جستجوی مقالات مرتبط با کلیدواژه « خاک آلوده » در نشریات گروه « عمران »

The cement-based stabilization/solidification (S/S) method is widely used in modifying soils polluted by heavy metals (HMs), although it may face technical, economic, and environmental limitations. Therefore, the present work was designed to investigate the effectiveness of a type of geopolymer based on the steel slag (SGP) and its combination with microparticles of zeolite (SGPZ), compared to cement (as a traditional additive), in enhancing the stability of S/S products. In so doing, different percentages (0 to 250 mg/g-soil) of SGP, SGPZ, and sole cement were separately added to the S/S samples containing different concentrations of lead (including 5000, 10000, 20000 and 40000 mg/kg-soil). After adequate curing (up to 28 days), a set of macro and micro scale experiments were performed to assess the long-term performance of the amended soil samples using a laboratory accelerated aging procedure that simulated 25, 50, 75 and 100 years of exposure to the acid rain and wet and dry (W-D) cycles in the field. It was found that, while low amounts of cement (PC) would greatly reduce the initial bioavailability of pollution in the pore fluid of soil, increasing the contact time of the PC-treated specimens upon harsh conditions, especially in the presence of high level of Pb, would dramatically diminish the efficiency of the precipitation mechanism as well as the degree of encapsulation process which play a significant role in increasing the ability of S/S sample to release the toxic ions stabilized/solidified previously. At simulated 100 years, the toxicity characteristic leaching procedure leached Pb from the PC-treated sample with 250 mg/g-soil binder would exceed the permitted threshold of pollution leaching (≥ 5 mg/L) by 508%, indicating that meeting the S/S regulation limits requires a large consumption of cement. The study showed that, unlike treatment conditions with the same level of PC, the use of novel cement-free S/S binders (especially SGPZ) would significantly limit the negative influences of the environmental changes on HM remobilization risks. In addition, the mechanical characteristics of those series of samples were sometimes up to 1.4 times higher than that of the soil modified with cement alone. Based on the X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images, this enhancement can be mainly due to i) reduction in the adverse HM-binder interactions, ii) intensification in the level of hydration reactions, iii) formation of secondary complex hydrated phases (e.g., Hydrotalcite: Mg6Al2CO3(OH)16.4H2O), and iv) creation of a three-dimensional network of solidification in the system containing geopolymer, wrapping the matrix of S/S products against the structure disintegration upon contact to the aggressive environments. Therefore, under the destroying impacts of acid attack and W-D scenario, adding 25% SGPZ composite could pass the S/S regulation limits. In general, based on the obtained results, the use of geopolymer (especially containing zeolite) is suggested as an effective and environmentally friendly alternative for sustainable soil improvement, even with the high contents of HM ions. Following the USEPA and UKAE standards to achieve the safe S/S performance, the optimal dosage of GP binder was determined to be approximately 6 mg/g-soil per 1 g/kg of lead in the sample.

Soil pollution by oil hydrocarbons is one of the most important kinds of pollution. In this study, clay soil from the CL class were contaminated with gasoil synthetically in 3, 6 and 9 percent by weight, and then the soil containing 6 percent of pollution reinforced with polypropylene fibers at amounts of 0.25, 0.5, 0.75 and 1 percent by weight. According to the results in all samples, Atterberg limits were reduced compared to the base soil. By increasing the percentage of contamination from 0 to 6 percent, the liquid limit and plastic index of the contaminated samples decreased. Moreover by increasing the amount of contamination to 9 percent, these values increased. Investigation of changes trend and amount of compaction characteristics (maximum dry density and optimum moisture) of samples also showed that with soil contamination, maximum dry density and optimum moisture content, had an upward and descending trend compared to the corresponding values in base soil, respectively. According to the results, the presence of contaminant in the soil was led to a decrease of consolidation coefficient, decrease of void ratio, increase of coefficient of volume compressibility and increase of permeability coefficient. The highest rate of decrease in consolidation coefficient (equivalent to 1.7 percent) and the highest increase in permeability coefficient (equivalent to 23.01 percent) was related to the contaminated sample reinforced with 0.75 percent by weight of fibers.

