Mining environments: the good, the bad, and the ugly

Since the first scientific observations on mining environments over 400 years ago, we have gained some phenomenal knowledge on mine, land and waterways degradation and related environmental protection issues. Yet today, we continue to be faced with numerous challenges, including the recurring failure of mine waste repositories, the unconstrained production of acid rock drainage and the widespread dispersal of contaminants from mine sites into the environment. More than ever, environmental scientists have important contributions to make as they provide the data necessary for rational decision-making in critical areas such as resource development, environmental protection, waste management and remediation, as well as mine, land and waterway rehabilitation. The most urgent problem facing environmental scientists working on mining environments is the quantification of the interactions that control the distribution of contaminants in rocks, soils, sediments, waters and biota. We must precisely describe the chemistry and mineralogy of contaminants and understand their long-term behaviour. We need to drastically improve our scientific efforts to explain environmental processes at mine sites on all scales, including micro and macro scales as well as in 3-D and 4-D. In addition, we must improve our predictions on mine drainage, aquifer and final void water quality. While the rehabilitation of many mine sites and waste repositories is pursued by using best practices, we must continue to search for innovative, cost-effective remediation technologies and sustainable rehabilitation practices. Evaluations of recently rehabilitated mine sites could produce data on the successes and failures of rehabilitation efforts. Such studies should sharpen our ideas on the factors leading to contaminant dispersal and the development of new remediation technologies. The rehabilitation of mine sites and secure disposal of mine wastes require a new precision in the total description of mine sites and an understanding whether our current rehabilitation practices are sustainable in the long term. There is reason for optimism that the required progress is possible. Such optimism is based on the phenomenal advances in our ability to observe and describe mining environments. However, detailed studies of natural, mined, contaminated and rehabilitated environments are necessary if we are to quantify the variables controlling the containment and dispersal of contaminants and if we are to develop innovative remediation protocols. Our efforts could ensure that the 21st century goes down in history as that of “green technologies”

Environmental review of the Radium Hill mine site, South Australia

The Radium Hill uranium deposit, in semi-arid eastern South Australia, was discovered in 1906 and mined for radium between 1906 and 1931 and for uranium between 1954 and 1961 (production of 969,300 t of davidite ore averaging 0.12 % U3O8). Rehabilitation was limited to removal of mine facilities, sealing of underground workings and capping of selected waste repositories. In 2002, gamma-ray data, plus tailings, uncrushed and crushed waste rock, stream sediment, topsoil and vegetation samples were collected to assist in the examination of the current environmental status of the mine site. The preliminary data indicate that capping of tailings storage facilities did not ensure the long-term containment of the low-level radioactive wastes due to the erosion of sides of the impoundments. Moreover, active wind erosion of waste fines from various, physically unstable waste repositories causes increasing radiochemical (up to 0.94 μSv/h) and geochemical (Ce, La, Sc, Th, U, V, Y) impacts on local soils and sediments. However, measured radiation levels of soils and sediments are at or below Australian Radiation Protection Standards (20 mSv/a averaged over five consecutive years). Additional capping and landform design of the crushed waste and tailings repositories are required in order to minimise erosion and impacts on surrounding soils and sediments

Existence of families of spacetimes with a Newtonian limit

J\"urgen Ehlers developed \emph{frame theory} to better understand the relationship between general relativity and Newtonian gravity. Frame theory contains a parameter $\lambda$, which can be thought of as $1/c^2$, where $c$ is the speed of light. By construction, frame theory is equivalent to general relativity for $\lambda >0$, and reduces to Newtonian gravity for $\lambda =0$. Moreover, by setting \ep=\sqrt{\lambda}, frame theory provides a framework to study the Newtonian limit \ep \searrow 0 (i.e. $c\to \infty$). A number of ideas relating to frame theory that were introduced by J\"urgen have subsequently found important applications to the rigorous study of both the Newtonian limit and post-Newtonian expansions. In this article, we review frame theory and discuss, in a non-technical fashion, some of the rigorous results on the Newtonian limit and post-Newtonian expansions that have followed from J\"urgen's work