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Biochar has been reported to mitigate short-term methane (CH4) emissions from paddy soil. Currently, CH4 mitigation by biochar has primarily focused on the abundance and variations of methanogens and methanotrophs, and changes in their activities during methane production and consumption. However, long-term effects of biochar on methane mitigation from paddy soil remain controversial. This review overviewed the existing mechanisms for CH4 mitigation as a result of biochar application. In addition, the two existing opinions on the long-term CH4 mitigation effect upon biochar application were highlighted. Combining the already explored mechanisms of fresh biochar on CH4 mitigation from paddy soil and a novel discovery, the potential mechanisms of biochar on long-term methane emission response were proposed. This review also revealed the uncertain responses of biochar on long-term CH4 mitigation. Therefore, to achieve carbon neutral goal, it is important to further explore the mechanisms of long-term CH4 mitigation under biochar application.

BackgroundThe aim of this study was to examine environmental factors associated with inflammatory bowel disease (IBD) in Yunnan Province, a southwestern highland region of China.MethodsIn this nested case-control study, newly diagnosed ulcerative colitis (UC) cases in 2 cities in Yunnan Province and Crohn’s disease (CD) cases in 16 cities in Yunnan Province were recruited between 2008 and 2013. Controls were matched by geography, sex and age at a ratio of 1:4. Data were collected using the designed questionnaire. Conditional logistic regression models were used to estimate adjusted odds ratios (ORs).ResultsA total of 678 UC and 102 CD cases were recruited. For UC, various factors were associated with an increased risk of developing UC: dietary habits, including frequent irregular meal times; consumption of fried foods, salty foods and frozen dinners; childhood factors, including intestinal infectious diseases and frequent use of antibiotics; and other factors, such as mental labor, high work stress, use of non-aspirin non-steroidal anti-inflammatory drugs and allergies (OR > 1, p < 0.05). Other factors showed a protective effect: such as consumption of fruits, current smoking, physical activity, and drinking tea (OR < 1, p < 0.05). For CD, appendectomy and irregular meal times increased the disease risk (OR >1, p < 0.05), whereas physical activity may have reduced this risk (OR < 1, p < 0.05).ConclusionsThis study is the first nested case-control study to analyze the association between environmental factors and IBD onset in a southwestern highland region of China. Certain dietary habits, lifestyles, allergies and childhood factors may play important roles in IBD, particularly UC.

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