Electrokinetic (EK) remediation is a very effective option for the soil decontamination; however, its efficiency depends on several factors. In the present study, the ability of Ethylene-diaminete-traacetic-acid (EDTA) and pulse current to improve this method for treating fine-grained soils containing heavy metals (HMs) was investigated. In so doing, first, the studied sample (mainly kaolinite) was mixed with a concentration of 5000 mg/kg zinc (Zn) and lead (Pb) and then subjected to an electrokinetic test with voltage gradient of 2 V(DC)/cm2 (in the form of continuous current and pulse) under 7, 14 and 28 days. The pulse current used was ON for 30 minutes and OFF for 10 minutes. In this process, different concentrations of EDTA (including a concentration of 0.1 M and 0.2 M) were also added to the anode and cathode reservoirs, separately and simultaneously. The obtained results showed that in the conditions of continuous current and without EDTA addtion (the common EK method), the EK removal efficiency, especially for lead, was not noticeable. According to the changes in the microstructure of soil sample and its electrical conductivity (EC) between the anode and the cathode electrodes, the reason can be ascribed to the decrease in current density due to precipitation of pollutants in the soil matrix and decresing the HMs transportation in the cathode side, as clearly confirmed by the XRD patterns and EC tests. In this case, increasing the test time from 7 to 28 days (despite more energy consumption) mainly caused the change of the pollution position in the around of anode side and the HMs removal in the cathode side is not enhanced, indicating that there is a limited effect (about 20%) on the total efficiency of the EK tests. It was found that the addition of EDTA only in the form of catholyte solution, even with the equivalent concentration of soil pollution, has a low effect on improving the electrokinetic response. On the other hand, the presence of the chelating agent in both reservoirs of the EK device, especially by applying the pulse current (with a frequency equal to 36 cycles/day) accelerates the treating process of EK remediation. In fact, as the results of macro-structural tests, scanning electron microscope (SEM) images and X-ray diffraction (XRD) analyses indicated, such improvement can be attributed to two major changes in soil-pollutant interaction. First of all, the presented EK method, by developing the penetration of the acid front towards the cathode side and limiting the polarization ability of clay particles, causes the formation of flocculation and reduces the soil ability to keep pollutants. Also, this system greatly reduces the contribution of insoluble phases through the processes of redissolution and formation of the stable complexes as well as generates a disturbance in the initial formation of metal precipitation due to the reduction in the hydrolysis reaction of the cathode part. Synergy of these changes has an prominent role in accelerating the EK mechanisms; so that compared to the conventional EK model, while reducing energy consumption by 25%, it can also increase the removal efficiency by nearly 2.6 times.

Contamination of soils with petroleum products, in addition to being an environmental problem, also makes it difficult from the point of view of geotechnical engineering and doubts the use of this soil following structures, road pavements, and other constructed structures. Sridharan et al. (1981) reported an increase in soil settlement due to contamination of the region's soil with hydrocarbons, resulting in damage to industrial buildings. In recent decades, due to the importance of studying the geotechnical behavior of contaminated soils with petroleum products, many studies have been conducted on the physical and chemical properties of these soils. Much research has been done on the geotechnical properties of fine-grained and coarse-grained soils contaminated with petroleum products (Shin and Das, 2001; Ratnaweera and Meegoda, 2006; Rahman et al., 2010; Al-Aghbari, 2011; Kermani and Ebadi, 2012; Karpuzcu et al., 2018). In this study, the emphasis is on the evaluation of the polluting effect of gas oil as a pollutant with a specific gravity less than water on the fine-grained and coarse-grained behavior of soil. For this aim, a set of geochemical (including XRD and XRF analyzes), geotechnical tests (including grain size distribution, gas evaporation, Atterberg limits, and unconfined compression strength), as well as observation by scanning electron microscopy on contaminated Clayey Sand by gas oil was done.

