خيارات البحث
النتائج 3741 - 3750 من 6,560
Fish habitat evaluation based on width-to-depth ratio and eco-environmental diversity index in small rivers النص الكامل
2020
Sekine, Masahiko | Wang, Jianing | Yamamoto, Kōichi | Kanno, Ariyo
We estimated the performance of river fish habitat evaluation using width-to-depth ratio (WDR) in comparison with eco-environmental diversity (EED) to propose an inexpensive and easy-to-use habitat evaluation procedure, which is applicable to small river construction works. WDR calculation costs less than that of EED. For verification, 25 stations in eight rivers were selected and fish were captured using electrofishing. pH, electrical conductivity, turbidity, dissolved oxygen (DO), water temperature, fraction of forest, farmland, and residential area in each basin were measured to examine possible influence of water quality. Results show that there is no major water quality issue in the target rivers. Although fish habitat is classified as good when WDR is higher than 6, it cannot be evaluated by WDR when it is lower than 6. EED has positive relationship with fish habitat for any WDR value. Thus, if a river geometry design in a river work results in WDR higher than 6, no measures need to be taken regarding fish habitat condition; however, if it is less than 6, it is necessary to examine whether the construction work lowers the EED or not.
اظهر المزيد [+] اقل [-]Behavior of Aluminum Compounds in Soft-Water Lakes Subjected to Experimental Reclamation with Polyaluminum Chloride النص الكامل
2020
Łopata, Michał | Augustyniak, Renata | Grochowska, Jolanta | Parszuto, Katarzyna | Tandyrak, Renata | Wiśniewski, Grzegorz
The research presented in this work concerns the potential aluminum load of soft-water lake ecosystems as a result of performing chemical reclamation works. On a semitechnical scale, different doses of PAC-type aluminum coagulant (polyaluminum chloride) were tested. The required doses of coagulant (on average, 11 mg Al/L) were determined based on the amount of phosphorus that is bioavailable in the lake ecosystem. The research covered the lake water, near-bottom and interstitial water, and bottom sediments of five lakes with low alkalinity (0.4–2.5 meq/L) and low calcium contents (5–35 mg Ca/L). The experiments were conducted in situ for 2 years using mesocosms with a volume of approximately 20 m³. The effectiveness of the flocculation and sedimentation processes of coagulant flocs was closely related to changes in water pH caused by acidic coagulant application, and the corresponding transformation level ranged from 39.8 to 99.8%. In the waters of these lakes, where the alkalinity did not reach 1 meq/L, the coagulant used in doses adequate for intensive full-scale projects caused high water pollution with dissolved aluminum fractions (from 0.05 ± 0.01 to 4.67 ± 1.32 mg Al/L). In all lakes, the penetration of dissolved aluminum into the interstitial water of the bottom sediment was limited to the first 5-cm layer. After the application of coagulant, the aluminum content in the bottom sediments significantly increased in proportion to the amount of the PAC used (by 12–96% in terms of a 5-cm surface layer of sediment). Within 2 years of the research, solid fractions (flocks) of the coagulant moved to a depth of 5–10 cm below the bottom level. Due to high release rates of aluminum from the applied aluminum treatments, modifications to the treatment protocols are needed in soft-water lakes.
اظهر المزيد [+] اقل [-]Measured and predicted acute toxicity of phenanthrene and MC252 crude oil to vertically migrating deep-sea crustaceans النص الكامل
2020
Turner, Nicholas R. | Bera, Gopal | Renegar, D Abigail | Frank, Tamara M. | Riegl, Bernhard M. | Sericano, José L | Sweet, Stephen | Knap, Anthony H.
