classifications shows that watersheds dominated by the climatic component are located
along the Allegheny Front while watersheds dominated by the geomorphic component are located in the Allegheny Plateau and
Valley and Ridge physiographic provinces. These variations between the Allegheny Plateau and Valley and Ridge physiographic
provinces suggest that, to accurately model streamflow, modeling needs be done based on natural physiographic boundaries rather
than political boundaries. In this physiographic setting, elevation seems to be a major control. 相似文献
986.
Nsikak U. Benson Joseph P. Essien Francis E. Asuquo Adeola L. Eritobor 《Environmental monitoring and assessment》2014,186(9):5519-5529
Polycyclic aromatic hydrocarbons (PAHs) in surface microlayer (SML) and subsurface water (SSW) of Lagos Lagoon were investigated using gas chromatography-electron capture detector (GC-ECD) technique to ascertain their occurrence and spatial distribution, origin, enrichment, and carcinogenicity. Total PAH (ΣPAH) concentrations ranged from 9.10 to 16.20 μg L?1 in the SML and 8.90 to 13.30 μg L?1 in the SSW. ΣPAH concentrations were relatively higher in the SML than the underlying SSW samples. The enrichment factors (EFs) of ΣPAHs ranged from 0.76 to 1.74 while the EFs of the individual PAHs varied from 0.50 to 2.09. In general, the EFs values calculated in this study were consistent or slightly less than the EFs reported for similar coastal seawater ecosystems. A correlation between the EFs of fluoranthene and pyrene indicated a positive significant value (R?=?0.9828, p?<?0.0001, n?=?6). Source analyses using the phenanthrene/anthracene and fluoranthene/pyrene ratios indicated the dominance of petrogenic-derived PAHs. Furthermore, enhanced concentrations of BaP (strong carcinogenicity) in SML and SSW samples, which resulted in higher EFs, could pose serious ecological and human health risks. 相似文献
987.
Paola M. Mwanamoki Naresh Devarajan Florian Thevenon Emmanuel K. Atibu Joseph B. Tshibanda Patience Ngelinkoto Pius T. Mpiana Kandasamy Prabakar Josué I. Mubedi Christophe G. Kabele Walter Wildi John Poté 《Environmental monitoring and assessment》2014,186(10):6821-6830
This study was conducted to assess potential human health risks presented by pathogenic bacteria in a protected multi-use lake-reservoir (Lake Ma Vallée) located in west of Kinshasa, Democratic Republic of Congo (DRC). Water and surface sediments from several points of the Lake were collected during summer. Microbial analysis was performed for Escherichia coli, Enterococcus (ENT), Pseudomonas species and heterotrophic plate counts. PCR amplification was performed for the confirmation of E. coli, ENT, Pseudomonas spp. and Pseudomonas aeruginosa isolated from samples. The results reveal low concentration of bacteria in water column of the lake, the bacterial quantification results observed in this study for the water column were below the recommended limits, according to WHO and the European Directive 2006/7/CE, for bathing water. However, high concentration of bacteria was observed in the sediment samples; the values of 2.65?×?103, 6.35?×?103, 3.27?×?103 and 3.60?×?108 CFU g?1 of dry sediment for E. coli, ENT, Pseudomonas spp. and heterotrophic plate counts, respectively. The results of this study indicate that sediments of the Lake Ma Vallée can constitute a reservoir of pathogenic microorganisms which can persist in the lake. Possible resuspension of faecal indicator bacteria and pathogens would affect water quality and may increase health risks to the population during recreational activities. Our results indicate that the microbial sediment analysis provides complementary and important information for assessing sanitary quality of surface water under tropical conditions. 相似文献
988.
