Act Force Gold®, Butaforce®, and Atraforce® are among the most commonly used pesticides in Nigeria. The lethal concentrations and the respective toxic units for the three pesticides were determined. The genotoxic effects of the three pesticides were investigated in the red blood cells of Clarias gariepinus using micronucleus (MN) assay. The 96 h LC50 was 4.75, 4.84, and 54.74 mg L−1 for Act Force Gold®, Butaforce®, and Atraforce®, respectively. The toxic units in ascending order of toxicity were 1.83, 20.66, and 21.05 for Act Force Gold®, Butaforce®, and Atraforce® respectively. The estimated safe levels based on NAS/NAE varied from 4.75 × 10−1–4.75 × 10−5 in Act Force Gold® through 4.64 × 10−1–4.85 × 10−5 in Butaforce® to 5.74–5.74 × 10−5 in Atraforce®. Fish specimens were exposed to the pesticides and sampling was done at regular intervals at days 1, 7, 14, and 21 and after another 7-day recovery period. The results obtained indicated concentration- and duration-dependent increase in % MN formation with maximum values of 3.40 ± 0.25 for Act Force Gold® on day 14 and 3.05 ± 0.36 and 2.35 ± 0.14 for Butaforce® and Atraforce® respectively on day 7 of exposure. The 7-day recovery period could not reverse the trend as the % MN values obtained were significantly different from the control. The results further support the use of MN assay in assessing the toxicity of aquatic pollutants and can be used in the monitoring of aquatic ecosystems.
Environmental Science and Pollution Research - Plastics are synthetic polymers known for their outstanding durability and versatility, and have replaced traditional materials in many applications.... 相似文献
Food processing facilities often use antimicrobial quaternary ammonium compound (QAC) sanitizers to maintain cleanliness. These QACs can end up in wastewaters used as feedstock for anaerobic digestion. The aim of this study was to measure the effect of QAC contamination on biogas production and structure of microbial communities in thermophilic digester sludge. Methane production and biogas quality data were analyzed in batch anaerobic digesters containing QAC at 0, 15, 50, 100 and 150 mg/L. Increasing sanitizer concentration in the bioreactors negatively impacted methane production rate and biogas quality. Microbial community composition data was obtained through 16S rRNA gene sequencing from the QAC-contaminated sludges. Sequencing data showed no significant restructuring of the bacterial communities. However, significant restructuring was observed within the archaeal communities as QAC concentration increased. Further studies to confirm these effects on a larger scale and with a longer retention time are necessary. 相似文献
Minimizing particles in water is a key goal for improving drinking water quality and safety.The media filtration process,as the last step of the solid–liquid separation process,is largely influenced by the characteristics of flocs,which are formed and controlled within the coagulation process.In a laboratory-based study,the impacts of the physical characteristics of flocs formed using aluminum sulfate on the filtration treatment of two comparative water samples were investigated using a photometric dispersion analyzer and a filterability apparatus.In general,the optimum dosage for maximizing filterability was higher than that for minimizing turbidity under neutral p H conditions.For a monomeric aluminum-based coagulant,the charge neutralization mechanism produced better floc characteristics,including floc growth speed and size,than the sweep flocculation mechanism.In addition,the charge neutralization mechanism showed better performance compared to sweep flocculation in terms of DOC removal and floc filterability improvement for both waters,and showed superiority in turbidity removal only when the raw water had high turbidity.For the different mechanisms,the ways that floc characteristics impacted on floc filterability also differed.The low variation in floc size distribution obtained under the charge neutralization mechanism resulted in the flocs being amenable to removal by filtration processes.For the sweep flocculation mechanism,increasing the floc size improved the settling ability of flocs,resulting in higher filter efficiency. 相似文献
This short paper presents an investigation on how human activities may or may not affect precipitation based on numerical simulations of precipitation in a benchmark case with modified lower boundary conditions, representing different stages of urban development in the model. The results indicate that certain degrees of urbanization affect the likelihood of heavy precipitation significantly, while less urbanized or smaller cities are much less prone to these effects. Such a result can be explained based on our previous work where the sensitivity of precipitation statistics to surface anthropogenic heat sources lies in the generation of buoyancy and turbulence in the planetary boundary layer and dissipation through triggering of convection. Thus only mega cities of sufficient size, and hence human-activity-related anthropogenic heat emission, can expect to experience such effects. In other words, as cities grow, their effects upon precipitation appear to grow as well. 相似文献
