Soil mapping and cultural heritage

Transcription

1 Soil mapping and cultural heritage

2 Bredhøj excavation

3 Bredhøj, analytical data Ap OM% Fe% mantel core Iron pan subsoil

4 Coffin and the girl from the Egtved mound, 1370 BC

5 Haute couture anno BC

6 Questions How many burial mounds do we have with anaerobe cores Where are they located? Are the preservation conditions stable? a) for protected mounds b) for non-protected mounds

7 Mapping of burial mounds with pans Investigation sites

8 boring i gravhøj

9 Auger samples burial mounds

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11 Soil description system Type of burial mound a) shape, age, land use The individual sod. a)a,e,b,c-material (A, AE, AC etc) b)colour, texture, stones, geology c)gley, nodules and iron pan d)artefacts

12 Results Mounds with anaerobe iron pan encapsulated core is only found in a restricted area of Jutland In about 5% of the burial mounds in Jutland we found a iron pan encapsulated core. Burial mounds with iron pan encapsulated core are often found specific mound groups Non-protected burial mounds lose about 1 cm per year in height due to ploughing

13 Non-protected mounds Preservation conditions

14 Core and iron pan

15 Kongsted, broken down coffin with remnants of a man

16 Kongsted, Legs of a man from about 3300 years ago

17 Kongsted, plough furrows from about 3300 years ago

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22 The lesson to be learned Skelhøj anaerobe core under destruction

23 Core under destruction, why

24 Core under destruction, why?

25 Core under destruction

26 Conclusion on preservation conditions The preservation conditions are good if the iron pan has not been broken by grave robbers. The core will be full of water. Unfortunately this is normally not the case. If the iron pan is broken, the water will run away and the preservation conditions change slowly. Today it happens in several protected mounds If trees are grown on the mound their deep going roots will speed up the change of preservation conditions because they have a huge water uptake In non-protected mounds the ploughing will decline the height with about 1 cm per year and when the mound fill becomes too thin the good preservation conditions will disappear.

27 What to do Soil mapping the protected and non-protected mounds in selected parts of Jutland where burial mounds with anaerobe core previously have been found. Excavate the non-protected mounds with iron pans. Do not touch the protected mounds with water-filled anaerobe cores. Protected mounds with iron pans and blue/grey cores must excavated, because the good preservation condition are disappearing Trees growing on burial mound with iron pans must be cut down. Legislation about trees on burial mounds is under preparation An application for a mapping of mounds with iron pan encapsulated cores is under elaboration

28 The Danish Soil Classification, why? From 1939 to 1975 the farmland area dropped from sqkm to sqkm It raised a need for soil maps for planning and administration purposes at national and county level The Danish government decided to finance a national soil mapping

29 Basic requirements The areas should be classified on the basis of permanent stable characteristics The results should clearly illustrate the range of fertile and infertile soils The maps should be made in such a way that they might be used in future regional planning The mapping should be finished within 3 years (price app Euro)

30 The soil map, scale 1: Classified area Texture of the plowlayer and subsoil (12 classes) Slope (3 classes) Subsoil geology (app. 50 classes) Not classified area Urban zone Forest Coastal dune sands, small arable areas, lakes etc

31 Organisation In December 1975 ADK was established to undertake the soil sampling, database handling and construction of the maps at scale 1: Crew: 3 AC and 1 technician + some students from the Universities. The soil sampling was done by local agronomists and the soil analyses were done at a research laboratory.

32 Mapping slopes and surface geology Slope classes Three slope classes delineated on topographic maps at scale 1:25000 <6 degrees, 6-12 degrees and >12 degrees Surface geology Dominant surface geology is shown in a 25ha grid based on the Danish geological surveys map which cover 75% of the country

33 Soil sampling for texture analyses ADK distributed topographic maps and questionnaires to local agronomists (advisors) who registered existing texture analyses The agronomists were asked to recommend suitable locations for forthcoming soil sampling ADK combined the recommendation with information on topography and surface geology and the final sampling sites were chosen The agronomists undertook the soil sampling topsoil samples (0-20cm) and 6000 subsoil samples (35-55cm) were taken

