Pebble red

As Kieselrot or Kieselrotasche is called a red slag , which at one during the Second World War applied roasting reduction process for copper recovery was incurred. In Germany it was delivered in the 1950s and 1960s and was mainly used as a surface for sports fields. Furthermore, municipalities in France, Belgium, Holland and Denmark were supplied. The dioxin contamination of Kieselrot was only discovered in 1991. As a result, numerous playgrounds and sports fields were closed and renovated. Silica red contains a typical dioxin pattern in which highly chlorinated dibenzofurans dominate. It also contains other highly chlorinated compounds such as hexachlorobenzene and polychlorinated biphenyls .

history

Since the late 1930s, copper shale deposits with a copper content of only 1.3–1.5% have been mined in the copper smelter in Marsberg (Westphalia) in the Sauerland region by a successor company of Stadtberger Hütte AG . In order to get as much copper as possible from the low-concentration ore, the roasting reduction process was used: Soluble copper salts were formed that could be leached from the cooled raw ore . The remaining slag was deposited in heaps . The combination of carbon, sulfur and chlorine at a comparatively low roasting temperature resulted in considerable contamination of the roasted material with highly toxic, highly chlorinated organochlorine compounds such as dioxin (see Formation and pollution ).

In the summer of 1938, shortly after production started at the copper smelter in Marsberg in the Sauerland region, there was major cattle deaths in the Marsberg district. The works manager of the hut assumed damage of 600,000 to 800,000 Reichsmarks. In 1939, the operations manager of the copper smelter warned the management of the then Hermann Göring works of contamination of the environment.

From 1955 until at least 1967 the Marsberg civil engineering company Möllmann & Pohle mined 400,000 - 800,000 tons of the slag. It was sold under the name Marsberger Kieselrot as a surface for sports and playgrounds as well as for road and path construction . The material was mainly used in North Rhine-Westphalia, Hesse, Lower Saxony and Bremen. According to the Spiegel (19/1991), at least 800,000 tons of dioxin slag are said to have been marketed.

It was not until 1991 that soil examinations revealed extremely high levels of dioxins near sports and playgrounds, the surface of which was pebble red. The slag from the Sauerland copper smelter was quickly identified as the cause.

Although blood tests of a total of 98 people found “only slightly increased exposure to some of the children” despite the high level of soil contamination , which “according to the current state of knowledge cannot be classified as a health risk” because there is only “little transfer to humans”, it was recommended to block these for precautionary reasons and "urgently rehabilitate".

While North Rhine-Westphalia, Bremen and Hamburg released dioxin-contaminated sports grounds again in 1991 according to the initial results of a study on residents of Marsberg, states such as Bavaria, Lower Saxony, Hesse and Baden-Württemberg continued to keep their sports facilities closed.

Studies show that dioxin-contaminated dusts were blown into the immediate vicinity from the contaminated areas. It is assumed that they acted as sources of emissions for dioxins for years.

Individual examples

In Bochum "According to a decree of the state government of July 13, 1991 (...) all areas could be used without health damage". However, pebble red could have "effects on the environment". Nevertheless, the city of Bochum gradually freed all places of the slag. The renovation was not completed by 2014.

According to a publication by the Chemical Investigation Office in Nuremberg in 1991, even a blockade is not enough: "To ensure the safety of the residents of the sports facilities concerned," it says, "blocking the facility is not enough". “In order to prevent the contaminated material from being blown away”, it is necessary “to seal the sports fields or tracks with foil so that no more dust can be discharged”. “In the long term”, however, there is only a complete replacement of the contaminated soil, which has to be “classified as hazardous waste”.

After the connections had been clarified, around 1,400 sports and children's playgrounds were closed in Germany. Some of the sports grounds were reopened for use some time later. Today, most of them have been renovated , which was understood, for example, in accordance with the decree of the State Environment Ministry of North Rhine-Westphalia in the nineties as “long-term protection including leaving the area on the surface and applying a barrier layer” . However, this relatively inexpensive method of renovation entails additional costs, because disposal with additional construction costs either occurs later or, in the case of the cities of Bottrop and Schwerte, also carries the risk of re-penetration to the surface.

