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201.
Joshua M. Allen Amy A. Cuthbertson Hannah K. Liberatore Susana Y. Kimur Anurag Manth Marc A. Edwards Susan D. Richardson 《环境科学学报(英文版)》2017,29(8):271-284
Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water (Lake Huron) with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal, reports of skin rashes have sparked questions surrounding tap water in some Flint homes. This study investigated the presence of contaminants, including disinfection by-products (DBPs), in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water. Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible. 相似文献
202.
Pote DH Way TR Kleinman PJ Moore PA Meisinger JJ Sistani KR Saporito LS Allen AL Feyereisen GW 《Journal of environmental quality》2011,40(2):402-411
Poultry litter provides a rich nutrient source for crops, but the usual practice of surface-applying litter can degrade water quality by allowing nutrients to be transported from fields in surface runoff while much of the ammonia (NH3)-N escapes into the atmosphere. Our goal was to improve on conventional titter application methods to decrease associated nutrient losses to air and water while increasing soil productivity. We developed and tested a knifing technique to directly apply dry poultry litter beneath the surface of pastures. Results showed that subsurface litter application decreased NH3-N volatilization and nutrient losses in runoff more than 90% (compared with surface-applied litter) to levels statistically as low as those from control (no litter) plots. Given this success, two advanced tractor-drawn prototypes were developed to subsurface apply poultry litter in field research. The two prototypes have been tested in pasture and no-till experiments and are both effective in improving nutrient-use efficiency compared with surface-applied litter, increasing crop yields (possibly by retaining more nitrogen in the soil), and decreasing nutrient losses, often to near background (control plot) levels. A paired-watershed study showed that cumulative phosphorus losses in runoff from continuously grazed perennial pastures were decreased by 55% over a 3-yr period if the annual poultry litter applications were subsurface applied rather than surface broadcast. Results highlight opportunities and challenges for commercial adoption of subsurface poultry litter application in pasture and no-till systems. 相似文献
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204.
new habitats are created, community assembly may follow independent trajectories, since the relative importance of dispersal limitation, priority effects, species interactions, and environmental gradients can vary as assembly proceeds. Unfortunately, tracking community colonization and composition across decades is challenging. We compiled a multiyear community composition data set and reconstructed past communities with remains from sediment cores to investigate cladoceran assembly dynamics in six older (1920s) and two more recently formed (1950s) lakes. We found that current communities cluster along a gradient of thermal stratification that is known to influence predation intensity. Assembling communities showed evidence for a greater influence of species sorting and a reduced influence of spatial structure since the first colonizations. However, lake community trajectories varied considerably, reflecting different colonization sequences among lakes. In the older lakes, small-bodied cladocerans often arrived much earlier than large-bodied cladocerans, while the two younger lakes were colonized much more rapidly, and one was quickly dominated by a large-bodied species. Thus, by combining contemporary community data with paleoecological records, we show that assembly history influences natural community structure for decades while patterns of ecological sorting develop. 相似文献
205.
The patterns of genetic diversity and connectivity were investigated in Cucumaria frondosa, the most abundant sea cucumber in the North Atlantic, to assist in the management and conservation of this ecologically
important marine invertebrate, which is the target of an emerging fishery. Mitochondrial DNA COI sequences of 334 C. frondosa were obtained and analyzed, mainly from its western North Atlantic range, where the commercial fishery is being developed,
with complementary sampling in the mid- and eastern North Atlantic. Analysis of molecular variance showed no significant (P > 0.05) differences among subpopulations in the western region suggesting that it constitutes one panmictic population. The
same analysis showed low, but significant differences between eastern and western Atlantic populations. Coalescent analyses
using isolation with migration models and a Bayesian skyline plot indicated historical divergence and a general increase in
population size prior to the last glacial maximum and highly asymmetric gene flow (nearly 100 times lower from west to east)
between sea cucumbers from North America and Norway. Results suggest that subpopulations of C. frondosa within the western North Atlantic have been highly connected. We propose that aided by the high-connectivity local subpopulations
can recover rapidly from natural (i.e., ice ages) or anthropogenic (i.e., overfishing) population declines through recruitment
from deep refugia. 相似文献
206.
This study measured and analyzed the outdoor airborne endotoxin concentration, on particulate matter (PM2·? and PM1?), for two cities in the interior of British Columbia, Canada. Samples were collected throughout one seasonal cycle, from October 2005 to September 2006. It was found that concentrations were generally highest in the summer and fall, and lowest in the winter and spring. Temperature and relative humidity were found to be most influential, with highest endotoxin concentrations recorded during warm periods and moderate relative humidity (35 to 75 percent). No clear association of concentration with wind direction was observed. Results were comparable between the two cities considered in this study, and concentrations were similar to or slightly higher than those reported by other studies considering urban locations. Endotoxin concentration was also found to be positively associated with agricultural dust sources identified by a source apportionment study conducted at one of the sampling locations. 相似文献
207.
