Shoulong Liu

Investigation of square fluidized beds using capacitance tomography: preliminary results

The fluidization conditions in a fluidized bed can vary dramatically, from bubbling to circulating fluidization. Considering the dielectric properties and the rapid movement of the solids in fluidized beds, electrical capacitance tomography (ECT) is particularly suitable for measuring the concentration and distribution of solids in fluidized beds. This paper reports the use of a square ECT sensor to investigate the behaviour of fluidized beds, showing the unique advantages of using ECT in measuring cross-sectional concentration profiles of solids. Different fluidization regimes manifest different characteristics, in terms of the concentration distribution of solids.

Novel bacterial sulfur oxygenase reductases from bioreactors treating gold-bearing concentrates

The microbial community and sulfur oxygenase reductases of metagenomic DNA from bioreactors treating gold-bearing concentrates were studied by 16S rRNA library, real-time polymerase chain reaction (RT-PCR), conventional cultivation, and molecular cloning. Results indicated that major bacterial species were belonging to the genera Acidithiobacillus, Leptospirillum, Sulfobacillus, and Sphingomonas, accounting for 6.3, 66.7, 18.8, and 8.3%, respectively; the sole archaeal species was Ferroplasma sp. (100%). Quantitative RT-PCR revealed that the 16S rRNA gene copy numbers (per gram of concentrates) of bacteria and archaea were 4.59 × 109 and 6.68 × 105, respectively. Bacterial strains representing Acidithiobacillus, Leptospirillum, and Sulfobacillus were isolated from the bioreactors. To study sulfur oxidation in the reactors, pairs of new PCR primers were designed for the detection of sulfur oxygenase reductase (SOR) genes. Three sor-like genes, namely, sorFx, sorSA, and sorSB were identified from metagenomic DNAs of the bioreactors. The sorFx is an inactivated SOR gene and is identical to the pseudo-SOR gene of Ferroplasma acidarmanus. The sorSA and sorSB showed no significant identity to any genes in GenBank databases. The sorSB was cloned and expressed in Escherichiacoli, and SOR activity was determined. Quantitative RT-PCR determination of the gene densities of sorSA and sorSB were 1,000 times higher than archaeal 16S rRNA gene copy numbers, indicating that these genes were mostly impossible from archaea. Furthermore, with primers specific to the sorSB gene, this gene was PCR-amplified from the newly isolated Acidithiobacillus sp. strain SM-1. So far as we know, this is the first time to determine SOR activity originating from bacteria and to document SOR gene in bioleaching reactors and Acidithiobacillus species.

Investigation of poly (β-L-malic acid) production by strains of Aureobasidium pullulans

Abstract Eight strains of the genus Aureobasidium obtained from culture collections were tested for their capability to produce poly(β-L-malic acid) (PMA). Four of the tested strains showed positive results. The most productive strain, A. pullulans CBS 591.75, was used to study the production of PMA in stirred-tank reactors. It was found that PMA was mainly produced in the late exponential phase, and the production related positively to glucose consumption. At the beginning of the fermentation the pH increased from 4.0 to about 7.0; subsequently the pH decreased and remained stable at around 3.0–3.5 for several days. Temperatures higher than 25°C were detrimental to PMA production and cell growth. PMA production and cell growth at 20°C and 25°C exhibited no significant differences. PMA production and cell growth were studied under pH-controlled fermentation (at pH 2.0, 4.0, 5.5). The highest PMA production occurred at pH 4.0. PMA production was reduced at pH 2.0 although quite reasonable cell growth occurred at this pH value. Under optimized conditions 9.8 g PMA/l was produced during 9 days of fermentation in the stirred-tank reactors with an overall yield of 0.11 g PMA/g glucose. A procedure for the isolation of PMA and its separation from the other components of the fermentation broth was developed. The isolated PMA was characterized by 1H and 13C-NMR spectroscopy as well as by infrared absorption spectroscopy. Gel-permeation chromatography revealed a relative molecular mass of approximately 3000–5000 by comparison with polyethylene glycol standards.