Pathogens exert a strong selection pressure on organisms to evolve effective immune defences. In addition to individual immunity, social organisms can act cooperatively to produce collective defences. In many ant species, queens have the option to found a colony alone or in groups with other, often unrelated, conspecifics. These associations are transient, usually lasting only as long as each queen benefits from the presence of others. In fact, once the first workers emerge, queens fight to the death for dominance. One potential advantage of co-founding may be that queens benefit from collective disease defences, such as mutual grooming, that act against common soil pathogens. We test this hypothesis by exposing single and co-founding queens to a fungal parasite, in order to assess whether queens in co-founding associations have improved survival. Surprisingly, co-foundresses exposed to the entomopathogenic fungus Metarhizium did not engage in cooperative disease defences, and consequently, we find no direct benefit of multiple queens on survival. However, an indirect benefit was observed, with parasite-exposed queens producing more brood when they co-founded, than when they were alone. We suggest this is due to a trade-off between reproduction and immunity. Additionally, we report an extraordinary ability of the queens to tolerate an infection for long periods after parasite exposure. Our study suggests that there are no social immunity benefits for co-founding ant queens, but that in parasite-rich environments, the presence of additional queens may nevertheless improve the chances of colony founding success. 相似文献
Although Asia is thought to have played a critical role in the radiation of artiodactyls, the fossil record of stem selenodonts
(“dichobunoids”) remains dramatically poor in tropical Asian regions. In this study, we report a new dichobunid genus and
species Cadutherium kyaukmagyii and a new basal ruminant genus and species Irrawadymeryx pondaungi, from the late Middle Eocene Pondaung Formation, Central Myanmar. Although the scarcity of the present material prevents
any attempts to investigate the phylogenetic relationships of Cadutherium with contemporaneous forms from other Holarctic landmasses, this new form shed new light on the diversity of these small
rabbit-like ungulates during a key period of their evolutionary history. Reexamination of the small-bodied artiodactyls from
Pondaung leads us to propose new identifications of certain published specimens and, in turn, to investigate the temporal
and geographic distribution of taxa recognized in the Pondaung Formation. Although fragmentary, these potential new taxa reveal
an unsuspected diversity of small forms among artiodactyls of Pondaung. This addition to the Eocene record of dichobunoids
and early ruminants provides further insight in the diversity of dental patterns among small artiodactyls from the Pondaung
Formation and attests to the antiquity of these groups in Southeast Asia. 相似文献
Gridded precipitation datasets are becoming a convenient substitute for gauge measurements in hydrological modeling; however, these data have not been fully evaluated across a range of conditions. We compared four gridded datasets (Daily Surface Weather and Climatological Summaries [DAYMET], North American Land Data Assimilation System [NLDAS], Global Land Data Assimilation System [GLDAS], and Parameter‐elevation Regressions on Independent Slopes Model [PRISM]) as precipitation data sources and evaluated how they affected hydrologic model performance when compared with a gauged dataset, Global Historical Climatology Network‐Daily (GHCN‐D). Analyses were performed for the Delaware Watershed at Perry Lake in eastern Kansas. Precipitation indices for DAYMET and PRISM precipitation closely matched GHCN‐D, whereas NLDAS and GLDAS showed weaker correlations. We also used these precipitation data as input to the Soil and Water Assessment Tool (SWAT) model that confirmed similar trends in streamflow simulation. For stations with complete data, GHCN‐D based SWAT‐simulated streamflow variability better than gridded precipitation data. During low flow periods we found PRISM performed better, whereas both DAYMET and NLDAS performed better in high flow years. Our results demonstrate that combining gridded precipitation sources with gauge‐based measurements can improve hydrologic model performance, especially for extreme events. 相似文献
Environmental Economics and Policy Studies - U.S. output has steadily outpaced the rise in greenhouse gas (GHG) emissions over the past several decades. The decoupling of these two trends... 相似文献