A fundamental question of sexual selection theory concerns the causes and consequences of reproductive skew among males. The
priority of access (PoA) model (Altmann, Ann NY Acad Sci 102:338–435, 1962) has been the most influential framework in primates living in permanent, mixed-sex groups, but to date it has only been
tested with the appropriate data on female synchrony in a handful of species. In this paper, we used mating data from one
large semi-free ranging group of Barbary macaques: (1) to provide the first test of the priority-of-access model in this species,
using mating data from 11 sexually active females (including six females that were implanted with a hormonal contraceptive
but who showed levels of sexual activity comparable to those of naturally cycling females) and (2) to determine the proximate
mechanism(s) underlying male mating skew. Our results show that the fit of the observed distribution of matings with sexually
attractive females to predictions of the PoA model was poor, with lower-ranking males mating more than expected. While our
work confirms that female mating synchrony sets an upper limit to monopolization by high-ranking individuals, other factors
are also important. Coalitionary activity was the main tactic used by males to lower mating skew in the study group. Coalitions
were expressed in a strongly age-related fashion and allowed subordinate, post-prime males to increase their mating success
by targeting more dominant, prime males. Conversely, females, while mating promiscuously with several males during a given
mating cycle, were more likely to initiate their consortships with prime males, thus reducing the overall effectiveness of
coalitions. We conclude that high-ranking Barbary macaque males have a limited ability to monopolize mating access, leading
to a modest mating skew among them. 相似文献
208.
Charles G. Morton Justin L. Huntington Greg M. Pohll Richard G. Allen Kenneth C. McGwire Scott D. Bassett 《Journal of the American Water Resources Association》2013,49(3):549-562
Agricultural irrigation accounts for a large fraction of the total water use in the western United States. The Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) remote sensing energy balance model is being used to estimate historical agricultural water use in western Nevada to evaluate basin‐wide water budgets. Each METRIC evapotranspiration (ET) estimate must be calibrated by a trained user, which requires some iterative time investment and results in variation in ET estimates between users. An automated calibration algorithm for the METRIC model was designed to generate ET estimates comparable to those from trained users by mimicking the manual calibration process. Automated calibration allows for rapid generation of METRIC ET estimates with minimal manual intervention, as well as uncertainty and sensitivity analysis of the model. The variation in ET estimates generated by the automated calibration algorithm was found to be similar to the variation in manual ET estimates. Results indicate that uncertainty was highest for fields with low ET levels and lowest for fields with high ET levels, with a seasonal mean uncertainty of approximately 5% for all fields. In addition, in a blind comparison, automated daily and seasonal ET estimates compared well with flux tower measurement ET data at multiple sites. Automated methods can generate first‐order ET estimates that are similar to time intensive manual efforts with less time investment. 相似文献
209.
210.
Summary. Increased abundance of several aliphatic benzyl
and phenylethyl alkanoates were previously associated with
reduced defoliation of
Eucalyptus globulus Labill. by the
autumn gum moth (Mnesampela privata Guenée) in two
clonally replicated F2 families. We examine the robustness
of this association by comparing the abundance of the
implicated foliar wax compounds with defoliation levels in
three plantation sites and a genetics trial in northern
Tasmania. At all locations, the aliphatic alkanoate, benzyl
n-tetracosanoate (C24), was found in significantly higher
abundance in the foliar wax of E. globulus trees that had displayed low M. privata damage (designated resistant) compared to trees that had displayed high damage (designated
susceptible). Further, when sites were combined, benzyl
n-tetracosanoate (C24) accounted for 16 % of variation in
field defoliation. Field defoliation was also positively correlated
to M. privata oviposition both in the field and on
foliage sprigs in a cage. In the cage bioassay, oviposition
accounted for 20 % of variation in field defoliation
making it a better predictor of tree defoliation in the field
than either field oviposition, which accounted for 9 % of
variation, or screening foliage for the abundance of benzyl
n-tetracosanoate (C24). Despite both benzyl n-tetracosanoate
(C24) and oviposition being related to field defoliation, there
was no statistically significant relationship between the
abundance of benzyl n-tetracosanoate (C24) and oviposition
in the field or cage bioassay. Further work is therefore
required to determine if increased levels of this compound in
the foliar wax operates as a direct deterrent to M. privataoviposition. 相似文献