城市居民食物磷素消费变化及其环境负荷——以厦门市为例

城市磷代谢不但关系到居民食品安全,还影响到城市生态系统的环境质量。快速的城市化进程及由此带来的居民生活水平的提高,会改变食物消费的数量、质量和结构,从而对城市磷代谢产生重要影响。分析了1988-2010年厦门市经食物消费进入城市系统的磷素变化动态,在此基础上对人均食物磷消费量与相关社会经济因子进行了Spearman相关分析,并计算了居民食物磷素消费的环境负荷。研究结果表明:(1)随着厦门城市化进程的推进,食物磷素消费总量波动上升;人均食物磷素消费量呈M型变化,两个峰值分别出现在1998年和2003年;高磷含量食物如奶制品、水产品,在人均食物磷素消费量中所占比例剧增,分别由0.3%和6.8%上升至14.9%和15.5%。(2)人均粮食磷素消费量与恩格尔系数、平均家庭人口数呈高度正相关, 与人均可支配收入、食物价格指数以及具有大学学历以上人口比重呈高度负相关;而植物油、瓜果、畜禽肉、蛋类、奶类和水产品磷素消费量则与粮食所呈现的相关性相反。(3)随着食物磷素消费总量的增加,磷素的环境负荷总量也呈剧增趋势,尤其进入土壤的磷素量剧烈上升,所占比例由59.7%增至85.1%,这可能与禁磷措施的实行、污水处理率的提高、处理工艺的改进等有关。

Changes in phosphorus consumption and its environmental loads from food by residents in Xiamen City

Urban phosphorus metabolism is of particular importance due to the global scarcity of phosphorus, food security of residents, and potential impacts on urban environment and peri-urban ecosystems. The world is rapidly urbanizing with significant changes in living standards, including the quantity, quality and structure of daily food consumed. As a result, urban phosphorus metabolism through food consumption, which is an important process of the metabolism, has been significantly impacted. The purpose of this study is to analyze the variation in food phosphorus consumption by Xiamen residents, its environmental loads in 1988-2010, and to examine the associated economic and social factors by using the Spearman correlation analysis. The key stocks and flows of phosphorus through food consumption were explored using a material flow analysis (MFA) approach to develop a conceptual model of phosphorus flow for urban food consumption. The results showed that there was a fluctuating growth in the total food phosphorus consumption, reached 1,128.88 t in 2010 because of the resident population boom; and the dynamic change in per capita phosphorus consumption varied between 315 g and 380 g, showed an M-shape with the two modes in 1998 and 2003. In addition, high phosphorus food increased sharply. For example, dairy products and aquatic products accounted for 0.3% and 6.8% of the per capita phosphorus consumption, respectively, in 1988, but the proportion reached 14.9% and 15.5%, respectively, in 2010. The results of the correlation analysis showed that there was a significant positive correlation between per capita phosphorus consumption in grain and the Engel coefficient, as well as the average number of people in the family. However, there was a significant negative correlation with per capita disposable income, the food price index and the proportion of college graduates. The correlation between per capita phosphorus consumption in other kinds of food, such as plant oil, fruits, meat, eggs, dairy products and aquatic products, and these factors was opposite. The correlations were significant negative between these kinds of food and the former group of socio-economic factors, but with the latter group of socio-economic factors the correlations were significant positive. The variation of food phosphorus consumption was not significantly correlated with these socio-economic factors, so these socio-economic factors mainly exerted their influence on per capita phosphorus consumption in all kinds of food. As the total food phosphorus consumption increased, the environmental load of phosphorus from food leaped, the value in 2010 tripled over that in 1991. The proportion of phosphorus in the soil significantly increased from 59.7% to 85.1%, which partly due to a growing amount of kitchen waste and the landfilled sludge. Since the phosphorus mainly remained in soil and water, the proportion of phosphorus in the water decreased accordingly. Other factors which may have influenced the results are including a prohibition of phosphorus on detergents, and improvements in wastewater treatment. Thus, it has become the most important mission to develop and implement efficient strategies to facilitate phosphorus recycling. Relevant solutions for improving phosphorus recycling efficiency should be studied in the future to establish a strong coordination between urban and peri-urban areas for nutrient recycling to attain sustainable development.