Slags, steelmaking, converter

Toxicity to terrestrial plants

Description of key information

ABS: Hordeum vulgare (barley)  ISO 11269-2 and NF X 31201: 14 d-NOEC 510 g/kg (germination), 640 g/kg (growth). Lactuca sativa (lettuce): 410 g/kg (both germination and growth)
Slags are effiecient fertilizers for plants
The chronic NOEC is estimated to be 100 g/kg soil for weathered slags.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:

100 000 mg/kg soil dw

Additional information

Laboratory guideline studies on acute toxicity

To evaluate the possible ecotoxicity of slags under guideline conditions in the laboratory, slags, ferrous metal, blast furnace (air cooled – ABS) were tested by a single application according to the OECD Guideline 208 in regard to seedling emergence and early stages of growth of the three terrestrial plants, wheat (Triticum aestivum), mustard (Sinapis alba), and cress (Lepidium sativum). The LC₅₀of emergence refers to the appearance of the seedlings above the soil surface, being the concentration of slags at which the emergence rate is 50 % of that of the controls. The EC₅₀of growth is determined from the shoot fresh weight and is the concentration of slags at which the decrease in growth is 50 % of that of the control. The slags were tested up to a maximum concentration of 10000 mg/kg soil dw which exceeds the maximum of concentration given by the test guideline OECD 208 by a factor 10.

 

No significant inhibitory effect was exerted by slags on growth (shoot fresh weight), survival, and emergence of any of the three species wheat (Triticum aestivum), mustard (Sinapis alba), and cress (Lepidium sativum) up to the maximum concentration of 10000 mg/kg dw soil. All 21d-EC₁₀ are > 10000 mg/kg soil dw (Fresenius 2010).

In germination and growth tests according to ISO 11269-2 and NF X 31201, ABS did not affect germination and growth (dry matter increase) of Hordeum vulgare (barley) and Lactuca sativa (lettuce). The NOECs were 510 g/kg for germination and 640 g/kg for growth of barley and 410 g/kg for both germination and growth of lettuce (LECES 1999).

Extended laboratory study

The effect of steelmaking slags (SMS) added to oxisol soil was evaluated for Sorghum spec. In extended laboratory experiments sorghum plants were grown for 36 days in pots in oxisol with SMS added up to 21.2 t/ha. The pH varied between 4.8 (controls) and 7.4 (SMS, 21.2 t/ha, no pH controls done). The dry matter production and the metal content in plants were plotted against each other and a correlation analysis was performed.

The dry matter production of sorghum was highest when the concentration of SMS added to oxisol was approximately 9.6 t/ha. The study clearly shows that SMS functions as a liming agent/fertilizer for sorghum in sightly acidic oxisol (Costa et al. 1992).

Field studies on chronic toxicity

Field studies in Germany and Austria of up to 50 years duration demonstrated improved agricultural yield by application of slags, ferrous metal, blast furnace (ABS/GBS), slags, steelmaking, converter (BOS), and slags, steelmaking (ladle slags, SMS) as fertilizers, in comparison to liming with limestone (CaCO₃) or burnt lime (CaO).

The application of ABS/GBS and SMS in amounts of annual lime loss did not lead to significant increases of the Cr or V content in the soils. Although the long-term use of BOS caused an slight accumulation of aqua regia extractable Cr and V in the soils, all slag applications led to improved soil fertility also in comparison to liming with burnt lime or limestone, and did not negatively affect the microbiological activities in soils. There is no risk of trace element accumulation in soils or plants (Rex 2005).

The growth of trees planted close to road sections constructed from slags (ABS, SMS) or natural rock (as controls) under regular and stagnant moisture conditions was monitored for three years. Trees from 151 sites near existing roads were monitored in regard to their viability.

The mean SO₄^2-concentration in soil and the total sulfur content of leaves was not influenced by the sulfur content of the slag material used in road construction. There were no relevant differences in the content of several trace elements or in the viability of trees planted near the road test sections.

Slag as a road construction material of existing roads had no adversive effect on the viability of trees planted near these roads. The viability of trees in the vicinity of slag roads was much better than in the vicinity of roads from natural rock material, presumably due to the fertilizing and pH buffering effect of ferrous slags (FEhS 1991).