Stabilization/solidification (S/S) has emerged as a cost-effective method for treating a variety of wastes, particularly heavy metal (HM) contaminated soils. Among the many available fixing agents, Portland cement (PC) has been used extensively for the remediation of contaminated sites. However, there are significant environmental and technical impacts associated with PC application. Thus, the present research was conducted to address the efficacy of cement and nano-clay mixture in enhancing the S/S process. In so doing, artificially contaminated soils were first prepared by mixing kaolinite with zinc (Zn) at levels of 0 to 2%. Afterward, tow type of nano-clay (Na-Montmorillonite and Na-Cloisite), cement and cement/nano-clay (CNC) were separately added to the sample, and then, a set of macro and micro level experiments including batch equilibrium, pH, toxicity characteristic leaching procedure (TCLP), unconfined compression strength (UCS), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analyses were carried out at various curing periods (1, 7 and 28 days) to assess the effectiveness of the additives. The results obtained show that the addition of nano-clay can increase the HM retention capability of soil; however, this may be partly lost when the treated soil are subjected to acidic TCLP solution. In addition, with increasing the HM content, due to the decrease in buffering capacity of system and the restructuring of the clay particles, the soil remediation potential at presence of nano-clay is decreased considerably. It was found that the application of sole cement may significantly enhance the HM retention capacity of soil. But in this case, the physicochemical reactions of Zn ions with cement could hinder and/or reduce the generation of hydration products phases such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), resulting in the degradation of cementation structure-bonding of S/S matrix, as clearly confirmed by the formation of calcium zincate and the diminution in the cementitios compounds peak intensity in the XRD patterns of cement-treated soils. Therefore, the leaching characteristics and the mechanical properties of the S/S material with sole cement are adversely affected by increasing the amount of HM ions. As a result, a large quantity of cement (20 wt% per one percent of HM) and a long time of curing (≈ 28 days) should be employed to meet the full needs of HM immobilization in contaminated soil and give the EPA-acceptable UCS value (≥ 0.35 MPa). The TCLP and XRD test results indicate that the cement/nano-clay combination can expedite the S/S process and alleviate the deleterious influences of metal ions and acidic attack on the stabilized sample. The EDX analyses also support the increase in the development of hydration reactions and the formation of cementing materials in the presence of CNC, providing the enhancement of binding capacity that will lead to the greater strength (up to 50%) in comparison to cement application. Hence, the CNC binary system is more efficient in modifying the contaminated soil with a lower amount of binder (to about 40%) and shorter curing ages (by nearly 4 times) than that of the sole cement. Overall, it is concluded that the cement/nano-clay mixture can be utilized as an effective S/S amendment and CNC content of 15 wt% per 1% of HM can successfully remediate the contaminated soil after 7 days of curing.

Heavy metals are elements that exhibit metallic properties such as ductility, malleability, conductivity, cation stability, and ligand specificity. They are characterized by relatively high density and high relative atomic weight with an atomic number greater than 20. Clay and other soils may become contaminated by the accumulation of heavy metals and metalloids through emissions from the rapidly expanding industrial areas, mine tailings, disposal of high metal wastes, leaded gasoline and paints, land application of fertilizers, animal manures, sewage sludge, pesticides, wastewater irrigation, coal combustion residues, spillage of petrochemicals, and atmospheric deposition. Heavy metal contaminants in addition to geotechnical problems creation and change in the soil strength parameters especially in clay soils, can cause environmental and human health risks due to penetrate through the groundwater. Most commonly heavy metal found at contaminated sites are lead (Pb), chromium (Cr), arsenic (As), zinc (Zn), cadmium (Cd), copper (Cu), mercury (Hg), and nickel (Ni). Also, freezing and thawing cycles have a significant effects on the behavior of stabilized clay soils specially on the heavy metal contaminated clay soils stabilized by cement od other additives. So, by population increasing, advancement of technology and consequently increase in heavy metals emissions, as well as being a quarter of the earth surface in the cold regions and the necessity of building design and construction on these soils, it seems necessary to study the impact of the freezing and thawing cycles on the stabilized clay soils. Different additives such as cement, lime, gypsum, fly ash and other additives were used for stabilization and solidification of heavy metal and oily contaminated soils, the cement is more practical among the stabilizer additives, because of its compatibility with pollutants and high efficiency, low cost and easy access. In this research used cement for stabilization of the lead heavy metal contaminated soil exposed to freezing and thawing cycles. According to the importance of the soil settlement in the clay soils, one dimensional consolidation test was conducted on the experimental samples. Also, due to extensive use of bentonite clay soil in contaminated sites, bentonite clay sample was used for experimental studies. The results of this research indicate that in most cases the critical cycle is a cycle 7. Also, The soil strength parameters such as over-consolidation stress increased about 2 to 8 times in different conditions by cement stabilization. Also, stabilization of heavy metal contaminated by cement clay soils that exposed to freezing and thawing cycles reduce the Cc and Cs coefficients of bentonite clay samples about 50 to 80 percent depending on number of freezing and thawing cycles and heavy metal concentration in bentonite clay sample and also causing preconsolidation in soft clay soils or normally consolidated soils throug the pozzolanic reactions of soil and cement at a low time. Furthermore, the optimum content of cement in contaminated and uncontaminated samples in different freezing and thawing cycles is variable, but in most cases is about 5% to 10% depending on number of freezing and thawing cycles and heavy metal concentration in bentonite clay sample. In continence, stabilization efficacy and the formation of hydrated compounds of cement and clay soil was investigated by using pH chemical test.

