Modeling the Groundwater Pollution Along the Lower Course of the Tundzha River,

Radko Petkov National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, , Bulgaria [email protected]

Abstract At present mankind has faced more seriously than ever the problem of environmental protection. Under the conditions of the contemporary stage of social-economic development, the optimal solution of this issue is possible if environmentally friendly technologies are designed and implemented and strict control on emissions from pollution sources and other measures are realized. The existence of 7 Natura 2000 protected areas along the lower reaches of the Tundzha River requires, when developing new projects and facilities, to apply an ecological approach to site selection from the viewpoint of minimum impact on groundwater quality. The problem becomes particularly relevant, if the rather diverse nature and character of groundwater contaminants are taken into account. Groundwater represents a major source for meeting water demand in many settlements (for drinking and irrigation purposes) and the control on preserving this source is of strategic importance. In ecological respect, the location of facilities has to be substantiated as early as at the design stage in such a manner that possibly minimal impact on groundwater is achieved, so that water quality in the respective region could be preserved in the process of water use. The selection of an optimal site for such facilities, aimed at maintaining water quality within the range of the specified norms, is a task, which is practically still intractable. Prior to the construction of a given object that under certain circumstances might be a potential source of groundwater pollution, it is expedient to make a preliminary assessment and prediction of contamination in the area, intended for the facility site, with the aim of defining its optimal positioning in conformity with the norms for groundwater quality and cost of this object. The case with fixed location of the pollution sources, when contaminant migration to the water bodies is considered, represents a similar problem. Without the element of optimizing the pollution sources site location, the problem is solved using simulation models. The paper shows the numerical modeling of groundwater pollution in the terraces along the lower course of the Tundzha River. The proposed hydrodynamic model of the problem will be in a 3D non-stationary case (x,y,z,t) of migration of non-conservative admixtures for non-pressure head groundwater flow. Keywords : optimizing the pollution sources, groundwater pollution, head groundwater flow, contaminant migration.

Introduction Infiltration of atmospheric precipitation represents a relatively high share of the recharge of groundwater filtration flow. The understanding of these processes is essential for defining the hydro-environmental risk of groundwater pollution with ingredients released by industrial enterprises. Hydrogeological conditions are favourable for the processes of contaminant accumulation in groundwater. The relatively high groundwater levels shorten the way of vertical filtration of precipitation. When fallen on arable land, rainfall provides the possibility of migration of contaminants that have not been assimilated by the plants by means of descending infiltration to the aquifer layers. During the recent decades the trend towards increased contaminant amounts is also observed for surface water. Many of the water intake facilities are built on alluvial-proluvial deposits of river terraces, where the

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 1 groundwater is in direct hydraulic connection with the river flow. In this way nitrates reach drinking water too, although sanitary-protection zones are available.

Impacts on groundwater status resulting from anthropogenic activities Point sources of groundwater pollution - landfills, earth lagoons, former uranium mines, tailing ponds, industrial sites, settlements without sewage systems, petroleum stations. Settlements without sewage systems and landfills (not meeting the requirements of environmental legislation) are the most important point sources for the groundwater status. They are sources of ammonium and sodium emissions. This is the result of poor management of landfills or absence of an insulating screen on their bottom, as well as the presence or absence of waste water treatment plants in the settlements. All existing dumps and landfills, not conformable with the national and European legislation, had been subject to closure till July 2009. The construction of new regional landfills with reliable hydraulic insulation layers in the base is envisaged at the places, where necessary. The new future facilities are intended to serve several municipalities. The earth lagoons are typical earth formations, encountered at distilleries and rose-distilleries, in livestock- and poultry-breeding farms. Diffuse sources of groundwater pollution and land use survey Agriculture has been considered as a source of groundwater diffuse pollution. The arable lands from the Land Use Map are attributed to the underground water bodies and the vulnerability of the upper soil layer to contaminant permeation has been evaluated. The unregulated landfills, dunghills, etc., as well as leakages from overworked pipes of sewage systems, are also important diffusion sources. Programme for rural development • National Agri-environment Programme for Bulgaria • Strategy for the construction of regional landfills for waste released from settlements • Programmes for improving the environmental status aggravated by economic activities in the past • Identification of vulnerable areas with nutrient components in groundwater • Development of good agricultural practices in vulnerable areas Specific problems of groundwater management in the region of the Tundzha River - Pollution with ammonium, phosphates, nitrates, manganese and iron; - Uranium deposits, inoperative at present – a great part of them have a local monitoring network, tailored to the specific hydrological, hydrogeological, climatic, agrotechnical, mining and technical conditions of the respective site; - Soil pollution with heavy metals – typical for areas with atmospheric pollution, significant discharges of wastewater, intensive chemical impact on agriculture and loaded traffic. The largest share of arable lands with heavy metal pollution is in the Plovdiv and Haskovo districts; - Soil salinization – closely linked to irrigation, since groundwater is not properly regulated and as a result water mineralization is increased. The largest areas with soil salinization are in the Sliven and Plovdiv (Belozem village) regions; - Increased sulphate content in the region of the East Maritsa basin.

Characteristics of groundwater in the East Aegean region Geological structure

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 2

Fig. 1. The East Aegean basin Groundwater The territory of the Tundzha municipality falls within the - hydrogeological region. It incorporates the similar Yambol and Elhovo syncline forms, which are filled with Neogene deposits and alluvial sediments of the Tundzha River and its tributaries – the Popovska, Kalnitsa, Arapliiska and Yavuz Dere Rivers. The main aquifer horizon in the region is the alluvial one. The Neogene sediments are moderately aquiferous only in the region of Elhovo-Izgrev-Boyanovo. The Quaternary here is represented only by the alluvial deposits of the Tundzha River and its bigger tributaries. The width of the Tundzha terrace is from 1 to 4 km. It becomes narrower due to the lateral and under-riverbed rock threshold at the Konevets village, ending at the rock threshold near the Knyazhevo village. In both places the larger part of the terrace groundwater flow is discharged in the river. The thickness of the terrace deposits ranges from 8 to 25 m, the gravelly-sandy layer occupying more than half of it. The rest part belongs to the clays, which are found mainly in the uppermost zone of the section. The water transmissivity reaches up to 1000-1200 m²/d, and the water level transfer – 5.5 10³m²/d. The recharge of the aquifer horizon is realized at the expense of precipitation. It is supposed that the fissure and fissure-karst water from the bedrock discharged in the valley also takes part in the recharge. Having these hydrogeological characteristics, the alluvial deposits are referred to as strongly aquiferous ones. The total mineralization of groundwater in the Yambol-Elhovo region is from 0.7 to 1.13 g/l and the general hardness is 6.2-13.3 mg.equ/l. The water macro composition is quite diverse. The predominating points are with hydrocarbonate-calcium-magnesium water.

Soils and soil resources The territory of the Tundzha municipality refers to the Mediterranean soil district, the Middle Thrace – Tundzha province. The soil cover is characterized by great diversity. The prevailing soil types are smolnitzas, lessivated, planosols, solonchaks, solonetz soils and sedimentary soil types (Appendix 6, Appendix 7). 1. Chernozem – smolnitzas (Vertisols, VR, FAO, 1988), represented by common (leached – eutric, VRe), carbonate (calcic) and gleyic (meadow smolnitzas). The smolnitzas are characterized by a thick soil profile, well expressed humus horizon (50-70 cm), relatively high humus content (2.5-3.5 %) and a relatively homogeneous profile. According to their mechanical composition they are slightly clayey to heavily sandy-clayey. The soil reaction changes from slightly acidic to alkaline, with a very high sorption capacity and saturation with bases. These soils are treated with difficulty because under drought conditions they form wide (more than 1 cm) and deep (at least 50 cm) cracks. For this reason it is necessary to keep the required optimal periods for their cultivation. They are suitable for growing cereal and technical crops.

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 3 2. Leached cinnamon and cinnamon-like soils, represented by cinnamon-like (leached cinnamon – chromic, LVx), smolnitza-like (cinnamon smolnitza-like – vertic, LVv), light (pseudo-podzolic – albic, LVa). These soils are with well expressed thick illuvial-clayey Bt-horizon, differentiated profile with high sorption capacity of the silt and saturation with bases (higher than 50 %). The soils represent fully-developed deep soils with a profile from 90-100 to 150-200 cm when erosion is absent. However, the surface horizon A is with a low thickness – from 18 to 25 cm for the heavier soils and up to 35 cm for the more sandy ones. The mechanical composition is diverse and is due not only to the inherited granulometric composition of the soil-formation materials or paleosoil processes, but mostly to the redistribution in the process of lessivage. The surface horizon of the soils is slightly-, medium- or heavy- sandy-clayey, and in Вt they are significantly more clayey (up to 60 % of clay) and the humus content is relatively high – up to 3 - 4%. 3. Soil types with accumulation of salts, represented by Solonetz (SN) and Solonchak (SC) soils The Solonchaks are secondarily formed soils, often originating from salinated former bog, meadow-bog, meadow-chernozem and other soils. For this reason they exhibit diverse morphology, but always possess their most typical feature – the high water soluble salt content – more than 1 %. The most often encountered salts are NaCl, Na2SO4, Na2CO3. According to their mechanical composition they are medium to heavy-clayey, with рН in the range 7.8-8.5, with good humus reserves, and significant amount of total nitrogen, phosphorus and potassium. 3.1. The solonetz soils contain in their sorption capacity exchangeable sodium in amounts higher than 15 %. The exchangeable sodium determines a number of special morphologic, physical, physicochemical, air and agronomic properties – high density, stickiness, strongly alkaline reaction, low humus content, low productive moisture content, low aeration, etc. These properties as a whole restrict their use for agricultural activities. To restore their fertility, it is necessary to carry out three melioration procedures – plaster manipulation, drainage and washing out by irrigation. 4. Alluvial soils (Fluvisols, FL), represented by rich (eutric, FBe) and deluvial-meadow (gleyic) soils. The alluvial soils are formed by the young (Quaternary) deposits of the rivers and are found on the floodplain and the first non-floodplain terrace of the Tundzha River. The groundwater level is high and the soils are subjected to periodic flooding and deposition of new alluvium. With respect to their mechanical composition the soils are gravelly-sandy to slightly clayey. They are crumbly, airy, warm, and this predetermines their easy cultivation. These qualities make them very suitable for agriculture – growing of vegetables, fruits and herbaceous meadow species. At the same time, their high filtration capacity predetermines their vulnerability towards pollution. This imposes the necessity of introducing monitoring to evaluate their status. As a result of the analysis of the soil types, distributed on the territory of the municipality, the conclusion can be drawn that considerable soil resources are available for the development of a number of sub- branches of plant growing – cereal, industrial, permanent crops (vineyards) and forage crops.

Hydrodynamic model of thermodispersion of non-conservative admixtures in porous media

Differential equation, describing a 3-D non-stationary convective-dispersive transfer in a dimensionless form ( Petkov, 2011 ) [13]:

∂ ∂ C ∂ ∂ C ∂ ∂ C ∂ (Dxx ( )) + (Dyy ( )) + (Dzz ( )) − (u xC) − ∂ x ∂ x ρ ∂ y ∂ y ρ ∂ z ∂ z ρ ∂ x (1) ∂ ∂ ∂ C − (u C) − (u C) −ψ = ∂ y y ∂ z z ∂ t

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 4 Differential equation, describing a 3-D non-stationary filtration in a dimensionless form:

∂ ρ ∂ H ∂ ρ ∂ H ∂ ρ ∂ H ∂ H (2) (M x ) + (M y ) + (M z ) = S ∂ x υ ∂ x ∂ y υ ∂ y ∂ z υ ∂ z ∂ t Equation of heat conductivity:

2 2 2 ∂T ∂ ∂ ∂ ⎛ ∂ T ∂ T ∂ T ⎞ (3) (u T) (u T) (u T) ⎜ ⎟ σ + x + y + z = α⎜ 2 + 2 + 2 ⎟ ∂ t ∂ x ∂ y ∂ z ⎝ ∂ x ∂ y ∂ z ⎠

Equation of state: ρ = ρ(c,T) ν =ν (c,T) (4) where: С(x,y,z,t) is concentration of solute substances; ux, uy, uz – dimensionless components of the velocity vector in the respective directions; T – temperature of the entering solute substances, Dxx, Dyy, Dzz – coefficients of hydrodynamic dispersion; H (x, y, z, t) is a dimensionless pressure-head of the movement; – a source of pollution; knx ,kny ,knz – coefficients of permeability along the directions х, у and z; L1, L2, L3 – linear lengths, determining the filtration area; t* – the time period of investigated migration; Mx, My, Mz – dimensionless parameters; x,y,z – dimensionless coordinates; ν and ρ – kinematic viscosity and density of the filtration flux, which depend on the concentration of migrating substances in case of active admixtures or are constants in case of migrating passive admixtures. For convenience in the calculations, equations (1, 2, 3, 4) are transformed to a dimensionless form (Petkov, 2009) [12]. Prior to defining the initial and boundary conditions, we have to note that in the case of non-conservative solute substance migration the equations (1, 2, 3 and 4) cannot be solved independently of each other due to the mutual interrelation between the concentration in (1) and the velocity field in (2), in contrast to the case with conservative solute substance migration, when such an approach is possible. This is important and brings certain difficulties that have to be overcome in the numerical solution of the system of equations. Conjugated optimization model When building a certain object (facility) that might be a real or potential contaminant of groundwater, the usual task to be set is to determine the distribution (migration) of the contaminant in time and the groundwater space, considering the object as a pollution source of certain intensity. This is called the direct problem. When the location of the pollution source with certain contaminant intensity is sought for, so that the degree of groundwater pollution in a given area will not exceed a fixed limit, the task is considered as the inverse of the direct problem. Suppose that an object has to be constructed on the territory of a given municipality, which will be considered as a pollution source with certain intensity. Water supply wells are built on the territory of the municipality in certain zones or a water source exists with strictly defined water quality that should not be aggravated. Hence the task is set forth to select the contaminant localization in such a manner that its functioning should not lead to water quality deterioration in the wells or in the water source. This problem is relevant even in the cases when the object of pollution is built according to an ecologically friendly technology with full treatment of the contaminating substances, but markedly hazardous situations are possible with unexpected consequences if emergencies or accidents occur ( Petkov, 2008 ) [11]:.

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 5 , i=1,2,3 (5)

P is an indefinite function of (x,y,z,t). In case of a point source of pollution the expression for P is P =δ(x- x1)δ(y-y1)δ(z-z1) δ(t-τ), where t is the time of functioning of the pollution source, with the respective initial and boundary conditions.

* ∂ u * C (x,y,z,τ) = 0; i C = 0 on S; (6) ∂ n C * ∂ ( ) ρ = 0 on ∑ , (7) ∂ xi where: S and ∑ are the free boundary and the boundary of the area, in which the solution is sought for. The choice of Р provides the possibility for positioning the source or sources in certain points or areas. Choosing different functions for P, it is possible to obtain various functional and respective conjugated equations. The conjugated problem makes it possible with one-time solution to determine the optimum localization of the groundwater pollution sources in such a manner that the admissible sanitary norms should not be exceeded. The heat transfer conjugated equation for porous media is obtained in a similar manner. Suppose that it is necessary to locate a new enterprise in the vicinity of a settlement, resort complex, etc., so that the ecological norm should not be violated, keeping it minimal or within the range of the admissible limits. Suppose also that the enterprise discharges harmful substances in the soil with intensity Q, which migrate to groundwater in consequence. Consider the migration process of the admixtures (contaminants) in the domain, described by the system

(1)-(4) with initial and boundary conditions. If it is necessary to determine a domain G1CΩ(t) in such a manner that if a pollution source or sources with intensity Q are localized in the domain G1CΩ(t), the total amount from G1 at every moment t should not exceed a certain concentration С1. If the point source with intensity G in the point (x0, y0, z0) is considered, the functional has the form: τ * J3 = Q∫C (x0 , y0 ,z0 )dt , (8) 0 where С* is the solution of the conjugated problem (5) with the respective initial and boundary conditions for:

ψ = Qδ(x-x1)δ(y-y1)δ(z-z1), (9) where δ is the function of Dirac, and (x1,y1,z1) G2. Using the conjugated problem to determine the domain, where the pollution source will be localized, it will be necessary only to satisfy the inequality:

J3 (x,y,z) ≤ G1 (10)

The points in the domain , for which (131) is satisfied, represent the domain G2, which is sought for. * After obtaining С , numerical integration is applied to determine J3.

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 6 A software programme has been composed using the С++ language on the basis of the approach illustrated above, which provides possibilities to determine the location of the pollution source by one-time solution of the conjugated problem and to use the duality of the functionals when the hydrology of the domain Ω ( t ) is known. The following input data are used for the tests: Mx = 1.84786, My = 0.038554, Mz = 0.025637, H = 0.5, Dx = 0.002215, Dy = 0.039454, Dz = 0.0074311, A1 = 0, A2 = 0.0911, A3 = 1, B1 = 0.0058, B2 = -0.0552, B3 = 1, С0 = 0.9 for (0.4 ≤ y ≤ 0.6) and С0 = 1 for (0.77 ≤ y ≤ 0.92), t* = 360

Fig. 2. Ammonium nitrate pollution in space Fig. 3. Isolines of the equal concentrations of for t = 65Δt pollution with ammonium nitrate in plan for t = 65Δt.

As in the case with the examples considered so far, the developed “Nonsteady_Termo_Dispersion-RP” software has been applied for determining the influence of density and viscosity on the process of filtration dispersion.

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Fig. 4. Isolines of the equal concentrations of Fig. 5. Isolines of the equal concentrations of pollution with ammonium nitrate in plan for t = 230Δt pollution with ammonium nitrate for t = 200Δt

Conclusion A conjugated optimization model for the migration of non-conservative admixtures for a 3-D non-stationary case without pressure head has been obtained. The advantage of the model over the simulation models is that the latter require multiple solutions of the direct problem, which are rather time consuming with respect to the computation procedure. The obtained models provide the possibility of one-time solution of the inverse problem for optimizing the localization of the sources of groundwater pollution.

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BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 8 11. Petkov R. Ecologo-economic Optimization of the Location of Sources Polluting Groundwater. BALWOIS, Ohrid, Republic of Macedonia 2006; fp.338. 12. Petkov R. Numerical modeling of fertilizer and pesticide pollution of groundwater. Journal of Balkan Ecology, 2009;12(2): 199-209 13. Petkov R. Modeling Pollution With Mineral Fertilizers and Pesticides. International Conference “100 year Bulgarian Soil Science” 16-20 may 2011; 759-763.

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