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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 Wastewater Treatment Plant (WWTP)

M. TEOHAROV and I. ATANASSOVA "N. Poushkarov" Institute of Soil Science, BG - 1080 Sofia,

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, 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 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). The compo- Soils around a Wastewater Treatment sition is low to medium sandy loam. All Plant. Impact on Some Soil Properties" by profiles are dominated by the 1- 25 and Atanassova et al. (2006). The contents of 0.25 - 0.05 mm fraction, which might be a clay comprise from 25 - 5% and 9 - 14 % prerequisite for faster water filtration and of the particle mass distribution along the easier contamination of soils and ground depth of the soil profile, Table 1a. These waters with heavy metals, if it were not data in addition to other studies point out Morphological and Mineralogical Analysis of Alluvial-Meadow Soils... 793

Table 1a2 Some genetic and mineralogical properties (% of the thee most abundant mineral phases) of the Gleyic-Eutric Fluvisols Sample No Profile No 2 (11) (12) (13) (14)

Horizon AI ACg CIgCIIg Depth (cm) 0 - 18 18 - 37 37 - 58 58 - 75 Structure, Slight Slight unsteady, Mica particles, subangular subangular Inclusions, blocky to blocky- structureless, mica quartz grains, non- comcretions crumb, crumb, unsteady unsteady, particles silicate Fe spots fine mica and stains. Colour 10YR 5/2 10YR 6/3 10YR 6/4 10YR 6/6 light grayish light light yellowish brown yellowish-brown brown brownish Hydromor- phism +++ Total Organic 1.25 0.41 0.33 0.51 Carbon, % Humus, % 2.16 0.69 0.57 0.88 Clay, g.kg -1 90 62 39 140 Mineralogy Sm > (~ 61%)> K Sm (~62%) > Sm (~47 %)~V Sm (~87%) > ~Ill, Chl, Sm-Chl > (~41%) > K> Ill, Sm- K ~ Ill, Sm-Chl, K > Ill Ill, Sm-Chl Sm-Ill, Sm-Chl Sm-Ill that the alluvial-meadow soils from the first mineralogical composition of the soils and (upper) flooded terrace of Iskar river and type of clay (soil) formation as a whole. its tributaries are coarse textured and the The humus has a humic character and one skeletal fraction is missing. The heavier of the profiles (Profile 1) contains carbon- mechanical composition for Profile 1 is ates, which is a characteristic feature of most probably due to the finely dispersed the soils with mollic properties found in the sediment materials, which have been trans- Sofia Valley. According to Grishina crite- ported from the Pliocene and Quaternary ria (1986), humus content is low (~2%) covers of Sofia Valley through surface and very low (<2%), decreases down the runoff and river waters. These parent soil profile, but does not fall below 0.5% materials exert substantial influence on the (with the exception of horizon CG (60-85 794 M.Teoharov and I. Atanassova

Table 1 b Morphology and mineralogy of the control soils Control soil (16) (17) (18)

Horizon A AIgAIIg Depth (cm) 0 - 22 22 - 53 53 - 75 Structure, Subangular blocky to Slight subangular Subangular blocky, Inclusions, slightly crumb blocky unsteady Fe-concretions comcretions Colour 10YR 5/4 10YR 5/4 10YR 5/4 yellowish-brown yellowish-brown to Fe-concretions yellowish 7,5YR 4/6 Hydromorphism + ++ Total Organic 0.69 0.54 0.42 Carbon, % Humus, % 1.19 0.93 0.72 Mineralogy Sm (~75 %)>K~ Ill, Sm (~72%) >K> Ill, Sm (~74%)>K > Ill, Sm-Ill, Sm-Chl Sm-Ill Sm-Chl, Sm-Ill * abbreviations: Sm = smectite; Ill = illite; K = kaolinite; Chl = chlorite; V = vermiculite; Sm-Chl = mixed layer smectite-chlorite; Sm-Ill = mixed layer smectite – illite with predominance of smectite layers > 40% cm), profile 1) which is a proof of a well determine both the vertical and the hori- characterized meadow-steppe humus for- zontal movement and transportation of mation process in depth of the profile. In sludge contained pollutants.

