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The Risk of the Soil Salinization of the Eastern Part of Žitný Ostrov

The Risk of the Soil Salinization of the Eastern Part of Žitný Ostrov J. Hydrol. Hydromech., 60, 2012, 1, 57­63 DOI: 10.2478/v10098-012-0005-4 THE RISK OF THE SOIL SALINIZATION OF THE EASTERN PART OF ZITNÝ OSTROV VIERA KOVÁCOVÁ, YVETTA VELÍSKOVÁ Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava, Slovak Republik; Mailto: kovacova@uh.savba.sk; veliskova@uh.savba.sk, phone: +421 2/49 268 263 Salinization is an increasing enviromental problem in ecosystems. The assessment of total dissolved solids (TDS), pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), alkalinity and the concentrations of main ions makes possible to identify salinization and alkalization degree. The saltaffected soils occur in the south part and south-east part of Zitný ostrov, where the dry and mild summer climate, evaporation soil water regime and mineralized groundwater create conditions for development of the saline and alkaline soils. Five localities with highly-mineralized groundwater were monitored to evaluate salinity and alkality in the period 1989­2006. At the bottom horizons in localities 1 ­ 5 evaporative residues (salt content) reached value 0.1 ­ 0.2 %. In 2006 dry evaporative residues (salt content) was higher than 0.2 %, EC was higher than 250 mS m-1 at the bottom horizons in localities 1, 2, 4. The mentioned data allow us to state that salinization and alkalization of soils is developing, it starts from the bottom of soil horizons through middle part of the soil profile up to the top horizons. This phenomenon was observed in all investigated soils in different stages of development. KEY WORDS: Salinization, Alkalization, Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC), Exchangeable Sodium Percentage (ESP). Viera Kovácová: RIZIKO SALINIZÁCIE PÔDY VO VÝCHODNEJ CASTI ZITNÉHO OSTROVA. J. Hydrol. Hydromech., 60, 2012, 1; 28 lit., 2 obr., 5 tab. Salinizácia v ekosystémoch je stále významnejsí enviromentálny problém. Stanovenie celkového mnozstva rozpustených látok (TDS), elektrickej vodivosti (EC), sodíkového adsorpcného pomeru (SAR) a obsahu výmenného sodíka (ESP) umozuje identifikáciu kritického potenciálu salinizácie a degradácie pôdy. Záujmové územie bolo vymedzené vo východnej casti Zitného ostrova, kde suché a horúce klimatické podmienky spolu s vysokomineralizovanými podzemnými vodami sú prícinou translokácie solí do pôdneho profilu. Bolo monitorovaných 5 lokalít v období 1989 ­ 2006. Namerané údaje poukazujú na vzrastajúci obsah solí, ktorý v r. 2006 dosiahol 0,1 ­ 0,2 % v celom pôdnom profile vo vsetkých monitorovaných lokalitách, hodnoty EC 200 ­ 400 mS m-1 v spodných horizontoch vytvárajú podmienky pre rozvoj zasolených pôd. KÚCOVÉ SLOVÁ: salinizácia, alkalizácia, celkové rozpustené látky (TDS), sodíkový adsorpcný pomer (SAR), elektrická vodivos (EC), výmenné sodíkové percento (ESP). Introduction Zitný ostrov ­ natural conditions, geology and parent materials Zitný ostrov is the south-west part of Slovakia, where fluvial sedimensts are dominant. In the evapotranspiration regime carbonates in fluvial carbonate sediments have been preserved, formed in alluvial soils of whole alluvial river plains. Parent materials and soil forming processes influenced the occurence prevailingly calcareous soil character. In alluvial areas of lowland rivers Calcaric Flu- visols, in depressions Fluvi-Calcaric Phaeozems, Fluvi-mollic Calcaric Gleysols to Calcaric Gleysols occur. On older alluvial sediments Calcaro-haplic Chernozems are spread. In lower lying southernmost parts with mineralized groundwaters, locally also saline soils are occuring (Fig. 1, 2). Lowland area is covered by Quaternary cover, and that is why underlying Neogene sediments crop out only locally, in tectonically elevated parts. Their development was influenced in Quaternary period by three basic factors: fluvial and aeolian activities, and solifluction. Extensive alluvial plains originated in descending parts of lowland. Most 57 V. Kovácová, Y.Velísková spread parent materials are fluvial sediments, loess complexes, aeolian sands and proluvial (slopes) sediments. Their extension, genesis and texture are narrowly connected with geomorphological features of lowlands, particularly territorial tectonic mobility. Contributing factors has also play a role zonal climatic distribution of precipitationtemperature (evapotranspiration ­ versus perlocation water regime) and groundwater mineralization changes. These factors affect particularly carbonate preservation. Their presence is a significant component part affecting the final character of pedogenetic processes (Curlík, Sefcík, 1999; Granec, Surina, 1999; Cervenka, 1970; Sútor, Stekauerová, 2000; Burger, Celková, 2007, 2009). The objective of this contribution is to evaluate the state of salinization and alkalization of the soil profile in localities with high-mineralized groundwater. Fig. 1 . Localisation of the studied area. Legend Fluvisols calcaric associated with Fluvicalcaric Gleysols Fluvi-calcaric Phaeozems developed on calcareous alluvial deposits Calcaro-haplic-Chernozems, associated with Fluvi-Calcaric Phaeozems and Calcaro-haplic Phaeozems developed on calcareous alluvial deposits Regosols arenic associated with ArenicFluvi-gleyic Phaeozems on alluvial sand (in depressions) Fig. 2. Dominant soil groups of the area. Development of saline soils The salt-affected soils occur in the south part and south-east part of Zitný ostrov. The dry and warm