Refinar búsqueda
Resultados 621-630 de 5,098
Agronomic benefits of biochar as a soil amendment after its use as waste water filtration medium
2018
Werner, Steffen | Kätzl, Korbinian | Wichern, Marc | Buerkert, Andreas | Steiner, Christoph | Marschner, Bernd
In many water-scarce countries, waste water is used for irrigation which poses a health risk to farmers and consumers. At the same time, it delivers nutrients to the farming systems. In this study, we tested the hypotheses that biochar can be used as a filter medium for waste water treatment to reduce pathogen loads. At the same time, the biochar is becoming enriched with nutrients and therefore can act as a fertilizer for soil amendment. We used biochar as a filter medium for the filtration of raw waste water and compared the agronomic effects of this “filterchar” (FC) and the untreated biochar (BC) in a greenhouse pot trial on spring wheat biomass production on an acidic sandy soil from Niger. The biochar filter showed the same removal of pathogens as a common sand filter (1.4 log units on average). We did not observe a nutrient accumulation in FC compared to untreated BC. Instead, P, Mg and K were reduced during filtration while N content remained unchanged. Nevertheless, higher biomass (Triticum L. Spp.) production in BC (+72%) and FC (+37%) treatments (20 t ha⁻¹), compared with the unamended control, were found. There were no significant differences in aboveground biomass production between BC and FC. Soil available P content was increased by BC (+106%) and FC (+52%) application. Besides, mineral nitrogen content was reduced in BC treated soil and to a lesser extent when FC was used. This may be explained by reduced sorption affinity for mineral nitrogen compounds on FC surfaces. Although the nutrients provided by FC decreased, due to leaching in the filter, it still yielded higher biomass than the unamended control.
Mostrar más [+] Menos [-]Ground ozone concentrations over Beijing from 2004 to 2015: Variation patterns, indicative precursors and effects of emission-reduction
2018
Cheng, Nianliang | Chen, Ziyue | Sun, Feng | Sun, Ruiwen | Dong, Xin | Xie, Xiaoming | Xu, Chunxue
Based on ozone observation data from urban stations and the Dingling (DL) background station, we investigated the trend of ozone concentrations in Beijing during 2004–2015. For urban stations, both O3_1 h and O3_8 h increased stably with a clear and significant linear pattern and the increase rate was notably higher during the period of May to Sep. Meanwhile, the variation of O3_1 h and O3_8 h for the DL station did not demonstrate a regular pattern. During this period, the differences between the diurnal peak of ozone concentrations at the DL background station and urban stations decreased significantly due to the rapid urbanization of Beijing. Furthermore, we examined simultaneous variations of ozone and its precursors during 2015 Grand Military Parade and 2014 APEC meeting and evaluated the performances of different emission-reduction measures during the two specific events. For 2015 Grand Military Parade, emission-reduction measures were implemented 14 days in advance, which led to a notable decrease of ozone concentrations during the Parade period. For 2014 APEC meeting, emission-reduction measures were not implemented in advance, which led to incomplete VOCs reduction and high VOCs/NOx values, and thus a significant increase of ozone concentrations during the APEC period. The emission-reduction measures during APEC and PARADE periods both slowed down the accumulation and cut down the concentration peaks of ozone. We also analyzed simultaneous concentration variations of ozone and its precursors in long time-series. The results proved that compared with other precursors, NO2/NO was an effective indicator for ozone concentration in Beijing, especially in urban areas. The findings from this research provide useful reference for better monitoring and managing ozone concentrations in Beijing and other cities through properly designed and implemented emission-reduction measures.