Petrochemicals and transport fuel pollutants can change soil characteristics. The geomechanical and geotechnical behaviors of oil contaminated soil are therefore reviewed to ascertain their potential reuse as engineering material. Cook et al. (1992), Puri et al. (1994), Meegoda & Ratnaweera (1994) and Al-Sanad et al. (1995) reported the reduction in shear strength and stress-strain behaviors of clays, significant reduction in permeability, strength and compressibility of the contaminated soil, reduction in maximum dry density and optimum moisture content and increase in liquid and plastic limits of the soil. The reuse of contaminated soil as civil engineering materials is one of the effective alternative methods of disposing contaminated soil. However, this is subject to either the containment of the agent of contamination in soil or effective remediation of the contaminated soil. The pollutants can alter the consolidation characteristics of clayey soil, increasing the total or differential settlements of the foundations of engineering structures resting on it. This paper studies the effects of gasoline on geotechnical characteristics of commercial montmorillonite clay as, one of the most abundant clay minerals. The bentonite clay is artificially contaminated by gasoline. For this propose, bentonite clay is mixed with 4, 8, 12, and 16% of dry weight of soil by gasoline. Results show that with increasing gasoline, liquid limit increases 11% and the maximum dry density and optimum moisture content are decreased 1.5% and 40%, respectively. Unconfined compression strength and the cohesion of bentonite clay with increasing gasoline decrease more than 60%. The compressibility index with increasing gasoline up to 4 % increases, then it decreases between 4 % to 12 % of gasoline, and finally with increasing gasoline to 16 %, the compressibility index increases again. A linear model for evaluating compressibility index (Cc) of contaminated soil mainly composed of high plasticity clay is presented on the basis of liquid limit.

This paper has investigated the affect of quicklime on engineering behaviour of contaminated soils from the Tabriz Oil Refinery. The type of contamination of studied soil was alkali hydrocarbons that had more than 14 carbon atoms (C14) and is classified in the solid phase. The laboratory tests that were undertaken are included the pH, Atterberg limits, standard compaction, uniaxial compressive strength and direct shear test. The quicklime is added to samples in 1%, 3%, 5%, and 7% of values based on weight percentages and the results of tests are investigated at curing time of 1, 3, 7, 14, 21 and 28 days. Base on the results of improvement process of contaminated soils using quicklime, the soil plasticity has been decreased. To assessment of accuracy of the affect of quicklime on contaminated soils, pH values are determined. Based on results, with addition of 5% of quicklime, the pH value was increased and then stabled that is showing the stopping of reaction between quicklime and soil. The pH values of improved contaminated clayey for 1%, 3% and 5% of added quicklime were 10.56, 11.87 and 12.52, respectively. Also, the pH values of improved silty sand for the same of added quicklime were 10.13, 11.63 and 12.17, respectively. According to the results of different researcher, the suitable pH for reaction between soil and quicklime is 12.4. Thus, adding of quicklime to the contaminated soils from Tabriz oil refinery is efficient for soil improvement. The results of compaction test indicated a decrease in maximum dry density and an increase in optimum water content for improved contamination soils. The results of compaction test are according to the results obtained by other researchers on uncontaminated soils. According to the values of UCS measured in the uniaxial compression strength tests on improved contaminated soils, there is a direct correlation between UCS and quicklime content. Base on the relationship of consistency and compression strength of soils, the CL and SM samples changes from soft consistency to hard consistency at the quicklime content of 5%. Regarding to results, the clayey soils with contamination of 66.4 mg/kg and the clayey soils with contamination more than 66.4 mg/kg, by 3% and 5% of added quicklime showed maximum strength, respectively. The optimum quicklime for contaminated silty sandy soil is not under the contamination effect and was 3% of values based on weight percentages. Comparing the uniaxial compressive strength of improved soil samples showed that the sample with low oil material contamination had high strength. Also, with increase of curing time, the uniaxial compressive strength has been increased. Direct shear test were carried out to find the effect of quicklime on strength parameters of contaminated soils from Tabriz oil refinery. The present results show a direct correlation between quicklime content and both internal friction angle and cohesion with increasing of quicklime content. The result indicate that oil material contaminated soils of Tabriz oil refinery can be stabilized satisfactory with addition of 3% and 5% quicklime.

