Articles
DETERMINATION OF SUBSTRATE QUALITY FOR EXTENSIVE GREEN ROOF ACCORDING TO FLL GUIDELINE
Article number
938_56
Pages
431 – 436
Language
English
Abstract
The presented study focuses on the quality review of substrates from the German market designed for extensive greening, according to the German FLL guideline (2008). They were mainly made up of broken bricks, lava, pumice, broken expanded clay, broken expanded slate, oil shale cinder, coal cinder, etc. and mostly mixed with compost material.
In total, 22 substrates designed for either single layer or multi-layer systems were studied.
The maximum water capacity ranged between 13.6 and 55.4% (vol.). The permeability ranged from 12.7 mm/min to more than 440 mm/min for broken expanded clay substrate.
Referring to grain size distribution, the values of the studied substrates were mainly beyond the FLL requirements, due to a too high proportion of fine particles often present in the organic part of the substrates.
Concerning chemical parameters, pH values ranged from 5.2 to 10.6; moreover substrates displayed a non-buffered pH, which is expected to be reduced over the time.
With regard to nutrients, nitrogen (N), phosphorus (P) and potassium (K) were extracted in CaCl2/DTPA (CAT) and calcium-acetate-lactate (CAL). N values ranged from 0.5 to 246 mg/L, whereby substrates containing high amounts of organic matter mostly displayed the highest values, and to the contrary, substrates with a high level of mineral content (broken expanded clay, lava, zeolite) generally displayed very low measurable nitrogen.
Therefore, concerning those substrates, a suitable N-fertilisation seems to be fundamental to ensure satisfactory plant growth.
Concerning P and K, the values ranged from between 1 to 107 mg/L for P with values exceeding FLL limits and 13 to 972 mg/L for K. Regarding the heavy metal analysis, only the values for Ni gave unsatisfactory results for some substrates (the values ranged from 2.8 to 106 mg/kg). In each examined substrate, one parameter at least exceeded the FLL limits, indicating the difficulties of fulfilling the FLL requirements.
In total, 22 substrates designed for either single layer or multi-layer systems were studied.
The maximum water capacity ranged between 13.6 and 55.4% (vol.). The permeability ranged from 12.7 mm/min to more than 440 mm/min for broken expanded clay substrate.
Referring to grain size distribution, the values of the studied substrates were mainly beyond the FLL requirements, due to a too high proportion of fine particles often present in the organic part of the substrates.
Concerning chemical parameters, pH values ranged from 5.2 to 10.6; moreover substrates displayed a non-buffered pH, which is expected to be reduced over the time.
With regard to nutrients, nitrogen (N), phosphorus (P) and potassium (K) were extracted in CaCl2/DTPA (CAT) and calcium-acetate-lactate (CAL). N values ranged from 0.5 to 246 mg/L, whereby substrates containing high amounts of organic matter mostly displayed the highest values, and to the contrary, substrates with a high level of mineral content (broken expanded clay, lava, zeolite) generally displayed very low measurable nitrogen.
Therefore, concerning those substrates, a suitable N-fertilisation seems to be fundamental to ensure satisfactory plant growth.
Concerning P and K, the values ranged from between 1 to 107 mg/L for P with values exceeding FLL limits and 13 to 972 mg/L for K. Regarding the heavy metal analysis, only the values for Ni gave unsatisfactory results for some substrates (the values ranged from 2.8 to 106 mg/kg). In each examined substrate, one parameter at least exceeded the FLL limits, indicating the difficulties of fulfilling the FLL requirements.
Authors
L. Carrillo, M. Jauch, E. Meinken
Keywords
single layer, multi-layer, green roofs, substrate, physical parameters, chemical parameters, water capacity, nutrients
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