Zeolite synthesized from fly ash (ZFA) without modification is not efficient for the purification of NH4+ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 (≥0.9 mol/L) resulted in a limited maximum phosphate immobilization capacity (PIC). It was concluded that through a previous mild acid treatment (e.g. 0.01 mol/L of H2SO4), ZFA can be used in the simultaneous removal of NH4+ and P at low concentrations simulating real effluent. 相似文献
The influences of relative humidity (RH) on the heterogeneous reaction of NO2 with soot were investigated by a coated wall flow tube reactor at ambient pressure. The initial uptake coefficient (γinitial) of NO2 showed a significant decrease with increasing RH from 7 to 70%. The γinitial on “fuel-rich” and “fuel-lean” soot at RH = 7% was (2.59 ± 0.20) × 10?5 and (5.92 ± 0.34) × 10?6, respectively, and it decreased to (5.49 ± 0.83) × 10?6 and (7.16 ± 0.73) × 10?7 at RH = 70%, respectively. Nevertheless, the HONO yields were almost independent of RH, with average values of (72 ± 3)% for the fuel-rich soot and (60 ± 2)% for the fuel-lean soot. The Langmuir-Hinshelwood mechanism was used to demonstrate the negative role of RH in the heterogeneous uptake of NO2 on soot. The species containing nitrogen formed on soot can undergo hydrolysis to produce carboxylic species or alcohols at high RH, accompanied by the release of little gas-phase HONO and NO.
This work provides insights on the solubilization products after a simultaneous combination of alkaline and ultrasonic(ALK + ULS) pre-treatment of sewage sludge.Soluble chemical oxygen demand(SCOD) increased from 1200 to 11,000 mg/L after such treatment. Organics with molecular weight around 5.6 k Da were solubilized because of the synergistic effect of ultrasound and alkali. Organics with molecular weight larger than300 k Da increased from 7.8% to 60%, 16% and 42.3% after ULS, ALK and ALK + ULS treatment, respectively. Excitation emission matrix fluorescence spectroscopy analysis identified soluble microbial product-like and humic acid-like matters as the main solubilization products. Sludge anaerobic biodegradability was significantly enhanced with the simultaneous application of ALK + ULS pre-treatment. ALK + ULS pre-treatment resulted in 37.8% biodegradability increase compared to the untreated sludge. This value was higher compared to the biodegradability increase induced by individual ALK pre-treatment(5.7%) or individual ULS pre-treatment(20.7%) under the same conditions applied. 相似文献
Biogenic volatile organic compounds (BVOCs) have significant effects on atmospheric chemistry, ozone formation and secondary organic aerosol formation. Considering few investigations about BOVCs emissions in north China where is facing serious air pollution in recent years, emissions of various BVOCs from 24 dominant forest species in Beijing were measured from June to September in 2018, using a dynamic headspace sampling method. More than one hundred BVOCs in the collected samples were identified by using an automatic thermal desorption-gas chromatography/mass spectrometry, and their emission rates based on leaf biomass were calculated. Isoprene and monoterpenes were verified to be the dominant BVOCs emitted from the tree species, accounting for more than 50% of the total BVOCs. Generally, broad-leaved species displayed high isoprene emission rates, especially the Platanus occidentalis (21.36 µg/(g?hr)), Robinia pseudoacacia (11.55 µg/(g?hr)), and Lonicera maackii (9.17 µg/(g?hr)), while coniferous species emitted high rates of monoterpenes, such as Platycladus orientalis (27.18 µg/(g?hr)), Pinus griffithii (23.11 µg/(g?hr)), and Pinus armandii (7.42 µg/(g?hr)). High emission rates of monoterpenes from the broad-leaved species of Buxus megistophylla (13.07 µg/(g?hr)) and Ligustrum vicaryi (5.74 µg/(g?hr)), and high isoprene emission rate from the coniferous tree of Taxus cuspidata (5.86 µg/(g?hr)) were also observed. The emission rates of sesquiterpenes from each tree were usually 10–100 times smaller than those of isoprene and monoterpenes. Additionally, relatively high emission rates of oxygenated volatile organic compounds and other alkenes than isoprene and monoterpenes were also found for several tree species. 相似文献
Due to freshwater supplement scarcity and heavy human activities, the fresh water wetland ecosystem in Yellow River Delta
is facing disintegrated deterioration, and it is seriously affecting the health of the Yellow River ecosystem. This paper
identifies the restoration objectives of wetland aiming to protect ecological and economic values and development as well
as the water resources of the Yellow River. The hydraulic and groundwater coupling model and Landscape Ecological Decision
and Evaluation Support System (LEDESS) of the Yellow River Delta were established to calculate environmental flows of degraded
wetlands. LEDESS is a computer-based model developed and used to assess and evaluate the effects of land-use changes on nature.
In this study, LEDESS is used to assess and evaluate the ecological effects and the restoration possibilities considering
several environmental flows’ supplement scenarios. This included the changes of suitable habitat conditions and its ecological
carrying capacities for indicator species, e.g., Red-crowned crane (Grus japonensis), Oriental stork (Ciconia boyciana), and Saunder’s gull (Larus relictus), and changing of ecological patterns. The results showed that replenishing fresh water to wetlands is one of the effective
adaptive measures to mitigate wetland degradation and improve its habitat quality and carrying capacities. This study indicated
that landscape ecology approach is not only considered as a good way to solve complex problems in ecosystem management but
also can be used to decide on the environmental flows and assess its ecological effects in large-scale wetland rehabilitation.
This integrated method could make environmental flows estimated and assessment more rational than the results of hydrologic
methods. It could assist decision makers to “see” the ecological effects after water supplementing and so alleviate the contradictions
between environmental flows and production water demands, and can facilitate the implementation of environmental flows in
most countries with water resources shortage. 相似文献