Profile 2 in the CIIg horizon (layer) is ob- The composition of the clay fraction is served higher humus content in compari- shown in Table 1 and of Profile 1 in Fig- son with the preceding horizon. This is an ure 1. The clay minerals are almost uni- indication that soil formation has passed formly distributed along the two soil pro- through two stages and was accompanied files No 1 and No 2. The main compo- by interruption. It can be concluded, that nents are smectite minerals giving basal this soil profile has two parts: one has un- signals at 1.58 - 1.60 nm, accompanied by dergone initial soil formation and the other kaolinite and illite, as well as mixed lay- contemporary polygenesis of alluvial- ered smectite-chlorite and/or smectite-il- meadow soil. Obviously, the length and lite. Only Mg-saturated samples are shown frequency of flooding have predetermined in Figure 1, because of the predominant layer alteration of the subprofiles and the and categorical presence of smectite. The length of the bioproductive period of plant presence of mixed-layered silicates is an biomass. indication for the deep alteration in the The geomorphological analysis shows composition of the clay minerals in these that soil and hydrogeologic conditions pre- profiles due to clay mineral synthesis. One Morphological and Mineralogical Analysis of Alluvial-Meadow Soils... 795

Fig. 1. Diffractograms of the clay fraction composition of Samples No3 (a), No 4 (b) and No 6 (c) of Profile 1, Mg-saturated, air-dry possibility is that chlorite has been trans- Conclusions formed into mixed-layered minerals. The clay minerals of the soil profiles studied In cases of sewage sludges deposition show great similarity to the clay mineral on Gleyic-Eutric Fluvisols, the soil aggre- content of the Vertisols from typical ac- gates of the surface horizons have become cumulative parts of the relief. The forma- unsteady and easy to disintegrate. In the tion process of those Vertisols was also lower horizons (layers) the susceptibility related to the lack of drainage, prevail- to disintegration and the sandy properties ing conditions of accumulative relief ac- are genetic features and the formation of companied by hydromorphic meadow and structural aggregates was low. In the ho- meadow-bog like processes in the initial rizons underlying the sludge layers and stage of the Vertisol formation. In our susceptible to the sludge influence, the study, the character of the relief has pre- processes of organic residue deposition determined the accumulation of highly dis- and the root system development have persed minerals such as smectite. been terminated due to the toxic effect of 796 M.Teoharov and I. Atanassova the sludge contained pollutants. The clay Jounal of Agricultural Science, 12: 51-62. fraction derived from the respective hori- Donchev, D., 1997. Physical and socio-eco- zons was dominated by smectite (> 60% nomical geography. "Prof. M. Drinov", almost in all the soils studied). However, Sofia, 729 pp. (Bg). the soils studied are in general coarse tex- FAO. Guidelines for Soil Description. 2006. tured and in cases of intensified hydrologic Fourth edition, Rome, Italy, 95 pp. regime, an increased leaching might take FAO-ISRIC-ISSS, 1998. World Reference place, moreover if pH drops below 6. Our Base for Soil Resources. Soil resources re- previous study showed that the storage of port No. 84, FAO, Rome, Italy sewage sludge on these Fluvisols had Grishina, L. A., 1986. Humusfarmation and caused considerable perturbations in the humus status of soils. Publishing house soil properties, which could lead to unex- "Moscow University", 243 pp. (pp. 409- pected changes in the behavior of some 414) (Ru). inorganic and organic pollutants present in Gorbunov, N., 1971. Methods of Mineralogi- the sludge. cal and Micro-morphological Study of Soil. Consequently, actions should be under- Nauka Press, Moscow, pp. 5-15 (Ru). taken by the authorities of the WWTP for Munsell Soil Color Charts, 2000. Revised carefully monitored and risk assessed stor- Washable Edition. Munsell Color, New age of sludges originating from the waste- York, USA water treatment, combined if needed by Raikov, L.1961. Soils from the flood and the additional remediation measures. first non-flood terrace of Maritza River, BAS, 126 pp. (Bg). References Teoharov, M., 2004. Correlation of soils indi- cated in map and classificarion of Bulgaria Atanasova, I., S. Marinova, M. Teoharov and with World Reference base (WRBSR, 2002). E. Filcheva, 2005. Present Status of past Soil Science, Agrochemistry and Ecology, sewage sludge soils. Impact on Cd and Pb 39 (No 4): 3-13 (Bg). mobility. Proceedings. Nat. conf. with Int. Teoharov, M and N. Ninov, 2005. Sustainable part. "Management, use and protection of development of agriculture in Petrich Re- soil resources. 15-19 may, Sofia, Bulgaria, gion. Publish SciSet AGRI Ltd., 156 pp. 409-414. pp.(Bg). Atanasova, I., S. Marinova, M. Teoharov and Tjurin, I., 1951. To the method of analysis for E. Filcheva, 2006. Sewage sludge soils comparative study of the soil humus com- around a wastewater treatment plant. Im- position. Annual book of Soil Science In- pact on some soil properties. Bulgarian stitute "V. V. Dokuchaev", 38 (Ru).

Received August, 12, 2006; accepted September, 23, 2006.