The city of Bottrop was "very surprised" in 2013 that the method recommended by the state was obviously not safe. According to this, controls again showed "very high dioxin values on the surface", since the surface layer had been destroyed by softening and smoothing the square. The city administration had known since 1992 that there was a layer of pebbles under the playground in Schwerte-Ost. There, too, the material was covered with soil following a decree by the State Environment Ministry. In 2015, according to a communication from the Lower Soil Protection Authority of the Unna district, the assessment was still made that “the existing coverage was sufficient”. In 2017, a renovation study in mixed surface samples again revealed pollution from pebble red: The cause was found to have resulted in "weather-related wear and tear on the surface layer". The administration closed the playground. Due to the increased disposal volume including the surface layer, the renovation of the facility and the football field on Lindenweg is "now in the seven-figure range". The city of Schwerte has submitted funding applications.

Generation and pollution of pollutants

The copper shale deposits processed in Marsberg in the Sauerland region with a copper content of only 1.3–1.5% contained up to 10% bitumen , along with other impurities . In order to get as much copper as possible from the low-concentration ore, the roasting reduction process was used : up to 8% table salt and 2% pyrite were added to the copper shale , then the mixture was roasted at temperatures of 450 to 600 ° C. Soluble copper salts were formed, which could be leached from the cooled raw ore . The remaining slag was deposited in heaps . The combination of carbon, sulfur and chlorine at a comparatively low roasting temperature caused considerable contamination with highly chlorinated organochlorine compounds through de novo synthesis in the roasted material . Chlorobenzenes , chlorophenols , polychlorinated biphenyls and polychlorinated naphthalenes were detected in the slag . It also contained sulfur-containing compounds such as chlorinated benzothiophenes .

The polychlorinated dibenzodioxins and dibenzofurans have the greatest importance among the pollutants in the slag . The particularly high proportion of the highly chlorinated dibenzofuran congeners is characteristic of the dioxin pattern of silica red . The total content of dioxins was determined to be 10,000–100,000 ng I-TEQ / kg dry matter.

Content of polychlorinated dioxins (PCDD) and furans (PCDF) of silica red in µg / kg
Cl ₁ DD - Cl ₃ DD	k. A.	Cl ₁ DF - Cl ₃ DF	k. A.
Cl ₄ DD	9	Cl ₄ DF	100
Cl ₅ DD	23	Cl ₅ DF	244
Cl ₆ DD	32	Cl ₆ DF	615
Cl ₇ DD	k. A.	Cl ₇ DF	1675
Cl ₈ DD	530	Cl ₈ DF	3140
Total PCDD	730	Total PCDF	6311

Health consequences

In the case of abrasions , so-called " dirty tattoos " can occur if particles penetrate deeper into the skin when falling and thus remain permanently in the skin without surgery and damage the skin, e.g. B. wound healing impairing or carcinogenic potential can develop there.

Individual evidence

↑ Der Spiegel: Export hit Kieselrot , issue 18/1991, April 29, 1991, accessed on October 30, 2018.

↑ ^a ^b ^c ^d Karlheinz Ballschmiter , Reiner Bacher: Dioxins . Verlag Chemie (VCH), Weinheim 1996, ISBN 3-527-28768-X .

↑ Der Spiegel: Many Bitterfelds , issue 17/1991, April 22, 1991, accessed on June 3, 2018.

^ Schul-AG Kieselrot from Kassel: Chapter 3.4 The distribution of "Kieselrot" ( Memento from April 22, 2005 in the Internet Archive ) .

↑ Der Spiegel: Poisons - Cycle of Death , Issue 19/1991, May 6, 1991, accessed on June 2, 2018.

↑ J. Wittsiepe, U. Ewers, F. Selenka: PCDD / F exposure after exposure to pebble red ( Memento from June 13, 2007 in the Internet Archive ) . in DECHEMA (Ed.): Criteria for assessing organic soil contamination: dioxins and phthalates . Pp. 409-430, Frankfurt (1995).

↑ Solution: Raise guide values , TAZ, November 15, 1991.