Glass recycling in cement production--an innovative approach

An innovative approach of using waste glass in cement production was proposed and tested in a laboratory and cement production plant. The laboratory characterization of 32 types of glass show that the chemical composition of glass does not vary significantly with its color or origin but depends on its application. The alkali content of glass, a major concern for cement production varies from 0 to 22%. For the glass bottles mainly found in Hong Kong waste glasses, the alkali content (Na2O) ranges from 10 to 19% with an average around 15%. There is no significant change of the SO2 content in the gas exhaust of the rotary kiln when about 1.8 t/h of glass bottles were loaded along with the 280-290 t/h raw materials. The content of NOx, mainly depends on the temperature of the kiln, does not show significant change either. The SO3 content of the clinker is comparable with that obtained without the loading of glass. The alkaline content shows a slight increase but still within three times the standard deviation obtained from the statistical data of the past year. The detailed analysis of the quality of the cement product shows that there is not any significant impact of glass for the feeding rate tested.     

城市污泥堆肥中水溶性有机物的理化特性变化

通过透析和XAD-8树脂等方法研究了城市污泥堆肥过程中水溶性有机物(DOM)的理化特性变化.结果表明,随着堆肥的进行,堆肥DOM的浓度和pH值分别降低了58.4%和9.5%;DOM中小分子组分和亲水性组分分别减少了13.1%和9.2%,而大分子组分与疏水性组分有所增加,疏水性组分/亲水性组分由0.89增至1.29;DOM中C、H、N、S含量和C/H、C/N、C/S、C/(N+S)均呈降低趋势.这些变化趋势与堆肥过程中有机物的变化规律一致,因此,堆肥DOM的理化特性能用以表征堆肥的腐熟度.     

Surfactant-induced changes in gravity fingering of water through a light oil

Gravity-driven preferential flow (fingering) can greatly affect how one fluid displaces another in the subsurface. We have studied the internal properties of these preferential flow paths for water, with and without surfactants, infiltrating into oil saturated porous media using synchrotron X-rays, and miniature tensiometers to characterize fluid content and pressure relationships. We also used a light transmission technique to visualize overall flow pattern. Capillary pressure and water content decrease behind the front, similar to fingers in air-dry sand, with quantitative differences for five different surfactants with surface tensions ranging from 4–21 g/s². Using unstable flow theory, the finger widths, capillary pressure drops within the fingers, finger tip lengths, and finger splitting dynamics were scaled successfully with interfacial tension, fluid density, and the contact angle using the fingers in air–water systems as the reference.     

Variations between rice cultivars in root secretion of organic acids and the relationship with plant cadmium uptake

To attempt to understand certain mechanisms causing the variations between rice cultivars with regard to Cd uptake and accumulation, pot soil experiments were conducted with two rice cultivars at different levels of Cd, i.e., 0 (the control), 10, 50 mg Cd kg⁻¹ soil. The two rice cultivars differ significantly with regard to Cd uptake and accumulation. Root secretions of low-molecular-weight organic acids (LMWOA) for each treatment were measured with ion chromatography. The results showed that LMWOA concentrations in the soil planted with Shan you 63 (a high soil Cd accumulator) were all higher than those in the soil planted with Wu yun jing 7 (low soil Cd accumulator) at different soil Cd levels, although the magnitudes of the differences varied for individual LMWOA and depend on soil Cd concentrations. For all six LMWOA, there were significant differences at P < 0.05 or < 0.01 levels for soils treated with 10 and 50 mg kg⁻¹ Cd. The magnitude of the differences was greater under soil Cd treatments, especially at relatively low levels (for example, 10 mg Cd kg⁻¹ soil), than in the control. Acetic acid and formic acid constituted more than 96% of the total concentration of the six LMWOA, while citric acid constituted only about 0.1%. The rice cultivar with higher concentrations of LMWOA in soil accumulated more Cd in the plants. The results indicate that LMWOA secretion by rice root, especially in Cd-contaminated soils, is likely to be one of the mechanisms determining the plant Cd uptake properties of rice cultivars.     

