Alteration parameters affecting the Luxor Avenue of the Sphinxes-Egypt

Science of the Total Environment 626 (2018) 710–719

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Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv

Alteration parameters affecting the Luxor Avenue of the Sphinxes-Egypt El-Gohary M. a,⁎, Redwan M. b a b

Conservation Dept., Faculty of Archaeology, Sohag Univ., 82524 Sohag, Egypt Geology Dept., Faculty of Science, Sohag Univ., 82524 Sohag, Egypt

H I G H L I G H T S

G R A P H I C A L

A B S T R A C T

• The weatherability states affecting the Avenue of the Sphinxes was investigated. • Different extrinsic and intrinsic disintegration agents affect stone alteration. • Burial, solar effects, moisture and groundwater are the main deterioration factors. • Breaking of statues heads, salt and abrasion were the most important damage. • Cleaning, desalination, consolidation and reducing human impacts are recommended.

a r t i c l e

i n f o

Article history: Received 18 October 2017 Received in revised form 24 December 2017 Accepted 24 December 2017 Available online xxxx Editor: Toshio Yamaguchi Keywords: Avenue of the Sphinxes Burial effects Solar effects Alteration

a b s t r a c t Stone alteration in the environment is caused by various extrinsic disintegration agents, besides, their intrinsic properties “mineralogical composition, textures and internal structure”. Therefore, the purpose of the current study was to evaluate the weathering state affecting the Luxor Avenue of the Sphinxes by studying its chemical, mineralogical and physio-mechanical characteristics, in addition to morphological features. Scientific techniques, such as X-ray fluorescence (XRF), X-ray diffraction (XRD), Petrographical microscopy (PM), Cathodoluminescence (CL), Environmental Scanning Electron Microscope (ESEM) and micro energy-dispersive X-ray fluorescence (μ-EDXRF) were used. The results showed that quartz represents more than 96% of the sandstones and the main cement of the grains is quartz overgrowth. Alteration and formation of kaolinite was clearly observed. Halite, sylvite and bischofite were the main salts that affected the statues representing approx. 78.40%. The study also provided information about the different deterioration factors affected the Avenue of the Sphinxes namely; burial environment, solar effects, soil moisture and groundwater. These caused some deterioration forms such as soiling & crusting, breaking down most of the statues heads, saturation forms, salt crystallizations and stone abrasion. Cleaning, desalination and consolidation using different materials and techniques, in addition to reducing the human anthropogenic impacts are recommended for future conservation of the Luxor Avenue of the Sphinxes. © 2018 Elsevier B.V. All rights reserved.

1. Introduction

⁎ Corresponding author. E-mail address: [email protected] (M. El-Gohary).

https://doi.org/10.1016/j.scitotenv.2017.12.297 0048-9697/© 2018 Elsevier B.V. All rights reserved.

Alteration and damage of natural building materials are neglected in studying the geomorphic system of all environments (Viles, 2011). This is known as the breakdown and decay of geological materials due to the aggressiveness of dominated environmental conditions (Robinson and