summer climate, evaporation soil water regime and mineralized groundwater create here convenient conditions for development and spreading of the saline and alkaline soils. These soils are developing slowly from the initial stages to the well developed ones. As a consequence of this long lasting process the slightly and middle saline and alkaline soils as well as typical solonchaks and solonetzes occur in monitored area. The network of monitoring sites therefore respects mentioned fact and the soil in different stages of development are monitored. Two processes in the development of the saltaffected soils can be recognised: 1. Process of salinization is conditioned by the presence of neutral sodium salts, mainly NaCl and Na2SO4. The indicators of salinization are dry evaporative rezidue > 0.2% and electrical conductivity of saturated soil extract EC > 400 mS m-1. Low stage of salinization is running at EC 200 ­ 400 mS m-1 or evaporative rezidue of salts 0.1­0.2 %. The result of salinization processes are middle saline soils and solonchaks. 2. Process of alkalization is conditioned by the presence of alkaline sodium salts, mainly Na2CO3, NaHCO3, Na2SiO3. The indicators of alkalizaton are exchangeable sodium percentage ESP > 5 % and pH 8 or higher. The result of alkalization processes are middle alkaline soils and solonetz. In natural conditions both of this processes are represented by different rate and the result is the mixture of both this processes, one of them is dominant. The relationship between electrical conductivity and degree of salinity is presented e.g. in U.S Salinity Laboratory Staff, 1954; Recommended Chemical Soil Test Procedures, 1998; Burger, Celková, 2009. Groundwater Groundwater in eastern part of Zitný ostrov is supplied by infiltrating Danube water primarily. Groundwater influenced the soil cover development and some chemical particularities connected with their mineral content and hydrothermic regime (local salinization). Saline soils are widespread in some localities reflecting the predominance of sodium chloride in groundwaters and soil solutions. Sodic soils are subject to severe structural degradation and restrict plant performance through poor soil-water and soil-air relations. Sodicity is shown to be a latent problem in saline-sodic soils where deleterious effects are evident. A classification of soils based on total dissolved solids, electrical conductivity, sodium adsorption ratio, exchangeable sodium and pH is outlined in studies Barzegar et al., 1994; Burger, Celková, 2004; Curtin et al., 1994a,b; Feitz et al., 2002; Hanes, 1999; Kaledhonkar et al. 2001; Kovácová, 2009b. Sodium is one of the most abundant cations in natural waters. Na+ cation is very conservative, does not enter oxidation-reduction reactions, cannot be precipitated by chemical reactions, it remains stable in solution. Nevertheless, sodium significantly participates in ion-exchange processes. Cation ion-exchange in common natural waters tends to replace divalent cations in a solution by monovalent cations. Sodium in solids-low waters (below 1 g l-1) occurs in the form of cation Na+. In solids-richer solutions, the element is combined in several complexes and ion pairs controlled by the type of water chemistry (most frequently NaCO3-, NaHCO3(aq) and NaSO4-). Much sodium gets to soil profile from mineralized waters and through human activities (Rapant, Vrana, Bodis, 1999; Kovácová, 2009a; Burger, 2007; Burger, Celková, 2009; Pitter, 1981; Richter, Kreitler, 1993; Yong et al., 1992). State of salinization at Zitný ostrov area In arid and semi-arid conditions with evapotranspiration regime and mineralized groundwater dissolved ions gets to the upper layers of soil and become the main reason for soil salinization. Mea- sured basic characteristics of groundwater chemical composition indicate, that Na levels in interested area are higher then average (Tab. 1). Sodium content for all investigated groundwaters SR has median 9.1 mg l-1 (Rapant, Vrana, Bodis, 1999), but in studies area average sodium content is calculated 21.06 mg l-1 (min. 1.1 mg l-1, max. 260.0 mg l-1). Problems of high salinity have been associated with groundwater level and irrigation of soils in arid and semi-arid areas where the soils are generally fragile in structure and susceptible to water logging. Land salinity is closely related to other land degradation processes such as soil erosion, acidification and structural decline. It is estimated that 0.16 % of the soils is salt-affected (the highest part in Komárno ­ 0.28 %, Nové Zámky ­ 0.37 %, Saa ­ 0.23% districts). Groundwater quality monitoring results in selected localities leads to the conclusion, that the groundwater quality is worsening and the soil salinization hazard is increasing in the monitored period (Burger, 2007; Burger, Celková, 2004, 2009; Dulovicová, Velísková, 2007; Kaledhonkar et al., 2001). One of the requirements imposed by the Water Framework Directive (WFD, 2000/60/EC) is to analyse and predict the future changes of surface waters quality. To asses the development of a stream´s pollution one must consider all sources of pollution and understand how water quality evolves over time (Pekárová et al., 2009). Sites description According to the climatic characteristics this territory belong to warm climatic area. Average annual precipitation sum is ranging from 520 to 650 mm. Number of summer days (temperature > 25 o C) is higher than 70 in south-east part of Zitný ostrov. Arid and semi-arid conditions with evapotranspiration regime the mineralized