A fundamental requirement for the monitoring and study of natural environments is the ability to collect high-quality samples of solid, liquid, and gaseous phases. It is through the collection of such samples that analyses can be performed to define existing undisturbed conditions or to delineate impacts of human activity. The collection of high-quality samples is the first step in the overall process of environmental protection and, if an acceptable sample cannot be obtained, then the subsequent tasks of analysis, interpretation, and response may be of little benefit. In recognition of this importance, the Mine Environment Neutral Drainage (MEND) Program has commissioned Canect Environmental Control Technologies Ltd., a subsidiary of Norecol Environmental Consultants Ltd., to prepare this manual of sampling methodology.
A major environmental concern today is the disturbance of natural environments by human activities which result in the development of acidic conditions. This disturbance occurs during industrial activity where air emissions result in acidic rainfall and during mining and excavation where reactive sulfide minerals are exposed to the atmosphere. It is an objective of the MEND Program to examine the evolution of acidic conditions during mining activity. Acidic conditions at a mine sites can develop in rock piles, on mine walls, and in tailings impoundments which hold the waste products from ore processing. This manual specifically addresses sampling methods for tailings impoundments and their surrounding basins.
A multidisciplinary environmental study in the vicinity of a tailings impoundment involves the collection of solid, liquid, and pore-gas samples. These samples may be used for physical, chemical, and microbiological analysis and must be of high quality with minimal disturbance. The optimum methods for collection of high-quality samples are dependent on such factors as site-specific conditions and equipment availability, which preclude the development of a rigid prescriptive guide for sampling methodology. The collection of high-quality samples may not even be feasible at some impoundments, requiring a compromise on quality. As a result, this manual is designed to offer guidance and recommendations on the selection of appropriate sampling methodology while recognizing the importance of site-specific conditions and the value of on-site decision making. Emphasis is placed on maximizing sample quality by minimizing both sample disturbance and artificial contamination during sampling. Because subsurface environments are often chemically reducing (anoxic), a significant source of sample disturbance and contamination is exposure to the atmosphere.
This manual contains several indexes in Chapter 2 to summarize the solid, liquid and pore gas phase methods according to such factors as the type of required equipment and the degree of isolation from the atmosphere. A flowchart is also presented in Chapter 2 to summarize the indexes and to guide the selection of potentially appropriate methodology.
The methods for collection of samples in this manual are divided into three primary chapters covering solid, liquid, and pore-gas phases. The concise presentation of each method explains the objectives, descriptions, advantages and disadvantages. Chapter 3 presents the methods for collecting solid-phase samples, divided into the general categories of (1) heavy-powered equipment including drill rigs, (2) light-powered equipment including samplers used in association with drill rigs, and (3) hand-operated equipment. Many of these methods for solid-phase sampling provide the necessary borehole or excavation needed for subsequent collection of subsurface groundwater and pore gas using piezometers, wells, and gas pons. Chapter 4 describes the methods for collecting liquid-phase samples, divided into categories on the basis of (1) collecting a sample during drilling, (2) physically separating water from a solid-phase sample, (3) sampling from a well installed after drilling (4) sampling from installations established independently of drilling and (5) retrieving a groundwater sample using a pump or bailer. In Chapter 5, methods for sampling pore gas are grouped on the basis of (1) collecting a sample during drilling, 2) establishing sampling ports after drilling, (3) installing sampling ports independently of drilling, and (4) employing a syringe sampler or on-site autoanalyzer.
Chapter 6 contains a summary of quality control recommendations for the collection of high quality solid, liquid and pore-phase samples. The chapter is based on the individual recommendations in Chapters 3, 4 and 5.
