Refinar búsqueda
Resultados 2101-2110 de 4,308
Ultrasonic Soil Washing with Fish Oil Extract to Remove Polychlorinated Dibenzo-p-dioxins (PCDDs), Dibenzofurans (PCDFs) from Highly Contaminated Field Soils Texto completo
2017
Vu, ChiThanh | Lin, Chitsan | Hung, Weiteng | Huang, Wen-Yen | Kaewlaoyoong, Acharee | Yotapukdee, Siwalee | Chen, Jenq-Renn | Shen, Yun-Hwei
PCDD/F-contaminated soil of a coastal region formerly involved in the production of pentachlorophenol (PCP) in Tainan City in southern Taiwan, has drawn wide concern throughout the island. This main goal of this study was to find an effective and environmentally friendly means of removing PCDD/Fs from its contaminated fields. We performed a soil washing experiment with fish extract using a combination of ultrasonification and mechanical double-blade stirring. The experiments were conducted under ambient temperature, at a soil/liquid ratio of 1:2.5, 700 rpm, and over a short duration. This combined method using fish extract removed 94.12% of the pollutant in moderately contaminated soils (5 washing cycles) and 94.51% in highly contaminated soils (10 washing cycles), mostly via particle collision and penetration. These findings highlight the benefits of PCDD/F partitioning between the particles and fish oil extract. This study is the first to use fish oil extract, a natural solvent, to treat soils highly contaminated with dioxins. Because fish oil extract is rich in non-toxic bio-surfactants (e.g., alcohols, acids, ketones, etc.), it may be used in this process to improve bioavailability and bioactivity of the soil making bio-attenuation and full remediation safer and more efficient.
Mostrar más [+] Menos [-]A review on the mechanism, risk evaluation, and prevention of coal spontaneous combustion in China Texto completo
2017
Kong, Biao | Li, Zenghua | Yang, Yongliang | Liu, Zhen | Yan, Daocheng
In recent years, the ecology, security, and sustainable development of modern mines have become the theme of coal mine development worldwide. However, spontaneous combustion of coal under conditions of oxygen supply and automatic exothermic heating during coal mining lead to coalfield fires. Coal spontaneous combustion (CSC) causes huge economic losses and casualties, with the toxic and harmful gases produced during coal combustion not only polluting the working environment, but also causing great damage to the ecological environment. China is the world’s largest coal producer and consumer; however, coal production in Chinese mines is seriously threatened by the CSC risk. Because deep underground mining methods are commonly adopted in Chinese coal mines, coupling disasters are frequent in these mines with the coalfield fires becoming increasingly serious. Therefore, in this study, we analyzed the development mechanism of CSC. The CSC risk assessment was performed from the aspects of prediction, detection, and determination of the “dangerous area” in a coal mine (i.e., the area most susceptible to fire hazards). A new geophysical method for CSC determination is proposed and analyzed. Furthermore, the main methods for CSC fire prevention and control and their advantages and disadvantages are analyzed. To eventually construct CSC prevention and control integration system, future developmental direction of CSC was given from five aspects. Our results can present a reference for the development of CSC fire prevention and control technology and promote the protection of ecological environment in China.
Mostrar más [+] Menos [-]Soil Contamination by Toxic Metals Near an Antarctic Refuge in Robert Island, Maritime Antarctica: A Monitoring Strategy Texto completo
2017
de Lima Neto, Elias | Guerra, Marcelo Braga Bueno | Thomazini, André | Daher, Mayara | de Andrade, André Medeiros | Schaefer, Carlos Ernesto G. R.
