789 Bulgarian Journal of Agricultural Science, 12 (2006), 789-796 National Centre for Agrarian Sciences Morphological and Mineralogical Analysis of Alluvial-Meadow Soils (Fluvisols) from the Region of Sofia Wastewater Treatment Plant (WWTP) M. TEOHAROV and I. ATANASSOVA "N. Poushkarov" Institute of Soil Science, BG - 1080 Sofia, Bulgaria Abstract TEOHAROV, M. and I. ATANASSOVA, 2006. Morphological and mineralogical analy- sis of alluvial-meadow soils (fluvisols) from the region of Sofia wastewater treatment plant (WWTP). Bulg. J. Agric. Sci., 12: 789-796 The present study includes morphological and mineralogical analysis of Gleyic-Eutric (Fluvisols) from the region of Sofia wastewater treatment plant advanced by sewage's sludge's deposition. The investigation shows that the soil aggregates of the surface horizons have become unsteady and easy to disintegrate. In the lower parts of the profiles the formation of structural aggregates was low. In the horizons underlying the sludge layers and susceptible to the sludge influence, the processes of organic residue deposition and the root system develop- ment have been terminated due to the toxic effect of the sludge contained pollutants. The clay mineralogical fraction derived from the respective horizons was dominated by smectite (> 60% almost in all the soils studied). Key words: Fluvisols, morphological and mineralogical properties, wasterwaters, sludges, pol- lutants Introduction In order to comply with environmental standards and regulations of the European Common geomorphological particu- Union (EU), Bulgaria will have to make larities major investments to establish and improve The usage and recycling of municipal its wastewater treatment facilities, as well and industrial wastewaters and sludges as secure safe disposal of the sewage slud- from their treatment combined with ges. In conformity with the EU rules (EU spreading inorganic and organic pollutants Directive 91/271/EEC), the Bulgarian Min- in the environment poses a global risk, es- istry of Environment and Waters has pecially in densely populated cities in the adopted the National Program for Priority world. Construction of Urban Wastewater Treat- 790 M.Teoharov and I. Atanassova ment Plants for populated areas of over conditions of the first upper flooded ter- 10.000 inhabitants. The hard wastes in race. Bulgaria comprise 13.6 % of the total The Sofia Wastewater treatment Plant wastes disposed in rivers, while the liquid is situated in the Northern part of the val- wastes are around 86.4% (Donchev, ley together with the deposition basins 1997). Very often they cause soil, ground "drying fields" and land areas for storage and surface water pollution. In situations of the solid sludge as a final product from of dust storms, substantial air pollution also the wastewater treatment. The problems takes place. mentioned above combined with the speci- The Sofia territory and the Sofia valley ficity of the regional conditions have caused are characterized with a heavy demo- the initiation of a preliminary investigation graphic, technogenic and municipal load. of the soil cover in the area of Sofia The problem with the wastewaters and WWTP. solid wastes acquires increasing impor- The aim of this study was to evaluate tance. the morphological and mineralogical char- For solving the above-mentioned prob- acteristics of sludge treated soils and their lem, one has to take into account a num- possible impact on the behavior of the ber of factors. sludge contained pollutants. The problems On the one hand, the physico-geo- on the impacts of sludge on other soil prop- graphic peculiarities of the capital and the erties and their change state were tackled Sofia Valley, which is situated on pliocene in another paper "Present status of sew- lake sediments and quaternary deposits age sludge treatmed soils. Impact on Cd comprising 3 - 4 terraces. In the Southern and Pb mobility" by Atanassova et al. peripheral part of the Sofia Valley, i.e. (2005). Gorna Banya, Ovcha Kupel, Pancharevo and the centre of Sofia, are situated the Material and Methods springs. The Eastern part of the Valley is low and flat and is occupied largely by the Soils were sampled in May 2004. The terraces of Iskar and Lesnovska rivers. study site was located in the very vicinity The Valley levels down to the North and of "Benkovski" waste water treatment the lowest point of 506 m is where the plant. Two soil subplots were studied on Iskar River enters its gorge with the Balkan which sludge had been deposited. At Pro- Mountains. Because of these geomorpho- file 1, sewage sludge unprocessed with logical conditions of the relief, the heavi- flocculants had been deposited 2 years est flood damages in the summer of 2005 before soil sampling. Profile 2 was char- were encountered in the above-mentioned acterized by the influence of sewage regions. These conditions are also prereq- sludge processed with flocculants of about uisites for different kind of environmental 5-6 month storage on soil. A control sub- pollution. A characteristic feature of the plot (0 - 75 cm) at about 10 meters off the two river terraces in the Northern part of deposition field was also analyzed. The Soil the valley is the elevation of the ground Profiles 1 and 2 were analyzed following water level. The bogging that has taken removal of the sludge layers 0-40 cm at place is a proof of the above-mentioned Profile 1 and 0-20 cm at Profile 2. peculiarities. All that affects the hydrologic The chemical, physico-chemical and Morphological and Mineralogical Analysis of Alluvial-Meadow Soils... 