[Effects of biochar application three-years ago on global warming potentials of CH4 and N2O in a rice-wheat rotation system.] / 生物炭施用3年后对稻麦轮作系统CH4和N2O综合温室效应的影响.

To evaluate the long-term effects of biochar amendment on greenhouse gas emissions (GHGs), a field experiment was conducted to examine the effects of 3-year field-aged biochar (B3) and fresh biochar (B0) on global warming potential (GWP) and greenhouse gas intensity (GHGI) of methane (CH4) and nitrous oxide (N2O) in a typical rice-wheat rotation system. Four treatments were established as control without nitrogen fertilizer (CK), urea without biochar (N), urea with fresh biochar amended in 2015 (NB0), and urea with 3-year field-aged biochar amended in 2012 (NB3). Results showed that both the NB0 and NB3 treatments obviously increased soil pH, soil organic carbon (SOC), total nitrogen (TN) and influenced the potential activity of functional microorganisms related to GHGs compared to the N treatment. Relative to the N treatment, the NB3 treatment significantly improved crop yield by 14.1% while reduced the CH4 and N2O emissions by 9.0% and 34.0%, respectively. In addition, the NB0 treatment significantly improved crop yield by 9.3%, while reduced the N2O emission by 38.6% though increased the CH4 emissions by 4.7% relative to the N treatment. Moreover, both the NB0 and NB3 treatments could significantly reduce both GWP and GHGI, with NB3 being more effective in simultaneously mitigating the GHGs emissions and enhancing crop yield. Since field-aged biochar showed obvious effects on GHGs mitigation and carbon sequestration after 3 years, biochar incorporations had long-term effect on GHGs mitigation and crop production in the rice-wheat rotation system.

[Pollution Level and Health Risk Assessment of Heavy Metals in Atmospheric PM2.5 in Nanjing Before and After the Youth Olympic Games].

The influence of human activities on the atmospheric environment has attracted people's attention. This study reported the dynamic changes in PM2.5 concentration, its heavy metal compositions and health risk assessment from April to September, 2014 in Nanjing when the Youth Olympic Games ( YOG) was held. The results showed that the mass levels of PM2.5 ranged from 26.39 to 80.31 µg · m⁻³ from April to September. The mass levels of PM2.5 met the level II standard of ambient air quality in China (24 h average concentration, 75 µg · m⁻³) in months of April, May and July while met the level I standard (24 h average concentration, 35 µg · m⁻³) in August during the YOG. The average mass concentration of PM2.5 reached 76.14 µg · m⁻¹ after the YOG, showing resilience of air pollution. The variations of heavy metals were not consistent with each other throughout the observation period. Principal component analysis indicated that emission sources significantly affected the variations of PM2.5 and its heavy metals. PM2.5 and all of the heavy metals decreased to their minimum values during the YOG, indicating the effectiveness of those temporary measures for reducing atmospheric pollutant before and during the YOG. The health risks of Cd, Cu, Ni and Pb in PM2.5 via breathing and dermal contact exposure were all within the acceptable ranges, but potential carcinogenic risk existed for Cr in PM2.5. There was potential non-carcinogenic health risk for adult males via breathing of Mn and greater non-carcinogenic health risk for children via dermal contact exposures to all these 6 heavy metals.

[Effects of biochar and nitrification inhibitor incorporation on global warming potential of a vegetable field in Nanjing, China].

The influences of biochar and nitrification inhibitor incorporation on global warming potential (GWP) of a vegetable field were studied using the static chamber and gas chromatography method. Compared with the treatments without biochar addition, the annual GWP of N2O and CH4 and vegetable yield were increased by 8.7%-12.4% and 16.1%-52.5%, respectively, whereas the greenhouse gas intensity (GHGI) were decreased by 5.4%-28.7% following biochar amendment. Nitrification inhibitor significantly reduced the N2O emission while had little influence on CH4 emission, decreased GWP by 17.5%-20.6%, increased vegetable yield by 21.2%-40.1%, and decreased the GHGI significantly. The combined application of biochar and nitrification inhibitor significantly increased both vegetable yield and GWP, but to a greater extent for vegetable yield. Therefore, nitrification inhibitor incorporation could be served as an appropriate practice for increasing vegetable yield and mitigating GHG emissions in vegetable field.

[Effects of farming managements on the global warming potentials of CH4 and N2O from a rice-wheat rotation system based on the analysis of DNDC modeling].

Taking a rice-wheat rotation system in the suburb of Nanjing, Jiangsu Province of East China as test object, this paper studied the fluxes of CH4 and N2O and their annual dynamics under different farming managements in 2010-2011, and the field observation data were applied to validate the process-based model, denitrification-decomposition (DNDC) model, aimed to approach the applicability of the model to this rotation system, and to use this model to simulate the effects of different environmental factors and farming managements on the global warming potentials (GWPs) of CH4 and N2O. The results showed that except in the treatment control and during wheat growth season, the simulated cumulative emissions of CH4 and N2O from the rotation system in all treatments were basically in coincide with the observed data, the relative deviations being from 7. 1% to 26.3%, and thus, the DNDC model could be applied to simulate the GWPs of cumulative emissions of CH4 and N2O as affected by various environmental factors or management practices. The sensitivity test showed that the GWPs of CH4 and N2O varied significantly with the changes of environmental factors such as the mean annual air temperature, soil bulk density, soil organic carbon, soil texture, and soil pH. Farming managements such as N fertilization, straw returning, and duration of mid-season drainage also had significant effects on the GWPs of CH4 and NO20. Therefore, the above-mentioned environmental factors and farming managements should be taken into account to estimate the greenhouse gases emission from the rice-wheat cropping system on site-specific or regional scale.