Effect of land use on the abundance and diversity of autotrophic bacteria as measured by ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO) large subunit gene abundance in soils

Elucidating the biodiversity of CO2-assimilating bacterial communities under different land uses is critical for establishing an integrated view of the carbon sequestration in agricultural systems. We therefore determined the abundance and diversity of CO2 assimilating bacteria using terminal restriction fragment length polymorphism and quantitative PCR of the cbbL gene (which encodes ribulose-1,5-biphosphate carboxylase/oxygenase). These analyses used agricultural soils collected from a long-term experiment (Pantang Agroecosystem) in subtropical China. Soils under three typical land uses, i.e., rice–rice (RR), upland crop (UC), and paddy rice–upland crop rotation (PU), were selected. The abundance of bacterial cbbL (0.04 to 1.25 × 108 copies g−1 soil) and 16S rDNA genes (0.05–3.00 × 1010 copies g−1 soil) were determined in these soils. They generally followed the trend RR > PU > UC. The cbbL-containing bacterial communities were dominated by facultative autotrophic bacteria such as Mycobacterium sp., Rhodopseudomonas palustris, Bradyrhizobium japonicum, Ralstonia eutropha, and Alcaligenes eutrophus. Additionally, the cbbL-containing bacterial community composition in RR soil differed from that in upland crop and paddy rice–upland crop rotations soils. Soil organic matter was the most highly statistically significant factor which positively influenced the size of the cbbL-containing population. The RR management produced the greatest abundance and diversity of cbbL-containing bacteria. These results offer new insights into the importance of microbial autotrophic CO2 fixation in soil C cycling.

Sepiolite is recommended for the remediation of Cd-contaminated paddy soil

Abstract This study aimed to assess the extractability of cadmium (Cd) and Cd uptake by rice after applying soil amendments of lime (Ca(OH)2) and sepiolite. A rice (Oryza sativa) cultivation experiment was conducted in a Cd-contaminated paddy field. After applying lime, sepiolite, and a mixture of the two as soil amendments, soil pH showed a significant increase (p<0.05), and Cd in soil extracted with NaNO3, CaCl2, and DTPA, was reduced by 61–100%, 52–98%, and 12–15%, respectively (p<0.05). The amount of exchangeable Cd showed a significant decrease in all treatments (p<0.05), and we found increases in the proportion of forms of carbonate-bound, Fe/Mn oxide-bound, and residual Cd in the soils, as measured by a sequential extraction method. The grain or rice straw biomass was neither significantly influenced by any amendment in the experiment, while the uptake of Cd by rice significantly decreased in all treatments (p<0.05). The results reveal no advantage in applying a mixture of sepiolite and lime compared with applying sepiolite alone in immobilizing Cd in the soil. The use of sepiolite or sepiolite mixed with lime was more effective than the use of lime alone in the immobilization of Cd in the soil. We therefore recommend sepiolite as a soil amendment to remediate Cd-contaminated paddy soil.

Spatial variability of soil microbial biomass carbon, nitrogen and phosphorus in a hilly red soil landscape in subtropical China