Deep-water column micronekton play a key role in oceanic food webs and represent an important trophic link between deep- and shallow-water ecosystems. Thus, the potential impacts of sub-surface hydrocarbon plumes on these organisms are critical to developing a more complete understanding of ocean-wide effects resulting from deep-sea oil spills. This work was designed to advance the understanding of hydrocarbon toxicity in several ecologically important deep-sea micronekton species using controlled laboratory exposures aimed at determining lethal threshold exposure levels. The current study confirmed the results previously determined for five deep-sea micronekton by measuring lethal threshold levels for phenanthrene between 81.2 and 277.5 μg/L. These results were used to calibrate the target lipid model and to calculate a critical target lipid body burden for each species. In addition, an oil solubility model was used to predict the acute toxicity of MC252 crude oil to vertically migrating crustaceans, Janicella spinacauda and Euphausiidae spp., and to compare the predictions with results of a 48-h constant exposure toxicity test with passive-dosing. Results confirmed that the tested deep-sea micronekton appear more sensitive than many other organisms when exposed to dissolved oil, but baseline stress complicated interpretation of results.
اظهر المزيد [+] اقل [-]Study of phenol biodegradation in different agitation systems and fixed bed column: experimental, mathematical modeling, and numerical simulation النص الكامل
2020
Ribeiro, Heraldo Baialardi | Bampi, Josiane | da Silva, Taina Cristini | Dervanoski, Adriana | Milanesi, Paola Mendes | Fuzinatto, Cristiane Funghetto | de Mello, Josiane Maria Muneron | da Luz, Cleuzir | Vargas, Gean Delise Leal Pasquali
Phenol degradation was studied in two different agitation systems in a batc h reactor (mechanical agitation and orbital agitation) and the support of the most efficient system was used for fixed bed bioreactor studies. The support used was coconut shell charcoal. The results showed that the mechanical agitation bioreactor was more effective in phenol removal, due to the amount of biomass adhered to the support (8.56 mg gₛᵤₚₚₒᵣₜ⁻¹), running at approximately 100% of the phenol biodegradation in 300 min. The toxicity analysis of the waters was moderate, because the EC₅₀,₄₈ₕ values in the analyzed samples are higher than 50%. Within the experimental data obtained from the batch system, it was possible to find the parameters of the kinetic model of Michaelis-Menten, which was used to simulate the bioreactor in a fixed bed. A mathematical model of a one-equation, which considers the effects of dispersion, convection, and reaction in the liquid phase, and diffusion and reaction inside the biofilm was used and the results obtained through numerical simulation were compared with the experimental results of the bioreactor in a fixed bed, and new operational conditions in the bed were simulated with good accuracy.
اظهر المزيد [+] اقل [-]Cytotoxic, Genotoxic, Mutagenic, and Phytotoxic Effects of the Extracts from Eragrostis plana Nees, 1841 (Poaceae), Grown in a Coal-Contaminated Region النص الكامل
2020
Artico, Leonardo Luís | Kömmling, Gizele | Clarindo, Wellington Ronildo | Menezes, Ana Paula Simões
Coal and its byproducts and mineral waste constitute complex mixtures, which contain a variety of chemical compounds that impact the ecosystems. For this reason, procedures are required to monitor coal-degraded areas, including the use of biomonitoring organisms. In this light, the aim of the present study was to evaluate the cytotoxicity, genotoxicity, mutagenicity, and phytotoxicity of the aerial part and root extracts from Eragrostis plana Nees collected in the surroundings of the Thermoelectric Power Plant President Médici-UTPM (Candiota, Brazil), through Allium cepa bioassay. Cytotoxicity, genotoxicity, and mutagenicity in the A. cepa meristematic cells were verified through the mitotic index (MI), chromosomal alterations, and micronucleus formation, respectively. In addition, the germination rate, vigor index, and morphological abnormalities were verified in A. cepa seedlings. Treatment with root extracts from E. plana (ACR) specimens collected in a coal-contaminated region resulted in the lowest MI values (8.9%, 12.7%, and 16.0%), representing the most cytotoxic effect when compared with the negative control—NC (dH₂O) (MI = 35.8%). ACR extract also was the most genotoxic and mutagenic sample compared with NC and other treatments. Phytotoxicity analyses corroborated the toxic action of ACR, presenting abnormal seedlings and change in vigor index. The high concentration of dissolved total chlorides and electrical conductivity presented in the root extracts of E. plana, which were grown in the carboniferous region, indicates an increase in the absorption of metallic ions and organic compound and supports the hypothesis that this species has bioaccumulator potential, being a new biomonitor model of coal-contaminated region.