M. El-Gohary, M. Redwan / Science of the Total Environment 626 (2018) 710–719

Williams, 1994; Jones, 2007). It presents a big threat to cultural resources, promoting decay and deterioration of human constructs (Pope and Rubenstein, 1999; Kipkorir and Kareithi, 2012). This system is closely intertwined with some synergistic variables, e.g. natural factors, organisms and human activities (Goudie, 1994; El-Gohary, 2015) by playing effective negative roles through three main mechanisms (biological, chemical, and physical) (White and Blum, 1995). Therefore, the current study was conducted to evaluate the weathering state affecting the Luxor Avenue of the Sphinxes by studying the chemical, mineralogical and physio-mechanical characteristics, in addition to morphological features. 1.1. Overview Luxor (Thebes) located at (25.69° N, 32.64° E) (NASA, 2016), was the religious capital of Egypt during the New Kingdom, and was the glorious city of the god Amon-Ra. It also contained many Pharaonic monuments, e.g. the processional avenue of the Sphinxes that was lined on both sides by 1200 statues of sphinxes (Basheer et al., 2014), (Fig. 1-a). The Avenue of the Sphinxes “ / ” was comprised of human headed lions over a one and a half mile (3 km) (Fig. 1-b). Often sphinxes depicted the king (pharaoh). A lion body could also be combined with the heads of other animals-for example the head of a ram or a falcon to represent a god (Blackman, 2012). The roadway was used once a year during the Opet festival “ / ” when the Egyptians paraded along it carrying the statues of Amun and Mut in a symbolic reenactment of their marriage (Coleman, 2010). The construction of the Avenue of the sphinxes began during the New Kingdom (1580–1085 BC) from the 18th dynasty rule of Amenhotep III (1388–1351 BC) (O'Connor and Cline, 1998), and finished during 30th dynasty rule of Nectanebo I (380–362 BC) (Depuydt, 2006). The roadway was renovated by the Ptolemaic Queen Cleopatra (51–30 BC) and later used by the Romans. Recently, 850 fragmented have been discovered along a section of the Sphinx road built during the reign of Amenhotep III (Hart, 2005). 1.2. Sources of alteration and damage The Avenue of the sphinxes was exposed to several deterioration factors over two essential phases. The first was the initiation phase; attributed to the effect of intrinsic deterioration factor (Burial effects) and the second was during the propagation phase owing to the effects of the extrinsic deterioration (Solar, Soil Moisture and Groundwater effects). These factors caused many serious actions that affected the statues due to the change of reactive phases both in the soil and the surrounding environment (DECC, 2008). They included; organic matter (soil components), sulfides, iron hydroxides and carbonates (Ibrahim, 2008; Blume et al., 2016) as well as the effects of the components of ground or interstitial water such as hydrogen ions and sulfates (Winter et al., 1998; Brewster Jr, 2000).

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1.2.1. Burial effects Archaeologists have often occupied themselves with many regional factors, particularly the burial environment. Buried archaeological stones are seriously affected according to the type of burial environments and their singular features. Buried materials could be affected by many factors such as soil, rain, sun, snow and wind, in addition to other natural phenomena, e.g. biogenic effects (Balek, 2002). Burial effects are the direct forms of degradation processes, resulting from the change of reactive phases in the soil or the site (Potter et al., 2005). These major changes are represented in fabric, composition, rigidity and pore structures and they are controlled by precursor sediment character, pore fluid, lithostatic and tectonic stresses (Wanless, 1983). As well as, the effects of other burial disadvantages such changing the physical, chemical, and drainage properties of the stones. Also, it may break solid foundations or artifacts or displace their position in relation to the site's stratigraphy, increasing loads at heads of slopes, leading to complete failure (Jones, 2007). Hence, it could be claimed that most of our statues with their pedestals (case study) were found destroyed and headless due to burial effects as previously reported by Boraik (2010). The statues were buried in a soil composed of clay, with sand and salt contents. Excavation date was started between 1998 and 2002 (El-Saghir, 1992; Boraik, 2013). 1.2.2. Solar effects These are one of the main factors which over time act during all atmospheric events, such as: rainfall, wind, air pressure and humidity, and negatively lead to the alterations of the monumental buildings (Gupta, 2013). These effects cause a change in the building stones over time especially to those directly exposed to weather through different mechanisms. The changing of colored surfaces (fading symptom) is the main form which have been created through the solar mechanism (ICOMOS-ISCS, 2008). This symptom is essentially owed to the temperature variations between day & night (micro effects) and summer & winter (macro effects) (Li, 2007). These faded surfaces take a pale appearance which is more frequently seen in natural construction stones and sometimes occur as vein shaped dark spots (black hard crusts) (Camuffo, 1995). Furthermore, solar effects can also lead to another severe mechanism (thermal expansions) (Hockman and Kessler, 1950). Both mechanisms can cause some deterioration forms such as cracks and breaks on stones especially with continuous temperature changes and material fatigue (Ismael, 2015). 1.2.3. Soil moisture and groundwater effects Both these variables are of the most important deterioration factors affecting Upper Egyptian buildings, especially after the construction of the Aswan High Dam (Dawoud, 1997; Campos, 2009). These deterioration processes take place through water logging and soil salinity (Shamrukh et al., 2001), in addition to the aggressive influences of moisten deposited layers and fine-grained alluvial soil through high value of dampness (El-Gohary, 2000; El-Gohary, 2016). On the contrary,

Fig. 1. Location map of the Avnuxe of Sphinxes (a), and human headed sphinxes of over one and a half miles (b).

