Effects of red-yellow soil acidification on seed germination of Chinese pine

Acid treatments significantly change the physical and chemical properties of red-yellos soil by lowering its pH value and leaching out aluminum(Al) ions that are harmful to the growth of plants.The structure of soil will be damaged,resulting in higher viscosity,higher water retention rate and lower air permeability of the soil.The germination rate of Chinese pine(Pinus tabulacformic Carr.)seeds sowed in soil treated with sulphuric acid(H2SO4) decreased compared to that for untreated soil.The direct cause was the large amount of Al ions leached out because of low pH values(≥3.5).The added acid decreased the soil aggregation and increased the number of micro-aggregates(under 250 μmin diameter).Such changes increased the soil‘s viscosity,which tied the pine needles to the soil after the seeds had germinated and prevented the seedlings from fully developing.     

Correlation of PCDD/PCDF and CO values in a MSW incinerator--indication of memory effects in the high temperature/cooling section

The correlation of PCDD/PCDF levels with the CO emissions in a full-scale municipal waste incinerator was assessed during a four-week measurement effort. PCDD/PCDF concentrations in fly ashes-containing more than 99% of the total PCDD/PCDF burden of the fluidized bed incinerator (FBI)-were measured and compared with the emitted CO concentrations. The CO concentration during the sampling time showed no significant correlation to the PCDD/ PCDF amount in fly ash (R2 = 0.078). However, a comparison of the time integrated CO concentration several hours before sampling lead to a correlation with the PCDD/PCDF burden. Maximum correlation was found for the time integrated CO values of 3 and 4 h before sampling (R2 = 0.467 and R2 = 0.457 respectively). This indicates a memory effect in the high temperature cooling section of several hours. Possible mechanisms leading to the memory effect are discussed. The correlation of PCDD/PCDF with CO concentration demonstrate that the combustion conditions play an important role for PCDD/PCDF formation in FBIs. However the variability in the correlation of CO to PCDD/PCDF levels show that other factors have a significant influence on PCDD/PCDF formation.     

Concentrations and compositions of organochlorine contaminants in sediments, soils, crustaceans, fishes and birds collected from Lake Tai, Hangzhou Bay and Shanghai city region, China

Contamination by persistent organochlorines (OCs), such as DDTs, hexachlorocyclohexane isomers (HCHs), chlordane compounds (CHLs), hexachlorobenzene (HCB) and polychlorinated biphenyls (PCBs) were examined in sediments, soils, fishes, crustaceans, birds, and aquaculture feed from Lake Tai, Hangzhou Bay, and in the vicinity of Shanghai city in China during 2000 and 2001. OCs were detected in all samples analyzed, and DDT and its metabolites were the predominant contaminants in most sediments, soils and biota. Concentrations of p,p'-DDT and ratio of p,p'-DDT to SigmaDDTs were significantly higher in marine fishes than those in freshwater fishes. While the use of DDTs has been officially banned in China since 1983, these results indicate a recent input of technical DDTs into the marine environment around Hangzhou Bay. Comparison of organochlorine concentrations in fishes collected from Lake Tai and Hangzhou Bay suggests the presence of local sources of HCHs, chlordanes and PCBs at Lake Tai. Higher proportions of penta- and hexa-PCB congeners in fishes at Lake Tai may suggest the use of highly chlorinated PCB product, such as PCB(5), around this lake. To our knowledge, this is a first comprehensive study to examine the present status of organochlorine contamination in various environmental media, such as sediments, soils and wildlife, in China.     

Control of mercury emissions from a municipal solid waste incinerator in Japan

The control of Hg emissions from a municipal solid waste incinerator (MSWI) is very important, because more than 78% of municipal solid waste (MSW) is incinerated. The Hg content of coal used in utility boilers is relatively low in Japan. In this study, recent trends in the Hg content of MSW in Japan and activated carbon (AC) injection as a control technology of Hg emission from an MSWI are discussed. The effect of AC injection on Hg removal from flue gas in an MSWI was investigated by pilot-scale experiments using a bag filter (BF). The injection of AC increases the Hg reduction ratio by 20-30% compared with cases without AC injection. The Hg reduction ratio increases as the flue gas temperature decreases. The Hg reduction ratio is closely related to the inlet Hg concentration and was expressed with a Langmuir-type adsorption isotherm.     