Ali Ercan M. Levent Kavvas Kara Carr Zachary Hockett Hossein Bandeh Timothy D. Mussen Dennis Cocherell Jamilynn B. Poletto Joseph J. Cech Jr. Nann A. Fangue 《Journal of the American Water Resources Association》2017,53(2):431-441
Most of the water diversions on the Sacramento and San Joaquin Rivers (California, United States) and their tributaries are currently unscreened. These unscreened diversions are commonly used for irrigation and are potentially harmful to migrating and resident fishes. A large flume (test section: 18.29 m long, 3.05 m wide and 3.20 m high) was used to investigate the hydraulic fields near an unscreened water diversion under ecologically and hydraulically relevant diversion rates and channel flow characteristics. We investigated all combinations of three diversion rates (0.28, 0.42, and 0.57 m3/s) and three sweeping velocities (0.15, 0.38, and 0.61 m/s), with one additional test at 0.71 m3/s and 0.15 m/s. We measured the three‐dimensional velocity field at seven cross sections near a diversion pipe and constructed regression equations of the observed maximum velocities near the pipe. Because the velocity components in three directions (longitudinal, transverse, and vertical) were significantly greater near the diversion pipe inlet compared with those farther from it, they cannot be neglected in the modeling and design of fish guidance and protection devices for diversion pipes. Our results should be of great value in quantifying the hydraulic fields that are formed around fish guidance devices to design more effective protection for fishes from entrainment into unscreened water‐diversion pipes. 相似文献
989.
Joseph A. Adeyemi Chris O. Adedire Airton da Cunha Martins-Junior Ana Carolina Paulelli Akinsola F. Awopetu Fabiana Roberta Segura 《毒物与环境化学》2017,99(5-6):999-1006
This study determined concentrations and speciation of arsenic (As) in rice samples obtained from the cities of Akure, Ore, Ondo and Ikare in Ondo State, south-western Nigeria. The estimated dietary intake of As from rice consumption for total As and the identified As species were compared with the As benchmark dose lower confidence limit. Analyses of rice from the four cities identified three As species: inorganic As, monomethylarsonic, acid and dimethylarsinic acid. Concentrations of total As and the As species differed significantly across the sampling locations (by a factor of 2.5 for total As). Mean levels (±S.D.) were 58.8 ± 0.7 µg/kg total As, 47.0 ± 0.6 µg/kg inorganic As, 0.33 ± 0.03 µg/kg monomethylarsonic acid, and 11.5 ± 0.1 µg/kg dimethylarsinic acid. The estimated mean dietary intakes were 4.1 µg/d total As, 3.3 µg/d inorganic As, 0.02 µg/d monomethylarsonic acid, and 0.8 µg/d dimethylarsinic acid. These values are below the benchmark dose lower confidence limit and comparable to, or lower than, those reported for other countries. Thus, consumption of rice cultivated in south-western Nigeria does not appear to have inherent As-associated health risks. 相似文献
990.
Linking empirical estimates of body burden of environmental chemicals and wellness using NHANES data
Biomonitoring of industrial chemicals in human tissues and fluids has shown that all people carry a “body burden” of synthetic chemicals. Although measurement of an environmental chemical in a person's tissues/fluids is an indication of exposure, it does not necessarily mean the exposure concentration is sufficient to cause an adverse effect. Since humans are exposed to multiple chemicals, there may be a combination effect (e.g., additive, synergistic) associated with low-level exposures to multiple classes of contaminants, which may impact a variety of organ systems. The objective of this research is to link measures of body burden of environmental chemicals and a “holistic” measure of wellness. The approach is demonstrated using biomonitoring data from the National Health and Nutrition Examination Surveys (NHANES). Forty-two chemicals were selected for analysis based on their detection levels. Six biological pathway-specific indices were evaluated using groups of chemicals associated with each pathway. Five of the six pathways were negatively associated with wellness. Three non-zero interaction terms were detected which may provide empirical evidence of crosstalk across pathways. The approach identified five of the 42 chemicals from a variety of classes (metals, pesticides, furans, polycyclic aromatic hydrocarbons) as accounting for 71% of the weight linking body burden to wellness. Significant interactions were detected indicating the effect of smoking is exacerbated by body burden of environmental chemicals. Use of a holistic index on both sides of the exposure-health equation is a novel and promising empirical “systems biology” approach to risk evaluation of complex environmental exposures. 相似文献