包头市水质自动监测站氨氮和高锰酸盐指数的比对分析

通过对内蒙古包头市环境监测站2012—2013年自动站监测的氨氮和高锰酸盐指数的监测结果和实验室手工监测结果进行比对,得出氨氮和高锰酸盐指数手工监测值和自动监测日均值、手工监测值和自动监测月均值无显著性差异且有显著线性关系,分析自动监测和手工监测结果的偏差产生的原因,氨氮、高锰酸盐指数自动监测与手工监测的比对相对误差的绝对值偏高,自动监测的结果作为定性参考值,定量必须采用实验室标准方法监测。     

Ammonia volatilization from a Chinese cabbage field under different nitrogen treatments in the Taihu Lake Basin, China

Ammonia(NH_3) volatilization is a major pathway of nitrogen(N) loss from soil-crop systems.As vegetable cultivation is one of the most important agricultural land uses worldwide,a deeper understanding of NH_3 volatilization is necessary in vegetable production systems.We therefore conducted a 3-year(2010–2012) field experiment to characterize NH_3 volatilization and evaluate the effect of different N fertilizer treatments on this process during the growth period of Chinese cabbage.Ammonia volatilization rate,rainfall,soil water content,p H,and soil NH_4~+were measured during the growth period.The results showed that NH_3 volatilization was significantly and positively correlated to topsoil p H and NH4+concentration.Climate factors and fertilization method also significantly affected NH_3 volatilization.Specifically,organic fertilizer(OF) increased NH_3 volatilization by 11.77%–18.46%,compared to conventional fertilizer(CF,urea),while organic–inorganic compound fertilizer(OIF) reduced NH_3 volatilization by 8.82%–12.67% compared to CF.Furthermore,slow-release fertilizers had significantly positive effects on controlling NH_3 volatilization,with a 60.73%–68.80% reduction for sulfur-coated urea(SCU),a 71.85%–78.97% reduction for biological Carbon Power~#174; urea(BCU),and a 77.66%–83.12% reduction for bulk-blend controlled-release fertilizer(BBCRF)relative to CF.This study provides much needed baseline information,which will help in fertilizer choice and management practices to reduce NH_3 volatilization and encourage the development of new strategies for vegetable planting.     

Mercury remediation potential of a mercury resistant strain Sphingopyxis sp. SE2 isolated from contaminated soil

A mercury resistant bacterial strain SE2 was isolated from contaminated soil.The 16 s rRNA gene sequencing confirms the strain as Sphingopyxis belongs to the Sphingomonadaceae family of the α-Proteobacteria group.The isolate showed high resistance to mercury with estimated concentrations of Hg that caused 50%reduction in growth(EC_(50)) of 5.97 and 6.22 mg/L and minimum inhibitory concentrations(MICs) of 32.19 and 34.95 mg/L in minimal and rich media,respectively.The qualitative detection of volatilized mercury and the presence of mercuric reductase enzyme proved that the strain SE2 can potentially remediate mercury.ICP-QQQ-MS analysis of the remaining mercury in experimental broths indicated that a maximum of 44%mercury was volatilized within 6 hr by live SE2 culture.Furthermore a small quantity(23%) of mercury was accumulated in live cell pellets.While no volatilization was caused by dead cells,sorption of mercury was confirmed.The mercuric reductase gene merA was amplified and sequenced.Homology was observed among the amino acid sequences of mercuric reductase enzyme of different organisms from a-Proteobacteria and ascomycota groups,     

Ammonia and greenhouse gas emissions from a subtropical wheat field under different nitrogen fertilization strategies

Minimizing soil ammonia (NH₃) and nitrous oxide (N₂O) emission factors (EFs) has significant implications in regional air quality and greenhouse gas (GHG) emissions besides nitrogen (N) nutrient loss. The aim of this study was to investigate the impacts of different N fertilizer treatments of conventional urea, polymer-coated urea, ammonia sulfate, urease inhibitor (NBPT, N-(n-butyl) thiophosphoric triamide)-treated urea, and nitrification inhibitor (DCD, dicyandiamide)-treated urea on emissions of NH₃ and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH₃ emission following N fertilization was characterized using active chamber method whereas GHG emissions of N₂O, carbon dioxide (CO₂), and methane (CH₄) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH₃-N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on N₂O-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH₃-N and N₂O-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO₂-C flux but had no effect on CH₄-C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH₃ and N₂O emissions in subtropical wheat production in Southern USA.     

