Biomedical subjects

Shenghui Han

Publications and source records attributed to Shenghui Han.

5 recordsLinked to original sources

PubMed2002

The Asian nitrogen cycle case study.

We analyzed nitrogen budgets at national and regional levels on a timeline from 1961-2030 using a model, IAP-N 1.0. The model was designed based upon the Inter-governmental Panel on Climate Change (IPCC) methods using Asia-specific parameters and a Food and Agriculture Organization of the United Nations (FAO) database. In this paper we discuss new reactive-nitrogen and its various fates, and environmental nitrogen enrichment and its driving forces. The anthropogenic reactive nitrogen of Asia dramatically increased from approximately 14.4 Tg N yr-1 in 1961 to approximately 67.7 Tg N yr-1 in 2000 and is likely to be 105.3 Tg N yr-1 by 2030. Most of the anthropogenic reactive-nitrogen has accumulated in the environment. We found that an increasing demand for food and energy supplies and the lack of effective measures to improve the efficiency of fertilizer nitrogen use, as well as effective measures for the prevention of NOx emissions from fossil-fuel combustion, are the principal drivers behind the environmental nitrogen-enrichment problem. This problem may be finally solved by substituting synthetic nitrogen fertilizers with new high-efficiency nitrogen sources, but solutions are dependent on advances in biological technology.

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PubMed2002

[Determination of net exchange of CO2 between paddy fields and atmosphere with static poaque-chamber-based measurements].

We firstly introduced the method for determining the net ecosystem exchange fluxes of CO2 (NEE) between croplands and atmosphere, based on field measurements using static opaquechamber/gas chromatography methods was introduced, and the application of this method in the FACE (free-air CO2 enrichment) study to examine the effects of elevated CO2 on the NEE over a typical paddy ecosystem was carried out, because of lacking in observation data for some necessary parameters, e.g., dark maintenance respiration coefficient, only the minimum value of NEE (NEEmin) was calculated based on opaque-chamber measurements. The NEEmin data indicate that CO2 elevated by 200 +/- 40 mumol.mol-1 significantly increased the ecosystem uptake of atmospheric CO2 by a factor ca. 3. To accurately determine the NEE based on opaquechamber measurements, dark maintenance respiration coefficient, above-ground biomass and root: shoot, i.e. R:S, ratio of root to shoot should be observed over the whole growing season.

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PubMed2002

[Effects of elevated atmospheric CO2 on CH4 and N2O emissions from paddy fields].

Effects of elevated atmospheric CO2 on CH4 and N2O emissions during the paddy rice-growing season were examined in a FACE (free-air carbon dioxide enrichment) study. The emission fluxes of CH4 and N2O from paddy rice fields were measured using methods based on static opaque-chamber and gas chromatography techniques. Synthetic fertilizer N was amended for the rice-growing season at two rates, 150 and 250 kgN.hm-2 and the atmospheric CO2 was enriched by 200 mumol.mol-1. At both N levels, the preliminary results indicate that no significant effect of CO2 enrichment on CH4 and N2O emissions from the rice paddy fields was detected. The result on CH4 emissions is inconsistent with the most literatures, and the result on N2O emissions is consistent with the most literatures.

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PubMed2002

[Measurement of CO2 profiles in non-waterlogged soil in a FACE study].

A method was specially designed and applied for measuring CO2 concentration of soil air over the non-waterlogged period of a rice-wheat rotation on an available area of about 1.6 m2 in a FACE (free-air CO2 enrichment) study. Based on measuring the CO2 concentration over the soil profile of 0-30 cm in depth using this method, the CO2 profile in the soils of wheat fields under elevated and ambient CO2 and the bare land under ambient CO2 was investigated and some preliminary results were obtained. Within 0-30 cm in soil depth, CO2 in the pores of the upper soil layers vertically diffused upwards much more quickly than that in the lower soil layers. During the period with active wheat growth, elevated atmospheric CO2 by 200 +/- 40 mumol.mol-1 significantly increased the CO2 concentration in soil air within 0-30 cm in depth by 14% +/- 5% (t-test, P < 0.001).

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PubMed2002

[Field measurement of NO and NO2 exchanges between cultivated lands and the atmosphere in a FACE study].

A method for measuring NO and NO2 exchanges between cultivated lands and the atmosphere in a FACE (free-air CO2 enrichment) study is described. With this method, gas is sampled with a technique of static-opaque-chamber and the fluxes of NO and NO2 exchanges are determined by analyzing the NO and NO2 concentrations with a chemiluminescent NOx analyzer. Application of this method in the FACE study of a rice-wheat ecosystem has indicated that reliable data on the exchange fluxes could be obtained. Over the non-waterlogged period of a rice-wheat rotation, net emission of NO from the fields was observed, while net uptake of NO2 occurred. The daily net emission of NO did not correlated with the soil temperature, but negatively depended upon soil moisture (R2 = 0.82, P < 0.001). A significant seasonal variation in the net uptake of NO2 was observed, which was regulated by wheat growth status. The daily uptake of NO2 depended upon both soil temperature and soil moisture. The dependence for each could be described with a parabola function (for soil temperature: R2 = 0.74, P < 0.001; for soil moisture: R2 = 0.69, P < 0.001). An elevation of atmospheric CO2 by 200 +/- 40 mumol.mol-1 mitigated the net emission of NO by 19% (t-test P = 0.096) and might be possible to reduce the net uptake of NO2 by 10% (t-test P = 0.26), which was likely due to the stimulated wheat growth.

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