Abstract Soil microbial biomass (SMB) is considered to be an important indicator of soil fertility and biological quality, and it presents strong spatial heterogeneity in relation to soil properties (e.g. soil texture, organic carbon, total nitrogen) and topography at various spatial and temporal scales. In the present study, geostatistics were used to analyze the spatial variability of soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in a hilly red soil landscape (446 ha) in subtropical China. Five hundred and twenty-three soil samples at a soil depth of 0–20 cm were randomly collected from paddy fields, dry lands, orchards and wood lands in the study region. Significant negative correlations (r = −0.69 to −0.54) of MBC, MBN and MBP with elevation were observed. The Steins Matérn, Spherical and Gaussian models with effective ranges of 157, 252 and 213 m were best-fitted to the sample semivariograms of original MBC, MBN and MBP variables, respectively. All three SMB variables exhibited moderate spatial dependence. After detrending the elevation impact, the normal score transformed MBC and MBP still retained their moderate spatial autocorrelations with slightly decreased effective ranges, whereas the normal score transformed MBN demonstrated a very strong spatial dependence with a much shorter effective range of 70 m. Spatial distributions of the three SMB variables were estimated using both ordinary kriging (OK) and regression kriging (RK) with elevation as the predictor. The kriging predictions showed that soil MBC, MBN and MBP had overlapping spatial patterns, and furthermore the RK interpolations showed more details in space than the OK interpolations, with improved prediction accuracy. The spatial distribution of soil MBN demonstrated more hotspots than the other two SMB variables, implying that MBN might be more sensitive to environmental disturbances (such as fertilization, tillage and crop rotations).

Soil microbial C:N ratio is a robust indicator of soil productivity for paddy fields

Maintaining good soil productivity in rice paddies is important for global food security. Numerous methods have been developed to evaluate paddy soil productivity (PSP), most based on soil physiochemical properties and relatively few on biological indices. Here, we used a long-term dataset from experiments on paddy fields at eight county sites and a short-term dataset from a single field experiment in southern China, and aimed at quantifying relationships between PSP and the ratios of carbon (C) to nutrients (N and P) in soil microbial biomass (SMB). In the long-term dataset, SMB variables generally showed stronger correlations with the relative PSP (rPSP) compared to soil chemical properties. Both correlation and variation partitioning analyses suggested that SMB N, P and C:N ratio were good predictors of rPSP. In the short-term dataset, we found a significant, negative correlation of annual rice yield with SMB C:N (r = −0.99), confirming SMB C:N as a robust indicator for PSP. In treatments of the short-term experiment, soil amendment with biochar lowered SMB C:N and improved PSP, while incorporation of rice straw increased SMB C:N and reduced PSP. We conclude that SMB C:N ratio does not only indicate PSP but also helps to identify management practices that improve PSP.

Effectiveness of simultaneous applications of lime and zinc/iron foliar sprays to minimize cadmium accumulation in rice

Due to the large area of Cd-contaminated paddy soils worldwide, low-cost measures to reduce the accumulation of Cd in rice plant are necessary. A field experiment was therefore conducted to investigate the reducing effect of lime combined with foliar applications of Zn (ZnSO4) or Fe (EDTA·Na2Fe) on Cd concentrations in brown rice on a Cd-contaminated paddy soil. The results indicated that liming alone or in combination with foliar sprays of Zn or Fe increased the soil pH by 0.27-0.63 units. However, limited effects of lime or lime combined with foliar applications of Zn/Fe on soil DTPA-extractable Cd, rice grain and rice straw biomass were observed. Liming alone significantly reduced the Cd concentration in brown rice and rice straw by 31.8% and 42.3%, respectively. The Cd concentrations in brown rice decreased by 25.5% and 65.4% and in rice straw by 53.0% and 68.1% after liming combined with foliar applications of Fe and Zn, respectively. In contrast, liming combined with foliar spraying of Fe significantly increased the transfer ratio of Cd from the rice straw to the grain. As a low-cost technique, lime application combined with foliar application of ZnSO4 could be recommended for the remediation of Cd-contaminated paddy soils.

ECT Visualization of Two Phase Flows

Electrical capacitance tomography (ECT) has been under rapid development in recent years. However, as a relatively new technology, ECT is far from mature and its applications are rather appliance-dependent, i.e. the sensor design, calibration, and data interpretation etc., depend on the understanding of the specific situations for ECT measurement. The authors have experimented several sensing strategies and developed algorithms for 3D image presentation and online iterative image reconstruction, and applied ECT to the measurement of several typical cases of two phase flows, which is reported in this paper.© 2004 ASME