Inorganic geochemical analysis of sediment has played a central role in palaeolimnology since its establishment as a research field. This chapter outlines methods that can be applied, explores the issues affecting reliability of interpretations, and refers readers to the appropriate literature. A distinction is made between inorganic geochemical palaeolimnology and inorganic geochemistry in general. While sharing many techniques and information sources, the two subjects differ fundamentally in purpose. Inorganic geochemistry aims to understand the chemical properties of the natural world, and the behaviour of chemical substances within it. Geochemical palaeolimnology uses such information to describe and quantify the environment. Furthermore, whereas palaeolimnological analysis is about lake, catchment or even landscape scale processes, geochemistry often considers minute scales. This contrast in scale has lead to conflicting interpretations. Geochemists working with laboratory experiments, and studying speciation and small-scale mobility, emphasize complexity. Palaeolimnologists, on the other hand, tend to look at large scale phenomena, and often find consistent patterns, even where a full geochemical understanding is lacking. The two disciplines should not be seen as separate. Inorganic geochemistry feeds into geochemical palaeolimnology because it is important to have a good understanding of the behaviour of the elements being measured. Conversely, palaeolimnological data can help to constrain geochemical models. Nevertheless, the contrasts in purpose and scale must be kept firmly in mind. A further distinction is made between organic and inorganic methods. For many inorganic elements, behaviour is highly dependent upon organic substances, and the two topics cannot be treated in isolation. Rather, inorganic methods must include a basic evaluation of organic components.

Inorganic Geochemical Methods in Palaeolimnology

In Publication 103 (ICRP, 2007), the Commission included a section on the protection of the environment, and indicated that it would be further developing its approach to this difficult subject by way of a set of Reference Animals and Plants (RAPs) as the basis for relating exposure to dose, and dose to radiation effects, for different types of animals and plants Subsequently, a set of 12 RAPs has been described in some detail (ICRP, 2008), particularly with regard to estimation of the doses received by them, at a whole-body level, in relation to internal and external radionuclide concentrations; and what is known about the effects of radiation on such types of animals and plants A set of dose conversion factors for all of the RAPs has been derived, and the resultant dose rates can be compared with evaluations of the effects of dose rates using derived consideration reference levels (DCRLs) Each DCRL constitutes a band of dose rates for each RAP within which there is likely to be some chance of the occurrence of deleterious effects Site-specific data on Representative Organisms (ie organisms of specific interest for an assessment) can then be compared with such values and used as a basis for decision making It is intended that the Commission's approach to protection of the environment be applied to all exposure situations In some situations, the relevant radionuclide concentrations can be measured directly, but this is not always possible or feasible In such cases, modelling techniques are used to estimate the radionuclide concentrations This report is an initial step in addressing the needs of such modelling techniques After briefly reviewing the basic factors relating to the accumulation of radionuclides by different types of biota, in different habitats, and at different stages in the life cycle, this report focuses on the approaches used to model the transfer of radionuclides through the environment It concludes that equilibrium concentration ratios (CRs) are most commonly used to model such transfers, and that they currently offer the most comprehensive data coverage The report also reviews the methods used to derive CRs, and describes a means of summarising statistical information from empirical data sets Emphasis has been placed on using data from field studies, although some data from laboratory experiments have been included for some RAPs There are, inevitably, many data gaps for each RAP, and other data have been used to help fill these gaps CRs specific to each RAP were extracted from a larger database, structured in terms of generic wildlife groups In cases where data were lacking, values from taxonomically-related organisms were used to derive suitable surrogate values The full set of rules which have been applied for filling gaps in RAP-specific CRs is described Statistical summaries of the data sets are provided, and CR values for 39 elements and 12 RAP combinations are given The data coverage, reliance on derived values, and applicability of the CR approach for each of the RAPs is discussed Finally, some consideration is given to approaches where RAPs and their life stages could be measured for the elements of interest under more rigorously controlled conditions to help fill the current data gaps

https://journals.sagepub.com/doi/pdf/10.1016/j.icrp.2011.08.009

Environmental Protection: Transfer Parameters for Reference Animals and Plants:

Geochronology of high latitude lake sediments

The influence of inland water bodies on the global carbon cycle and the great potential for long-term carbon burial in them is an important component of global limnology. We used paleolimnological methods to estimate changes in carbon burial rates through time in a suite of natural lakes in the US state of Iowa which has watersheds that have been heavily modified over the last 150 years. Our results show increasing carbon burial for all lakes in our study as agriculture intensified. Our estimates of carbon burial rates, before land clearance, are similar to the published worldwide averages for nutrient-poor lakes. In nearly all the cases, burial rates increased to very high levels (up to 200 g C m−2 y−1) following agricultural development. These results support the idea that the increased autochthonous and allochthonous carbon flux, related to anthropogenic change, leads to higher rates of carbon burial. Further, these results imply that the fraction of global carbon buried by lakes will be increasingly important in the future if worldwide trends in anthropogenic eutrophication continue.

Impacts of Eutrophication on Carbon Burial in Freshwater Lakes in an Intensively Agricultural Landscape

the International Atomic Energy Agency CRP on “The assessment of soil erosion through the use of Cs-137 and related techniques as a basis for soil conservation, sustainable agricultural production, and environmental quality” (D1.50.05) and the IAEA CRP on “Soil erosion and sediment assessment studies by environmental radionuclid es and their applications to soil conservati on measures” (F3.10.01).

Bibliography of publications of 137 cesium studies related to erosion and sediment deposition

In this paper we test the utility of the mud deposition boundary depth (mud DBD) theory (Rowanet al. 1992) as a means of maximizing sampling efficiency in paleolimnological investigations, particularly those that apply to210Pb dating. The mud DBD is defined by the relationship between near bottom wave velocity and particle threshold velocity, with wave and particle threshold theory simplified to terms of exposure and depth. Mud DBD theory can be used to define the depositional zone in lakes, and within the depositional zone defined by the mud DBD: 1) there is a high probability of obtaining a representative core, 2) variation in mass sediment accumulation rate (MSAR) is not correlated with water depth, and 3) variation in MSAR is considerably reduced from the whole lake average. This suggests that mud DBD theory can account for the effects of sediment focusing, and that the mud DBD defined depositional zone is the zone to which fine-grained sediments are focused. Finally, we have shown that to optimize sampling effort, 5 to 10 cores within the depositional zone are necessary for a reasonably precise estimate of the mean mass sediment accumulation rate. In addition, the use of mud DBD theory prior to sampling can dramatically reduce the cost associated with analyzing large numbers of cores for210Pb.

D. J. Rowan

Papers

Sediment focusing and210Pb dating: a new approach