Variations in the chemical properties of landfill leachate

Landfill leachates were collected and their chemical properties analyzed once every two months over a ten-month period from the Gin Drinkers' Bay (GDB) and Junk Bay (JB) landfills. The contents of solids, and inorganic and organic components fluctuated considerably with time. In general, the chemical properties of the two leachates correlated negatively (P<0.05) with the amounts of rainfall prior to the sampling periods. However, magnesium and pH of the leachates remained relatively constant with respect to sampling time. The JB leachate contained higher average contents of solids and inorganic and organic matter than those of GDB with the exception of trace metals. Trace metals were present in the two leachates in trace quantities (<1.0 mg/liter). The concentrations of average ammoniacal nitrogen were 1040 and 549 mg/liter, while chemical oxygen demand (COD) values were 767 and 695 mg/liter for JB and GDB leachates, respectively. These results suggest that the leachates need further treatment before they can be discharged to the coastal waters.     

Comparison of trace metal contents of sediments and mussels collected within and outside Tolo Harbour,Hong Kong

Sediments collected from Tap Mun (within Tolo Harbour) and Yim Tin Tsai (outside Tolo Harbour) were extracted sequentially and the copper, cadmium, and chromium contents were determined. Total contents of copper, cadmium, chromium, and arsenic were also detected by acid digestion. The level of heavy metal extracted was higher in sequential extraction (which extracted all forms of metal ions) than total acid digestion. Among the four heavy metals studied, only copper showed a significantly higher (P<0.001) level in samples collected from Yim Tin Tsai (16.10 mg/kg) than that from Tap Mun (3.19 mg/kg). Such a difference in copper level is mainly attributed to the significantly higher (P<0.05) levels of copper in the organic, carbonate, and sulfide forms, whereas there was no significant difference (P>0.05) in the exchangeable and sorbed forms. Green-lipped mussel (Perna viridis) samples collected from the two sites were dissected into seven parts (gill, byssus, siphon, shell, digestive gland, soft tissue, and adductor muscle) and the concentrations of copper, cadmium, chromium, and arsenic were measured. The highest concentration of copper was obtained in the byssus. A higher concentration of copper was also noted in the mussels collected from Yim Tin Tsai than those collected from Tap Mun. No specific trend was revealed for the other metals tested. Chromium and arsenic concentrations were found to be independent of the body size of the mussels. Copper had a lower concentration in larger mussels and cadmium level was found to decrease with size. In addition, the mussels collected from Tap Mun were much larger than those collected from Yim Tin Tsai.     

Structural and photocatalytic properties of TiO2 films fabricated on silicon substrates by MOCVD method

Silicon(111) and Silicon(100) were employed for fabrication of TiO2 films by metal organic chemical vapor deposition( MOCVD).Titanium(Ⅳ) isopropoxide(Ti[O(C3H7)4]) was used as a precursor. The as-deposited TiO2 films were characterized with FE-SEM, XRD and AFM. The photocatalytic properties were investigated by decomposition of aqueous Orange Ⅱ. And UV-VlS photospectrometer was used for checking the absorption characteristics and photocatalytic degradation activity. The crystalline and structural properties of TiO2 film had crucial influences on the photodegradation efficiency. For MOCVD in-situ deposited films on Si substrates, the photoactivities varied following a shape of “M”: at Iower(350℃ ), middle(500℃ ) and higher(800℃ ) temperature of deposition, relative lower photodegradation activities were observed. At 400% and 700% of deposition, relative higher efficiencies of degradation were obtained, because one predominant crystallite orientation could be obtained as deposition at the temperature of two levels, especially a single anatase crystalline TiO2 film could be obtained at 700℃.     

Metal removal studied by a laboratory scale immobilized microalgal reactor

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环境污染系统的灰色投入产出模型

将投入产出模型与灰色理论结合起来，建立了以灰色预测为基础的环境污染系统灰色投入产出模型，探索了如何从污染物总量控制目标出发来规划和发展生产。     

Ecological restoration of mine degraded soils,with emphasis on metal contaminated soils

This paper reviews the ecological aspects of mined soil restoration, with special emphasis on maintaining a long-term sustainable vegetation on toxic metal mine sites. The metal mined soils are man-made habitats which are very unstable and will become sources of air and water pollution. Establishment of a vegetation cover is essential to stabilize the bare area and to minimize the pollution problem. In addition to remediate the adverse physical and chemical properties of the sites, the choice of appropriate vegetation will be important. Phytostabilization and phytoextraction are two common phytoremediation techniques in treating metal-contaminated soils, for stabilizing toxic mine spoils, and the removal of toxic metals from the spoils respectively. Soil amendments should be added to aid stabilizing mine spoils, and to enhance metal uptake accordingly.