Tim Allott

A spatial and seasonal assessment of river water chemistry across North West England

This paper presents information on the spatial and seasonal patterns of river water chemistry at approximately 800 sites in North West England based on data from the Environment Agency regional monitoring programme. Within a GIS framework, the linkages between average water chemistry (pH, sulphate, base cations, nutrients and metals) catchment characteristics (topography, land cover, soil hydrology, base flow index and geology), rainfall, deposition chemistry and geo-spatial information on discharge consents (point sources) are examined. Water quality maps reveal that there is a clear distinction between the uplands and lowlands. Upland waters are acidic and have low concentrations of base cations, explained by background geological sources and land cover. Localised high concentrations of metals occur in areas of the Cumbrian Fells which are subjected to mining effluent inputs. Nutrient concentrations are low in the uplands with the exception sites receiving effluent inputs from rural point sources. In the lowlands, both past and present human activities have a major impact on river water chemistry, especially in the urban and industrial heartlands of Greater Manchester, south Lancashire and Merseyside. Over 40% of the sites have average orthophosphate concentrations >0.1mg-Pl(-1). Results suggest that the dominant control on orthophosphate concentrations is point source contributions from sewage effluent inputs. Diffuse agricultural sources are also important, although this influence is masked by the impact of point sources. Average nitrate concentrations are linked to the coverage of arable land, although sewage effluent inputs have a significant effect on nitrate concentrations. Metal concentrations in the lowlands are linked to diffuse and point sources. The study demonstrates that point sources, as well as diffuse sources, need to be considered when targeting measures for the effective reduction in river nutrient concentrations. This issue is clearly important with regards to the European Union Water Framework Directive, eutrophication and river water quality.

Arsenic retention and release in ombrotrophic peatlands.

Organic matter can play an important role in the mobility and fate of As in the environment, but there is a lack of data on As biogeochemistry in ombrotrophic peatlands. The aim of this study was to investigate As retention and release in atmospherically contaminated ombrotrophic peat soils in the Peak District National Park (UK). Solid phase As concentrations in the peat soils exceed 25 mg kg(-1). Solid phase As and Fe concentrations are closely correlated at sites where the peat is subjected to drying and oxic conditions. In a wetter zone of the bog, solid phase As and Fe distributions are decoupled, suggesting that As retention in these systems is not solely controlled by the presence of Fe oxides. Comparison of solid phase As and Pb distributions reveals that As has been subjected to post-depositional mobility in areas of water table fluctuation. Conversely, at permanently waterlogged locations As is immobile. Detailed stream water sampling reveals that As is released from the organic-rich uplands soils into the fluvial system. Dissolved As concentrations are highly variable, with values ranging from 0.20 to 7.28 microg l(-1). Stream water As concentrations are elevated during late summer stormflow periods when there has been re-wetting of the peat after significant water table draw-down. Dissolved As is strongly correlated to dissolved organic carbon under stormflow and baseflow. The results of this study suggest that organic matter plays an important role in As dynamics in ombrotrophic peatlands, but further work is needed to identify the exact As binding and release mechanisms. Drying and re-wetting of ombrotrophic peat soils and associated changes in redox status has the potential to lead to increased As mobility. Further work is needed to provide information on how predicted climate change will influence As cycling at sites containing a legacy of atmospheric contamination.

Contrasting vulnerability of drained tropical and high‐latitude peatlands to fluvial loss of stored carbon

Carbon sequestration and storage in peatlands rely on consistently high water tables. Anthropogenic pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to increased release of older carbon from the peat profile but with marked differences related to peat type. Very low DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored peat carbon. High-latitude peatlands appear more resilient to drainage; 14C measurements from UK blanket bogs suggest that exported DOC remains young ( 500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age.

Storage and behavior of As, Sb, Pb, and Cu in ombrotrophic peat bogs under contrasting water table conditions.

Concentration depth profiles and inventories of solid-phase As, Sb, Pb, and Cu were determined in ²¹⁰Pb-dated cores from an ombrotrophic peat bog in northwest England. Cores were collected from the peat dome and adjacent to an eroding gully. Down-core distributions of As, Sb, Pb, and Cu in the dome core are almost identical. The water table is close to the dome surface with only short-term draw-down. Under these conditions, As, Sb, Pb, and Cu are immobile, allowing the reconstruction of trends in historical contaminant deposition. The peak in atmospheric deposition of As, Sb, Pb, and Cu (4.59, 2.78, 147, and 26.7 mg m⁻² y⁻¹, respectively) occurred during the late 19th century. Stable Pb isotope ratios reveal that Pb deposition during this period was from indigenous and foreign sources. The mean water table is much lower at the gully edge, and there are pronounced interannual fluctuations. These conditions have not affected the integrity of the Pb and Cu records but have caused postdepositional mobilization and redistribution of As and Sb. Cumulative inventories show significant loss of As and Sb at the gully edge site. Long-term water table draw-down in ombrotrophic peat bogs has the potential to alter the geochemistry and fate of previously deposited As and Sb.