اظهر المزيد [+] اقل [-]Phytoextraction from Chromium-Contaminated Soil Using Moso Bamboo in Mediterranean Conditions النص الكامل
2020
Ranieri, Ezio | Tursi, Angelo | Giuliano, Silvia | Spagnolo, Vincenzo | Ranieri, Ada Cristina | Petrella, Andrea
An experimentation has been carried out in simulated Mediterranean and tropical laboratory conditions aimed to show the Moso bamboo capability of phytoextraction chromium from contaminated soil. Electronic microscopy supported the analyses performed on soil and on the different plant tissues. A preliminary test on the bamboo has been carried out in laboratory evaluating his growth with irrigation in Mediterranean conditions (600 mm/year) and tropical conditions (1.800 mm/year). A test of the bamboo tolerance of was also carried out by measuring his growth with irrigation with a solution of 100 mg Cr/l, reporting not significant damages to the plant tissues. Subsequently chromium phytoextraction was tested highlighting that bamboo removes Cr from soil with a percentage ranging from 43% (600 mm/year) to 47.4% (1.800 mm/year) of the total content in soil. Lastly, the distribution of chromium in the different fragments of the bamboo plants has been performed. It has been shown that approx. 69% of chromium, in Mediterranean conditions, was in the rhizomes and approx. 68% in tropical conditions. A slightly higher tendency to chromium translocation to leaves has been shown in tropical conditions than in Mediterranean conditions.
اظهر المزيد [+] اقل [-]Polymer types ingested by northern fulmars (Fulmarus glacialis) and southern hemisphere relatives
2020
Kühn, Susanne | Oyen, van, Albert | Bravo Rebolledo, Elisa L. | Ask, Amalie V. | Franeker, van, Jan Andries
Although ingestion of plastic by tubenosed seabirds has been documented regularly, identification of the polymer composition of these plastics has rarely been described. Polymer assessment may assist in identifying sources and may indicate risks from additives occurring in specific types of polymers. Using known test materials, two identification methods Fourier transform infrared spectroscopy and near infrared spectroscopy (FTIR and NIR) were compared. Although both methods were found to be similarly suitable for identification of plastic polymers, a significant difference was observed in identification of natural materials. FTIR frequently misclassified natural materials as being a synthetic polymer. Within our results, an 80% match score threshold functioned best to distinguish between natural items and synthetics. Using NIR, the historical variability of plastics ingested by northern fulmars (Fulmarus glacialis) from the Dutch sector of the North Sea was analysed for three time periods since the 1980s. For the more recent decade, variability between fulmars from different regions in the northeast Atlantic was investigated. Regional variation was further explored by analysing plastics obtained from the stomachs of southern hemisphere relatives of the fulmar (southern fulmar, cape petrel, snow petrel) and Wilson’s storm petrel. Results show that proportional abundance of polymer types in these seabirds is closely related to the plastic categories that they ingest (e.g. pellets, foam, fragments). The uptake of different plastic categories and related polymer types most likely reflects spatial and temporal variations in availability rather than ingestion preferences of the birds.
