Singh Shweta, Compton Jana E, Hawkins Troy R, Sobota Daniel J, Cooter Ellen J
Ag. & Biological Engg/Env. & Ecological Engg, Purdue University, West Lafayette, IN, USA.
U.S. Environmental Protection Agency, Western Ecology Division, Corvallis OR, USA.
Ecol Modell. 2017 Sep 24;360:194-203. doi: 10.1016/j.ecolmodel.2017.06.015.
Nitrogen (N) presents an important challenge for sustainability. Human intervention in the global nitrogen cycle has been pivotal in in providing goods and services to society. However, release of N beyond its intended societal use has many negative health and environmental consequences. Several systems modeling approaches have been developed to understand the trade-offs between the beneficial and harmful effects of N. These efforts include life cycle modeling, integrated management practices and sustainability metrics for individuals and communities. However, these approaches do not connect economic and ecological N flows in physical units throughout the system, which could better represent these trade-offs for decision-makers. Physical Input-Output Table (PIOT) based models present a viable complementary solution to overcome this limitation. We developed a N-PIOT for Illinois representing the interdependence of sectors in 2002, using N mass units. This allows studying the total N flow required to produce a certain amount of N in the final product. An Environmentally Extended Input Output (EEIO) based approach was used to connect the physical economic production to environmental losses; allowing quantification of total environmental impact to support agricultural production in Illinois. A bottom up approach was used to develop the N-PIOT using Material Flow Analysis (MFA) tracking N flows associated with top 3 commodities (Corn, Soybean and Wheat). These three commodities cover 99% of N fertilizer use in Illinois. The PIOT shows that of all the N inputs to corn production the state exported 68% of N embedded in useful products, 9% went to animal feed manufacturing and only 0.03% was consumed directly within the state. Approximately 35% of N input to soybean farming ended up in animal feed. Release of N to the environment was highest from corn farming, at about 21.8% of total N fertilizer inputs, followed by soybean (9.2%) and wheat farming (4.2%). The model also allowed the calculation of life cycle N use efficiency for N based on physical flows in the economy. Hence, PIOTs prove to be a viable tool for developing a holistic approach to manage disrupted biogeochemical cycles, since these provide a detailed insight into physical flows in economic systems and allow physical coupling with ecological N flows.
氮（N）对可持续发展构成了重大挑战。人类对全球氮循环的干预在为社会提供商品和服务方面发挥了关键作用。然而，超出预期社会用途的氮排放会带来许多负面的健康和环境后果。已经开发了几种系统建模方法来理解氮的有益和有害影响之间的权衡。这些努力包括生命周期建模、综合管理实践以及针对个人和社区的可持续性指标。然而，这些方法并没有在整个系统中以物理单位将经济和生态氮流联系起来，而这可以更好地为决策者呈现这些权衡。基于实物投入产出表（PIOT）的模型是克服这一局限性的可行补充解决方案。我们使用氮质量单位为伊利诺伊州开发了一个2002年的氮实物投入产出表，以体现各部门之间的相互依存关系。这使得我们能够研究在最终产品中生产一定量氮所需的总氮流。基于环境扩展投入产出（EEIO）的方法被用于将实体经济生产与环境损失联系起来；从而能够量化对伊利诺伊州农业生产的总体环境影响。采用自下而上的方法，利用物质流分析（MFA）追踪与前三大商品（玉米、大豆和小麦）相关的氮流，开发了氮实物投入产出表。这三种商品占伊利诺伊州氮肥使用量的99%。实物投入产出表显示，在玉米生产的所有氮输入中，该州出口了有用产品中所含氮的68%，9%进入动物饲料生产，而该州内直接消耗的仅占0.03%。大豆种植氮输入的约35%最终进入动物饲料。氮向环境的排放中，玉米种植最高，约占总氮肥输入的21.8%，其次是大豆（9.2%）和小麦种植（4.2%）。该模型还能够根据经济中的实物流计算氮的生命周期氮利用效率。因此，实物投入产出表被证明是制定全面方法来管理被扰乱的生物地球化学循环的可行工具，因为它们能够详细洞察经济系统中的实物流，并允许与生态氮流进行实物耦合。