groundwater become the main reason for soil salinization. The salt-affected soils occur in monitored area in the eastern part of Zitný ostrov (Fig. 2), where dry and warm summer climate, evaporation soil water regime and hig-mineralized groundwater (Tab. 1) create conditions for development and spreading of the saline and alkaline soils. These results abduced Kobza et al. (2002) too. These soils are developing slowly from the initial stages to the well developed ones. As a consequence of this long lasting process the slightly and middle saline and alkaline soils as well as typical solonchaks and solonetzes occur. In the 5 monitored localities (1 ­ Veké Kosihy, 2 ­ 59 V. Kovácová, Y.Velísková Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) the soils in different stages of the development were investigated. In the bottom horizons in localities 1, 2, 4, 5 reached evaporative residues (salt content) value 0.1 ­ 0.2 %, but in year 2006 at all of the soil profile. The soil types and average groundwater levels in monitored loc. 1­5 are presented in Tab. 2. T a b l e 1. Basic characteristics of groundwater chemical composition (2006). Basic statistical characteristics of groundwater chemical composition n = 128 Mean Min. pH 7.32 5.76 TDS [mg l-1] 643.0 49.2 Ca2+ + Mg2+ [mmol l-1] 3.561 0.120 Conductivity[µS cm-1] 688.1 54.5 Free CO2 [mmol l-1] 0.77 0.12 Na+ [mg l-1] 21.06 1.10 K+ [mg l-1] 5.53 0.05 NH4- [mg l-1] 0.068 0.025 Ca2+ [mg l-1] 91.93 2.40 Mg2+ [mg l-1] 30.81 0.50 Fe2+ [mg l-1] 0.075 0.005 Mn2+ [mg l-1] 0.069 0.003 Cl- [mg l-1] 22.69 1.06 SO42- [mg l-1] 70.70 0.30 NO32- [mg l-1] 14.88 0.25 PO43- [mg l-1] 0.184 0.005 HCO3- [mg l-1] 353.32 3.05 T a b l e 2. Soil types and average groundwater levels in monitored localities 1 ­ 5. Max. 9.89 1935.8 13.021 2200.0 11.5 260.00 114.00 6.900 352.70 114.55 6.547 2.931 89.00 1019.00 39.90 7.600 937.85 Locality Soil type Fluvi-calcaric Phaeozems, associated with Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Fluvi-calcaric Phaeozems, associated with Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Calcaric Fluvi-mollic Gleysols Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Calcaric Fluvi-mollic Gleysols Average groundwater levels [cm] 250a 215b 198c 110a 105b 101c 90a 95b 107c 325a 260b 217c 246a 225b 215c Veké Kosihy Okolicná Calovec Zlatná na Ostrove Kamenicná a ­ 1989, b ­ 1999, c ­ 2006 Materials and methods Soil samples were taken in depths (0­110 cm) from soil profiles ( determining the spatial variability of sodicity). The soils were air-dried and passed through a 2-mm sieve. Soluble salts were detected by measuring electrical conductivity (EC). Electri60 cal conductivity (EC) and soluble ions (Na+, Ca2+, Mg2+, K+, SO42- and Cl-) were determined on saturated-paste extracts. The concentrations of Na+, Ca2+, Mg2+, K+ were determined by atomic absorption spectroscopy (AAS); SO42- and Cl- by ionselective electrode. The basis of the salinization model is the sodium adsorption ratio (SAR) ­ a relationship between Na+, Ca2+ and Mg2+ concentrations that predicts the Na+ status of the soil exchange complex when the exchange of cations within the soil comes into equilibrium with the soil solution (Recommended Chemical Soil Test Procedures, 1998; US Salinity Laboratory Staff, 1954 ). It is given by the following expression: Results and discussion At the beginning of measurement (in 1989) evaporative residues achieved values < 0.1 %, electrical conductivity EC < 250 mS m-1 ­ that is the non-saline stage. During the 1989 ­ 2006 the values increased gradually due to higher-mineralized groundwater composition (Tab. 2), EC increased in all layers and all monitored localities and achieved values 250 mS m-1 < EC < 400 mS m-1 ­ that is defined as slightly saline stage. In the 5 monitored localities (1 ­ Veké Kosihy, 2 ­ Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) the soils in different stages of the development were investigated. In the bottom horizons in localities 1, 2, 4, 5 reached evaporative residues (salt content) value 0.1 ­ 0.2 %, but in year 2006 at all of the soil profile. The presented data measured in year 1989 ­ ­ 2006 illustrate the contemporary processes salinization and alkalization in the monitored soils. The alkalization is however more significant and dominant in site No. 4. The mentioned a data allow us to state that salinization and alkalization of soils start from the bottom of soil horizons through middle part of the soil profile up to the top horizons (Tab. 3, 5). SAR = Na Ca + Mg (1) where ionic concentrations are expressed in mol l-1, SAR in units [mol l-1]0,5, but for convenience, units will be omitted hereafter. Presence of sodium is a potential cause of structural instability when Na occupies more than 1015% of the exchange sites (Curtin et al., 1994a). SAR is related to the exchangeable-Na ratio (ESP) of the soil by the following equation: ESP = kg SAR, (2) where kg is the Gapon selectivity coefficient, and ESP ­ estimated as exchangeable Na/(CEC ­ exchangeable Na), where CEC is the effective cationexchange capacity. To predict how much exchangeable Na will accumulate in soil the value of kg must be known. T a b l e 3. Evolution of salinization and alkalization of the soil profiles in monitored sites 1 ­ 5 (1 ­ Veké Kosihy, 2 ­ Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) in the time period 1989 ­ 2006. Loc. Depth [cm] 0 ­ 10 10 ­ 30 30 ­ 50 50 - 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 Evap. res. [%] 1989 1999 2006 0.03 0.07 0.12 0.08 0.09 0.09 0.10 0.10 0.13 0.12 