Phosphorus (P) in agricultural ecosystems is an essential and limited element for plants and microorganisms. However, environmental problems caused by P accumulation as well as by P loss have become more and more serious. Oxygen isotopes of phosphate can trace the sources, migration, and transformation of P in agricultural soils. In order to use the isotopes of phosphate oxygen, appropriate extraction and purification methods for inorganic phosphate from soils are necessary. Here, we combined two different methods to analyze the oxygen isotopic composition of inorganic phosphate (δ18OP) from chemical fertilizers and different fractions (Milli-Q water, 0.5 mol L?1 NaHCO3 (pH = 8.5), 0.1 mol L?1 NaOH and 1 mol L?1 HCl) of agricultural soils from the Beijing area. The δ18OP results of the water extracts and NaHCO3 extracts in most samples were close to the calculated equilibrium value. These phenomena can be explained by rapid P cycling in soils and the influence of chemical fertilizers. The δ18OP value of the water extracts and NaHCO3 extracts in some soil samples below the equilibrium value may be caused by the hydrolysis of organic P fractions mediated by extracellular enzymes. The δ18OP values of the NaOH extracts were above the calculated equilibrium value reflecting the balance state between microbial uptake of phosphate and the release of intracellular phosphate back to the soil. The HCl extracts with the lowest δ18OP values and highest phosphate concentrations indicated that the HCl fraction was affected by microbial activity. Hence, these δ18Op values likely reflected the oxygen isotopic values of the parent materials. The results suggested that phosphate oxygen isotope analyses could be an effective tool in order to trace phosphate sources, transformation processes, and its utilization by microorganisms in agricultural soils. 相似文献
Wastewater treatment plants (WWTPs) have been recognized as important sources for anthropogenic greenhouse gas (GHG) emission. The objective of the study was to thoroughly investigate a typical industrial WWTP in southern Taiwan in winter and summer which possesses the emission factors close to those reported values, with the analyses of emission factors, mass fluxes, fugacity, lab-scale in situ experiments, and impact assessment. The activated sludge was the important source in winter and summer, and nitrous oxide (N2O) was the main contributor (e.g., 57 to 91 % of total GHG emission in a unit of kg carbon dioxide-equivalent/kg chemical oxygen demand). Albeit important for the GHGs in the atmosphere, the fractional contribution of the GHG emission to the carbon or nitrogen removal in wastewater treatment was negligible (e.g., less than 1.5 %). In comparison with the sludge concentration or retention time, adjusting the aeration rate was more effective to diminish the GHG emission in the activated sludge without significantly affecting the treated water quality. When the aeration rate in the activated sludge simulation was reduced by 75 %, the mass flux of N2O could be diminished by up to 53 % (from 9.6 to 4.5 mg/m2-day). The total emission in the WWTP (including carbon dioxide, methane, and N2O) would decrease by 46 % (from 0.67 to 0.36 kg CO2-equiv/kg COD). However, the more important benefit of changing the aeration rate was lowering the energy consumption in operation of the WWTP, as the fractional contribution of pumping to the total emission from the WWTP ranged from 46 to 93 % within the range of the aeration rate tested. Under the circumstance in which reducing the burden of climate change is a global campaign, the findings provide insight regarding the GHG emission from treatment of industrial wastewater and the associated impact on the treatment performance and possible mitigation strategies by operational modifications.