Can further mitigation of ammonia emissions reduce exceedances of particulate matter air quality standards?

Several studies point out the importance of agricultural emissions to particulate matter (PM) concentrations, and particularly of NH₃ emissions to PM_2.5. Our study used three different chemical transport models (CHIMERE, EMEP and LOTOS-EUROS) to quantify the reductions of PM_2.5 and PM₁₀ concentrations due to reductions of NH₃ emissions beyond the Gothenburg Protocol (GP), as well as due to the GP alone compared to 2009. Simulations of PM_2.5 and PM₁₀ concentrations using 2009 meteorology were undertaken for five emission scenarios: 2009 emissions (as the reference simulation), GP emissions in 2020, and further 10%, 20% and 30% NH₃ emission reductions in EU27 beyond the GP. The modelling results for the scenarios with further 10%, 20% and 30% NH₃ agriculture emission reductions in EU27 beyond the GP show that the reduction achieved in PM concentrations is not linear with the emission reductions. In fact, the results from the study show that the impact of ammonia emissions reduction is significantly more efficient when the emission reduction rises. Moreover, based on the evaluation on 2009, the modelling study shows that the expected impact of ammonia emissions on the formation of particulate ammonium was underestimated by all models. This would imply that the role of ammonia on PM concentration and exceedances of PM_2.5 and PM₁₀ limit values is likely to be even larger than quantified in this study. This study shows that the implementation of the emission reductions imposed by the revised GP for 2020 will not suffice to achieve compliance with PM limit values everywhere in Europe; hence further European and local measures may be considered. NH₃ emissions from agriculture can be further reduced with the implementation of proven and feasible measures (substitution of fertilizers, improved storage of manure, way fertilizer injections, etc., …), in order to reduce PM concentrations and their impacts on human health across Europe.     

高炉洗气含氰废水除氰方法研究—气化分离与富集

本文用ＣＯ２气体气体化分离含氰废水中的氰，用乙醛等醛类吸收富集挥发出来的氰化氢而使氰以回收利用。气化分离除氰后，水中残余氰的浓度小于０．５ｐｐｍ。对醛类与ＨＣＮ反应的动力学和热力学性质的研究和吸收试验表明，乙醛等低分子醛能快速和完全地吸收气化分离出的ＨＣＮ，并得到α－羟基腈、羟基酸及其盐等系列产品。     

Impacts of pH and ammonia on the leaching of Cu(II) and Cd(II) from coal fly ash

Many coal-fired power plants are implementing ammonia-based technologies to reduce NO(x) emissions. Excess ammonia in the flue gas often deposits on the coal fly ash. Ammonia can form complexes with many heavy metals and change the leaching characteristics of these metals. This research tends to develop a fundamental understanding of the ammonia impact on the leaching of some heavy metals, exemplified by Cu(II) and Cd(II), under different pH conditions. Batch results indicated that the adsorption is the main mechanism controlling Cu(II) and Cd(II) leaching, and high concentrations of ammonia (>5,000 mg/l) can increase the release of Cu(II) and Cd(II) in the alkaline pH range. Based on the chemical reactions among fly ash, ammonia, and heavy metal ion, a mathematical model was developed to quantify effects of pH and ammonia on metal adsorption. The adsorption constants (logK) of Cu(2+), Cu(OH)(+), Cu(OH)(2), and Cu(NH(3))(m)(2+) for the fly ash under investigation were respectively 6.0, 7.7, 9.6, and 2.9. For Cd(II), these constants were respectively 4.3, 6.9, 8.8, and 2.6. Metal speciation calculations indicated that the formation of less adsorbable metal-ammonia complexes decreased metal adsorption, therefore enhanced metal leaching.     