0.15 0.21 0.10 0.08 0.15 0.12 0.06 0.18 0.15 0.11 0.19 0.19 0.13 0.22 0.06 0.04 0.14 0.08 0.11 0.17 0.04 0.06 0.12 0.05 0.10 0.16 0.04 0.11 0.11 0.05 0.10 0.14 0.04 0.03 0.10 0.10 0.16 0.21 0.07 0.09 0.11 0.13 0.14 0.15 0.09 0.10 0.09 0.11 0.12 0.16 EC [mS m-1] 1989 1999 2006 49 72 96 67 60 69 95 115 128 213 250 305 36 68 95 59 71 90 61 108 113 207 210 215 40 56 76 48 62 70 75 90 99 155 180 199 51 30 67 55 40 58 119 83 115 242 207 291 30 40 50 57 49 80 91 56 85 120 126 170 pH/H2O 1989 1999 2006 7.6 7.2 7.3 7.8 7.5 7.3 7.9 7.6 8.1 7.8 8.0 8.1 7.2 7.3 7.2 7.5 7.6 7.4 7.4 8.0 7.9 7.9 8.1 8.2 7.1 7.1 7.2 7.2 7.3 7.4 7.3 7.4 7.5 7.5 7.6 7.7 7.5 7.3 7.6 7.2 7.6 7.5 7.8 8.0 7.5 8.1 8.1 8.6 7.2 7.2 7.4 7.1 7.3 7.5 7.2 7.4 7.6 7.8 7.5 7.9 ESP [%] 1989 1999 2006 1.8 2.1 2.6 2.5 2.7 3.5 6.8 7.6 8.5 7.9 8.2 9.1 1.4 1.8 1.9 3.1 2.4 2.9 2.7 2.9 8.6 8.4 8.2 9.7 2.6 1.9 1.9 3.7 3.9 4.2 5.8 6.2 7.5 8.3 8.7 9.1 1.2 1.1 0.9 2.8 1.7 1.1 9.6 7.3 8.2 9.7 10.1 11.5 0.8 1.2 1.4 1.0 2.5 3.9 2.7 3.9 4.7 5.6 8.8 9.5 V. Kovácová, Y.Velísková T a b l e 4. Participation of individual ions in the soil profile in monitored localities 1 ­ 5 (in 1999). Cl[mg/ 100g] 7.5 7.4 13.5 13.3 8.6 11.5 16.2 17 28.6 23.5 28 16 6.7 15.7 9.2 11.4 15.8 18.5 23.1 20.7 SO42[mg/ 100g] 2 2 3.8 15.5 6 7.4 8.2 8.1 42.5 35 18 17 44.1 69.6 64.3 65.2 11.0 9.1 19.7 22.1 HCO3[mg/ 100g] 25.6 38.2 40.3 41.2 135 114 195 187 94.5 90.6 79 85 150.9 133.8 144.2 80 45.8 92.7 108 135 NO3[mg/ 100g] 7.5 4.2 4 5.2 4.1 2.9 3.1 3.5 3.5 2.9 2.2 6.8 6.1 4.2 3.1 2.8 5.7 3.2 2.8 4.6 Na+ [mg/ 100g 22 26.8 50 63.5 4 5.2 5.9 6.8 10 11.5 7 18 68.5 97.7 98.9 61.6 12.1 8.5 18.9 17.6 K+ [mg/ 100g] 9.8 2.3 1 0.8 0.9 0.8 0.8 0.9 1 0.7 0.6 0.9 2.8 4.2 3.1 2.1 0.8 1 0.9 1.5 Ca2+ [mg/ 100g] 24.5 12.5 8.5 8.2 20.5 22.4 16.5 12.7 24 19.5 15.2 13 18.2 19.2 16.4 12 28 17.2 21.5 27.5 Mg2+ [mg/ 100g] 6 7.5 6.5 7.4 4.2 3.8 3.5 5 5.9 9.3 7.4 6.2 4.8 2.4 1.2 6.9 5.9 7.6 8.9 10.7 Loc. Depth [cm] 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 pH/ H2O 7.13 7.36 7.22 7.22 6.82 6.0 6.72 6.95 7.42 7.10 6.92 7.01 8.6 8.2 8.3 8 7.3 7.2 7.5 7.9 pH/ KCl 6.15 6.98 6.89 6.85 6.53 6.45 6.49 6.72 7.20 6.73 6.58 6.79 7.90 7.71 7.81 7.30 6.9 6.7 7.1 7.5 T a b l e 5. Stage of salinization and alkalization in monitored localities 1 ­ 5. 1 2 3 4 5 Veké Kosihy Okolicná Calovec Zlatná na Ostrove Kamenicná slightly solonchak slightly solonchak slightly solonchak, slightly solonetz slightly solonchak, medium solonetz slightly solonchak, slightly solonetz Differences in data of the evaporative residues (salt content), EC, ESP and pH in individual years support considerable variability in the intensity of saline and alkaline processes within the very small areas. Generally, salinization of the monitored saltaffected soils slightly increase due to mineralization of groundwater. The trendlines of groundwater salinization have increasing character. In groundwater of the eastern part of Zitný ostrov was ascertain salinization risk from middle (medium) to high rate: 75 < EC< 300 mS m-1, 10 < SAR < 38 (Burger, Celková, 2009). A distinct change of an intensity of saline and alkaline processes was confirmed, but it is not hazardeous stage (Tab. 5). Much sodium gets to soil profile just from mineralized water. Proportion of sodium to the other ions is in Tab. 4. Summary and conclusion The salt-affected soils occur in the southern and south-eastern part of Zitný ostrov, where the dry and warm summer climate, evaporation soil water 62 regime and highly-mineralized groundwater create convenient conditions for development of the saline and alkaline soils. As a consequence of this long lasting process the slightly and medium saline and alkaline soils occur in monitored area. Values of the evaporative residues (salt content), EC, ESP and pH in individual years shows considerable variability of saline and alkaline processes. Generally, the development of monitored saltaffected soils slightly increases due to increasing of mineralization of groundwater in the observed period. Five localities with highly-mineralized groundwater were monitored to consider salinity and alkality in the period 1989­2006. In localities 1 ­ 5 evaporative residues (salt content) reached value 0.1 ­ 0.2 % at the bottom horizons, but in year 2006 all of the soil profiles contained increased values of salts. At the bottom horizons evaporative residues was higher than 0.2 % in 2006, EC in loc. 1, 2, 4 was higher than 250 mS m-1 ­ that is the salinization potential for development of saline soils. Values of ESP > 11 % and pH > 8.5 were measured in site 4 in year 2006 ­ the alkalization is dominant there. The mentioned data allow us to state that salinization and alkalization of soils is in progress and start from the bottom of soil horizons through middle part of the soil profile up to the top horizons. During the 1989 ­ 2006 values of evaporative residues, EC, ESP and pH increased along soil profile. The objective of this contribution was to estimate the state of salinization and alkalization of the soil in localities with high-mineralized groundwater. The results leads to the conclusion, that the groundwater quality is deteriorating and increased the soil salinization hazard. Acknowledgements. This research was supported by ITMS 26240120014 Center of excellence for protection and use of landscape and biodiversity supported by the Research & Development Operational Programme funded by the ERDF and APVV-027410. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Hydrology and Hydromechanics de Gruyter

The Risk of the Soil Salinization of the Eastern Part of Žitný Ostrov