34 Sampling sites

35 Analyses Texture: 2µm, 20µm, (63µm), 200µm, 2000µm Hydrometer method and sieving Organic C: Determined by a Leco-apparatus Lime: Determined by treating the samples with HCl and capture the carbondioxide in bariumhydroxide

36 Texture analyses

37 Sample library

38 Texture classification

39 Map construction The borders on the soil maps were drawn by the crew at ADK in cooperation with the local agronomists The drawing of the borderlines was based on the texture analyses, landscape analyses, the surface geology maps and the local knowledge from the agronomists involved. The maps were digitized and all analytical data were stored in a database. The software was developed as a Ph.D. study at Århus University

40 Soil map from Aabenraa

41 The use of the data base Protection of fertile farmland around towns and villages Irrigation need for farming at county level It became obvious that additional data were needed for a proper regional planning

42 Geomorphological map of Denmark

43 Subsoil texture

44 Wetlands

45 Soil chemical and physical data By combining the different soil maps an area can be characterized as follows: Topsoil: Fine sand (MCC2) Subsoil: loam (MCC5) Drainange: not wetland Geomorphology: Weichsel moraine In order to use the soil maps in planning there was a huge need for soil profile analytical data, chemical as well as physical

46 Profile sampling sites

47 Soil classification

48 Profile description

49 Soil profile description scheme

50 Analyses Texture (hydrometer + sieving) Total carbon (dry combustion) Total nitrogen (Kjeldahl) Total organic and inorganic phosphorous ph(h 2 O) and ph(cacl 2 ) Lime content (Scheibler) Exchangeable acidity at ph 8.1 (Pipers method) Exchangeable bases (NH 4 Ac-extraction at ph7) DCB, oxalate and pyrophosphate iron and aluminium KCl-extractable H and Al Soil water retention (Pressure plate apparatus)

51 The use of the databases Irrigation need for agriculture production at county level Irrigation permission Hunting zones Economical compensation for drainage The potential drainage need at national level Mapping of potential set aside area Carbon storage in Danish soils Nitrate leaching from farmland Phosphor pollution of streams due to soil erosion Today the soil maps are the normal soil data input in regional modelling

52 Environmental problems Ochre polution of Danish watercourses Severe ochre polution of Danish streams has frequently occured due to drainage of farmland. The ochre polution was believed to be due to oxidation of pyrite. In order to prevent ochre polution of the streams a mapping of potential acid soils was conducted The mapping should be done within a 3 years period Based on the mapping a legislation should be made to stop the ochre polutions of the streams.

53 Normal stream

54 Ochre from drains

55 Ochre poluted streams

56 Location of pyrite in the landscape In delta regions and lagunes where sea water is meeting fresh water. Inland wetland areas which are enriched with ferro iron and sulfate from higher parts of the landscape Soil material with high content of pyrite is called sulfidic soil materials

57 Fluvisols and gleysols

58 Histosols

59 Sampling area

60 Camp site and equipment for mapping potential acid sulfate soils

61 Sampling area

62 Travelling to sampling site

63 Augering in wetland

64 Samples

65 Soil description scheme

66 Determination of colour and ph

67 Potential acidity analytical results for lime free samples A sample is potential acid sulfate if: ph drop below 3.0 within 16 weeks of oxidation and ph drops more than one unit within that period

68 Potential acidity lime containing samples Potential acid sulfate if: %pyrite x 34 meq/100g > (Ca + Mg) meq/100g

69 Potential acid sulfate soil classes Class 1: > 50% acid sulfate soil profiles Class 2: 20-50% acid sulfate soil profiles Class 3: 2-20% acid sulfate soil profiles Class 4: <2% acid sulfate soil profiles An acid sulfate soil profile is a profile containing at least one acid sulfate soil sample

70 Map showing potential acid sulfate soils

71 Red 50%-100% Yellow 20%-50% Green 20%-2% Blue: <2% Potential acid sulfate soil

72 Ochre investigation areas if the farmer wants to drain

73 The law If a farmer wants to drain a field within class 1,2 or 3, the following has to be done A soil surveyor has to take soil samples from the field and the samples are analysed for potential acidity If the samples are negative the farmer an drain If a sample is positive the county administration decides what to do. They can forbid the drainage or they can tell the farmer what to do before drainage can be done