Sulphur leaching from headwater catchments in an eroded peatland, South Pennines, U.K

A detailed investigation into sulphur leaching in peatland headwater catchments in the South Pennines, UK shows that, despite significant reductions in sulphur emissions, sulphur remains a key acidifier. This sulphur can be considered as legacy atmospheric pollution, stored within the peat by processes of dissimilatory sulphate reduction and now being leached into the regions surface waters. Persistently lower water tables at gully edge locations define a thick erosional acrotelm that is vulnerable to aeration, oxidation and flushing throughout the year, and not solely confined to periods of drought. Stream discharge behaves as a two-end member system, whereby pre-event water, rich in DOC and sulphate, is diluted by event water as a result of event water flowing through fast flow pathways such as macropores and overland flow. A rapid increase in water table elevation during the storm and a decrease in elevation after the storm indicate that event water has infiltrated the peat and has then been released into the stream. Streamwaters in peat dominated upland catchments with high densities of gullying have high concentrations of sulphate and low concentrations of DOC, whereas the reverse is true for those catchments with low densities of gullying. This is consistent with the concept that high concentrations of sulphate can suppress the solubility of DOC. A significant store of sulphate exists within South Pennine peats, and continued gully erosion will enhance sulphur leaching meaning that the timescale involved for any depletion is uncertain. It is therefore important that models predicting recovery from acidification in these upland systems include an understanding of how this stored sulphur is being leached, especially with respect to gully erosion, climate change and reduced precipitation.

Ammonium release from a blanket peatland into headwater stream systems

Hydrochemical sampling of South Pennine (UK) headwater streams draining eroded upland peatlands demonstrates these systems are nitrogen saturated, with significant leaching of dissolved inorganic nitrogen (DIN), particularly ammonium, during both stormflow and baseflow conditions. DIN leaching at sub-catchment scale is controlled by geomorphological context; in catchments with low gully densities ammonium leaching dominates whereas highly gullied catchments leach ammonium and nitrate since lower water tables and increased aeration encourages nitrification. Stormflow flux calculations indicate that: approximately equivalent amounts of nitrate are deposited and exported; ammonium export significantly exceeds atmospheric inputs. This suggests two ammonium sources: high atmospheric loadings; and mineralisation of organic nitrogen stored in peat. Downstream trends indicate rapid transformation of leached ammonium into nitrate. It is important that low-order headwater streams are adequately considered when assessing impacts of atmospheric loads on the hydrochemistry of stream networks, especially with respect to erosion, climate change and reduced precipitation.

Peatland Restoration and Ecosystem Services: Science, Policy and Practice

Peatlands provide globally important ecosystem services through climate and water regulation or biodiversity conservation. While covering only 0.4 per cent of the Earth’s surface, degrading peatlands are responsible for nearly a quarter of carbon emissions from the land-use sector. Bringing together world-class experts from science, policy and practice to highlight and debate the importance of peatlands from an ecological, social and economic perspective, this book focuses on how peatland restoration can foster climate change mitigation. Featuring a range of global case studies, opportunities for reclamation and sustainable management are illustrated throughout against the challenges faced by conservation biologists. Written for a global audience of environmental scientists, practitioners and policy makers, as well as graduate students from natural and social sciences, this interdisciplinary book provides vital pointers towards managing peatland conservation in a changing environment.

Contrasting controls on arsenic and lead budgets for a degraded peatland catchment in Northern England

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 ± 21.3 gPb ha(-1) y(-1) and 60.4 ± 10.5 gAs ha(-1) y(-1)), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters.

A conceptual framework for ecosystem restoration applied to industrial peatlands

Introduction The extraction of peat for fuel on an industrial basis started in the seventeenth century in eastern and northern Europe as the supply of wood for energy declined. The use of peat for energy in North America has always been small in scale. The demand for horticultural peat rose steadily after World War II on both continents (http://peatmoss.com/what-is-peat-moss/the-history-of-peat/). Currently, Europe and North America use peatmoss-peat extensively for landscaping, professional greenhouse production, hydrocarbon spills and waste water treatment. To date, in Canada, the main horticultural peat producers have impacted close to 20 000 ha. To place this into context, Canadas peatland extent is estimated to be around 125 000 000 ha with industrial activities mostly located on the southern margins of the peatland distribution. Most of the industrial peatlands are still in operation (16 000 ha), whereas close to 2000 ha have been restored according to the approach described below. With the rising awareness of goods and services provided by wetlands in the 1980–90s (Costanza et al. 1997), the international industrial peat sector recognised the impacts their activities had on peatland functions and developed a strategy for responsible peatland management. Several countries have since developed their own strategy and encourage the restoration of industrial peatlands (Clarke and Rieley 2010). For the case of Canada, peatland restoration is particularly driven by their main US horticultural clients, who demand responsible management of wetlands, driven by their interior policy on wetlands (NAWCA 1989). Based on two decades of trial-and-error experiments on restoring industrial peatlands, we have created a restoration framework. This framework draws on the ideas of assembly rules and restoration ecology. In this chapter, the framework is applied to restoring peatlands, but it should be applicable to the restoration of any ecosystem. Assembly rules and restoration ecology The union of assembly rules and restoration ecology should be beneficial for both areas of ecology (Keddy 1999; Temperton et al. 2004). Assembly rules are a helpful tool for restoration because, if the constraints of community membership are defined, restoration efforts can focus on manipulating these constraints to steer succession towards the desired community (Temperton et al. 2004). Restoration ecology has been criticised for being a haphazard collection of individual cases (Keddy 1999).

Reservoirs as hotspots of fluvial carbon cycling in peatland catchments

Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km2) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO2(aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition.