Ayres R U
Department of Engineering and Public Policy, Carnegie-Mellon University, Pittsburgh, PA 15213, USA.
Proc Natl Acad Sci U S A. 1992 Feb 1;89(3):815-20. doi: 10.1073/pnas.89.3.815.
Long-term ecological sustainability is incompatible with an open materials cycle. The toxic heavy metals (arsenic, cadmium, chromium, copper, lead, mercury, silver, uranium/plutonium, zinc) exemplify the problem. These metals are being mobilized and dispersed into the environment by industrial activity at a rate far higher than by natural processes. Apart from losses to the environment resulting from mine wastes and primary processing, many of these metals are utilized in products that are inherently dissipative. Examples of such uses include fuels, lubricants, solvents, fire retardants, stabilizers, flocculants, pigments, biocides, and preservatives. To close the materials cycle, it will be necessary to accomplish two things. The first is to ban or otherwise discourage (e.g., by means of high severance taxes on virgin materials) dissipative uses of the above type. The second is to increase the efficiency of recycling of those materials that are not replaceable in principle. Here, also, economic instruments (such as returnable deposits) can be effective in some cases. A systems view of the problem is essential to assess the cost and effectiveness of alternative strategies.
长期的生态可持续性与开放的物质循环不相容。有毒重金属（砷、镉、铬、铜、铅、汞、银、铀/钚、锌）就是这一问题的典型例子。这些金属正通过工业活动以远高于自然过程的速度被释放并扩散到环境中。除了矿山废弃物和初级加工造成的环境损失外，这些金属中有许多被用于本质上具有耗散性的产品中。此类用途的例子包括燃料、润滑剂、溶剂、阻燃剂、稳定剂、絮凝剂、颜料、杀生剂和防腐剂。为了封闭物质循环，有必要完成两件事。首先是禁止或以其他方式抑制（例如，通过对原生材料征收高额开采税）上述类型的耗散性用途。其次是提高那些原则上不可替代的材料的回收效率。在这方面，经济手段（如可退还押金）在某些情况下也可能有效。对该问题采用系统观点对于评估替代策略的成本和有效性至关重要。