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shallow groundwater moves upwards through capillary forces leading to a high rate of evaporation from the stone surface of the ground (Alkhaier et al., 2009; Doehne, 2002). Both previous mechanisms lead to continuous transport of salts in an upward direction when water is available from the saturated zone (Høybe, 2005), where they crystallize causing different forms of deterioration, such as discoloring (Miglio and Hunt, 1993), stress and strains owing to the expansion during crystallization (Warke and Bernard, 2000; Rodriguez-Navarro and Doehne, 1999). These effects create some severe deterioration forms affecting the statues, such as: soiling and crusting features, broken down of the most statues heads, saturation form, crystallizing of some salt types and stone abrasion (Fig. 2-a, b).

linked with a PDF2 database was employed. Petrographical microscopy (PM), using “Leica optical microscope-4500 P attached to DFC500 Camera-Leica Microsystems was used to obtain the samples petrological characteristics”. Furthermore, Cathodoluminescence (CL), “Hotcathode-CL microscope Simon-Neuser HC2-LM was operated at 14 kV and a current density of ~10 mA/mm2”. Cathodoluminescence used to identify any diagenetic processes and cement phases present. The thin-sections were coated with carbon to prevent any build-up of electrical charge. Luminescence images were obtained on-line using a digital video camera attached to the microscope.

2. Sampling and characterization techniques

μ-EDXRF M4-Tornado; an energy-dispersive, non-destructive elemental X-Ray Fluorescence Spectrometer analysis was used for the chemical analysis of the samples. The analysis was set for 50 kV, and 600 μA, polychromatic beam, polycapillary lense beam of 15 μm diameter and 2× flash Silicon Drift Detectors (SDD) with 2 ms measuring time per pixel size and high count rate capability. Finally, Elemental mapping of the samples was realized. ESEM, “FEI Quanta 600 FEG Environmental Scanning Electron Microscope” coupled with an energy dispersive X-ray detector “EDX Apollo XL Silicon Drift Detector; EDAX-AMETE” was used for detailed characterization, identification, and quantification of both crystalline and amorphous phases, in addition to studying the morphological features of the samples.

A total of six sandstone samples (Fig. 3) were collected from the bodies of five statues. Geologically, the blocks used in the production of the statues were originally from the Gebel el-Silsileh that composed mainly of friable and poorly cemented Nubian sandstones (Klemm and Klemm, 1993). A few samples were selected for producing polished thin sections on a dry basis regarding cutting and polishing and glued using Canada balsam to glass slides for further mineralogical, elemental and morphological identifications. Three water samples were extracted from the stone samples and used for hypothetical salt combination (stone salt content).

2.2. Techniques for elemental and morphological analysis of stones

2.1. Techniques for mineralogical analysis of stones 2.3. Techniques for chemical analysis of salts The bulk mineralogy of the samples after grinding to grain sizes less than 5 μm with a RS 200 instrument with an agate milling set (Retsch GmbH), was detected by X-ray diffraction (XRD), using a “Philips PW 3710 series automated powder diffractometer, with monochromated CuKα (mean wavelength of 1.542 Å) radiation. It was operated at 40 kV and 30 mA, glancing angles 2θ between 2° and 65°, using a secondary graphite crystal monochromator”. For data evaluation, Galaxy software

Hydrochemical analysis had been quantified in order to find the type and percentage of rock's salt content in the samples from the extracted water solutions prepared from the collected rock samples (1 g stone: 100 ml deionized water) following the method of Rhoades (1982). The major cations (K+, Na+ and Mg2+) in the extracted water derived from the stone samples were analyzed using Atomic Absorption

a

b

c

d

Fig. 2. Photographs showing some severe deterioration forms affecting the statues due to different sources of alteration (Burial, Solar, Soil moisture & groundwater effects).