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J. Hydrol. Hydromech., 60, 2012, 1, 57­63 DOI: 10.2478/v10098-012-0005-4 THE RISK OF THE SOIL SALINIZATION OF THE EASTERN PART OF ZITNÝ OSTROV VIERA KOVÁCOVÁ, YVETTA VELÍSKOVÁ Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava, Slovak Republik; Mailto: kovacova@uh.savba.sk; veliskova@uh.savba.sk, phone: +421 2/49 268 263 Salinization is an increasing enviromental problem in ecosystems. The assessment of total dissolved solids (TDS), pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), alkalinity and the concentrations of main ions makes possible to identify salinization and alkalization degree. The saltaffected soils occur in the south part and south-east part of Zitný ostrov, where the dry and mild summer climate, evaporation soil water regime and mineralized groundwater create conditions for development of the saline and alkaline soils. Five localities with highly-mineralized groundwater were monitored to evaluate salinity and alkality in the period 1989­2006. At the bottom horizons in localities 1 ­ 5 evaporative residues (salt content) reached value 0.1 ­ 0.2 %. In 2006 dry evaporative residues (salt content) was higher than 0.2 %, EC was higher than 250 mS m-1 at the bottom horizons in localities 1, 2, 4. The mentioned data allow us to state that salinization and alkalization of soils is developing, it starts from the bottom of soil horizons through middle part of the soil profile up to the top horizons. This phenomenon was observed in all investigated soils in different stages of development. KEY WORDS: Salinization, Alkalization, Total Dissolved Solids (TDS), Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC), Exchangeable Sodium Percentage (ESP). Viera Kovácová: RIZIKO SALINIZÁCIE PÔDY VO VÝCHODNEJ CASTI ZITNÉHO OSTROVA. J. Hydrol. Hydromech., 60, 2012, 1; 28 lit., 2 obr., 5 tab. Salinizácia v ekosystémoch je stále významnejsí enviromentálny problém. Stanovenie celkového mnozstva rozpustených látok (TDS), elektrickej vodivosti (EC), sodíkového adsorpcného pomeru (SAR) a obsahu výmenného sodíka (ESP) umozuje identifikáciu kritického potenciálu salinizácie a degradácie pôdy. Záujmové územie bolo vymedzené vo východnej casti Zitného ostrova, kde suché a horúce klimatické podmienky spolu s vysokomineralizovanými podzemnými vodami sú prícinou translokácie solí do pôdneho profilu. Bolo monitorovaných 5 lokalít v období 1989 ­ 2006. Namerané údaje poukazujú na vzrastajúci obsah solí, ktorý v r. 2006 dosiahol 0,1 ­ 0,2 % v celom pôdnom profile vo vsetkých monitorovaných lokalitách, hodnoty EC 200 ­ 400 mS m-1 v spodných horizontoch vytvárajú podmienky pre rozvoj zasolených pôd. KÚCOVÉ SLOVÁ: salinizácia, alkalizácia, celkové rozpustené látky (TDS), sodíkový adsorpcný pomer (SAR), elektrická vodivos (EC), výmenné sodíkové percento (ESP). Introduction Zitný ostrov ­ natural conditions, geology and parent materials Zitný ostrov is the south-west part of Slovakia, where fluvial sedimensts are dominant. In the evapotranspiration regime carbonates in fluvial carbonate sediments have been preserved, formed in alluvial soils of whole alluvial river plains. Parent materials and soil forming processes influenced the occurence prevailingly calcareous soil character. In alluvial areas of lowland rivers Calcaric Flu- visols, in depressions Fluvi-Calcaric Phaeozems, Fluvi-mollic Calcaric Gleysols to Calcaric Gleysols occur. On older alluvial sediments Calcaro-haplic Chernozems are spread. In lower lying southernmost parts with mineralized groundwaters, locally also saline soils are occuring (Fig. 1, 2). Lowland area is covered by Quaternary cover, and that is why underlying Neogene sediments crop out only locally, in tectonically elevated parts. Their development was influenced in Quaternary period by three basic factors: fluvial and aeolian activities, and solifluction. Extensive alluvial plains originated in descending parts of lowland. Most 57 V. Kovácová, Y.Velísková spread parent materials are fluvial sediments, loess complexes, aeolian sands and proluvial (slopes) sediments. Their extension, genesis and texture are narrowly connected with geomorphological features of lowlands, particularly territorial tectonic mobility. Contributing factors has also play a role zonal climatic distribution of precipitationtemperature (evapotranspiration ­ versus perlocation water regime) and groundwater mineralization changes. These factors affect particularly carbonate preservation. Their presence is a significant component part affecting the final character of pedogenetic processes (Curlík, Sefcík, 1999; Granec, Surina, 1999; Cervenka, 1970; Sútor, Stekauerová, 2000; Burger, Celková, 2007, 2009). The objective of this contribution is to evaluate the state of salinization and alkalization of the soil profile in localities with high-mineralized groundwater. Fig. 1 . Localisation of the studied area. Legend Fluvisols calcaric associated with Fluvicalcaric Gleysols Fluvi-calcaric Phaeozems developed on calcareous alluvial deposits Calcaro-haplic-Chernozems, associated with Fluvi-Calcaric Phaeozems and Calcaro-haplic Phaeozems developed on calcareous alluvial deposits Regosols arenic associated with ArenicFluvi-gleyic Phaeozems on alluvial sand (in depressions) Fig. 2. Dominant soil groups of the area. Development of saline soils The salt-affected soils occur in the south part and south-east part of Zitný ostrov. The dry and warm summer climate, evaporation soil water regime and mineralized groundwater create here convenient conditions for development and spreading of the saline and alkaline soils. These soils are developing slowly from the initial stages to the well developed ones. As a consequence of this long lasting process the slightly and middle saline and alkaline soils as well as typical solonchaks and solonetzes occur in monitored area. The network of monitoring sites therefore respects mentioned fact and the soil in different stages of development are monitored. Two processes in the development of the saltaffected soils can be recognised: 1. Process of salinization is conditioned by the presence of neutral sodium salts, mainly NaCl and Na2SO4. The indicators of salinization are dry evaporative rezidue > 0.2% and electrical conductivity of saturated soil extract EC > 400 mS m-1. Low stage of salinization is running at EC 200 ­ 400 mS m-1 or evaporative rezidue of salts 0.1­0.2 %. The result of salinization processes are middle saline soils and solonchaks. 2. Process of alkalization is conditioned by the presence of alkaline sodium salts, mainly Na2CO3, NaHCO3, Na2SiO3. The indicators of alkalizaton are exchangeable sodium percentage ESP > 5 % and pH 8 or higher. The result of alkalization processes are middle alkaline soils and solonetz. In natural conditions both of this processes are represented by different rate and the result is the mixture of both this processes, one of them is dominant. The relationship between electrical conductivity and degree of salinity is presented e.g. in U.S Salinity Laboratory Staff, 1954; Recommended Chemical Soil Test Procedures, 1998; Burger, Celková, 2009. Groundwater Groundwater in eastern part of Zitný ostrov is supplied by infiltrating Danube water primarily. Groundwater influenced the soil cover development and some chemical particularities connected with their mineral content and hydrothermic regime (local salinization). Saline soils are widespread in some localities reflecting the predominance of sodium chloride in groundwaters and soil solutions. Sodic soils are subject to severe structural degradation and restrict plant performance through poor soil-water and soil-air relations. Sodicity is shown to be a latent problem in saline-sodic soils where deleterious effects are evident. A classification of soils based on total dissolved solids, electrical conductivity, sodium adsorption ratio, exchangeable sodium and pH is outlined in studies Barzegar et al., 1994; Burger, Celková, 2004; Curtin et al., 1994a,b; Feitz et al., 2002; Hanes, 1999; Kaledhonkar et al. 2001; Kovácová, 2009b. Sodium is one of the most abundant cations in natural waters. Na+ cation is very conservative, does not enter oxidation-reduction reactions, cannot be precipitated by chemical reactions, it remains stable in solution. Nevertheless, sodium significantly participates in ion-exchange processes. Cation ion-exchange in common natural waters tends to replace divalent cations in a solution by monovalent cations. Sodium in solids-low waters (below 1 g l-1) occurs in the form of cation Na+. In solids-richer solutions, the element is combined in several complexes and ion pairs controlled by the type of water chemistry (most frequently NaCO3-, NaHCO3(aq) and NaSO4-). Much sodium gets to soil profile from mineralized waters and through human activities (Rapant, Vrana, Bodis, 1999; Kovácová, 2009a; Burger, 2007; Burger, Celková, 2009; Pitter, 1981; Richter, Kreitler, 1993; Yong et al., 1992). State of salinization at Zitný ostrov area In arid and semi-arid conditions with evapotranspiration regime and mineralized groundwater dissolved ions gets to the upper layers of soil and become the main reason for soil salinization. Mea- sured basic characteristics of groundwater chemical composition indicate, that Na levels in interested area are higher then average (Tab. 1). Sodium content for all investigated groundwaters SR has median 9.1 mg l-1 (Rapant, Vrana, Bodis, 1999), but in studies area average sodium content is calculated 21.06 mg l-1 (min. 1.1 mg l-1, max. 260.0 mg l-1). Problems of high salinity have been associated with groundwater level and irrigation of soils in arid and semi-arid areas where the soils are generally fragile in structure and susceptible to water logging. Land salinity is closely related to other land degradation processes such as soil erosion, acidification and structural decline. It is estimated that 0.16 % of the soils is salt-affected (the highest part in Komárno ­ 0.28 %, Nové Zámky ­ 0.37 %, Saa ­ 0.23% districts). Groundwater quality monitoring results in selected localities leads to the conclusion, that the groundwater quality is worsening and the soil salinization hazard is increasing in the monitored period (Burger, 2007; Burger, Celková, 2004, 2009; Dulovicová, Velísková, 2007; Kaledhonkar et al., 2001). One of the requirements imposed by the Water Framework Directive (WFD, 2000/60/EC) is to analyse and predict the future changes of surface waters quality. To asses the development of a stream´s pollution one must consider all sources of pollution and understand how water quality evolves over time (Pekárová et al., 2009). Sites description According to the climatic characteristics this territory belong to warm climatic area. Average annual precipitation sum is ranging from 520 to 650 mm. Number of summer days (temperature > 25 o C) is higher than 70 in south-east part of Zitný ostrov. Arid and semi-arid conditions with evapotranspiration regime the mineralized groundwater become the main reason for soil salinization. The salt-affected