Journal of Environmental Science for Sustainable Society
Online ISSN : 1881-5073
ISSN-L : 1881-5073
Volume 7
Displaying 1-2 of 2 articles from this issue
  • Thi Kim Thanh HA, Morihiro MAEDA, Thi Ngoc Anh HA
    2015 Volume 7 Pages 1-8
    Published: 2015
    Released on J-STAGE: March 29, 2016
       This study investigated nitrous oxide (N2O) emission and the environmental parameters responsible for its generation in Ru Cha mangrove sediment (Thua Thien Hue, Vietnam). To determine cumulative amounts of N2O emission from different sediment layers, closed incubation experiments were conducted at 25ºC for 7 days in 100 mL glass bottles that contained 5 g of sectioned sediments (0‒5, 5–10 and 10‒15 cm depths) and 25 mL of the ambient water. Cumulative amounts of N2O emission decreased with sediment depth, which coincided with decreases in the density of denitrifiers, and contents of total organic carbon, total nitrogen and ammonium from upper to lower sediment layers. A similar incubation experiment was conducted using the 0–5 cm sediment layer to investigate the effect of different nitrate (NO3-) concentrations (0, 1, 3 and 5 mg N L-1) on potential N2O emission. Nitrous oxide emission increased with NO3- addition, indicating that N2O emission was limited by NO3-. Nitrate was completely removed from the solution in all NO3- treatments by denitrification. Nitrous oxide emission accounted for 20%, 55% and 100% of the amounts of NO3- removed in 1, 3 and 5 mg N L-1 treatments, respectively. Our laboratory experiments suggest that the Ru Cha mangrove forest could be a hotspot of N2O emissions when sediment receives high NO3- inputs.
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  • Thi Kim Thanh HA, Morihiro MAEDA, Taku FUJIWARA, Hideaki NAGARE, Satos ...
    2015 Volume 7 Pages 9-15
    Published: 2015
    Released on J-STAGE: March 29, 2016
       A short-term study was conducted to investigate the effects of additions of rice husk products on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from paddy soil at different soil moisture contents. Soil amended with raw rice husk (RR, 2% on a dry weight basis), rice husk char (RC, 2%), rice husk ash (RA, 2%) or no amendment (CT) was incubated at 40%, 60%, or 80% water-holding capacity (WHC) in a 100-mL bottle for 120 h. Results showed that N2O emission was lower at 40% WHC compared with other WHC treatments. At 60% and 80% WHC, N2O emissions peaked at 24 h of incubation in most treatments. The highest emission of N2O was recorded in the RR addition at 80% WHC. Additions of RC and RA decreased cumulative N2O emissions from soil at 24 h (by 24% at 60% WHC and 51% at 80% WHC for RC, and 90% at 60% WHC and 80% WHC for RA) compared with the CT treatment. Regardless of the soil moisture content, RR enhanced cumulative CO2 emission for 120 h, whereas no significant difference was detected among RC, RA and CT treatments (P > 0.05). Our short-term results indicated that application of rice husk char or ash to soil reduced N2O emission, whereas direct incorporation of rice husk into soil enhanced CO2 and N2O emissions.
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