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Fig. 3. Photographs showing the locations and sampling points (the blue area refers to nonaffected samples and green color for affected samples). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Spectroscopy (AAS), “Perkin Elmer AAS Analyst 400”, Spectrophotometer “Unico-1200” after the solution acidified to preserve metals in solution by adding a few drops of HNO3 (69% concentration) until the pH waslowerthan2(controlledbypHpaper).Forthemainanions(Cl−, SO−− , and NO− 4 3 ) was measured using manual titration, turbidimetric and spectrophotometer methods respectively. Cl− was determined by back titration with potassium thiocyanate (Volhard's Method) (Caldwell and Moyer, 1935). SO− 4 was measured by turbidimetric method by converting sulfate to a barium sulfate suspension (Sheen et al., 1935). The resulting turbidity is determined by spectrophotometer and compared with a curve prepared from standard sulfate solution. NO− 3 was determined spectrophotometrically using a complex formed by nitration of salicylic acid under highly acidic conditions (DEWAS, 1981). The hypothetical salt combinations of the dominated salt within the stone pores were presented in equivalent percentages “epm %” based on the reaction between the ions of the strong acids (Cl−, SO2− 4 ,) form chemical combination with alkalis (Na+ and K+) and the rest of the acid radicals combine with the alkaline earths (Mg2+). Excess cations in water will combine with the acids (NO− 3 ) (Collin, 1923). The relations between the concentrations of dissolved cations and anions are illustrated in the form of adjacent vertical bar graphs, the height of which is equivalent to the total concentration of either cations or anions. The deduced salt combinations between major anions and cations represent the formation of the main groups of hypothetical salts combinations in the water (Collin, 1923).

3. Results 3.1. XRD mineralogy, PM & CL petrography XRD analytical results confirm that the stone of the statues can be divided into two types; the first is related to the nondeteriorated parts (Fig. 4-a) composed essentially of pure Quartz (SiO2) approx. (96–100%) and the second refers to the affected parts (Fig. 4-b) and is composed of Quartz (SiO2) approx. (85%), ~10% Kaolinite-1A. (Al2Si2H4O9) and finally about ~5% Microcline (KAl Si3O8). Petrographical investigation results reveal that the non-affected (a, b and e) and affected (c, d and f) samples mainly composed of subrounded to sub-angular, medium to coarse-grained quartz with finer grain sizes and higher surface areas in addition to frequent silica overgrowths. Furthermore, the samples grain contact is pointed to elongated and they are characterized by enriched iron and titanium oxides cement and cavity filling with feldspars and kaolinite. Sandstone samples are composed of approx. (96% quartz). According to Tucker (1981), this type belongs to quartz arenite (Fig. 5-a, b, c, d). CL clearly attests that the main cement of the grains is quartz overgrowth (silica cement) (Fig. 5-e, f) or iron oxides that frequently fill the secondary porosity. 3.2. Water origin of saline water The main salt components of the analyzed samples include K+, Na+ − and Mg2+ as the major cations and Cl−, SO2− 4 , and NO3 as the major

Fig. 4. XRD spectra of (a) non-affected sample (b) affected sample; for each one a comparison with spectra of the revealed minerals is reported.

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Fig. 5. Photomicrographs of polished thin sections of the investigated samples showing (a) compacted quartz grains with frequent silica overgrowths (under plane light), besides, (b) the same sample (under crossed polars), X-5, c. iron and titanium oxides cement and cavity filling (under plane light), (d) the same sample (under crossed polars), X-20, (e–f) cathodoluminescence (CL) images of the same samples, X-10. Non-affected sample represented by a, b and e, affected sample represented by c, d and f.

anions. Their concentrations and saturated salts using hypothetical combination of water method were listed in (Tables 1-a and 1-b).

color in the samples (Fig. 6). Kaolinite is represented by patches of AlSi that are recognized at certain hot spots filling the cavities upon silicate dissolution.

