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One of the benefits of the combined heat and power (CHP) systems is reducing greenhouse gases (GHG) in the national level. These systems are installed in the close vicinity of local communities and their pollution can directly affect the local environment. This paper studies the adverse environmental effects of a 2 MW gas-burning CHP (GB-CHP) system in a residential community in Mashhad, Iran. We compare the amount of C O 2 and N O x emissions from the GB-CHP with the conventional choice of supplying electricity from the central power plants and heat from the locally installed boilers. The results show that the GB-CHP system increases local C O 2 and N O x emissions by approximately two and six times, respectively. The N O x emission is increased from 3.1 tonnes to 18.7 tonnes. The C O 2 emission increases from 3623 tonnes to 7238 tonnes. Furthermore, we use Gaussian Dispersion model to estimate the concentration of these emissions in the local area using the weather conditions of the most polluted times of the previous year. The results show that for a 3-meter stack, the maximum concentration of C O 2 and N O x are 14.8 m g / m 3 and 38.1 μ g / m 3 , respectively. Our analysis shows that increasing the height of the GB-CHP stack from 3 meters to 10 meters reduces the concentration by 40%. [ABSTRACT FROM AUTHOR]

The change of O 2 content in soil caused by aerated irrigation (AI) must inevitably affect the production and emissions of CO 2 and N 2 O from soils. This paper described in-situ observation of CO 2 and N 2 O emissions from AI soils with static chamber-GC technique, in order to reveal the effects of AI on CO 2 and N 2 O emissions from soils of greenhouse tomato fields in autumn-winter season. CO 2 and N 2 O emissions from AI soils mainly concentrated in the blooming and fruit setting period compared to other periods. AI increased cumulative emissions of CO 2 and N 2 O by 11.8% (p = 0.394) and 10.0% (p = 0.480), respectively, compared to the control. The integrative global warming potential of CO 2 and N 2 O on a 100-year horizon for the AI treatment was 6430.60 kg ha −1 , increased by 11.7% compared with that for the control (p = 0.356). Both the emissions of CO 2 and N 2 O from AI soils had the exponential positive correlation with soil water-filled pore space (WFPS). The highest peak of CO 2 and N 2 O fluxes from AI soils was observed at 46.7% and 47.5% WFPS, with WFPS ranging from 43.3% to 51.5% and from 45.6% to 52.3% during the whole growth stage, respectively. In addition, the average yield for the AI treatment (34.52 t ha −1 ) was significantly greater (17.4%) compared with that of the control (p = 0.018). These results suggest that AI do not significantly increase the integrative greenhouse effect caused by CO 2 and N 2 O from soils of greenhouse tomato fields, but significantly increase the tomato yield. The research results provide certain theoretical foundation and scientific basis for accurately evaluating the farmland ecological effect of AI technique. [ABSTRACT FROM AUTHOR]