So far, different methods have been applied to clean up soils contaminated with oil. Bioremediation is one of the clean up technologies which uses microorganisms or microbial processes to degrade oil contaminations in soils. This study evaluates the applicability of cow manure as bioremediation alternative for soils spiked with petroleum hydrocarbons. Target contaminant of this research was diesel fuel which was spiked at 60000 mg/kg sample on a dry weight basis. The major goal of this research was to find the appropriate mix ratio of cow manure for enhancing diesel fuel degradation during contaminated soil composting. The ratios of contaminated soil to cow manure were 1:0.15, 1:0.3, 1:0.5 and 1:1 as wet weight basis in 3 replicates. To examine the circumstances conditions on degradation process, we determined the C/N, C/P and total bacterial count (TBC) of treatments at start, week 5 and week 11(end of study). Total petroleum hydrocarbons (TPH) were measured by USEPA standard method 8015B using GC-FID. The degradation of diesel fuel was significantly enhanced by the addition of cow manure as compared to the control treatment and TPH degradation results were better described using a second- order kinetic model. The experimental data indicated that the most degradation rates occurred in the first 5 weeks. By week 5, 50% of the original TPH was removed in the1:1 treatment. After this period, degradation trend of diesel fuel showed a lower removal rate. At the end of study, the most active degradation of TPH was observed at the soil to cow manure mix ratio of 1:1 with 62% removal whereas the 1:0.5 treatment degraded 58% of TPH contamination. No statistically significant difference was observed between 1:1 and 1:0.5 treatments (p<0.05). Statistical analysis showed high correlations among the amount of TPH degraded and TBCs(r = 0.733).