The anthropogenic effects of Antarctic refuge buildings and research stations on the surrounding soils are scarcely investigated, especially when the structures are small-sized, and sporadically used or visited. The Coppermine Peninsula (Robert Island, South Shetland Islands archipelago) possesses one of the richest flora in Antarctica, being classified as an Antarctic Specially Protected Area (ASPA). There, a small refuge (Luis Risopatrón) has been seasonally occupied for scientific purposes since 1957, although no studies on the anthropic disturbances in the surroundings soils are reported. The aim of this study was the determination of the potentially toxic metals (Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn) mass fractions in surface soils (n = 40) collected at the surroundings of the Luis Risopatrón refuge. Enrichment factors (EF) and geoaccumulation index (I gₑₒ) were also calculated, using Zr as the reference element, in order to evaluate the anthropogenic impacts of these small buildings in the studied area. The main contaminants were Pb and Zn, which presented EF and I gₑₒ values ranging from 1.0 to 18.3 and from −1.8 to 3.5. The mass fractions of these elements determined after an aqua regia extraction varied from 5.4 to 102 mg kg⁻¹ Pb and from 43 to 210 mg kg⁻¹ Zn. These results highlight that a small refuge can show environmental disturbance from low to moderate, with few hotspots with heavily contaminated soils. Environmental monitoring strategy for similar refuges anywhere in Antarctica is recommended.
Mostrar más [+] Menos [-]As and Cd Sorption on Selected Si-Rich Substances Texto completo
2017
Peng, Hua | Ji, Xionghui | Wei, Wei | Bocharnikova, Elena | Matichenkov, Vladimir
The processes of pollutant sorption by soil components control their mobility, migration, and transformation in the soil-plant system and depend on numerous properties, among which the elemental composition and surface area are dominant. In a laboratory experiment, the sorption of As and Cd by Si-rich substances differing in surface area, solubility of Si, and mineralogical composition was studied. The adsorption data were fitted to the linear, logarithmic, exponential, Langmuir, and Freundlich equations. Both size of the particles and mineral solubility of Si affected the As and Cd sorption. In the systems with lower initial concentrations of As and Cd, size of the particles had more pronounced effect on the sorption capacity. In the systems with high initial concentrations of As and Cd, the concentration of monosilicic acid was more significant than the surface area.
Mostrar más [+] Menos [-]Enhanced Arsenic Mobility in a Dystrophic Water Reservoir System After Acidification Recovery Texto completo
2017
Weiske, Arndt | Hegewald, Tilo | Werner, Ingo | Schaller, Jörg | Dudel, E Gert
Arsenic concentrations in a drinking water reservoir system in the Eastern Ore mountains (Osterzgebirge, Germany) were observed over a 17-year period. The region experienced an environmental change during the past 20 years with decreasing acid, sulphur and nitrogen deposition and a recovering vitality of forested catchment sites. An increase of the arsenic content in the reservoir waters during that change was observed. This was caused by a diminished nitrate supply leading to lower redox potential in the sediments favouring sediment arsenic release. The recent annual cycle in the Altenberg reservoir water arsenic concentration was found to be independent from artificial aeration of the hypoxic hypolimnion during the summer stratification. However, we found a strong seasonal dependent change in water As concentration, with a maximum in autumn and a minimum in spring. The low productive system is driven by peat derived organic matter. For the recent arsenic catchment yield coherencies to dissolved organic carbon export and runoff intensity were found, indicating rising arsenic loads due to climate-related soil organic matter destabilization. Thus, in the reservoir system, both dry and wet climate conditions can increase the water As concentrations due to an internal arsenic release and a catchment arsenic import.
Mostrar más [+] Menos [-]Chlorobenzene Release During Thermal Drying of Sludge: Mechanism and Source Texto completo
2017
Dai, Zhixi | Tian, Lixun | Liu, Chongxuan | Weng, Huanxin
A dispersive liquid–liquid microextraction (DLLME) method was optimized for the detection of chlorobenzene (CB) compounds in the drying process of municipal and dyeing sludge. Compared with traditional methods, the optimized DLLME not only has a lower limit of detection but also saves analysis time and requires less amount of organic solvent. Using this method in analyzing CB release during sludge drying, we found that drying temperature is the main factor controlling the amount of chlorobenzene release during sludge drying. In addition, we found that most CBs were released when sludge drying entered into the second falling rate stage, i.e., a period when sludge moisture content was low and temperature was high. By analyzing organic matter content in association with CB release during sludge drying, the relationship between organic matter transformation and chlorobenzene release was established. The results provide scientific basis and technical support for assessing the risks of the secondary pollution of CBs from sludge drying.