[Temporal and spatial variations of total nitrogen and total phosphorus in the typical reaches of Qinhuai River].

The year-round concentrations of total nitrogen (TN) and total phosphorus (TP) were monitored from June 2010 to May 2011 in the typical reaches of the Qinhuai River. The spatial and temporal variations in TN and TP concentrations and the pollution status of the river water were investigated using typical statistics analysis. Results showed that the river water was seriously polluted in terms of TN and TP, and that the concentrations of both TN and TP showed high spatial and temporal variations. The average TN concentrations of the river water in the traditionally managed agricultural area, intensively managed agricultural area, and urban area were 1.80, 3.97 and 9.25 mg L(-1), respectively; The corresponding average TP concentrations were 0.03, 0.11 and 0.50 mg L(-1), respectively, showing similar spatial patterns with those of TN. The spatial variations in TN and TP concentrations in river water indicated that the urban area and intensively managed agricultural area, rather than the traditionally managed agricultural area, were the major sources for TN and TP in the river water. The average TN concentrations of river water during the wet season and dry season were 1.89 and 4.58 mg x L(-1), respectively; and the corresponding average TP concentrations were 0.11 and 0.14 mg x L(-1), respectively. The temporal variations indicated that the pollution status of the river water was more serious during the dry season than that during the wet season. Assessment results of eutrophication indicated that the majority of Qinhuai River reaches were in the stage of eutrophication, thus deserving immediate controlling measures.

[N2O emission from an intensively managed greenhouse vegetable field in Nanjing suburb, Jiangsu Province of East China].

By using static opaque chamber and gas chromatography, this paper studied the dynamic changes of N2O fluxes and their relationships with soil temperature, soil moisture content, and soil nitrate and ammonium contents in an intensively managed greenhouse celery-Tung choy-Bok choy-amaranth rotation field and in a bare fallow land in Nanjing suburb. The cumulative N2O emission from the rotation vegetable field was as high as 137.2 kg N x hm(-2), being significantly higher than that from the bare fallow land (29.2 kg N x hm(-2)), and the N2O-N emission factor of the rotation vegetable field ecosystem was up to 4.6%. In the rotation field, the planting of Tung choy had the greatest contribution to the annual cumulative N2O emission, occupying 53.5% of the total, followed by the planting of Bok choy (31.9%), celery field (4.5%), and amaranth (4.8%). The N2O flux of the rotation field had significant positive correlation with soil temperature, the Q10 being 2.80, but no significant correlations with soil moisture content and soil nitrate and ammonium contents.

[Distribution characteristics of soil profile nitrous oxide concentration in paddy fields with different rice-upland crop rotation systems].

To investigate the dynamic distribution patterns of nitrous oxide (N2O) in the soil profiles in paddy fields with different rice-upland crop rotation systems, a special soil gas collection device was adopted to monitor the dynamics of N2O at the soil depths 7, 15, 30, and 50 cm in the paddy fields under both flooding and drainage conditions. Two rotation systems were installed, i.e., wheat-single rice and oilseed rape-double rice, each with or without nitrogen (N) application. Comparing with the control, N application promoted the N2O production in the soil profiles significantly (P < 0.01), and there existed significant correlations in the N2O concentration among the four soil depths during the whole observation period (P < 0.01). In the growth seasons of winter wheat and oilseed rape under drainage condition and with or without N application, the N2O concentrations at the soil depths 30 cm and 50 cm were significantly higher than those at the soil depths 7 cm and 15 cm; whereas in the early rice growth season under flooding condition and without N application, the N2O concentrations at the soil depth 7 cm and 15 cm were significantly higher than those at the soil depths 30 cm and 50 cm (P < 0.05). No significant differences were observed in the N2O concentrations at the test soil depths among the other rice cropping treatments. The soil N2O concentrations in the treatments without N application peaked in the transitional period from the upland crops cropping to rice planting, while those in the treatments with N application peaked right after the second topdressing N of upland crops. Relatively high soil N2O concentrations were observed at the transitional period from the upland crops cropping to rice planting.

[Seasonal variation patterns of NH4(+) -N/NO3(-) -N ratio and delta 15 NH4(+) value in rainwater in Yangtze River Delta].

By using a customized manual rainwater sampler made of polyvinyl chloride plastic, the molar ratio of NH4(+) -N/NO3(-) -N and the natural 15N abundance of NH4(+) (delta 15 NH4(+) in rainwater was monitored all year round from June 2003 to July 2005 at three observation sites (Changshu, Nanjing, and Hangzhou) in the Yangtze River Delta. The results indicated that at the three sites, the NH4(+) -N/NO3(-) -N ratio and the delta 15 NH4(+) value in rainwater had the similar seasonal variation trend, being more obvious in Changshu (rural monitoring type) site than in Nanjing (urban monitoring type) and Hangzhou (urban-rural monitoring type) sites. The NH4(+) -N/NO3(-) -N ratio peaked from early June to early August, declined gradually afterwards, and reached the bottom in winter; while the delta 15 NH4(+) value was negative from late June to mid-August, turned positive from late August to mid or late November, became negative again when winter dominated from December to March, but turned positive again in next May and negative again in next July. These seasonal variation patterns of NH4(+) -N/NO3(-) -N ratio and delta 15 NH4(+) value were found in relation to the application of chemical nitrogen fertilizers during different crop growth periods, and also, the alternation of seasons and the NH3 volatilization from other NH3 emission sources (including excrements of human and animals, nitrogen- polluted water bodies, and organic nitrogen sources, etc.), which could be taken as an indicator of defining the sources and form composition of NH4(+) in atmospheric wet deposition and the intensity of various terrestrial NH3 emission sources.