Characterization of hardrock mining impacts near Rico, Colorado: Testing a geochemical technique for citizen science.

摘要

Past and present hardrock mining activities continue to adversely affect water quality in the western United States by contributing acidity and dissolved heavy metals which impair aquatic ecosystem health. The Abandoned Mine Lands Initiative comprised a multi-agency US government effort to address the issue by developing a scientific knowledge base and technical methods to assess and prioritize watershed remediation. The problem is pervasive in the west ; financial resources are thin and as a result, many current watershed remediation efforts are driven by citizen groups. The purpose of this study is to apply methods developed in the Abandoned Mine Lands Initiative to a stream impacted by hardrock mining in order to assess whether they are suitable for use and application by non-professional citizen scientists engaged in resource management decisions, and understand the policy issues with clean up at mine sites affecting public waterways.;The Town of Rico, Colorado, was the site of active hardrock mining from the nineteenth century onward. Numerous abandoned sites contribute or may potentially contribute dissolved metals pollution to the Dolores River. By combining injection of a conservative ionic tracer with synoptic sampling, this study characterized the location and amount of primary pollution sources near Rico using a mass loading analysis. Dissolved zinc and cadmium are of most concern for aquatic health. Combined sources contributed 0.9 kg/d of dissolved cadmium and 16 kg/d of dissolved zinc. The adit and ponds complex associated with the St. Louis Tunnel contributes close to 50% of cadmium load, and 80% of zinc load to the Dolores River. Sampling sites on the Dolores returned dissolved cadmium levels exceeding or near the state's chronic water quality standard.;Mass loading assessment using tracer studies and synoptic sampling is logistically sensitive and labor intensive, but not highly technical. Results from this study show that this method can be successfully utilized by citizen groups for baseline assessments, or monitoring of current or past remediation actions. Construction of a suitable injection set-up, and adequate personnel to perform the sampling, processing, and field data collection, can ensure robust result. While information from sampling can form the basis for more complex analyses, the detailed spatial characterization of water quality and pollution sources is the primary useful output to local resource decision-makers.;Citizen-based efforts at remediation are also currently hindered by pollution liability assigned through the complex legal framework surrounding abandoned mine sites. Additional inroads to the environmental problems posed by hardrock mining can be aided by careful reform of the 1872 Mining Law, which widely allows mining on public lands with little citizen input on location, and a coherent national strategy and funding framework for mine cleanup. Some mine pollution problems may be too complex or resource intensive to be approached by NGOs, in which case groups should focus on what is actually achievable and enlist government help when possible.