Mostrar más [+] Menos [-]Nitrate reduction pathways in the presence of excess nitrogen in a shallow eutrophic estuary
2018
Domangue, Rebecca J. | Mortazavi, Behzad
The eutrophication of estuaries results from increasing anthropogenic nutrient inputs to coastal waters. Ecosystem recovery from eutrophication is partly dependent on the ability of a system to assimilate or remove nutrients, and denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are important pathways for nitrogen (N) removal or retention. We measured rates of denitrification and DNRA over an annual cycle at two stations in Weeks Bay, AL, a shallow microtidal estuary receiving freshwater from two rivers with agricultural watersheds and high N inputs. We hypothesized that rates of DNRA would exceed denitrification in the sulfidogenic sediments in this estuary. Consistent with our hypothesis, we found that DNRA (44.4 ± 5.5 μmol N m−2 hr−1) exceeded in situ denitrification (0.9 ± 2.3 μmol N m−2 hr−1) and that even in the presence of abundant water column nitrate DNRA was favored over denitrification by a factor of two. DNRA is estimated to provide N to the water column at a rate equivalent to 15% of the N input that is retained within the estuary and is a significant component of the N budget in this highly impacted estuary. DNRA by retaining N in the system contributes to the N demand by primary producers and can impact this estuary through enhanced rates of primary production. Weeks Bay, like many coastal estuaries, experiences periods of hypoxia, blooms of harmful algae and fish kills. Future management efforts should focus on reducing nutrient input to this estuary without which the significant retention of N in this system through DRNA will contribute to the undesirable ecosystem attributes associated with eutrophication.
Mostrar más [+] Menos [-]Coastal landscape planning for improving the value of ecosystem services in coastal areas: Using system dynamics model
2018
You, Soojin | Kim, Min | Lee, Junga | Chon, Jinhyung
Coastal areas provide important ecosystem services and affect local tourism. However, these areas are also sensitive to coastal erosion. The purpose of this study was to simulate a landscape plan scenario to improve the value of ecosystem services. The Shinduri coastal area in South Korea which has important natural resources, such as coastal sand dunes and coastal forests. To simulate landscape changes, this study was conducted using system dynamics. The study progressed in three stages: first, an analysis of the landscape change behavior model of Shinduri in its current state and an evaluation of the value of ecosystem services was conducted. Second, a simulation was carried out by applying a coastal erosion scenario. Third, a simulation of landscape change was run, and the value of ecosystem services was estimated, with regard to afforestation, thinning, weeding and coastal sand dune restoration plan scenarios. The results were as follows: in the absence of disturbances, current landscape change models are stable, and the value of ecosystem services, which was $859,259 in 2014, has increased over time. However, the value of ecosystem services decreased when subjected to a coastal erosion scenario. The evaluation of value of ecosystem services under afforestation, thinning, weeding and coastal sand dune plan scenarios revealed an optimal landscape plan that focuses on a coastal sand dune restoration plan suggesting restoration of these dunes at a rate of 27.05 ha per year. When the coastal sand dune restoration plan is applied, the value of ecosystem services increases to $ 895,474 by 2054. The coastal sand dune restoration plan should prioritize the protection of the coastal sand dune area as component of the restoration of coastal ecological resources in the area. These findings could contribute to the ecological management and improvement of coastal ecosystem services.
Mostrar más [+] Menos [-]Interaction between Al2O3 and different sizes of GO in aqueous environment
2018
Liu, Xia | Xu, Xuetao | Sun, Ju | Duan, Shengxia | Sun, Yubing | Hayat, Tasawar | Li, Jiaxing
Although the aggregation of graphene oxide (GO) has been widely researched, the influence of the GO size on the homoaggregation behavior and its interaction with environmental media are still unexplored. In this work, critical coagulation concentration (CCC) values for GO with different sizes, from micro to nanosheet, were measured with NaCl and CaCl₂ electrolytes, and the results indicated that GO with the largest size presented the smallest CCC value. Aluminum oxide (Al₂O₃) was selected as a natural solid particle representative to mimic the interaction between GO and environmental media. Batch experiments were conducted in solution with different pH and ionic strength. Results indicated that the attachment capacity of large GO onto Al₂O₃ particles was greater than that of small GO. The experimental data were well fitted with Freundlich model. The electrostatic attraction and hydrogen-bonding interaction dominated the interaction process between GO and Al₂O₃. These findings are important for better understanding in the environmental fate and transport of GO.
