[Net ecosystem carbon exchange and its affecting factors in a deciduous broad-leaved forest in Songshan, Beijing, China]. / åŒ—äº¬æ¾å±±å¤©ç„¶è½å¶é˜”å¶æž—ç”Ÿæ€ç³»ç»Ÿå‡€ç¢³äº¤æ¢ç‰¹å¾åŠå ¶å½±å“å› å­.

Forests play an important role in terrestrial carbon cycles. The mechanism underlying carbon balance in temperate deciduous broad-leaved forests is not clear. In this study, net ecosystem exchange (NEE) and environmental factors, including air temperature (Ta), soil temperature (Ts), photosynthetically active radiation (PAR), vapor pressure deficit (VPD), soil water content (SWC) and precipitation (P) were continually measured using eddy covariance techniques in 2019 in a deciduous broad-leaved forest in Songshan, Beijing. We analyzed the characteristics of NEE and its response to environmental factors. The results showed that, at diurnal scale, the monthly averaged NEE exhibited a "U" shape curve (i.e., being a carbon sink over daytime while being a carbon source during nighttime) over the growing season. During the non-growing season, NEE was positive (i.e., carbon source) at diurnal scale. At the seasonal scale, NEE exhibited a unimodal curve. The annual cumulative NEE was -111 g C·m-2·a-1. Annual ecosystem respiration was 555 g C·m-2·a-1, while gross ecosystem productivity was 666 g C·m-2·a-1. Carbon sequestration peaked in June, while emission peaked in November. PAR was the dominant factor affecting daytime NEE (NEEd). VPD was the main factor that indirectly affected daytime NEEd, with an optimal VPD value that maximizes daytime NEE around 1-1.5 kPa. Soil temperature was the main factor affecting nighttime NEE (NEEn). SWC was a limiting factor for NEEn. Too high or too low SWC would inhibit NEEn, with an optimal SWC value of 0.28 m3·m-3.

[Changes in Heavy Metal Speciation and Release Behavior Before and After Sludge Composting Under a Phosphate-rich Atmosphere].

Sewage sludge is rich in organic matter, N, and P and could be used as a soil amendment to improve the status of soil organic matter, soil structural characteristics, and soil water retention capacity after aerobic composting. However, heavy metals in sewage sludge have become the main bottleneck limiting its land application. In addition, with the large-scale exploitation of phosphate rock resources in our region of interest, a large amount of phosphate tailings needs to be disposed and a large area of abandoned mining lands needs to be reclaimed. Phosphate tailings could be auxiliary materials for sewage sludge composting to immobilize heavy metals, and the compost could be applied for revegetation of the abandoned mining lands. The contents of As, Cr, Cu, Ni, Pb, Cd, and Zn were measured, and a successive extraction procedure was used to investigate the change in speciation of heavy metals in the sludge before and after the phosphate-rich composting. pH-dependent leaching tests were carried out to further evaluate the immobilization effects of composting on heavy metals and the release potential under different pH conditions. The results showed that the contents of heavy metals in the compost satisfied the corresponding threshold for land reclamation. Adding phosphate tailings greatly improved the stability of heavy metals during the composting process. The portion of stable residues of Pb, Cd, As, and Zn in the phosphate-rich compost was 84.00%, 58.00%, 68.50%, and 30.93%, respectively, compared with 68.10%, 30.50%, 40.32%, and 16.48% for the control, compost without adding the phosphate tailings. Meanwhile, the maximum leaching potential of As, Ni, Pb, Zn, and Cu in the phosphate-rich compost decreased from 3.692 mg·kg-1, 0.903 mg·kg-1, 0.217 mg·kg-1, 7.225 mg·kg-1, and 8.725 mg·kg-1 to 0.684 mg·kg-1, 0.586 mg·kg-1, 0.071 mg·kg-1, 2.603 mg·kg-1, and 6.935 mg·kg-1in the control, respectively, for pH 6-8.It could be concluded that the addition of phosphate tailings in the sludge composting lowered the risk of heavy metals in sewage sludge compost to make it favorable for beneficial use in abandoned mining land reclamation.

[Comparison of Different Leaching Methods for Heavy Metals in Sludge Fly Ash and Comprehensive Toxicity Evaluation].

