| Polycyclic aromatic hydrocarbons, as a typical toxic organic compounds and widely distributed in the environment, has lasting, refractory and certain toxic features. Research and study on the typical functional areas of polycyclic aromatic hydrocarbons in the subsurface distribution and the migration path are the hot and difficult spot in the field of environment engineering .Based on the comprehensive study of the domestic status quo and the study of low molecular weight polycyclic aromatic hydrocarbons (Phenanthrene), this paper makes theoretical and experimental analysis on the Phenanthrene and the vadose zone in the aquifer chemotactic migration naturalization process by using modern geochemical methods. It also researches in Zhang Irrigation District PAHs in the occurrence and distribution of time and space, analyses and simulates the Phenanthrene as the representative of hydrophobic organic contaminants in the soil-ground water in physical, chemical and biological processes and mechanisms, reveals the existence, distribution, migration and the end result of polycyclic aromatic hydrocarbons in the ground organic pollutants in the environment. At the same time, it couples Markov random process theory with pollutants in the underground environment of the system of migration and transformation process, using Markov model quantitative to describe environmental pollutants in the underground system migration, transformation and fate in order to enrich and improve the theoretical system of discipline for pollutant control technology research and the environmental qualitity inspection.A further study on the underground environment polycyclic aromatic hydrocarbons (Phenanthrene) Vertical distribution, as well as physical and chemical properties of soil and the distribution and migration of the Phenanthrene shows that: 1)The soil of polycyclic aromatic hydrocarbons (Phenanthrene)in Zhang Irrigation District in the vertical profile of the different depths are different, with the deepening of the lower section as the trend of changes in the Phenanthrene on the whole. For the sector to plow pan, the surface soil (5 to 20cm) in the Phenanthrene with gentle changes in the depth profile, high value content appears in this entry. In the Phenanthrene under the package, the content has undergone a sharp decline, below the 50 cm Phenanthrene content changes attributable to the flattening trend. 2)Soil organic carbon content, clay content, soil moisture content are important factors affecting the Phenanthrene vertical distribution and migration, but the moisture content of soil has minimal impact on the vertical migration of the Phenanthrene, generally the Phenanthrene is concentrated in the Phenanthrene organic carbon and high clay content, low soil moisture in the soil. 3),R espectively the binary correlation analysis of the Phenanthrene and total organic carbon, soil clay, soil moisture content and the Pearson obtained shows that the distribution of Migration of the Phenanthrene is of significant relevance with total organic carbon, but not with the moisture content and clay content, and this correlation is not causation, but with relations. Factor analysis by SPSS calculate the maximum contribution of the total organic carbon, and further identified vertical distribution of soil in the Phenanthrene and migration is mainly affected by the impact of total organic carbon.The experiment results of Phenanthrene in underground environment in the adsorption show that in the experiment for 90 min, the Phenanthrene adsorption in the soil saturation adsorption accounted for 90%, 2h in the tests, the Phenanthrene soil adsorption capacity reached equilibrium adsorption of the 98% , five hours in the tests, about 99% ,using eight hours as the balance time. All layers of soil samples to achieve equilibrium are in different times, with general sampling depth increases, the Phenanthrene adsorption capacity decreases, adsorption balance gradually shortens the time. Phenanthrene soil adsorption of the organic matter content has the positive correlation of soil samples, all floors of the Phenanthrene adsorption of the organic matter content with the size of the order is the same, basically A> B> C; layers of soil adsorption equilibrium time with organic matter content was negatively correlated. Desorption kinetics experiment at the beginning of the 30 min, the desorption of the Phenanthrene can achieve about 85 percent of the total, in about one hour, more than 95%, 4h over 98%. 