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101.
城市污泥堆肥中水溶性有机物的理化特性变化   总被引:13,自引:1,他引:12  
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.  相似文献   
102.
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.  相似文献   
103.
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.  相似文献   
104.
Arsenic, cadmium, chromium, and copper concentrations of the Pacific oyster,Crassostrea gigas, purchased from four different markets were determined in this project. In general, gill tissue had the highest proportion of metal contents (34%–67%) when compared with other tissue parts (mantle, viscera, and adductor muscle), except for arsenic, which showed the highest level in adductor muscle (44%). Smaller oysters (longitudinal length of soft body part less than 6 cm) had higher metal levels than larger ones (longitudinal length of soft body part more than 6 cm), except copper. None of the four metals examined showed an obvious seasonal trend, although cadmium levels seemed to be higher in autumn and winter months. Arsenic, cadmium, and copper levels in oysters purchased from different markets and different months obtained in the present study were higher when compared with past reports. Cadmium levels, as high as 10.98 mg/kg (dry weight basis) have been obtained. This approaches the safety limit that may be hazardous to human health. Continual monitoring of cadmium and other trace metals of toxicological significance to man in Hong Kong seafood is recommended.  相似文献   
105.
Co-cropping for phyto-separation of zinc and potassium from sewage sludge   总被引:2,自引:0,他引:2  
Wu QT  Hei L  Wong JW  Schwartz C  Morel JL 《Chemosphere》2007,68(10):1954-1960
The use of sewage sludge as a fertilizer and soil amendment has resulted in high concentrations of heavy metals in the soil limiting its use. The present study was carried out to find the possibility of phyto-separating toxic and beneficial elements from the sludge using suitable plants. Of the five plants tested the hyperaccumulator Sedum alfredii H achieved the greatest removal of Zn, while shoots of Alocasia marorrhiza accumulated high content of K. Co-cropping these two plants on the sludge verified the previous observations on A. marorrhiza and the shoots of this plant could accumulate more than 120 g K kg(-1) dry matter in the median growth stage. Zn hyperaccumulated in Sedum's shoots to an extent more than 10 g kg(-1) dry matter; K concentrated five to ten times in the Alocasia's shoots which could be used as a good organic-K-fertilizer. Hence, the two elements were simultaneously phytoseparated and could be recycled. Furthermore, cultivation of plants in the sludge resulted in significant decreases in total Zn but kept the favorable agronomic characteristics of the sludge material, such as pH, organic matter content, and NPK concentrations and ameliorated its biological stability. These results suggest that simultaneous phyto-separation of toxic and beneficial elements from sewage sludge are possible by co-cropping using specific plants without the input of any chemicals.  相似文献   
106.
Cheung KC  Leung HM  Kong KY  Wong MH 《Chemosphere》2007,66(3):460-468
Axial and ventral muscle from 10 each species of freshwater and marine fish purchased from markets in Hong Kong were analyzed for dichlorodiphenyltrichloroethane (total DDTs including DDE, DDD and DDT) and polycyclic aromatic hydrocarbons (PAHs). Among the 10 freshwater fish species, rice field eel (Monopterus albus) showed significantly higher levels of DDTs in both ventral (125 ng/g wet wt) and axial muscle (127 ng/g wet wt) than the other species. The highest concentration of PAHs was detected in catfish (Clarias fuscus), with 24.8 ng/g in ventral muscle and 9.1 ng/g in axial muscle. As to marine fish, snubnose pompano (Trachinotus blochii) showed significantly higher levels of DDT and its metabolites (1018 ng/g in ventral and 409 ng/g wet wt in axial tissues) than all other marine fish species. The overall concentrations of PAHs in marine fish species were 15.5-57.0 ng/g (axial muscle) and 18.1-118 ng/g wet wt (ventral muscle) where yellow seafin (Acanthopeyrus latus) and golden threadfin bream (Nemipterus virgatus) exhibited the highest concentrations of PAHs in the axial and ventral muscles, respectively. In general, results showed that levels of PAHs in Hong Kong market fish was low and do not expect to cause any concern for human consumption. However, the levels of DDTs in fish samples ranged from 1.10 to 1018 ng/g wet wt, and based on a fish consumption rate of 142.2g/day to calculate the screening value of 14.4 ng/g wet wt for human consumption (USEPA, 2000. Guidance for assessing chemical contaminant, data for use in fish advisories, vol. 1: fish sampling and analysis, third ed. EPA 823-R-95-007. Office of Water, Washington, DC), there were 9 out of 20 (45%) muscle samples of freshwater fish species and 14 out of 20 (70%) muscle samples of marine fish species had elevated levels of DDTs exceeded the screening value. It was also suggested to use ventral muscle for detecting concentrations of persistent organic pollutants in fish.  相似文献   
107.
Variations in the chemical properties of landfill leachate   总被引:4,自引:0,他引:4  
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.  相似文献   
108.
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.  相似文献   
109.
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℃.  相似文献   
110.
1IntroductionIndustrialwastewaters,particularlythosedischargedfrommanufacturingofprintedcircuitboard(PCB)andelectroplatingcon...  相似文献   
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