Mostrar más [+] Menos [-]Losses of Solids, Moisture, Nitrogen, Phosphorus, Potassium, Carbon, and Sulfur from Laying-Hen Manure in Storage Facilities Texto completo
2017
Lin, Xingjun | Zhang, Ruihong | Jiang, Shumei | El-Mashad, Hamed
The losses of total solids, moisture, nitrogen (N), phosphorus (P), potassium (K), carbon (C), and sulfur (S) were determined in two storage events of laying-hen manure immediately removed from three different housing systems in Iowa, USA. The three laying-hen houses were conventional cage (CC), enriched colony (EC), and aviary (AV). The houses held a nominal number of 200,000, 46,700, and 50,000 Lohmann LSL lite layers, respectively. The manure collected on belts in each house was cleaned out twice a week. A fraction of the cleaned out manure was transferred to designated storage rooms wherein losses of different components were determined in two storage events. Manure was loaded into the storage rooms over 171 days during the first storage event and over 185 days during the second storage event. The total storage periods were 202 and 245 days, respectively, for the first and second storage events. Manure was weighed, sampled, and analyzed before it was loaded into the storage rooms and at the end of each storage event. Mass balance calculations were used to determine the losses of different components. Statistical analyses show that the nutrient contents, on a wet basis, of manure loaded in CC, AV, and EC storage rooms were significantly different due to the differences in manure moisture contents. However, on a dry basis, they had no significant differences. The fresh manure cleaned out from the EC layer house was drier than that from the other two houses. Loaded-in nitrogen losses in the CC, AV, and EC storage rooms were 24.6, 12.9, and 20.8%, respectively. Nitrogen losses depended on house temperature, manure moisture, and pH. The average losses of loaded-in manure mass, moisture, and total solids during the two storage events were 27.6 ± 1.9, 33.8 ± 8.3, and 20.8 ± 7.0%, respectively. The losses of N, P, K, C, and S were 19.4 ± 13.4, 11.7 ± 5.6, 10.2 ± 6.8, 27.0 ± 6.5, and 8.3 ± 8.5% of their loaded-in amounts, respectively. The total loss of N, P, K, C, and S was 56% of the total loaded-in solids loss; thereof, the loss of N, P, and K was 7%, and C loss was 48%. The laying-hen-specific losses of N, P, K, C, and S were 0.34, 0.05, 0.08, 3.2 and 0.019 g day⁻¹ hen⁻¹, respectively. The results of this research are important for assessing impacts of stored manure on environment and nutrient losses. They can also be used to develop methodologies for the mitigation of the emissions from egg production facilities.
Mostrar más [+] Menos [-]Are distinct nitrous oxide emission factors required for cattle urine and dung deposited on pasture in western Canada? Texto completo
2017
Thomas, Ben W. | Gao, Xinlei | Beck, Ryan | Hao, Xiying
While some countries disaggregate N₂O emission factors for urine and dung deposited onto pastures, in Canada, distinct N₂O emission factors for beef cattle urine and dung have not been defined. To help address this knowledge gap, we conducted a 1-year study to quantify N₂O fluxes from beef cattle urine and dung patches on a semiarid tame pasture in western Canada, as well as to quantify the N₂O emission factors (EF3) for urine and dung as the percentage of applied N emitted as N₂O-N. Urine and dung were deposited when soil water-filled pore space was nearly 60%, a wet soil condition for the grazing season in the semiarid study region, which led to a burst of N₂O from urine in the first 14 days of the study (42% of total N emitted). Urine emitted more cumulative N₂O (P < 0.001) and had a greater N₂O emission factor (P = 0.002) than dung. The urine patch emitted 1.30 ± 0.47 g N₂O-N m⁻² year⁻¹, while the dung patch emitted 0.083 ± 0.020 g N₂O-N m⁻² year⁻¹ (mean values ± SD). The N₂O emission factor for urine was 1.32 ± 0.49%, while for dung it was 0.03 ± 0.02%. We conclude that more study is needed to determine if distinct N₂O emission factors are required for urine and dung deposited onto pasture in western Canada to more accurately estimate national N₂O inventories.