3.3. μ-EDXRF 3.4. ESEM-BSE investigations These investigations can provide a detailed chemical composition of grains that can't be identified using polarized microscope. They give the ability to detect the elements present and how the variations in their elements concentrations occur (Nylese and Anderhalt, 2014), as well as, it provides a list of elements that can be combined to give the composition of definite mineral(s) in the sample after comparing it to the different mineral species (Deer et al., 1966; Scruggd et al., 2000; Germinario et al., 2016). It provides faster information about the chemistry and phase distribution for larger areas with the possibility to extract definite analytical information from small region of interest, and individual lamina from the data cube even after the measurement (Nikonow and Rammlmair, 2016; Redwan et al., 2017). Moreover, the distribution of elements measured using the micro-XRF can be displayed through a wide variety of colors, and multiple maps that can be combined into a single image. Our result, listed in Table (2), proves that Si is relatively uniformly distributed within the thin sections due to the predominance of quartz grains; Al is a result of silicate minerals alteration; Fe is encountered in some samples as cement and cavity filling precipitates; and Ti oxides hot spots are enriched in samples. The overlapping of elements in the same areas means the combinations of these metals to form minerals (phase mapping). For example, orthoclase formed from the combination of K, Si, Al can be recognized in patches of magenta

The recorded XRD data of the investigated samples (Tables 1-a and 1-b & Fig. 3) suggested that the samples were divided into two categories (non-affected & affected). This might be due to the variation of the dominated weathering factors, particularly the evaporation process. Non-affected category (0–4% weathering prosecutes) were sheltered and were not exposed to the main deterioration factors, especially alternative cycles between heating and cooling or drying and dampening, as attested before by Luque et al. (2011). Affected category (5–15%

Table 1-a Components of the main salts of the investigated affected samples by AAS and Titration.

Table 1-b Main salts of the investigation samples using Hypothetical combination of water.

Sample

1

2

pH TDS mg/L

Unit

mg/l epm epm % mg/l epm epm % 6.80 6500.00

Cations

Anions

Investigations prove that there are deterioration symptoms noted, e.g. alteration steps of quartz-feldspars. Also, altered lithoclasts of sandstones show enriched hotspots of Ti-Fe minerals and typical kaolinite platelets. In addition, highly altered quartz pseudomorph after carbonates and authigenic quartz can be observed that in agreement with data observed in Pettijohn et al. (1987). Furthermore, dissolution only generated ghost structure (pseudomorph), where clasts are completely dissolved (Fig. 7-a, b). 4. Discussion 4.1. Mineralogical characteristics

Salt

K+

Na+

Mg2+

Cl−

SO2− 4

NO− 3

Categories

1065.00 27.24 32.91 964.00 24.65 20.23

1121.00 48.78 58.94 1365.00 59.40 48.73

82.00 6.74 8.15 460.00 37.83 31.04

2998.0 84.57 77.51 3086.0 87.05 78.33

1170.0 24.36 22.33 1148.0 23.90 21.51

11.02 0.18 0.16 11.50 0.19 0.17

Chloride (Cl)

Sulfate (SO4)

Nitrate (NO3)

Sub-categories ▪ ▪ ▪ ▪ ▪ ▪ ▪ ▪

NaCl KCl MgCl2 Na2SO4 Na2SO4·10H2O MgSO4·7H2O MgSO4·H2O Mg (NO3)2·6(H2O)

Salt

%

Halite Sylvite Bischofite Thenardite Mirabilite Epsomite Kieserite Nitromagnesite

49.44 25.49 3.12 10.85 10.94 0.16

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Table 2 Elemental components of the of (1) non-affected sample (2) affected sample by μ-EDXRF. Region of interest

Samples 1

Al2O3 SiO2 K2O CaO TiO2 Fe2O3 Zr As Minerals

2

1

2

3

4

5

1

2

3

4

5

– 0.27 – – – 97.52

24.82 61.14 0.87 0.60 0.33 12.25 – – Chlorite

– 99.96 – – – 0.04 0.01 – Qz.

8.44 70.25 20.79 0.19 0.01 0.31 – – K-Feld.

34.54 65.30 – 0.13 – 0.03 – – Kao.

24.89 67.58 1.43 1.80 0.46 3.82 – – Kao.

11.35 67.43 21.22 0.00 0.00 0.00 – – K-Feld.

– – – – 99.19 0.81 – – Rutile

0.00 6.29 0.00 1.88 – 91.82 – – Fe oxide

12.87 68.74 18.30 0.07 – 0.02 – – K-Feld.

0.45 Fe-oxide

weathering prosecutes), e.g. Kaolinite 10% that was present as final weathering components in crusting form through thermal stress that ultimately led to decreasing the integrity of the structure (Preucel, 2014). Furthermore, the presence of Microcline 5% was essentially due to its occurring as a main igneous mineral (Smith and Brown, 1988) dominated in the study area or using it as a locally produced building material (Kim and Rigdon, 1998). Petrographical investigation (Fig. 5-a, b, c, d) was also confirmed by the XRD results, where, the coarse-grained quartz in both two shapes (sub-rounded to subangular) were the main components of the samples. Also, there was the presence of finer weathering products composed of kaolinite and some filling igneous materials of feldspars. Kaolinite is formed due to the alteration and partial replacement of alkali feldspars due to kaolinization process (Parker, 1994) caused by the effect of chemical weathering, hydration and hydrolysis mechanism. The clays are squeezed between the sandstone grains. These processes enhance the dissolution and transport process where the durability of stone materials is degraded (Siegesmund and Török, 2014). Furthermore, Fig. (5-e, f) reported that this type of sandstone was cemented by quartz overgrowth (silica cement), known by silicified sandstone (Knox et al., 2009; El-Gohary, 2013a), in addition to the presence of some pigmented materials such as iron oxides that characterized Nubia sandstone (El-Sherbiny and Amin, 2012). It could be noted that the mechanical compaction and re-orientation of the grains were due to the early diagenetic features in the original sandstone beds from which the building stone blocks were cut as argued previously by Salman et al. (2010).

4.2. Chemical characteristics of salts By evaluating the results listed in Table (1-a), it can be noted that the − main components of salt types (K+, Na+, Mg2+, Cl−, SO2− 4 & NO3 ) were absent in XRD data due to the continuous leaching of salty crystals by the effects of ambient groundwater or the partial evaporation of Na+, K+ and Cl− emission (González et al., 2006; Aalil et al., 2016). Tables (1-a, 1-b) proved that the negative salt types present within the pores contained three main categories (Chloride, Sulfate and Nitrate). They played a harmful and effective deterioration role of the statues. On one hand, ions of halite, sylvite and bischofite were estimated approx. 78.05%, these are hygroscopic salts that primarily affect monumental stones in in the study area and around Egypt (Gauri and Holdren, 1981; El-Gohary, 2008). According to (Amoroso and Fassina, 1983; Torraca, 2009; El-Gohary, 2013b), these salts play their role through alternative crystallization and hydration mechanisms. These mechanisms could be enhanced during the effective chemical reaction and ion exchange among K+, Na+ or Mg2+ and stone components. Regarding thenardite and mirabilite components, they were present approx. 10.85%. They were the most destructive salts affecting the monumental stones primarily through the crystallization of mirabilite (Flatt, 2002; Steiger and Asmussen, 2008). In our case, the extensive damage and durability problems affecting the statues occurred especially with alternative wetting/drying cycles that caused the transformation from thenardite to mirabilite, and vice versa especially below 32 °C as attested before by Tsui et al. (2003) and Espinosa-Marzal and Scherer (2010). The ions of epsomite and kieserite represent approx.

Fig. 6. μ-EDXRF analytical results of a composite image, with single element maps, of (a) non-affected sample (b) affected sample.

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Fig. 7. SEM backscatter electron photomicrographs of polished thin sections of medium-fine grained quartz arenite with some close-up views showing the sample features in the affected sample. EDS for points, ×1 represent rutile, ×2 and ×4 represent alkali-feldspar, ×3 and ×5 represent deformed phases of feldspars and new formed kaolinite platelets and ×6 represent authigenic quartz.

