昆明市食物生产消费碳素动态变化

食物生产消费系统中碳素的梯级流动变化会产生一系列环境影响.基于1990—2013年昆明市食物生产消费变化,测算分析了农业生产的碳汇碳排量、城乡居民食物碳消费动态变化及食物碳消费带来的环境负荷变化.结果表明,食物生产系统中碳汇和碳排总量分别由1990年的705.44 Gg·a~(-1)和496.92 Gg·a~(-1)增长至2013年的1195.53 Gg·a~(-1)和1012.33 Gg·a~(-1),净碳汇水平为正值,但呈下降趋势;城镇居民人均食物碳消费量由61.42 kg·人~(-1)·a~(-1)减少至44.65 kg·人~(-1)·a~(-1),农村居民人均食物碳消费量由87.96 kg·人~(-1)·a~(-1)降至48.78 kg·人~(-1)·a~(-1),食物碳消费总量由336.00 Gg·a~(-1)波动下降到294.53 Gg·a~(-1).畜禽养殖粪便排放和肠道发酵是食物生产过程中的主要碳源,占到60%以上,其次是农用物资投入所产生的碳排放,约占30%,并呈增加态势,其中,化肥是农用物资碳排放的主要影响因素.食物消费造成的碳素环境负荷中,损失进入大气的碳素比例最高,占到80%,其次是土壤,最少的是水体.进入大气的碳素由1990年的270.63 Gg·a~(-1)波动下降至2013年的170.68 Gg·a~(-1),减少了36.93%,但进入土壤和水体的碳素明显增长,其中,厨余垃圾碳量由35.42 Gg·a~(-1)增加至129.84 Gg·a~(-1),增加了266.57%.昆明市作为低碳城市试点,需要采取针对性措施发展低碳农业及低碳消费.

Carbon dynamics of food production and consumption in Kunming City

Carbon cascades in the food production and consumption system cause a range of effects on the environment. Based on food production and consumption statistics in Kunming from 1990 to 2013, carbon sequestration and emission in food production, carbon consumption dynamics of urban and rural residents and their caused environmental load were measured and analyzed respectively. The results showed that the total amount of carbon sequestration and emission in food production system increased from 705.44 Gg·a^-1 and 496.92 Gg·a^-1 in 1990 to 1195.53 Gg·a^-1 and 1012.33 Gg·a^-1 in 2013 respectively, resulting in net carbon sequestration. But there was significant downward trends in net carbon sequestration. Per capita food carbon consumption of urban residents decreased from 61.42 kg·cap^-1·a^-1 to 44.65 kg·cap^-1·a^-1,with rural residents from 87.96 kg·cap^-1·a^-1 to 48.78 kg·cap^-1·a^-1. Total amount of food carbon consumption reduced from 336.00 Gg·a^-1 to 294.53 Gg·a^-1. Livestock fecal emissions and intestinal fermentation in food production process were the main carbon emission source, accounting for more than 60% of the total. Carbon emissions generated by agricultural inputs, such as chemical fertilizers etc, accounted for about 30%, showing an increasing trend during the time period 1990-2013. Concerning the environmental carbon emissions in the food consumption, about 80% was into the atmosphere, followed by soil water bodies. Environmental carbon emissions into the atmosphere decreased from 270.63 Gg·a^-1 in 1990 to 170.68 Gg·a^-1 in 2013, with a decrease percentage up to 36.93%. But the carbon loss into the soil and water bodies increased significantly. Carbon amount from kitchen waste increased from 35.42 Gg·a^-1 to 129.84 Gg·a^-1, with an increase percentage up to 266.57%. As China''s Pilot Low-carbon City, Kunming should pay more attention on developing low-carbon agriculture and low-carbon consumption through state-of-the-art measures.