Fly ash from sludge incineration was separated into five different sizes (<1 µm, 1-2.5 µm, 2.5-10 µm, 10-50 µm, and > 50 µm) by high-precision air classification equipment. The leaching of heavy metals was contrastively studied using the HJT 299-2007-sulfuric acid/nitric acid method, HJ 557-2009-Horizontal Oscillation Method, toxicity characteristic leaching procedure (TCLP), and European standard protocol (EN 12457-3) for the different size fractions of the fly ash. Based on the leaching results, an evaluation method for the comprehensive toxicity of heavy metal leaching was established. The results show that the content of heavy metals and the amount of leaching from the fly ash decrease with the increase in fly ash particle size. The leaching of the heavy metals Zn and Cu in the < 1 µm particle size range of TCLP leaching method was the highest, at 107.34 mg·kg-1 and 318 mg·kg-1, respectively. The TCLP and sulfuric acid/nitric acid methods of heavy metal leaching were more effective than the EU (EN 12457-3) and horizontal oscillation methods. According to the value of OPTI, the OPTI value of < 10 µm fly ash was much larger than that of fly ash that was > 10 µm. This indicated that the fly ash of particle size < 10 µm was more toxic and more harmful.

[Effects of ultrasonic pretreatment on drying characteristics of sewage sludge].

The high water content of sewage sludge has engendered many inconveniences to its treatment and disposal. While ultrasonic takes on unique advantages on the sludge drying because of its high ultrasonic power, mighty penetrating capability and the ability of causing cavitations. Thus this research studies the characteristics influences of ultrasonic bring to the sludge drying and effects of the exposure time, ultrasonic generator power, temperatures of ultrasonic and drying temperature on the drying characteristics of dewatered sludge. Results indicate that ultrasonic pretreatment could speed up evaporation of the free water in sludge surface and help to end the drying stage with constant speed. In addition, ultrasonic treatment can effectively improve the sludge drying efficiency which could be more evident with the rise of the ultrasonic power (100-250 W), ultrasonic temperature and drying temperature. If dried under low temperature such as 105 degrees C, sludge will have premium drying characteristics when radiated under ultrasound for a shorter time such as 3 min. In the end, the ultrasonic treatment is expected to be an effective way to the low-cost sludge drying and also be an important reference to the optimization of the sludge drying process because of its effects on the increase of sludge drying efficiency.

[Effect of additive and washing pre-treatment on heavy metal vaporization during sintering process of MSWI fly ash].

An experimental work was carried out to investigate the effect of additives (clay and coal fly ash) and washing-pretreatment on the stabilization of critical heavy metals (Cd, Cu, Zn, Pb, Cr, Ni) during a sintering process of municipal solid waste incinerator (MSWI) fly ash. The proportions of the three constituents were varied to adjust the mixture compositions. The washing time were 8 h, 16 h and 24 h. The material was compacted in cylindrical specimens at 3 kN and treated at 1,100 degrees C for 4 h. When the clay content was increased to 70%, the stabilized ratio was increased from 16.96% to 28.42% for Cd, from 10.58% to 37.02% for Pb, from 46.38% to 55.14% for Cu, from 42.14% to 64.47% for Zn, but the stabilized ratio of Ni and Cr was decreased. When coal fly ash was increased in the MSWI fly ash, the stabilized ratio was decreased from 16.96% to 4.67% for Cd, increased from 46.86% to 81.43% for Cu, but the addition of coal fly ash did not increased the stabilized ratio of Zn, Pb, Ni and Cr. Washing pre-treatment increased the stabilized ratio of Cd, Cu and Pb significantly. The leaching behavior of the heavy metals in the sintered products was studied by the toxicity characteristic leaching procedure (TCLP), the results showed that the leaching concentration of the six heavy metals were very low.

[PAHs of source separation household organic waste and composting production].

Composing treatments of source separation (SS) household bio-organic waste and straw mixed in 10:1, 16 kinds of PAHs in source separation household bio-organic waste and compost production were determined by gas chromatograph/mass spectrograph (GC-MS) according to U.S.EPA 8270 standard method. Comparing 16 kinds of PAHs content, distributing and biodegradability,we evaluated the PAHs risk in farmland and discoursed the impact factors of PAHs biodegradability in household bio-organic waste composting. The results show that SigmaPAH16 contents in source separation household bio-organic waste and composting production is 2.19 and 1.96 mg/kg DM, and the contents of naphthalene, fluorene, phenanthrene, fluoranthene are relatively higher than others. The percent of these four organic pollutions is 79.76% and 81.76% in PAH16, respectively. The benzene loop number of these four organic pollutions is 2-3, and it' s easily degradable non-carcinogen in farmland utilization. SigmaPAH16 biodegradability is 25.88%, and the content of PAHs in SS household bio-organic waste compost production fits the farmland utilization criteria.