S‌o‌i‌l i‌s g‌e‌n‌e‌r‌a‌l‌l‌y s‌u‌b‌j‌e‌c‌t‌e‌d t‌o d‌i‌f‌f‌e‌r‌e‌n‌t c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t‌s t‌h‌a‌t a‌r‌e b‌e‌i‌n‌g u‌s‌e‌d a‌n‌d e‌x‌c‌r‌e‌t‌e‌d i‌n‌t‌o t‌h‌e e‌n‌v‌i‌r‌o‌n‌m‌e‌n‌t. L‌e‌a‌k‌a‌g‌e o‌f t‌h‌e‌s‌e m‌a‌t‌e‌r‌i‌a‌l‌s c‌a‌n i‌n‌f‌l‌u‌e‌n‌c‌e i‌t‌s p‌h‌y‌s‌i‌c‌a‌l a‌n‌d m‌e‌c‌h‌a‌n‌i‌c‌a‌l c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s. A r‌e‌v‌i‌e‌w o‌f t‌e‌c‌h‌n‌i‌c‌a‌l l‌i‌t‌e‌r‌a‌t‌u‌r‌e i‌n t‌h‌i‌s f‌i‌e‌l‌d s‌h‌o‌w‌s s‌o‌m‌e c‌o‌n‌t‌r‌a‌d‌i‌c‌t‌i‌o‌n‌s b‌e‌t‌w‌e‌e‌n t‌h‌e r‌e‌s‌u‌l‌t‌s o‌f d‌i‌f‌f‌e‌r‌e‌n‌t r‌e‌s‌e‌a‌r‌c‌h, w‌h‌i‌c‌h r‌e‌v‌e‌a‌l‌s t‌h‌e i‌m‌p‌a‌c‌t o‌f s‌o‌i‌l a‌n‌d c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t t‌y‌p‌e o‌n t‌h‌e b‌e‌h‌a‌v‌i‌o‌r o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌e‌d c‌l‌a‌y‌e‌y s‌o‌i‌l. I‌n o‌r‌d‌e‌r t‌o i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e t‌h‌e e‌f‌f‌e‌c‌t‌s o‌f o‌r‌g‌a‌n‌i‌c c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n o‌n t‌h‌e p‌h‌y‌s‌i‌c‌a‌l a‌n‌d m‌e‌c‌h‌a‌n‌i‌c‌a‌l c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s o‌f c‌l‌a‌y‌e‌y s‌o‌i‌l, i‌n t‌h‌e p‌r‌e‌s‌e‌n‌t s‌t‌u‌d‌y, a s‌e‌r‌i‌e‌s o‌f i‌n‌d‌e‌x t‌e‌s‌t‌s, b‌e‌s‌i‌d‌e‌s o‌n‌e-d‌i‌m‌e‌n‌s‌i‌o‌n‌a‌l c‌o‌n‌s‌o‌l‌i‌d‌a‌t‌i‌o‌n (O‌e‌d‌o‌m‌e‌t‌e‌r t‌e‌s‌t‌s), h‌a‌s b‌e‌e‌n p‌e‌r‌f‌o‌r‌m‌e‌d. T‌w‌o t‌y‌p‌e‌s o‌f c‌l‌a‌y, K‌a‌o‌l‌i‌n‌i‌t‌e a‌n‌d B‌e‌n‌t‌o‌n‌i‌t‌e, w‌i‌t‌h l‌o‌w a‌n‌d h‌i‌g‌h p‌l‌a‌s‌t‌i‌c i‌n‌d‌e‌x‌e‌s a‌r‌e u‌s‌e‌d a‌s t‌h‌e b‌a‌s‌e s‌o‌i‌l‌s. A‌l‌s‌o k‌e‌r‌o‌s‌e‌n‌e a‌n‌d g‌a‌s‌o‌i‌l a‌r‌e a‌p‌p‌l‌i‌e‌d a‌s t‌h‌e o‌r‌g‌a‌n‌i‌c c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t i‌n f‌o‌u‌r d‌i‌f‌f‌e‌r‌e‌n‌t p‌e‌r‌c‌e‌n‌t‌a‌g‌e‌s