soils occur in monitored area in the eastern part of Zitný ostrov (Fig. 2), where dry and warm summer climate, evaporation soil water regime and hig-mineralized groundwater (Tab. 1) create conditions for development and spreading of the saline and alkaline soils. These results abduced Kobza et al. (2002) too. These soils are developing slowly from the initial stages to the well developed ones. As a consequence of this long lasting process the slightly and middle saline and alkaline soils as well as typical solonchaks and solonetzes occur. In the 5 monitored localities (1 ­ Veké Kosihy, 2 ­ 59 V. Kovácová, Y.Velísková Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) the soils in different stages of the development were investigated. In the bottom horizons in localities 1, 2, 4, 5 reached evaporative residues (salt content) value 0.1 ­ 0.2 %, but in year 2006 at all of the soil profile. The soil types and average groundwater levels in monitored loc. 1­5 are presented in Tab. 2. T a b l e 1. Basic characteristics of groundwater chemical composition (2006). Basic statistical characteristics of groundwater chemical composition n = 128 Mean Min. pH 7.32 5.76 TDS [mg l-1] 643.0 49.2 Ca2+ + Mg2+ [mmol l-1] 3.561 0.120 Conductivity[µS cm-1] 688.1 54.5 Free CO2 [mmol l-1] 0.77 0.12 Na+ [mg l-1] 21.06 1.10 K+ [mg l-1] 5.53 0.05 NH4- [mg l-1] 0.068 0.025 Ca2+ [mg l-1] 91.93 2.40 Mg2+ [mg l-1] 30.81 0.50 Fe2+ [mg l-1] 0.075 0.005 Mn2+ [mg l-1] 0.069 0.003 Cl- [mg l-1] 22.69 1.06 SO42- [mg l-1] 70.70 0.30 NO32- [mg l-1] 14.88 0.25 PO43- [mg l-1] 0.184 0.005 HCO3- [mg l-1] 353.32 3.05 T a b l e 2. Soil types and average groundwater levels in monitored localities 1 ­ 5. Max. 9.89 1935.8 13.021 2200.0 11.5 260.00 114.00 6.900 352.70 114.55 6.547 2.931 89.00 1019.00 39.90 7.600 937.85 Locality Soil type Fluvi-calcaric Phaeozems, associated with Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Fluvi-calcaric Phaeozems, associated with Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Calcaric Fluvi-mollic Gleysols Calcaric Fluvi-mollic Gleysols and Fluvi-haplic Phaeozems developed on calcareous alluvial deposits Calcaric Fluvi-mollic Gleysols Average groundwater levels [cm] 250a 215b 198c 110a 105b 101c 90a 95b 107c 325a 260b 217c 246a 225b 215c Veké Kosihy Okolicná Calovec Zlatná na Ostrove Kamenicná a ­ 1989, b ­ 1999, c ­ 2006 Materials and methods Soil samples were taken in depths (0­110 cm) from soil profiles ( determining the spatial variability of sodicity). The soils were air-dried and passed through a 2-mm sieve. Soluble salts were detected by measuring electrical conductivity (EC). Electri60 cal conductivity (EC) and soluble ions (Na+, Ca2+, Mg2+, K+, SO42- and Cl-) were determined on saturated-paste extracts. The concentrations of Na+, Ca2+, Mg2+, K+ were determined by atomic absorption spectroscopy (AAS); SO42- and Cl- by ionselective electrode. The basis of the salinization model is the sodium adsorption ratio (SAR) ­ a relationship between Na+, Ca2+ and Mg2+ concentrations that predicts the Na+ status of the soil exchange complex when the exchange of cations within the soil comes into equilibrium with the soil solution (Recommended Chemical Soil Test Procedures, 1998; US Salinity Laboratory Staff, 1954 ). It is given by the following expression: Results and discussion At the beginning of measurement (in 1989) evaporative residues achieved values < 0.1 %, electrical conductivity EC < 250 mS m-1 ­ that is the non-saline stage. During the 1989 ­ 2006 the values increased gradually due to higher-mineralized groundwater composition (Tab. 2), EC increased in all layers and all monitored localities and achieved values 250 mS m-1 < EC < 400 mS m-1 ­ that is defined as slightly saline stage. In the 5 monitored localities (1 ­ Veké Kosihy, 2 ­ Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) the soils in different stages of the development were investigated. In the bottom horizons in localities 1, 2, 4, 5 reached evaporative residues (salt content) value 0.1 ­ 0.2 %, but in year 2006 at all of the soil profile. The presented data measured in year 1989 ­ ­ 2006 illustrate the contemporary processes salinization and alkalization in the monitored soils. The alkalization is however more significant and dominant in site No. 4. The mentioned a data allow us to state that salinization and alkalization of soils start from the bottom of soil horizons through middle part of the soil profile up to the top horizons (Tab. 3, 5). SAR = Na Ca + Mg (1) where ionic concentrations are expressed in mol l-1, SAR in units [mol l-1]0,5, but for convenience, units will be omitted hereafter. Presence of sodium is a potential cause of structural instability when Na occupies more than 1015% of the exchange sites (Curtin et al., 1994a). SAR is related to the exchangeable-Na ratio (ESP) of the soil by the following equation: ESP = kg SAR, (2) where kg is the Gapon selectivity coefficient, and ESP ­ estimated as exchangeable Na/(CEC ­ exchangeable Na), where CEC is the effective cationexchange capacity. To predict how much exchangeable Na will accumulate in soil the value of kg must be known. T a b l e 3. Evolution of salinization and alkalization of the soil profiles in monitored sites 1 ­ 5 (1 ­ Veké Kosihy, 2 ­ Okolicná, 3 ­ Calovec, 4 ­ Zlatná na Ostrove, 5 ­ Kamenicná) in the time period 1989 ­ 2006. Loc. Depth [cm] 0 ­ 10 10 ­ 30 30 ­ 50 50 - 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 0 ­ 10 10 ­ 30 30 ­ 50 50 ­ 100 Evap. res. [%] 1989 1999 2006 0.03 0.07 0.12 0.08 0.09 0.09 0.10 0.10 