Mostrar más [+] Menos [-]Membrane Bioreactor (MBR) as Alternative to a Conventional Activated Sludge System Followed by Ultrafiltration (CAS-UF) for the Treatment of Fischer-Tropsch Reaction Water from Gas-to-Liquids Industries Texto completo
2017
Laurinonyte, Judita | Meulepas, RoelJ. W. | van den Brink, Paula | Temmink, Hardy
The potential of a membrane bioreactor (MBR) system to treat Fischer-Tropsch (FT) reaction water from gas-to-liquids (GTL) industries was investigated and compared with the current treatment system: a conventional activated sludge system followed by an ultrafiltration (CAS-UF) unit. The MBR and the CAS-UF systems were inoculated with municipal activated sludge and operated in parallel for 645 days with four interruptions using synthetic FT reaction water. Both treatment systems achieved a removal efficiency of 98 ± 0.1% within 60 days after inoculation, the COD influent concentration was 1014 ± 15 mg L⁻¹. This suggests that MBRs form a suitable alternative to CAS-UF systems for the treatment of FT reaction water from the GTL industries. Moreover, the total fouling rates (F ₜ) of the membranes used from day 349 till the end were assessed. The average F ₜ was 7.3 ± 1.0 10¹⁰ m⁻¹ day⁻¹ for CAS-UF membranes and 2.8 ± 00.7 10¹⁰ m⁻¹ day⁻¹ for MBR-MT membranes. This indicates that MBR systems for the treatment of FT reaction water from the gas-to-liquids industries are less prone to fouling than CAS-UF systems.
Mostrar más [+] Menos [-]Assessing Historical Mining and Smelting Effects on Heavy Metal Pollution of River Systems over Span of Two Decades Texto completo
2017
Strzebońska, Magdalena | Jarosz-Krzemińska, Elżbieta | Adamiec, Ewa
Research was conducted on the most polluted river system in Poland, impacted by active and historical mining. Bottom sediment, suspended particulate matter and river water were collected in 2014 from Przemsza river and its tributaries. Sampling points remained the same as those chosen in a 1995 study. This allowed the comparison of heavy metal accumulation in bottom sediment over a span of almost two decades. It was concluded that Przemsza river water and its tributaries are heavily contaminated with the following (in μg/dm³): Pb (0.99–145.7), Zn (48–5020), and Cd 0.12–12.72). Concentrations of metals in bottom sediment exceeded the background values by a factor of several hundred (100 times for Zn, 150 times for Pb, and 240 times for Cd). The arithmetic mean for metal concentration in fractions <63 μm sampled in 2014 has remained comparable to the level found in 1995 (in mg/kg): Zn 16,918 and 13,505, Pb 4177 and 4758, and Cd 92 and 134. It was determined that 20–50% more metals have accumulated in suspended matter, rather than in bottom sediment (in mg/kg): 20,498 Zn, Pb 5170, and 164 Cd. This exceeds the limits of the most polluted LAWA Class IV classification. Since the concentrations of Zn, Pb, and Cd increase drastically after the outlet of the Przemsza into the Vistula, it was concluded that river Przemsza is the cause of significant degradation of Vistula’s bottom sediment and suspended matter. A two-decade legacy of extremely high contamination of the Przemsza river sediments has persisted despite decreasing mining and smelting activity in the vicinity.
Mostrar más [+] Menos [-]