The blackberries rabbit hole

On Sunday i went to a small hidden spot to check if the blackberries were ripe for foraging. It is behind the playing field in the Bornitzstraße and you stumble very quick into dozens of blackberry bushes. No one was there and i started with the foraging until the small thought got bigger and bigger: “Is it safe to eat at this place? This was an industrial area, so aren’t they polluted?”. That question wandered through my mind and on the first sight there is trash here and there (although not in the front area), but was there a better way to find out if it was safe to eat?

It is not that easy as normal person. Areas with harmful soil changes or areas suspected of having harmful soil are noted in the soil pollution register (Bodenbelastungskataster - BBK). The data is based on investigations and is regularly updated by the responsible soil protection authority. However you can’t simply look into it without a good reason (and i think picking some blackberries is none). Although i don’t now if that area has a private owner or if that is public ground. So i only could make an educated guess here. I found one first clue in a map in FIS-Broker (Nährstoffspeicher- / Schadstoffbindungsvermögen der Böden 2015 (Umweltatlas))¹. At first i thought it is a good area with high nutrient storage / pollutant binding capacity but the area with the blackberries is just right over that area with low capacity. Not a good start.

For more hints i checked for pollution measurements and found the one just a street further, where the Dong Xuan Center is. In GDR times there was the VEB Elektrokohle² and the pollutant measurement found much relics from that time:

“Elevated levels of polycyclic aromatic hydrocarbons (PAH) in the soil were found all over the place (maximum value 5,086 mg/kg). 7,320 mg/kg phenols were found in the soil of the former phenol basin. MHC, heavy metal and cyanide contamination (area of the former electroplating shop) has been determined selectively; they are concentrated in the approx. 3 m thick filling.”³

So if that area was highly contaminated, then the other area could be too. So i looked at old maps to find out what was here in the past.

The blackberries are all right under the Reichsmonopolverwaltung. They did Spirits purification and storage⁴. There was also a metallurgy factory right next to it in the 40s^{5 6}.

In GDR times the former Reichsmonopolverwaltung was additionally used as an Oil Storage (Bärensiegel and VEB Pflanzen- und Ölmühle).

It seems not unlikely that there is pollution in the ground. I found a small hint from a soil cleaning firm that cleaned an old Reichsmonopolverwaltung. In their investigation they found gasoline, diesel, heating oil (MKW), BTEX, CHC / LHKW, cyanide, PAH, perfluorinated surfactants (PFT), phenols / chlorophenols, polychlorinated biphenyls (PCB) and heavy metals in soil and ground water. More points to probability of contamination, especially when the old tracks of the Industriebahn⁷ are still there and only overgrown from blackberries. The train track itself could also be a point of contamination. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are the two main pollutants. Creosote is one source for PAHs, which is a common impregnation agent for outdoor wood structures and if the train tracks are really old it can ooze out and contaminate the soil and the ground water. Heavy metals accumulate as well if the track was highly used.⁸

These points alone convinced me that foraging blackberries there was not a good idea but now i was curious how and in what form the blackberry accumulates the pollutants. I remembered a study from the TU Berlin about Urban Gardening. I have to read that again more further but what I remembered was that for example tomatoes on the balcony in the city center eventually turn into toxic waste contaminated with heavy metals. No other Autobahn in Germany has such bad soil in its vicinity as we do here in the city, where everything from exhaust gases accumulates forever and especially leafy greens are wonderful at passing on the pollutants to us. Typical urban gardening city plants were analyzed at the TU to what extent they absorb which pollutants and where they store them, i.e. what edible plants should be avoided in the city or to improve the air quality. The bottom line was that you don’t want tomatoes from the city’s Vorgärten, or spinach or herbs. Highly watery plants and leafy greens aren’t exactly something you want to eat if it was grown in the city. The rule of thumb here is that the toxins, especially heavy metals, migrate into the wood and therefore tree fruit are harmless. Trees are good, an edible balcony on the street however is poison.⁹

But this could be different for blackberries, i thought but then i found some studies which exactly looked into that question¹⁰. Turns out blackberries are a very good marker for soil pollution. Especially blackberry leaves due to long exposure to atmospheric pollutants are the largest reservoirs of heavy metals (so you don’t want any blackberry leaf tea, ever!). Blackberries themselves, sheltered by leaves and slowly ripening, accumulate smaller amounts of heavy metals. So even if the blackberry has more pollution in the leaves, it could still have accumulation from all the pollution from just being inside the city according to the TU study.

So should i buy blackberries in the supermarked instead? Well, then i have all the exposure of toxic pesticides¹¹ and so i have only the choice of what kills me more slowly or to pick up blackberries in a totally remote area with no (former) pollution source.

That curiousity of the simple question if these blackberries are edible and safe to eat made me kinda sad and more questions arise. Is there any place at all without a pollution source? Why is that Bodenbelastungskataster not open data? For me, i just take it as exercise of blackberry foraging without eating though.

---