Groundwater isotopes in ecohydrological analysis of peatland landscapes

The thesis demonstrates that studying natural isotopes in groundwater can improve ecohydrological approaches needed to understand the functioning of peatland in relation to their landscapes. In four case studies a relatively simple, time-effective, and integrated approach is used to complete scientific assessment of the hydrological changes in peatland ecosystems caused by humans. The case studies focus on both regional- and local hydrological systems. The research provides a step forward for management for the areas studied in this thesis. The research shows that despite complications in interpreting the results, radiocarbon dating of peat and groundwater can be used successfully in order to understand the effects of interferences with the hydrology within the landscape

Groundwater isotopes in ecohydrological analysis of peatland landscapes

The thesis demonstrates that studying natural isotopes in groundwater can improve ecohydrological approaches needed to understand the functioning of peatland in relation to their landscapes. In four case studies a relatively simple, time-effective, and integrated approach is used to complete scientific assessment of the hydrological changes in peatland ecosystems caused by humans. The case studies focus on both regional- and local hydrological systems. The research provides a step forward for management for the areas studied in this thesis. The research shows that despite complications in interpreting the results, radiocarbon dating of peat and groundwater can be used successfully in order to understand the effects of interferences with the hydrology within the landscape

Natural Isotopes and Ion Compositions Identify Changes in Groundwater Flows Affecting Wetland Vegetation in the Drentsche Aa Brook Valley, The Netherlands

This study uses groundwater isotopes and ion composition to verify model simulations and ecohydrological studies in the Drentsche Aa nature reserve in The Netherlands, which is representative for the northwestern wetland areas in the Ice Marginal Landscape zone. At eight field sites, a total of 24 samples were analysed for their 13C, 14C, 2H, and 18O isotopes and ionic composition. The isotopes indicate that most of the fen peatlands in the area depend on the exfiltration of sub-regional groundwater flows, which confirmed the previous model simulations and ecohydrological studies. At three sites, isotopes and ionic composition indicate that the groundwater from the sub-regional system has been replaced by local infiltrated rainwater, due to nearby groundwater abstractions for drinking water, which influenced the success rates of the restoration measures. Furthermore, the evidence from chloride and 14C contents was found to indicate the presence of more saline groundwater, which are influenced by the groundwater flows near salt diapirs. Groundwater abstractions may enhance the upward flow of the saline groundwater to eventually exfiltrate at the wetlands, affecting the biodiversity of the nature reserve

South African peatlands:A review of Late-Pleistocene-Holocene dvelopments using radiocarbon dating

South Africa has a limited number of peatlands and most of them are relatively small compared to those in cooler temperate regions in the northern hemisphere. We gathered 40 basal peat samples representative of South Africa’s peatlands to explore their development during the Late Pleistocene and Holocene. Depth profiles of nine of them were also investigated using radiocarbon dating, which yielded information on past environmental changes affecting South African peatlands. The data showed three peaks in the frequency of peatland initiation, which are consistent with available climatic and sea level fluctuation data: one after the Last Glacial Maximum (LGM) and two during the Mid to Late Holocene. Inland peatlands in mountain valleys showed optimal growing conditions during the glacial-interglacial transition, continuing until the Early-Holocene. This is due to the switch to the wet and warm interglacial climate. In contrast, coastal peatlands showed optimal initiation conditions over two phases during the Holocene, which is consistent with sea level rise peaks that led to optimal moist conditions occurring ca. 6,000–3,000 and 1,000 years ago. Sea level rise reduced groundwater drainage, which led to a rise in the primary groundwater table. However, data from some of the coastal peatlands indicate independence from the sea level fluctuation, and that they are rather controlled by climatic conditions and their local hydrogeomorphic setting, e.g. perched groundwater aquifers. Some peatland complexes show a pattern of phased initiation with peat initiation consistent with altitude difference, which could be due to a positive feedback of blocking caused by peat accumulation in lower reaches, reducing groundwater drainage to the sea

Natural isotopes support groundwater origin as a driver of mire type and biodiversity in Slitere National Park, Latvia

Contains fulltext : 219073.pdf (publisher's version ) (Open Access

The use of natural isotopes for identifying the origins of groundwater flows: Drentsche Aa Brook Valley, The Netherlands

This paper investigates the origin of various groundwater flows in a small brook valley reserve Drentsche Aa Valley in the northern part of the Netherlands. The aim was also to validate a hydrological model that simulated coupled particle flow in this area and also incorporated different scenarios for groundwater abstraction in order to predict future implications of groundwater abstraction on ecological values. Water samples from various sites and depths were analysed for macro-ionic composition, stable isotopes (2H and 18O) and also 14C. Three sites have 14C activities over 100%, indicating very recent water. The main groundwater discharge areas showed inflow of old groundwater up to 5000 years. Inflow of different groundwater flows of various ages could be detected most clearly from the 14C data. Downstream area that were affected by groundwater abstraction showed distinct infiltration characteristics, both in macro-ionic composition and contents of natural isotopes, to a depth of 6m below surface In the main exfiltration areas, we found that at 95 meters below the surface, the groundwater was characterized by a NaCl type groundwater facies. But the absolute concentrations were not high enough to conclude that double diffusive convection (DDC) near a salt diapir was responsible for this effect

Natural Isotopes Identify Changes in Groundwater Flows Affecting Wetland Vegetation in the Drentsche Aa Brook Valley, The Netherlands

Contains fulltext : 203585.pdf (publisher's version ) (Open Access

Natural isotopes and ion compositions identify changes in groundwater flows affecting wetland vegetation in the Drentsche Aa Brook Valley, The Netherlands

This study uses groundwater isotopes and ion composition to verify model simulations and ecohydrological studies in the Drentsche Aa nature reserve in The Netherlands, which is representative for the northwestern wetland areas in the Ice Marginal Landscape zone. At eight field sites, a total of 24 samples were analysed for their 13 C, 14 C, 2 H, and 18 O isotopes and ionic composition. The isotopes indicate that most of the fen peatlands in the area depend on the exfiltration of sub-regional groundwater flows, which confirmed the previous model simulations and ecohydrological studies. At three sites, isotopes and ionic composition indicate that the groundwater from the sub-regional system has been replaced by local infiltrated rainwater, due to nearby groundwater abstractions for drinking water, which influenced the success rates of the restoration measures. Furthermore, the evidence from chloride and 14 C contents was found to indicate the presence of more saline groundwater, which are influenced by the groundwater flows near salt diapirs. Groundwater abstractions may enhance the upward flow of the saline groundwater to eventually exfiltrate at the wetlands, affecting the biodiversity of the nature reserve