791 mechanical properties were reported in a found that the degree of gleyification was previous publication "Sewage Sludge Stor- low to medium. This was related to the age on Soils around a Wastewater Treat- hydromorphism and the formation of gleyic ment Plant. Impact on Some Soil Proper- stains and iron concretions. The colour ties" by Atanassova et al. (2006). Mor- (Munsell) is characterized with values in phological analysis was carried out at the the right chromatic region 10 YR (6/3 - terrain and indoor. For determination of the 6/6) or in 5YR possessing yellowish, rusty morphological characteristic was used and reddish shades. Guidelines for Soil Description (FAO, In the lowest part of the profile No 1 2006). Total organic carbon (TOC) was was formed a real gleyic horizon (G), analyzed by the modified Tjurin's method which is an indication, that these alluvial- o (120 C, 45 min, catalist Ag2SO4) (Tjurin, meadow soils had been swampy in the 1951). Colour was determined using past. As a result of hydromeliorative mea- Munsell Soil Colour Charts (2000). Min- sures they have changed their genetic eralogical analysis of the clay fraction characteristics and have evolved for com- (< 1 µ) was carried out by the method of paratively short period of time into meadow sedimentation, Gorbunov (1971). X-ray dif- and steppe soils. fraction analysis was carried out on The study on the morphological prop- diffractometer DRON-1, 2θ 2-30o, U=30 erties indicates that these soils possess a kV, I=9mA current and monochromatic simple soil profile and diagnostic solum A- Cu-Kα radiation, rotation velocity 2o/min. AC-C. The surface horizon is well shaped Soils were classified according to the and has subangular blocky to crumb-grain World Reference Base (FAO-ISRIC- structure. In cases of anthropogenic in- ISSS, 1998; Teoharov, 2004) as Gleyic- terference as is the case with the sewage Eutric Fluvisols. sludges disposed of on these soils, the soil aggregates of the surface horizons become Results and Discussion unsteady and easy to disintegrate. In the lower horizons (layers) the susceptibility The soils investigated had been formed to disintegration and the sandy properties on the first upper flooded terrace of Iskar are genetic features and the formation of River. An important role for their forma- structural aggregates is low. In the hori- tion have the hydrogeologic conditions - zons underlying the sludge layers and sus- the composition and contents of the allu- ceptible to the sludge influence, the pro- vial sediments, the hydrologic regime and cess of organic residue deposition by the the quantity of effluents, the frequency of above soil biomass and the root system flooding in the past and the flow and level has been terminated due to the toxic ef- of ground waters. If one has to judge from fect of the sludge contained pollutants. Our the processes of gleyification which are observations indicate that the grass hydro- dominant in the middle and especially in philic cover was totally decomposed, while the lower part of the soil profile, it must be the trees (poplar, birch) have dried up. concluded that ground waters even in con- According to the visual diagnostic exper- temporary conditions render substantial tise at the terrain, these processes have importance on the morphological proper- been developing for a 6-month (Profile 2) ties of soils. At the terrain studies it was to 2-year period (Profile 1) now. 792 M.Teoharov and I. Atanassova Table 1a1 Some genetic and mineralogical properties (% of the thee most abundant mineral phases) of the Gleyic-Eutric Fluvisols Sample No Profile No 1 (3) (4) (5) (6) Horizon A A1 ACg CG Depth (cm) 0 - 20 20 - 40 40 - 60 60 - 85 Structure, unsteady unsteady large, Crumb- subangular subangular unsteady blocky, Inclusions, blocky, subangular blocky, unsteady, comcretions powdered, blocky, fine mica, powdered, powdered, structureless, carbonate mica, fine mica, mica, nodulescarbonate quartz grains, quartz grains, nodules carbonate nodules grayish aggregates Colour 10YR 3/1 5YR 4/2 5YR 5/2 5YR 5/3 very dark grey olive light olive olive yellowish Hydromor- +++ phism Total Organic 0.96 0.70 0.64 0.20 Carbon, % Humus, % 1.66 1.20 1.10 0.24 Clay, g.kg -1 250 164 148 48 Sm (~71%) > Sm (~68%) > Sm (~60%) > Sm (60 %) Mineralogy* Ill > K K > Ill, K> Ill, > K~ > Chl, Sm-Ill Sm-Ill, Sm-Chl Sm-Ill, Sm-Chl Chl , Ill, Sm-Ill The analytical data point out that these for the neutral (pH 5.7 - 7.1, Profile 2) or soils do not differ in texture composition slightly alkaline (pH 7.5 - 8.4, Profile 1) of from their analogues along the valleys of these soils, ("Sewage Sludge Storage on Teoharov and Ninov, 2005).