(10.94%), they are related to the magnesium sulfate family. The presence of this family is mostly attributed to the manufacture of plaster (Bishop, 1943). According to Alaimo et al. (2002) it could be emphasized that the source of sulfate in our case study not only owe to anthropogenic origin, but also to the notable influences of sulfur oxidizing bacteria “Thiobacillus”, (Warscheid and Braams, 2000). Finally, the ions of nitromagnesite (approx. 0.16%) are mostly due to the fertilizer blends (El-Gohary, 2015) used in ambient cultivated lands, or it could be attributed to the activities of nitrifying bacteria (Mansch and Bock, 1998; Scheerer et al., 2009; Tiano, 2016) which through severe alteration processes and influences of nitrogen cycles finally led to the corroding and damaging of the statues' bodies. The same was reported by Kip and van Veen (2015) in a similar case. It is worth mention that the high value of salt components within the samples is attributed essentially to the synergetic reaction processes of saline water dominated in the study area with the stone components. In addition to the effects of continuous alterative cycles between heating and cooling characterize the study area that lead to drying and wetting mechanisms and finally composing salt crypto-efflorescence within the pores. The cryptoefflorescence of salt is a symptom identified as deposition of salt within the pores of the material exposed surface which can cause spalling and powdering (McArthur and Spalding, 2004). 4.3. Elemental and morphological features (Figs. 6 & 7) illustrate that the alteration in quartz-feldspars starting at the edges, was focused in crystal cracks and the zones of instability, and then spread out to the rest of the grain (Redwan et al., 2012). Furthermore, the presence of Ti-Fe minerals and typical kaolinite was attributed to that these platelets' developing different forms perpendicular to the grain boundaries. They indicate its formation from the alteration rather than by mechanical infiltration into sediments lying above the water table (Du Bernard and Carrio-

Schaffhauser, 2003). The observed authigenic quartz cement resulted due to the addressing of intense alterations and diagenitic processes in the samples that filed the pores within the grains (Meng et al., 2013). In addition, the pseudo-morph crystals of silica residuum were created after deprivation of K, Mg, Fe and Al from the crystals under very low pH conditions, as was noted by Jambor (2003). Consequently, the quantification of alterations and damages processes affected the statues could be divided into two phases; the first was before the statues' excavation and the second was after the excavation processes.

4.4. Alterations and damages affecting the statues 4.4.1. Pre-excavation alterations and damages This part is related essentially to the effects of the burial environment (burial effects), where the components of the statues were broken down through physical, chemical and biological weathering mechanisms which were mostly affected by the surrounding environment (Schaffer, 1972; Sousa et al., 2005). This environment was characterized by the presence of some unfavorable deterioration factors, such as ground and domestic waste water, damp or wet deposits and illegal excavation (El-Gohary, 2015). Physical effects (major internal mechanism); mostly affected the changing of shape and geometry of the statues. Where, the statues' bodies were modified and changed through influencing the alternative effects between crystallization and hydration processes (El-Gohary, 2013b). In addition, the effects of abrasion mechanism by acids and other harmful TDS dominated the ground water (Sease, 1994; Lech and Trewin, 2013). Chemical effects (Minor internal mechanism); their roles had no notable effects due to the absence of air currents and environmental stability of the burial conditions that preserved the statues bodies (CSAWS, 2016). Only the most notorious damage was due to soluble salts crystallizing when the solution in the pores finally dried out after excavation (Cronyn, 1990).

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4.4.2. After excavation alterations and damages These damages are mostly occurring after the excavation process, they are attributed to external deterioration factors (solar, soil moisture and groundwater). They played important synergetic roles in the degradation processes, where, it could be suggested that these processes suddenly happened after exposing the new environmental parameters. It is well known that Luxor lies in a desert climate with significant temperature differences between day and night and very little rainfall, in addition to some major rain storms on the eastern mountains (W/U in Luxor, 2016). These climate characteristics are created through the interaction among major air streams, their associated characteristics and radiation pattern, in addition to local physical features (Abraham et al., 2000). Our findings suggest that there are notable variations in the recorded Temperature degrees, especially during the unstable season (Mar., Apr., Oct. and Nov.) (C/ W in Luxor, 2016). These variations demonstrated that the deterioration process affecting the statues could be obvious after little time. Furthermore, our data suggest that most of the statues' stone blocks were broken down essentially by physical, chemical mechanisms as reported by (White and Blum, 1995; Wells et al., 1995; McFadden et al., 1998; Gupta, 2013) in similar cases. Physically, the stone blocks lost water to the atmosphere since air was drier than other surrounding deposits (higher temperature state) (McFadden et al., 2005). This was compounded by thermal actions, drying wind and sunshine (Gómez-Heras et al., 2006; Tutiempo Network, 2016) characterized by high values of temperature in the study area particularly over the last 30 years. Other physical mechanism affecting the statues included varying expansion amounts due to temperature differences between inward and outward statue material, especially with presence of salt damage mechanisms as argued by (Chapman, 1980; Johannessen et al., 1982). Finally, solar effects caused the changing of the statues surface appearance over time, (matt and pale) through fading mechanism that was essentially owed to temperature differences between day and night (Abd El-Aal, 2016). Chemically, due to deposited layers of fine-grained alluvial soil (several meters thick in the valley); large quantities of water were present in the study area since ancient times. As could be noted in Tables (1-a, 1b), the quality and quantity of ambient water, in addition to the structures materials seriously influenced more than physical action through corrosion mechanisms (Kucera, 1988). Practically, in our case, the presence of moisture (lower temperature state) arose as a result of water capillary movement (Karagiannis et al., 2016). This mechanism caused cracking in the stone body of the statues particularly with the effects of salt growth (Cardell et al., 2003).