Environmental Science and Pollution Research - Improved understanding of the fractionation and geochemical characteristic of rare earth elements (REEs) from steel plant emissions is important due... 相似文献
A simple online headspace solid-phase microextraction (HS-SPME) coupled with the gas chromatography-mass spectrometry (GC-MS) method was developed for simultaneous determination of trace amounts of nine estrogenic odorant alkylphenols and chlorophenols and their derivatives in water samples. The extraction conditions of HS-SPME were optimized including fiber selection, extraction temperature, extraction time, and salt concentration. Results showed that divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was the most appropriate one among the three selected commercial fibers, and the optimal extraction temperature, time, and salt concentration were 70 °C, 30 min, and 0.25 g/mL, respectively. The developed method was validated and showed good linearity (R2?>?0.989), low limit of detection (LOD, 0.002–0.5 μg/L), and excellent recoveries (76–126 %) with low relative standard deviation (RSD, 0.7–12.9 %). The developed method was finally applied to two surface water samples and some of these target compounds were detected. All these detected compounds were below their odor thresholds, except for 2,4,6-TCAS and 2,4,6-TBAS wherein their concentrations were near their odor thresholds. However, in the two surface water samples, these detected compounds contributed to a certain amount of estrogenicity, which seemed to suggest that more attention should be paid to the issue of estrogenicity rather than to the odor problem. 相似文献
An assessment of the heavy metal content and biological pollution burden of an abattoir dumpsite, an automobile carwash, the Ikpoba River, and a private water borehole located near the abattoir dumpsite was conducted in Benin City in Southern Nigeria, during the rainy and dry seasons. The water samples’ pH was lower than the permissible values, with the river water displaying color and possessing a slight odor. Iron concentrations exceeded the permissible limits for drinking water at all four of the sampling stations in the study area, although not in samples collected from the control station, station 5, a public water borehole that is located some distance away. Lead values were higher than drinking water standards in the samples collected from stations 1 through 4, with some exceptions during the rainy season. Copper, nickel, arsenic, chromium, and aluminum were detected in three out of the four sampling stations located within the study area. However, these metals were detected at levels that were within regulatory limits. The detection of three metals (iron, lead, and zinc) within the study area at levels exceeding drinking water limits suggested that a complete cycle of movement of pollutants into the sampling stations had occurred. Significant biological presences were also detected, as the Ikpoba River water had a standard plate count (SPC) of 130 most probable number (MPN) and a 22 MPN presumptive coliform count (PCC) or 22 MPN. However, Escherichia coli (E. coli) confirmatory tests recorded less than 2 MPN in both seasons. The study has shown that the quality of water in the river may be compromised by effluent discharges from the dumpsite and the carwash channel. Therefore, this situation requires more stringent enforcement of local environmental laws and maintenance of safe distances between domestic and industrial waste sources and domestic or private water wells. 相似文献
This work highlights the evolution of flood disasters and their impacts upon environmental and socioeconomic aspects both worldwide and in Small Island Developing States (SIDS) in particular. For our research, we reviewed the stress factors affecting flood disasters and performed surveys of two focus groups in Funchal municipality on Madeira Island (Portugal). Our research identifies the main causes of the serious impacts that flash floods can have on Funchal city. These include:
The occupation of floodplain areas,
Canalization of water courses,
Erosion and transport of soil from upstream hillslopes due to deforestation, and
Generally, one expects evapotranspiration (ET) maps derived from optical/thermal Landsat and MODIS satellite imagery to improve decision support tools and lead to superior decisions regarding water resources management. However, there is lack of supportive evidence to accept or reject this expectation. We “benchmark” three existing hydrologic decision support tools with the following benchmarks: annual ET for the ET Toolbox developed by the United States Bureau of Reclamation, predicted rainfall‐runoff hydrographs for the Gridded Surface/Subsurface Hydrologic Analysis model developed by the U.S. Army Corps of Engineers, and the average annual groundwater recharge for the Distributed Parameter Watershed Model used by Daniel B. Stephens & Associates. The conclusion of this benchmark study is that the use of NASA/USGS optical/thermal satellite imagery can considerably improve hydrologic decision support tools compared to their traditional implementations. The benefits of improved decision making, resulting from more accurate results of hydrologic support systems using optical/thermal satellite imagery, should substantially exceed the costs for acquiring such imagery and implementing the remote sensing algorithms. In fact, the value of reduced error in estimating average annual groundwater recharge in the San Gabriel Mountains, California alone, in terms of value of water, may be as large as $1 billion, more than sufficient to pay for one new Landsat satellite. 相似文献