SUITMA 2003 Nancy - Investigation of the small scale inorganic soil contamination variation and patterns between blocks of flats
SUITMA 2003 Nancy
| This abstract is about one of the papers of the Methodology for the study of urban soils and classification theme of the SUITMA 2003 Nancy symposium. |
| Harald Ertl,i | Wolfgang Burghardt.i |
- i - University of Essen - Department of Soil Technology.
Introduction
The German federal soil protection act (BBODSCHG 1998) and the North Rhine Westphalia provincial soil protection act (LBODSCHG 2000) require the production of soil contamination maps in agricultural, forested and urban areas. In contrast to agricultural and forested areas, there exists up to now no sophisticated procedure for the soil contamination mapping within residential and other urban areas. The method discussed recently (BARKOWSKI et al. 2002) is mainly based on the method used for agricultural and forested areas (HEIDBRINK and NEITE 2000), although the theoretical background of contamination mapping in urban areas is still unknown for the most part. In particular it is not known how large the spatial variability of soil contamination of an examined site is and whether spatial patterns of soil contamination are occurring. One of the key problems is the lack of information about the maximum sampling distance (biggest possible sampling grid distance for getting representative results) in urban areas. This information is needed for a representative determination of the contamination. Therefore the theoretical background of contamination mapping in urban areas must be established.
This study contributes to establish a more sophisticated sampling method for soil contamination mapping in urban areas by examining the small-scale horizontal spatial variability and structure of the inorganic soil contamination of a representative site of approx. 15 m x 36 m between two blocks of residential flats built in the 1950th in the northern part of the City of Essen, central Ruhr district, Germany.
Materials and methods
For the representative selection of the study site an aerial photo-interpretation and an overview survey of all blocks of flats constructed in the 1950th and 1960th were accomplished in the northern part of the City of Essen. The soils of this type of residential blocks cover about 11 % of the northern City area (KAMIETH 1985). 64 pits were surveyed and sampled using a 3 m grid. The soil survey included profile morphology, humus content, skeleton content and skeleton composition.
The main source of the soil contamination within the study area is the deposition of atmospheric dust (HILLER and MEUSER 1998). Consequently an enrichment of pollutants had to be expected near the soil surface. Therefore the samples had been taken in the continuous depth ranges 0-2, 2-5 and 5-10 cm. Selected samples were taken deeper than 10 cm in order to access the distribution of the contamination in the entire soil profile. All samples were taken volume-referred. In the laboratory the physical parameters wet and dry volume weight, water content, skeleton content and magnetic susceptibility were determined. Chemical parameters analyzed are pH value (DIN ISO 10390), CaCO3-equivalente content (Scheibler apparatus: DIN 19684-5), total carbon-, nitrogen- and sulfur-content (dry combustion CNS-autoanalyzer: DIN ISO 10694, 13878 and 15178) as well as the aqua regia-soluble (DIN ISO 11466) content of the elements antimony, arsenic, barium, lead, cadmium, chrome, iron, cobalt, copper, manganese, nickel, phosphorus, tin, titanium, vanadium and zinc (atom emission spectrometry: DIN EN ISO 11885).
The results were evaluated statistically, geochemically, spatially and geostatistically. Main parts of the spatial analysis included the calculation of maps of the spatial distribution of soil contaminants and the comparison of sampling grids with different spatial densities (4 to 61 sampling pits). The geostatistical analysis methods applied were variogram analysis and kriging. Additionally the hazards for humans and groundwater were assessed.
Results
The top soil inorganic contamination of the study site is high and confirms the major role of atmospheric dust deposition as source of the soil pollution. According to the German federal soil protection regulations (BBODSCHV 1999) the content of several elements (arsenic, lead, cadmium, copper, nickel, zinc) is harmful. Additionally there is a endangerment of the groundwater by the strong soil acidification and the depth transport of contaminants in the soil profile (most of all arsenic, antimony and vanadium).
With different spatial and geostatsitical methods a representative maximum sampling distance of 10 m is determined. The spatial variability of the investigation site (characteristic values: Variation coefficient: 10 %; Nugget effect: 30 %; Range: 15 m) is similar to the one of field and garden soils.
One north-south-oriented block of flats was located to the west and to the east of the study site. Between these two buildings clearly recognizable spatial patterns of the soil contamination have formed due to the influence of the buildings on the local wind circulation and the pollutant deposition. The deposition of the house heating emissions of the adjacent buildings is described by the pH value/barium group pattern (barium, lead, zinc, copper, tin, phosphorus) and the deposition of regional air pollution caused by industrial and mining activities by the manganese group pattern (manganese, iron, antimony, arsenic, cadmium, carbon, chrome, cobalt, nickel, nitrogen, sulfur, titanium, vanadium).
Conclusions
The results of this study are used to verify the sampling method described in the draft manual for soil contamination mapping given by BARKOWSKI et al. (2002). Suggestions are made for the representative sampling of the soil contamination of blocks of residential flats areas and for the handling of this kind of soil contamination by local planning and soil protection authorities.
The maximum sampling distance determined in our study is 10 m. It confirms the regulations of the draft manual (BARKOWSKI et al. 2002) for the sampling density. BARKOWSKI et al. (2002) demand minimum distances between the sample locations and buildings, trees, supply lines and land use borders of 10 to 20 m. These distances are too large to record the soil contamination representatively: The shape of the spatial patterns and the size of the open spaces between the blocks of flats cause a general underestimation of the soil contamination. Although the examined type of residential area has one of the largest portions of green spaces of all types of residential areas in the northern part of the City of Essen, there are only few residential areas which can be used for sampling by applying the proposed distances of 10 to 20 m. Therefore these distances have to be reduced.
In order to reduce the threat to humans and groundwater, local planning and soil protection authorities should check and improve the buffer capacity of the soils for inorganic soil contaminants, e.g. heavy metals, and perform actions against the soil acidification. An effective method is the application of lime. The sole mixing of the upper 20-30 cm of the soil, e.g. during the renewing of the green areas, is no suitable solution.
References
- Barkowski, D. et al. (2002): Grundlagen und Empfehlungen zur Erstellung digitaler Bodenbelastungskarten im Siedlungsbereich. Landesumweltamt Nordrhein-Westfalen (LUA). unpublished. 72 p.
- BBodschg (1998): Bundes-Bodenschutzgesetz. Bundesgesetzblatt 1998, Teil I, Nr. 16. p. 502.
- BBodschv (1999): Bundes-Bodenschutzverordnung. Bundesgesetzblatt 1999, Teil I, Nr. 36. p. 1554.
- Heidbrink, K. and H. Neite (2000): Leitfaden zur Erstellung digitaler Bodenbelastungskarten. Teil I: Außenbereiche. Landesumweltamt Nordrhein- Westfalen (LUA). LUA-Merkblatt Nr. 24. LUA, Essen. 115 p.
- Hiller, D.A. and H. Meuser (1998): Urbane Böden. Springer-Verlag, Berlin and Heidelberg. 161 p.
- Kamieth, H. (1985): Anthropogene Böden im urbanindustriellen Bereich. Erfassung und Bewertung für die ökologische Planung, dargestellt am Beispiel Essener Norden. Diploma thesis, University of Essen. unpublished. 139 p.
- LBoschg (2000): Landes-Bodenschutzgesetz Nordrhein-Westfalen. GV. NRW. p. 439.
