Coal mining‐derived ochres in the UK: a potential selenium trap

Thanks to the pioneering research of Paul Younger over the past 20 years, acid mine drainage in the UK has been recognized as a major environmental issue. Acid mine drainage and hydrous ferric oxide deposition are environmental hazards resulting from centuries of extensive coal mining activities across the UK. Oxidative weathering of pyrite in coal from spoil heaps and exposed bedrock can liberate trace elements, releasing them into local water systems. In addition to posing an environmental threat through water and ground contamination, ochres can also act as a remediation material, trapping elements such as selenium. Trace elements with a close association to iron oxides, such as selenium, may fix to the fine‐grained ochre materials, resulting in hyper‐enriched ochres. Selenium in coals has been known to cause an environmental issue in areas of North America but is also an important commodity for solar cells and nanotechnologies. Coal‐bearing areas of the UK, such as Northumberland, are known to contain a high selenium content, and coal‐derived ochres in these regions also contain significant selenium. The widespread occurrence of ochres in UK coal‐mining regions may therefore present a unique ‘E tech’ trace element source and prevent a toxicity problem for which they were once thought to be responsible.     

Near‐surface hydraulic conductivity of northern hemisphere glaciers

The hydrology of near‐surface glacier ice remains a neglected aspect of glacier hydrology despite its role in modulating meltwater delivery to downstream environments. To elucidate the hydrological characteristics of this near‐surface glacial weathering crust, we describe the design and operation of a capacitance‐based piezometer that enables rapid, economical deployment across multiple sites and provides an accurate, high‐resolution record of near‐surface water‐level fluctuations. Piezometers were employed at 10 northern hemisphere glaciers, and through the application of standard bail–recharge techniques, we derive hydraulic conductivity (K) values from 0.003 to 3.519 m day^?1, with a mean of 0.185 ± 0.019 m day^?1. These results are comparable to those obtained in other discrete studies of glacier near‐surface ice, and for firn, and indicate that the weathering crust represents a hydrologically inefficient aquifer. Hydraulic conductivity correlated positively with water table height but negatively with altitude and cumulative short‐wave radiation since the last synoptic period of either negative air temperatures or turbulent energy flux dominance. The large range of K observed suggests complex interactions between meteorological influences and differences arising from variability in ice structure and crystallography. Our data demonstrate a greater complexity of near‐surface ice hydrology than hitherto appreciated and support the notion that the weathering crust can regulate the supraglacial discharge response to melt production. The conductivities reported here, coupled with typical supraglacial channel spacing, suggest that meltwater can be retained within the weathering crust for at least several days. Not only does this have implications for the accuracy of predictive meltwater run‐off models, but we also argue for biogeochemical processes and transfers that are strongly conditioned by water residence time and the efficacy of the cascade of sediments, impurities, microbes, and nutrients to downstream ecosystems. Because continued atmospheric warming will incur rising snowline elevations and glacier thinning, the supraglacial hydrological system may assume greater importance in many mountainous regions, and consequently, detailing weathering crust hydraulics represents a research priority because the flow path it represents remains poorly constrained.     

Linking biogeochemical processes and historic primary producer communities in a SE USA sinkhole lake from the mid-Holocene to present

Many freshwater resources receive materials from human development causing a decrease in ecological services when compared to pre-disturbance periods. As a result, the understanding of eutrophication and limnological change has increased, but less attention has been given to systems under intense human impact that have not eutrophied so that drivers precluding eutrophication can be documented. The primary objective of this research was to reconstruct allochthonous inputs and in-lake processes for Long Pond, Georgia, USA from the mid Holocene to present and link them to primary producer community changes. Long Pond is a mesotrophic lake located in a highly altered watershed from agricultural and municipal land use and housing developments. A 5 m sediment core was collected from Long Pond, and organic matter, nutrients (C, N, P), metals (Al, Fe, Cu), and photosynthetic pigments were measured. Long Pond existed in three limnological states spanning the past ~6000 years. Prior to modern lacustrine conditions, Long Pond was a wetland/peat system that experienced the highest primary producer abundance recorded in the core. The modern lacustrine state began in the late Holocene and was characterized by increased connectivity with the surrounding watershed and low productivity. Human impacts began around 1900 AD and included high levels of phosphorus and metal deposition but moderate levels of primary producer abundance. As a result, in-lake dynamics are believed to be regulating the trophic status of Long Pond. Low concentrations of available phosphorus in the water column combined with high concentrations of sedimentary phosphorus may imply the binding of phosphorus to the sediments by certain materials such as aluminum and iron. Long Pond serves as an example of the complex in-lake processes that can occur from allochthonous inputs and autochthonous responses in lake systems thus complicating management decisions.     

A Mariner 9 atlas of the moons of Mars

This paper contains a complete set of the best enhancements of Mariner 9 high resolution television pictures of Phobos and Deimos, consisting of 27 different views of Phobos, and 9 of Deimos. Pertinent data about the pictures are arranged in convenient tabular and graphical form.