Mostrar más [+] Menos [-]The influence of liquid plant additives on the anthropogenic gas emissions from the combustion of coal-water slurries
2018
Nyashina, G.S. | Strizhak, P.A.
At present, coal is considered one of the main components for the production of cheap, high-energy and environmentally attractive slurry fuels. The latter can be produced on the basis of low-grade coal dust or coal processing wastes. Thus, coal-water slurries and coal-water slurries containing petrochemicals are produced. The involvement of coal and oil processing wastes expands the scope of raw materials, reduces the fuel costs from traditional energy sources and modifies the main economic characteristics of power plant performance. However, it also increases the impact of coal-fired thermal power stations on the environment. In the last 30–50 years, many efforts have been made to decrease the negative impact of human industrial activity on climate. Involving plant-based components in the process of energy generation to save energy and material resources looks very promising nowadays. This research studies the influence of adding typical bioliquids (bioethanol, turpentine, glycerol) on the concentration of anthropogenic emissions from coal-water slurry combustion. Relative mass concentrations of bioliquids varied in a small range below 20%. We focused on the concentration of the most hazardous sulfur and nitrogen oxides from the combustion of typical filter cakes, as well as plant-containing slurries. It was established that the concentration of sulfur oxides can be decreased (as compared to coal) by 75%, whereas that of nitrogen oxides by almost 30%. Using a generalizing criteria expression, we illustrated the main benefits of adding bioliquids to slurry fuels in comparison with coal. Adding 20% of glycerol was found to provide maximum advantages.
Mostrar más [+] Menos [-]Potential endocrine-disrupting effects of metals via interference with glucocorticoid and mineralocorticoid receptors
2018
Zhang, Jianyun | Yang, Ye | Liu, Weiping | Liu, Jing
As a result of human activities, the pollution of metals is becoming ubiquitous in the environment. Among various toxicological mechanisms of action, metals have been considered as endocrine-disrupting chemicals (EDCs) through interference with steroid receptors. However, information regarding the potential endocrine disruption of metals on glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) is especially scarce. In this study, a total of 16 metals were assessed for their GR/MR activities using luciferase reporter gene assay. None of the tested metals exhibited GR or MR agonistic activity, but a total of 7 and 5 candidate metals showed obvious GR and MR antagonistic properties, respectively. All 7 GR antagonistic metals [ BaCl₂, CoCl₂, CuCl₂, Pb(NO₃)₂, LiCl, SnCl₂ and ZnCl₂] inhibited glucocorticoid-responsive gene GILZ expression in J774A.1 cells. Further investigations indicated that the 5 MR antagonistic metals [ CdCl₂, Pb(NO₃)₂, LiCl, MnCl₂ and SnCl₂] antagonized aldosterone-inhibited hepatocellular carcinoma cell proliferation. Among these metals, Pb(NO₃)₂, LiCl, and SnCl₂ showed both anti-glucocorticoid and anti-mineralocorticoid activities. Comprehensive screening and evaluation of GR and MR antagonists and agonists among metals should be considered to better understand the ecological and health risks of metals.