[Experimental study on methane potentials of source-separated BMW and individual waste materials].

A laboratory procedure is described for measuring methane potentials of source-separated bio-organic municipal waste (BMW). Triplicate reactors with about 20 grams fresh material were incubated at 37 degrees C with 300 mL inoculum from Shenyang wastewater treatment plant and the methane production was followed over a 50 d period by regular measurement of methane on a gas chromatograph. At 37 degrees C, the methane production efficiency of source-separated BMW and individual waste materials was: starch > BMW > protein > food oil > fat > paper. For the source-separated BMW,starch,protein,food oil,fat and paper, the methane potential (CH4/VS) of 218.15, 209.11, 194.20, 238.86, 257.82 and 131.41 mL/g were found,and ultimate biodegradability of 6 difference materials were 67.73%, 72.88%, 65.84%, 78.38%, 74.11% and 47.98%, respectively.

[Migration characteristics of heavy metals during pilot melting process of incineration fly ash].

The characteristics of heavy metals (Cd, Pb, Zn, Cu, Cr and Ni) were studied during pilot melting process of waste incineration fly ash, and it mainly focused on the solidification of those heavy metals in molten slag. The experiment factors include temperature (1290 degrees C, 1320 degrees C and 1360 degrees C), additive (10% glass powder), slag cooling mode(water or air cooling), whose influence on the heavy metals' solidification in the molten slag was studied. The result shows: the solidification of the heavy metals (Pb, Zn, Cu, Cr and Ni) increase on certain degree with temperature's increasing; Adding 10% glass powder makes the solidification of heavy metals increase greatly except Zn; For Zn, Cu, Cr and Ni, the solidification using air cooling mode is higher than that using water cooling mode.

[Migration characteristics of heavy metals during sintering of fly ash from municipal solid waste incinerator].

The sintering process is used to stabilize the heavy metal in fly ash from municipal solid waste incinerator (MSWI). Migration characteristics of 6 targeted heavy metals (Cd, Pb, Cu, Ni, Cr and Zn) in the sintering process of MSWI fly ash were investigated by experiments. Effect of several factors including sintering temperature, residence time, molding pressure and particle diameter on the migration of heavy metals were discussed in details. The results show that cadmium and lead are volatile metals, while nickel, copper, chromium and zinc belong to involatilizable metals. The effects of sintering temperature, residence time, molding pressure and particle diameter on the stabilizing efficiency differ from each other. The study shows that most of heavy metals are stabilized during the sintering process. The stabilizing efficiency of heavy metals was different for different elements.

[Influence of liquid ceramic additive on binding of heavy metal during the vitrification of fly ash from municipal solid waste incinerator].

Vitrification process can effectively control the leachability of heavy metals in fly ash generated from municipal solid waste incinerator (MWSI). The use of liquid ceramic (LC) additive as a heavy metal chemical stabilization agent was evaluated for MSWI fly ash. The residuals of chromium, lead and zinc in slag increase by different degree with liquid ceramic additive at 1400 degrees C, while those of cadmium and copper decreases. The migrating characteristic of nickel is hardly affected by the additive less than 10%. The volatilization of Cr and Zn occurs after 61 minute with 10% addition of LC, and the binding efficiency of Cr decreases with increasing of melting temperature. The results indicate that the binding efficiency of heavy metals was affected greatly by LC additive and showed significant differences according to type of heavy metal during melting process. The short melting time (no longer than 33 min) is useful to obtain high binding efficiency of heavy metals.

[Influence of additives on decomposition of PCDD/Fs during MSWI fly ash melting process].

The melting process of municipal solid waste incinerator (MSWI) fly ash was investigated in order to study the influence of additives on decomposition characteristics of dioxins (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans, PCDD/Fs). The melting treatment of MWSI fly ash was performed at a batch-melting furnace with two types of additives, CaO and liquid ceramic (LC), at different melting temperatures, melting atmospheres and treatment times. The results demonstrate that the effect of CaO on PCDD/Fs' decomposition changed with the type of atmosphere. The decomposition and removal efficiency (DRE) of dioxins increased slightly with 20% CaO in an oxidative atmosphere, while it decreased obviously in an inert atmosphere. There is an important influence by liquid ceramic on the decomposition of PCDD/Fs. The DRE of PCDD/Fs in MSWI fly ash increased from 99.997% to 100% with the addition of LC increasing from zero to 10% at 1400 degrees C. The temperature, in which the PCDD/Fs were completely decomposed, decreased from 1460 degrees C to 1100 degrees C when 10% LC was added into fly ash.