Microbial fuel cell with three-dimensional electrodes for domestic wastewater treatment and electricity generation北大核心CSCD

A single chamber microbial fuel cell (MFC) with three-dimensional electrodes packed bed carbon felts was developed to treat domestic wastewater while simultaneously generating electricity. The influence of batch and continuous operation mode on treatment effectiveness and electricity production of the MFC was investigated to provide a reference for the application of the MFC. The MFC with a total working volume of 1 440 mL was operated in the fed-batch mode for 5 d repeatedly three times, and then shifted to the continuous mode. During the testing of the continuous mode, wastewater was continuously pumped into the anode compartment at a flow rate of approximately 0.2 mL/min, resulting in a hydraulic retention time of 5 d. During the batch test, the MFC obtained 91.1% chemical oxygen demand (COD) and 98.2% NH4 +-N removal, which accorded with the first criteria specified in the discharge standard of pollutants for municipal wastewater treatment plants in China (GB18918-2002). A maximum power density of 27.88 mW/m3 was achieved at a 51 Ω external resistor. During the continuous test, the COD removal efficiencies ranged from 83.2% to 97.4%. The concentration of NH4 +-N gradually decreased within 5 d and was then maintained below 9.45 mg/L, thus an enhanced removal performance of NH4 +-N was acquired. However, a low removal efficiency of total nitrogen was observed owing to the accumulation of NO3 --N in the effluent since day 11. Additionally, the MFC continually generated electricity with a maximum power density of 582.5 mW/m3 and average output voltage of 0.087 7 V during the stable period in the continuous operation mode. Moreover, 16S rRNA gene high-throughput sequencing showed that Thauera sp., Saprospiraceae-UN sp., and OPB56-UN sp. were identified as dominant populations. The results suggested that the organic matter associated with power generation was constantly utilized by the microorganisms in the reactor, which caused an excellent electricity generation performance during the continuous test. Therefore, the continuous operation mode could improve the low output voltage phenomenon in the MFC. Thauera sp., as a type of nitrate-reducing bacteria, was enriched in the autotrophic denitrifying microbial communities; therefore, bio-enrichment with denitrifying bacteria such as Thauera sp. could decrease the concentration of NO3 --N in the effluent during the continuous operation mode, which is expected to be an innovation for improvement of wastewater treatment. © 2018 Science Press. All rights reserved.     

A Relaxed Eddy Accumulation System for the Automated Measurement of Atmospheric Ammonia Fluxes

A continuous relaxed eddy accumulation system ispresented for the automated measurement of surface/atmosphere exchange fluxes of atmospheric ammonia (NH₃) at a single height. The new system features sampling by parallel plate denuder inlets, online chemical analysis using the conductivity cell of a commercially available NH₃ analyzer and online flux calculation. The effective detection limit of the system for air concentrations is 0.2 g m^-3 and it is estimated to resolve fluxes > ± 20 ng m^-2 s^-1, depending on the NH₃ concentration and turbulence. The performance of the system was tested in two measurement campaigns above agricultural grassland, in which it was compared with a 3-point continuous gradient system. During the first campaign, after urea application of 47 kg N ha^-1 in autumn, the REA system derived fluxes which were on average twice as large as the gradient fluxes, while concentrations agreed closely (on average within 4%). Possible reasons include differences in the footprint and an over-correction of the gradient flux in stable conditions. Due to wet and cold conditions, only 0.3% of the fertilizer N was volatilized as NH₃ during the first week. Results from the deployment of an improved system are presented for a summer day, 6 days after fertilization with calcium ammonium nitrate. The agreement of both concentrations (on average within 13%) and fluxes (26%) was very encouraging and similar to the agreement found between two state-of-the-art gradient systems with online analysis.     

Enhanced photoelectrocatalytic degradation of ammonia by in situ photoelectrogenerated active chlorine on TiO2 nanotube electrodes

TiO_2 nanotube(Ti NT) electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy(FE-SEM) and X-ray diffraction(XRD) were performed to characterize the TiNT electrodes. The linear voltammetry results under irradiation showed that the TiNT electrode annealed at 450°C presented the highest photoelectrochemical activity. By combining photocatalytic with electrochemical process, a significantly synergetic effect on ammonia degradation was observed with Na_2SO_4 as supporting electrolyte at pH 10.7. Furthermore, the photoelectrocatalytic efficiency on the ammonia degradation was greatly enhanced in presence of chloride ions without the limitation of pH. The degradation rate was improved by 14.8 times reaching 4.98 × 10~(-2) min~(-1) at pH 10.7 and a faster degradation rate of 6.34 × 10~(-2) min~(-1)was obtained at pH 3.01. The in situ photoelectrocatalytic generated active chlorine was proposed to be responsible for the improved efficiency. On the other hand, an enhanced degradation of ammonia using TiNT electrode fabricated in fluorinated organic solution was also confirmed compared to TiNT electrode anodized in fluorinated water solution and TiO_2 film electrode fabricated by sol–gel method. Finally, the effect of chloride concentration was also discussed.