o‌f 0, 3, 6 a‌n‌d 9 t‌o t‌h‌e b‌a‌s‌e s‌o‌i‌l. A‌l‌l s‌a‌m‌p‌l‌e‌s w‌e‌r‌e k‌e‌p‌t f‌o‌r s‌e‌v‌e‌n d‌a‌y‌s i‌n p‌o‌l‌y‌e‌t‌h‌y‌l‌e‌n‌e b‌a‌g‌s t‌o p‌e‌r‌f‌o‌r‌m a‌l‌l c‌h‌e‌m‌i‌c‌a‌l r‌e‌a‌c‌t‌i‌o‌n‌s b‌e‌f‌o‌r‌e t‌h‌e t‌e‌s‌t‌s. A‌f‌t‌e‌r t‌h‌a‌t, w‌a‌t‌e‌r i‌s u‌s‌e‌d t‌o s‌a‌t‌u‌r‌a‌t‌e a‌l‌l s‌a‌m‌p‌l‌e‌s n‌o‌r‌m‌a‌l‌l‌y w‌i‌t‌h‌i‌n 48 h‌o‌u‌r‌s. R‌e‌s‌u‌l‌t‌s o‌f p‌h‌y‌s‌i‌c‌a‌l t‌e‌s‌t‌s r‌e‌v‌e‌a‌l t‌h‌a‌t A‌t‌t‌e‌r‌b‌e‌r‌g l‌i‌m‌i‌t‌s i‌n‌c‌r‌e‌a‌s‌e, b‌y a‌n i‌n‌c‌r‌e‌a‌s‌e i‌n d‌e‌g‌r‌e‌e o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n, f‌o‌r b‌o‌t‌h c‌o‌n‌s‌i‌d‌e‌r‌e‌d s‌o‌i‌l‌s. A‌l‌s‌o, m‌a‌x‌i‌m‌u‌m d‌r‌y d‌e‌n‌s‌i‌t‌y i‌n‌c‌r‌e‌a‌s‌e‌s w‌i‌t‌h e‌n‌h‌a‌n‌c‌e‌m‌e‌n‌t o‌f t‌h‌e d‌e‌g‌r‌e‌e o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n. H‌o‌w‌e‌v‌e‌r, a‌c‌c‌o‌r‌d‌i‌n‌g t‌o t‌h‌e P‌r‌o‌c‌t‌o‌r c‌o‌m‌p‌a‌c‌t‌i‌o‌n t‌e‌s‌t‌s, t‌h‌e o‌p‌t‌i‌m‌u‌m m‌o‌i‌s‌t‌u‌r‌e c‌o‌n‌t‌e‌n‌t r‌e‌d‌u‌c‌e‌s w‌i‌t‌h d‌e‌g‌r‌e‌e o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n. T‌h‌i‌s i‌s i‌l‌l‌u‌s‌t‌r‌a‌t‌e‌d d‌u‌e t‌o t‌h‌e l‌u‌b‌r‌i‌c‌a‌t‌i‌o‌n o‌f g‌r‌a‌i‌n‌s d‌u‌r‌i‌n‌g c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n w‌i‌t‌h o‌r‌g‌a‌n‌i‌c m‌a‌t‌e‌r‌i‌a‌l. C‌o‌n‌s‌o‌l‌i‌d‌a‌t‌i‌o‌n t‌e‌s‌t‌s a‌r‌e c‌o‌n‌d‌u‌c‌t‌e‌d o‌n s‌a‌m‌p‌l‌e‌s i‌n t‌w‌o d‌i‌s‌t‌i‌n‌c‌t r‌e‌l‌a‌t‌i‌v‌e c‌o‌m‌p‌a‌c‌t‌i‌o‌n‌s o‌f 50% a‌n‌d 70%, a‌n‌d t‌h‌e r‌e‌s‌u‌l‌t‌s a‌r‌e i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e‌d i‌n e-L‌o‌g (p) c‌o‌o‌r‌d‌i‌n‌a‌t‌e‌s. B‌a‌s‌e‌d o‌n t‌h‌e r‌e‌s‌u‌l‌t‌s o‌f o‌n‌e d‌i‌m‌e‌n‌s‌i‌o‌n‌a‌l c‌o‌n‌s‌o‌l‌i‌d‌a‌t‌i‌o‌n t‌e‌s‌t‌s, c‌o‌m‌p‌r‌e‌s‌s‌i‌b‌i‌l‌i‌t‌y c‌o‌e‌f‌f‌i‌c‌i‌e‌n‌t i‌n‌c‌r‌e‌a‌s‌e‌s, w‌i‌t‌h a‌n i‌n‌c‌r‌e‌a‌s‌e i‌n c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t p‌e‌r‌c‌e‌n‌t‌a‌g‌e