Adsorption of Cu and Mn on covalently cross-linked alginate gel beads

The covalently cross-linked alginate gel beads were prepared by the reactions of Ca(2+)-doped alginate gel beads, which were formed by spraying a viscous alginate solution into a calcium chloride solution, with cyanogen bromide and following 1,6-diaminohexane. The cross-linking of alginate matrix decreased the mean bead diameter by about 30% and made the beads durable in some extent under alkaline conditions. The adsorption of metal ions on the covalently cross-linked alginate gel beads was rapid and reached at equilibrium within 30 min at 25 degrees C. Adsorption isotherms of Cu(II), Mn(II), and Ca2+ on the beads possessed a stepwise shape, which was firstly determined by Rorrer et al. [Ind. Eng. Chem. Res. 32 (1993) 2170] for cross-linked chitosan gel beads and explained by a pore-blockage mechanism. Higher selectivity was determined against Cu(II) over Mn(II) and Ca2+, especially at a low concentration region. These metal adsorption profiles for the covalently cross-linked alginate gel beads was almost the same as those for the un-cross-linked beads, indicating that the cross-linking reactions were performed without interfering the adsorption characteristics of alginate gel beads.     

Distribution characteristics of nonylphenols in the artificial Lake Shihwa, and surrounding creeks in Korea

Nonylphenols were determined from the water, suspended particle, and sediment samples taken from the Lake Shihwa in Korea and its surrounding creeks flowing through municipal and industrial areas, and into the lake. The nonylphenols were detected at the concentration ranges of 0.0-41.3 microg/l, 0.0-116.6 and 0.3-31.7 mg/kg in water, suspended particle and sediment samples respectively. The contamination levels of nonylphenols were increased along the down stream. Considerably high levels of nonylphenols were found at the industrial area compared to the municipal area. No remarkable differences were found between the isomer patterns of nonylphenols for the sample matrices of each sampling site, i.e. water, suspended solids and sediment. Strong correlations between water and sediment with 10(5.2) of the mean partition coefficient (Koc ) were observed. These indicate that most of nonylphenols came from industrial wastewater at high level. It is thought that the water quality of the Lake Shihwa is affected greatly by industrial environments surrounding.     

Effects of copper chloride on formation of polychlorinated dibenzofurans in model waste incineration in a laboratory-scale fluidized-bed reactor

Combustion experiments in a laboratory-scale fluidized-bed reactor have been performed to clarify the effects of copper chloride as a catalyst on polychlorinated dibenzofurans (PCDFs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl2 x 2H2O) as a catalyst, both of which contained polyvinyl chloride (PVC) as a chlorine source. Combustion temperature was set to 900 degrees C, and the amount of air supplied was twice as much as the theoretical amount. The experimental setup had been carefully planned to ensure avoidance of the influences of previous experiments. Results of these present experiments revealed that copper chloride in the waste increased the amount of PCDFs formed and made the homologue profile shifted towards the highly chlorinated species. Copper chloride contributes to PCDFs formation by promoting chlorination via catalytic reactions, whereby the reaction could be important in that organic matters are chlorinated directly by chlorinated compounds related to Deacon reaction such as copper chloride. It was elucidated that characteristic isomer distribution patterns appeared in case the waste contained copper chloride. It is probable in our experiment with copper chloride that PCDFs are mainly formed via catalytic reactions of copper compounds and carbon.     

Effects of copper chloride on formation of polychlorinated dibenzo-p-dioxins in model waste incineration

Combustion experiments in a laboratory-scale fluidized-bed reactor were conducted to elucidate the effects of copper chloride as a catalyst on polychlorinated dibenzo-p-dioxins (PCDDs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl₂ · 2H₂O), both of which contained polyvinyl chloride as a chlorine source. Combustion temperature was set to 900 °C, and the amount of air supplied was twice the stoichiometric ratio. The experimental setup was carefully planned to suppress the influences of experimental conditions except the waste composition. Results of these experiments showed that copper chloride in the waste increased the amount of PCDDs formed and made the homologue profile to shift towards the highly chlorinated species. Copper chloride contributes to the PCDDs formation by promoting chlorination, whereby the reaction is important in that organic matter is chlorinated directly by copper compounds. Copper chloride did not exert a great influence on the isomer distribution patterns of PCDDs, while there appeared a significant difference in the case of PCDFs. This points out the difference of the major formation mechanisms between PCDDs and PCDFs. PCDDs are less formed by the catalytic reactions from carbon/polycyclic aromatic hydrocarbons than PCDFs in our experimental conditions.     

Development of an empirical equation for the transverse dispersion coefficient in natural streams

In this study, a new empirical equation for the transverse dispersion coefficient has been developed based on the hydraulic and geometric parameters in natural streams using a regression technique. First, a total of 32 data sets in 16 streams were collected. Among those sets, 16 sets were used for deriving the new equation, and the other 16 sets were used for verifying the equation. Then, through dimensional analysis, it was found that the normalized transverse dispersion coefficient is associated with several parameters such as sinuosity, aspect ratio, and a friction term. The robust least square method was applied to estimate regression coefficients. The newly proposed equation was proven to be superior in explaining the dispersion characteristics of natural streams more precisely compared to the existing equations.