اظهر المزيد [+] اقل [-]Simulation of Nitrogen Pollution in the Shanxi Reservoir Watershed Based on SWAT Model النص الكامل
2020
A-long Li, Chen Haitao, Liu Yuanyuan, Lin Qiu and Wang Wenchuan
This study applied the Soil and Water Assessment Tool (SWAT) to the Shanxi Reservoir watershed, a drinking water source in Zhejiang Province, China. The important sources of non-point source pollution (NPS) in Shanxi reservoir watershed are agricultural fertilizer application, domestic sewage and livestock breeding, this brings new challenges to water source management. The simulated runoff and water quality parameters total nitrogen (TN) were compared to those of the observed values in the watershed. The Nash-Suttcliffe efficiency (NSE) was 0.94 for monthly runoff during the calibration period 2007-2010, and 0.84 during the validation period 2011-2012. The model can well satisfy the simulation of runoff. For monthly TN of Sancha water quality monitoring station, the NSE is 0.7 in the calibration period of March 2009 to April 2011, and 0.75 in the verification period of May 2011 to December 2012. For the Jiujiang water quality monitoring station, the model index parameters are slightly lower than Sancha, but it is also very good for water quality simulation. The four parameters of total nitrogen, organic nitrogen (ORGN), nitrate-nitrogen (NO3-N) and ammonia nitrogen (NH4-N) were used to analyse the nitrogen pollution of Shanxi Reservoir watershed. The multi-year monthly average results of nitrogen pollutant loadings show significant differences, with large fluctuations every month. ORGN and NH4-N showed a consistent trend, showing a steady growth trend from January to June, peaking in August and continuing to decline in other months, and NO3-N peaked in March. The pollution load of TN in Shanxi reservoir watershed ranged from 142.27 kg/km2 to 725.31 kg/km2, showing a large spatial difference. The pollution load of the tributary basin is weaker than that of the main stream, which generally shows an increasing trend from upstream to downstream. Overall, the pollutant load is consistent with land use and agricultural production and living conditions, showing typical characteristics of non-point source pollution. Through the establishment of regional nitrogen pollution model and the study of pollutant distribution characteristics, this study puts forward some suggestions for controlling the nitrogen pollution load of the Shanxi Reservoir watershed, optimizes the agricultural planting mode, and intercepts the pollution sources that are not directly discharged into the water body.
اظهر المزيد [+] اقل [-]Machine Learning Model for Revealing the Characteristics of Soil Nutrients and Aboveground Biomass of Northeast Forest, China النص الكامل
2020
Chunyan Wu, Lifeng Pang, Jun Jiang, Miaoying An , Yuanjun Yang
Declining soil quality and climate change may affect species diversity and forest biomass productivity in many temperate regions in the future. Our research objective is to reveal the characteristics of soil nutrients and biomass of forests in Northeast China with climate change. The purpose of this study was to determine the soil physical and chemical properties of mature broad-leaved forest in the cold temperate zone of Mt. Changbai, Jilin Province, by measuring pH, NH4 +, organic matter (%), C/N, available phosphorus, alkali-hydrolysable N, rapidly available K, and Cr etc., analysing species diversity characteristics, and estimating aboveground biomass (AGB) of tree species with machine learning models. The results showed that with the increase of soil depth, the soil physical and chemical parameters have a decreasing trend; with the increase of soil depth, the soil nutrient content decreased; the main tree species were the Acer barbinerve (6937), Carpinus cordata Bl. (6682) and Acer mandshuricum Maxim. (5447) etc. The total difference (SOR) showed a similar trend in the four directions and central point; the reference sample size at central point, north, west, south and east direction was 903, 954, 971, 1005 and 1016, respectively; GRNN model was the relatively best model among these models for modelling the aboveground biomass of the trees. Therefore, the diversity of tree species in north-eastern forests was affected by soil nutrients, climate change also has a significant impact on the aboveground biomass of northeast forests, which provides a theoretical basis for the management of northeast forests about soil physical and chemical properties and species diversity.
اظهر المزيد [+] اقل [-]Characterizing the Intensity and Dynamics Change Relationship Between the Land-Use and Landscape Pattern in the Ordos Bojiang Basin النص الكامل
2020
Harrison Odion Ikhumhen, Tianxin Li , Nametso Matomela
This paper seeks to analyse the present and future land-use change transition intensity (using Pontius intensity model) and landscape pattern using landscape metrics to investigate the relationship between the land cover regions, landscape pattern and the changes in the size of Bojiang lake in Ordos basin from 1987-2017. The accelerated changes in each land use region from 1987 and 2017 subsequently led to changes in landscape pattern. The changes experienced within 1987 and 2017 including the future changes indicated that the grassland and sparsely vegetated region increased significantly, dominating the study region which however indicated an increase in anthropogenic activities like agricultural activities in the study region. Based on our observation in this study, the change in each land use region although showed a significant relationship with the change in water region including Bojiang lake, other external factors also contributed to the changes in the size of the lake.
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