f‌o‌r b‌o‌t‌h s‌o‌i‌l‌s. A‌l‌s‌o, t‌h‌e e‌f‌f‌e‌c‌t‌s o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌i‌o‌n o‌n t‌h‌e c‌o‌n‌s‌o‌l‌i‌d‌a‌t‌i‌o‌n b‌e‌h‌a‌v‌i‌o‌r o‌f c‌l‌a‌y i‌n‌c‌r‌e‌a‌s‌e w‌i‌t‌h a‌n e‌n‌h‌a‌n‌c‌e‌m‌e‌n‌t i‌n r‌e‌l‌a‌t‌i‌v‌e c‌o‌m‌p‌a‌c‌t‌i‌o‌n. A‌s a r‌e‌s‌u‌l‌t, i‌t i‌s n‌e‌g‌l‌i‌g‌i‌b‌l‌e i‌n s‌o‌i‌l w‌i‌t‌h l‌o‌w r‌e‌l‌a‌t‌i‌v‌e c‌o‌m‌p‌a‌c‌t‌i‌o‌n. U‌s‌i‌n‌g t‌h‌e r‌e‌s‌u‌l‌t‌s o‌f t‌e‌s‌t‌s, a‌n e‌m‌p‌i‌r‌i‌c‌a‌l r‌e‌l‌a‌t‌i‌o‌n i‌s s‌u‌g‌g‌e‌s‌t‌e‌d b‌e‌t‌w‌e‌e‌n t‌h‌e c‌o‌m‌p‌r‌e‌s‌s‌i‌b‌i‌l‌i‌t‌y c‌o‌e‌f‌f‌i‌c‌i‌e‌n‌t o‌f c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌e‌d s‌o‌i‌l a‌n‌d i‌t‌s r‌e‌l‌a‌t‌i‌v‌e c‌o‌m‌p‌a‌c‌t‌i‌o‌n a‌n‌d l‌i‌q‌u‌i‌d l‌i‌m‌i‌t. C‌o‌m‌p‌a‌r‌i‌s‌o‌n o‌f t‌h‌e s‌u‌g‌g‌e‌s‌t‌e‌d e‌q‌u‌a‌t‌i‌o‌n w‌i‌t‌h o‌r‌d‌i‌n‌a‌r‌y r‌e‌l‌a‌t‌i‌o‌n‌s i‌n s‌o‌i‌l m‌e‌c‌h‌a‌n‌i‌c‌s t‌e‌x‌t‌s s‌h‌o‌w‌s a g‌r‌e‌a‌t d‌i‌f‌f‌e‌r‌e‌n‌c‌e, w‌h‌i‌c‌h p‌r‌o‌v‌e‌s t‌h‌e n‌e‌c‌e‌s‌s‌i‌t‌y f‌o‌r n‌e‌w s‌u‌g‌g‌e‌s‌t‌e‌d f‌o‌r‌m‌s i‌n c‌o‌n‌t‌a‌m‌i‌n‌a‌t‌e‌d s‌o‌i‌l. F‌i‌n‌a‌l‌l‌y, i‌t w‌a‌s c‌o‌n‌c‌l‌u‌d‌e‌d t‌h‌a‌t c‌h‌e‌m‌i‌c‌a‌l a‌n‌d o‌r‌g‌a‌n‌i‌c c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t‌s, l‌i‌k‌e k‌e‌r‌o‌s‌e‌n‌e a‌n‌d g‌a‌s o‌i‌l, w‌h‌i‌c‌h a‌r‌e n‌o‌t s‌o‌l‌u‌b‌l‌e i‌n w‌a‌t‌e‌r, a‌r‌e m‌o‌r‌e e‌f‌f‌e‌c‌t‌i‌v‌e i‌n c‌h‌a‌n‌g‌i‌n‌g t‌h‌e p‌h‌y‌s‌i‌c‌a‌l c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s o‌f s‌o‌i‌l, l‌i‌k‌e A‌t‌t‌e‌r‌b‌e‌r‌g l‌i‌m‌i‌t‌s a‌n‌d r‌e‌l‌a‌t‌i‌v‌e c‌o‌m‌p‌a‌c‌t‌i‌o‌n. H‌o‌w‌e‌v‌e‌r, c‌o‌m‌p‌a‌r‌e‌d t‌o t‌h‌e f‌i‌r‌s‌t c‌a‌t‌e‌g‌o‌r‌y, s‌o‌l‌u‌b‌l‌e o‌r‌g‌a‌n‌i‌c c‌o‌n‌t‌a‌m‌i‌n‌a‌n‌t‌s a‌r‌e m‌o‌r‌e e‌f‌f‌e‌c‌t‌i‌v‌e o‌n t‌h‌e m‌e‌c‌h‌a‌n‌i‌c‌a‌l a‌n‌d c‌o‌n‌s‌o‌l‌i‌d‌a‌t‌i‌o‌n c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s o‌f c‌l‌a‌y‌e‌y s‌o‌i‌l.