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Additionally, it could lead to the breaking of the body of the statues themselves (Fig. 8), through saturation by saline solutions and other TDS dominated in the groundwater, as previously reported by (Catherine, 1994; Wahed et al., 2015) in similar cases. Moreover, other factors affected the deterioration cycles especially those enhancing crack initiation; they being lithology, grain size and differences in latitude and altitude (Thomas and Goudie, 2000; McFadden et al., 2005; Gómez-Heras et al., 2006). Also, capillary transport of water and salts crystallization process were the main causes affecting the statues degradation. This process could crush the stone pores especially with repeated drying and re-wetting cycles (Balboni et al., 2011) and the effects of expansion during the crystallization processes (Koniorczyk and Gawin, 2006). These processes led to the presence of some above-mentioned salt types that finally created the main deterioration forms affecting the statues. Finally, it could be reported that the effects of both mechanisms were enhanced by human influences (Pope and Rubenstein, 1999) through lack of awareness and absence of an effective drainage system in the surround area, in addition to looting and vandalisms especially between 2011 and 2014, and the effects of biological processes (Eyssautier-Chuine et al., 2016). As well, the effects of plants growing in the study area caused other alteration effects through their root growth and related pressures, in addition to the chemical effects associated with their sap (El-Gohary, 2011; Puente et al., 2009). 5. Conclusion Some characterizing methods such as XRF, XRD, PM, CL, ESEM, μEDXRF and AAS technique were used for the evaluation of the deterioration patterns and weathering products of the Luxor Avenue of the Sphinxes to quantify their most important alteration parameters. Results obtained proved that most of these statues were highly affected by some deterioration patterns, such as soiling and crusting features, saturation forms, crystallizing of some salt types, breaking of the most statues' heads, abrasion and cracking. The latter three patterns were the most damaging since they induced detachment and loss of most of the statues' features. These patterns were caused through physical and chemical mechanisms related to inappropriate deterioration factors which dominated the study area, particularly burial effects, soil moisture and groundwater effects. Halite, sylvite, bischofite, are the main salt types identified in the deteriorated stones. Thenardite and mirabilite were the most effective salts derived from saline groundwater in the study area. Their presence in the porous stones might consolidate their deterioration, especially by crystallization and hydration pressures. In addition, there were the effects of stone deterioration and stresses caused by differential thermal expansions. Based on this study, some scientific actions should be considered to conserve the statues; including active and preventive procedures. On one hand, these procedures should contain cleaning processes, salt removal, applying of some mortars and filling materials, using some consolidants and water repellents. These procedures should be applied through suitable scientific techniques to conserve the affected stone surfaces and separate them from the severe environmental effects. On the other hand, maintenance should be taken into our consideration for minimizing all interventions in the future through conducting some important preventive procedures such as protection against all sources of moisture especially saline groundwater and protection against dirt particles and surface accumulations. Acknowledgments

Fig. 8. Photographs showing the breaking of one of the statues body through saturation by saline solutions and other dominated TDS, in addition to drying wetting alternative cycles.

We would like to express our sincere gratitude to Dr. Dieter Rammlmair and Mr. Dominic Göricke (BGR Hannover) for providing help in some of the analytical work. We also thank Yolanda Pico, associate editor and anonymous reviewers for their constructive comments, which helped us to improve the manuscript.

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