Mostrar más [+] Menos [-]The response of chironomid taxonomy- and functional trait-based metrics to fish farm effluent pollution in lotic systems
2018
Milošević, Djuradj | Stojanović, Katarina | Djurdjević, Aca | Marković, Zoran | Stojković Piperac, Milica | Živić, Miroslav | Živić, Ivana
The lotic habitats affected by trout farm waste are colonized with a particular invertebrate community of which chironomids are the most abundant group. However, there is little information available regarding how chironomid community structures respond to this type of pollution at the highest taxonomic resolution. Eight fish farms, together with their lotic systems as recipients, were used to test the variability of the chironomid community and its surrogates (taxonomic and functional metrics) across spatially arranged sampling sites to form a gradual decrease in the trout farm influence. The self organizing map (SOM) classified six different types of chironomid communities which were characteristic for both the control and affected habitats. The species indicator analyses listed 32 taxa as positive indicators of water pollution. The SOM and Kruskal-Wallis test revealed that the pattern of chironomid community structure obtained was mainly driven by six environmental parameters (Altitude, conductivity, distance from the outlet, hardness, HN₄-N, NO₃-N). Categorical principal components analysis (CATPCA) derived three models for each type of biotic metric, in which for diversity-, taxonomy- and functional feeding group-based metrics, the first two dimensions explained 55.2%, 58.3% and 55.4%, of the total variance respectively for 315 sampling sites. According to this analysis, the total number of taxa (S), abundance and the Shannon-Wiener index (H′) (as a diversity metric), as well as the proportion of Tanypodinae (as taxonomic group) and grazers/scraper (GRA) and gatherer collector (GAT)(as FFG metrics), were related to the outlet distance gradient, thus showing great potential to be used in the multimetric approach in bioassessment.
Mostrar más [+] Menos [-]Mobility of traffic-related Pd and Pt species in soils evaluated by sequential extraction
2018
Leopold, Kerstin | Denzel, Aline | Gruber, Andreas | Malle, Lisa
The aim of this study was to evaluate the mobility of platinum (Pt) and palladium (Pd) emissions from automotive catalysts in soils and to contribute to the risk assessment of platinum group metals (PGMs) discharged from catalysts in the environment. To address this question, for the first time risk assessment code (RAC) was applied to consider the results from sequential extraction of different Pd and Pt species from soils. For this purpose, model soil samples were prepared spiking defined Pd or Pt species, respectively, at known concentrations. In order to mimic emitted species as well as possible transformation products of traffic-related Pd and Pt emissions in soils, coated and uncoated elemental nanoparticles (cPd/cPt NPs, Pd/Pt NPs) and ionic divalent metal species (Pd(II)/Pt(II)) were applied. All model samples were characterized in detail and the developed sequential extraction scheme was validated. RAC values ranged between 24 and 8% revealing medium to low risk. The order of mobility for the studied species was found to be Pt(II) > cPd NPs » Pd(II) > Pd NPs > Pt NPs > cPt NPs. Furthermore, migration of Pd species in gravity columns was studied confirming highest transport of cPd NPs.
Mostrar más [+] Menos [-]Fragrances and PAHs in snow and seawater of Ny-Ålesund (Svalbard): Local and long-range contamination
2018
Vecchiato, Marco | Barbaro, Elena | Spolaor, Andrea | Burgay, Francois | Barbante, Carlo | Piazza, Rossano | Gambaro, Andrea
Polar regions are fragile ecosystems threatened by both long-range pollution and local human contamination. In this context, the environmental distribution of the Personal Care Products (PCPs) represent a major knowledge gap. Following preliminary Antarctic studies, Fragrance Materials (FMs) were analyzed in the seawater and snow collected in the area of Ny-Ålesund, Svalbard, to investigate local and long-range contamination. Polycyclic Aromatic Hydrocarbons (PAHs), including Retene, were determined in parallel to help the identification of the governing processes. Concentrations of FMs up to 72 ng L⁻¹ were detected in the surface snow near the settlement and at increasing distances, in relation to the prevailing winds. PAHs follow a similar scheme, with levels of Retene up to 1.8 μg L⁻¹, likely deriving from the occurrence of this compound in the coal dust due to the previous mining activities in the area. The snow seasonal deposition of FMs and PAHs was estimated in a snowpit dug at the top of the Austre Brøggerbreen glacier, indicating the long-range atmospheric transport (LRAT) of these compounds.
Mostrar más [+] Menos [-]