0.13 0.12 0.15 0.21 0.10 0.08 0.15 0.12 0.06 0.18 0.15 0.11 0.19 0.19 0.13 0.22 0.06 0.04 0.14 0.08 0.11 0.17 0.04 0.06 0.12 0.05 0.10 0.16 0.04 0.11 0.11 0.05 0.10 0.14 0.04 0.03 0.10 0.10 0.16 0.21 0.07 0.09 0.11 0.13 0.14 0.15 0.09 0.10 0.09 0.11 0.12 0.16 EC [mS m-1] 1989 1999 2006 49 72 96 67 60 69 95 115 128 213 250 305 36 68 95 59 71 90 61 108 113 207 210 215 40 56 76 48 62 70 75 90 99 155 180 199 51 30 67 55 40 58 119 83 115 242 207 291 30 40 50 57 49 80 91 56 85 120 126 170 pH/H2O 1989 1999 2006 7.6 7.2 7.3 7.8 7.5 7.3 7.9 7.6 8.1 7.8 8.0 8.1 7.2 7.3 7.2 7.5 7.6 7.4 7.4 8.0 7.9 7.9 8.1 8.2 7.1 7.1 7.2 7.2 7.3 7.4 7.3 7.4 7.5 7.5 7.6 7.7 7.5 7.3 7.6 7.2 7.6 7.5 7.8 8.0 7.5 8.1 8.1 8.6 7.2 7.2 7.4 7.1 7.3 7.5 7.2 7.4 7.6 7.8 7.5 7.9 ESP [%] 1989 1999 2006 1.8 2.1 2.6 2.5 2.7 3.5 6.8 7.6 8.5 7.9 8.2 9.1 1.4 1.8 1.9 3.1 2.4 2.9 2.7 2.9 8.6 8.4 8.2 9.7 2.6 1.9 1.9 3.7 3.9 4.2 5.8 6.2 7.5 8.3 8.7 9.1 1.2 1.1 0.9 2.8 1.7 1.1 9.6 7.3 8.2 9.7 10.1 11.5 0.8 1.2 1.4 1.0 2.5 3.9 2.7 3.9 4.7 5.6 8.8 9.5 V. Kovácová, Y.Velísková T a b l e 4. Participation of individual ions in the soil profile in monitored localities 1 ­ 5 (in 1999). Cl[mg/ 100g] 7.5 7.4 13.5 13.3 8.6 11.5 16.2 17 28.6 23.5 28 16 6.7 15.7 9.2 11.4 15.8 18.5 23.1 20.7 SO42[mg/ 100g] 2 2 3.8 15.5 6 7.4 8.2 8.1 42.5 35 18 17 44.1 69.6 64.3 65.2 11.0 9.1 19.7 22.1 HCO3[mg/ 100g] 25.6 38.2 40.3 41.2 135 114 195 187 94.5 90.6 79 85 150.9 133.8 144.2 80 45.8 92.7 108 135 NO3[mg/ 100g] 7.5 4.2 4 5.2 4.1 2.9 3.1 3.5 3.5 2.9 2.2 6.8 6.1 4.2 3.1 2.8 5.7 3.2 2.8 4.6 Na+ [mg/ 100g 22 26.8 50 63.5 4 5.2 5.9 6.8 10 11.5 7 18 68.5 97.7 98.9 61.6 12.1 8.5 18.9 17.6 K+ [mg/ 100g] 9.8 2.3 1 0.8 0.9 0.8 0.8 0.9 1 0.7 0.6 0.9 2.8 4.2 3.1 2.1 0.8 1 0.9 1.5 Ca2+ [mg/ 100g] 24.5 12.5 8.5 8.2 20.5 22.4 16.5 12.7 24 19.5 15.2 13 18.2 19.2 16.4 12 28 17.2 21.5 27.5 Mg2+ [mg/ 100g] 6 7.5 6.5 7.4 4.2 3.8 3.5 5 5.9 9.3 7.4 6.2 4.8 2.4 1.2 6.9 5.9 7.6 8.9 10.7 Loc. Depth [cm] 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 0­30 30­60 60­90 90­110 pH/ H2O 7.13 7.36 7.22 7.22 6.82 6.0 6.72 6.95 7.42 7.10 6.92 7.01 8.6 8.2 8.3 8 7.3 7.2 7.5 7.9 pH/ KCl 6.15 6.98 6.89 6.85 6.53 6.45 6.49 6.72 7.20 6.73 6.58 6.79 7.90 7.71 7.81 7.30 6.9 6.7 7.1 7.5 T a b l e 5. Stage of salinization and alkalization in monitored localities 1 ­ 5. 1 2 3 4 5 Veké Kosihy Okolicná Calovec Zlatná na Ostrove Kamenicná slightly solonchak slightly solonchak slightly solonchak, slightly solonetz slightly solonchak, medium solonetz slightly solonchak, slightly solonetz Differences in data of the evaporative residues (salt content), EC, ESP and pH in individual years support considerable variability in the intensity of saline and alkaline processes within the very small areas. Generally, salinization of the monitored saltaffected soils slightly increase due to mineralization of groundwater. The trendlines of groundwater salinization have increasing character. In groundwater of the eastern part of Zitný ostrov was ascertain salinization risk from middle (medium) to high rate: 75 < EC< 300 mS m-1, 10 < SAR < 38 (Burger, Celková, 2009). A distinct change of an intensity of saline and alkaline processes was confirmed, but it is not hazardeous stage (Tab. 5). Much sodium gets to soil profile just from mineralized water. Proportion of sodium to the other ions is in Tab. 4. Summary and conclusion The salt-affected soils occur in the southern and south-eastern part of Zitný ostrov, where the dry and warm summer climate, evaporation soil water 62 regime and highly-mineralized groundwater create convenient conditions for development of the saline and alkaline soils. As a consequence of this long lasting process the slightly and medium saline and alkaline soils occur in monitored area. Values of the evaporative residues (salt content), EC, ESP and pH in individual years shows considerable variability of saline and alkaline processes. Generally, the development of monitored saltaffected soils slightly increases due to increasing of mineralization of groundwater in the observed period. Five localities with highly-mineralized groundwater were monitored to consider salinity and alkality in the period 1989­2006. In localities 1 ­ 5 evaporative residues (salt content) reached value 0.1 ­ 0.2 % at the bottom horizons, but in year 2006 all of the soil profiles contained increased values of salts. At the bottom horizons evaporative residues was higher than 0.2 % in 2006, EC in loc. 1, 2, 4 was higher than 250 mS m-1 ­ that is the salinization potential for development of saline soils. Values of ESP > 11 % and pH > 8.5 were measured in site 4 in year 2006 ­ the alkalization is dominant there. The mentioned data allow us to state that salinization and alkalization of soils is in progress and start from the bottom of soil horizons through middle part of the soil profile up to the top horizons. During the 1989 ­ 2006 values of evaporative residues, EC, ESP and pH increased along soil profile. The objective of this contribution was to estimate the state of salinization and alkalization of the soil in localities with high-mineralized groundwater. The results leads to the conclusion, that the groundwater quality is deteriorating and increased the soil salinization hazard. Acknowledgements. This research was supported by ITMS 26240120014 Center of excellence for protection and use of landscape and biodiversity supported by the Research & Development Operational Programme funded by the ERDF and APVV-027410.

Journal

Journal of Hydrology and Hydromechanicsde Gruyter

Published: Mar 1, 2012

References