1.5h after desorption from the soil the concentration of the Phenanthrene will remain basically unchanged, and near unanimous. Phenanthrene adsorbed by the soil, can be desorpted , but desorption is low , the Phenanthrene in the desorption degree of soil layers is less than 10%. With the soil more rich in organic matter content (S1-A, S2-A,-B S2, S3-A, A-S4, S4-B), when the liquid level is less than 100μg, the adsorption capacity increases in a smooth, linearly increasing trend, and when the liquid concentrations is above 100μg, the adsorption capacity rapidly increases from a sudden jump, and then tends to slow down and thus the entire curve ladder appears there. In a relatively poor soil organic matter (S1-B and S1-C, C-S2, S3-B, C-S3, S4-C), then the Phenanthrene is in the solid phase and liquid-phase distribution is among the main role, showing certain linear relationship. With the linear model S1-B and S1-C, C-S2, S3-B, C-S3, S4-C better fitting the adsorption experiment data, S1-B, S3-B for the vadose zone soil samples , S1-C, C-S2, S3-C, S4-C were aquifer samples in the aquifer depleted organic soil particles adsorption of linear adsorption, and the correlation coefficient R were above 0.9627; Freundlich model is a fitting S1-A, S2-A,-B S2, S3-A, A-S4, S4-B adsorption data, all the samples were all relatively rich in organic matter with the soil aerated. Its value is between 0.5637~0.8784, the adsorption process shows that the non-linear shape, nonlinear correlation coefficient were above 0.9759. Of hydrophobic organic pollutants, the Phenanthrene adsorption-desorption process of obvious hysteresis phenomenon has its backward trend and has something to do with the content of organic matter. From the cycle of retardation coefficient (HI) values we can see in the low concentration of organic matter of the side Clay-rich soil samples, HI concentration was significantly higher than the side of a decreasing trend and the organic matter content of less sand soil samples on the contrary, low concentration side to high concentration side HI value is of the incremental trend.The soil surface evaporation experiments of the Phenanthrene show that the time to achieve the equilibrium concentration of volatile sand (S1-A) and loam (S4-A) are basically the same, about five days in achieving a balance, and clay (S2-A, S3-A) in about six days to achieve a balance, the half-life is volatile at the same time the smallest sand, followed by loam, clay is the largest, that is, S1-A S4-A> S2-A> S3-A, but the trend of the overall volatile soil samples is that the rate increases with increasing concentration, sand S1-A number shows more obvious changes. With increasing temperature, the evaporation rate of soil samples have also increased, the rate has always been volatile S1-A> S4-A> S2-A> S3-A, that is small clay loam, clay and sand; when it is-10℃, about 0.5, it remains the same basic values, but with the rise of temperature between 0 to 20℃, the trends of change ofδare becoming evident, when the temperature is higher than 20℃, the changes become stable, achieving basicδmaximum value. The increase in wind speed can be accelerated in soil surface of the volatile Phenanthrene, but also increases air exchange rate of soil and deep soil air, compared to the depths of the volatile Phenanthrene, the most obvious change is the change of sand, and when the wind speed is more than 2.5 m/s, the Phenanthrene in the soil samples in the most volatile in the wind will continue to increase, not volatile, but that is the downward trend. When the soil water content reaches 10% and more than 20%, the soil moisture evaporation rate of Phenanthrene in moisture soil is lower than the soil moisture of 15% to 20%. Moisture content by 15% to 20% is the largest rate, and when increased to more than 20% moisture, particularly when more than 30%, because the soil moisture content was more mud-Phenanthrene, evaporation rate of the Phenanthrene is slower.The results of Phenanthrene photochemical reaction experiment using GC/MS analysis of light after the Phenanthrene products proved a clear separation. At the same time, the comparison between peak separation and pure reagents charge-mass ratio (m/z) determines the three main Phenanthrene photodegradation products 1, 1'-phenyl-2, 2'-formaldehyde, dimethyl phthalate and phenol Phenanthrene. The rate of speed of the photolysis of Phenanthrene soil is: S1-A> S4-A> S2-A> S3-A, that is, the sand of the speed of the photolysis is more than clay soil and clay, four half-life of the soil-all is between 5 ~ 10, the speed of the fastest- S1-A is 1.7 times than the slowest- S3-A, the difference between sand and clay is obvious. The depth of light of Phenanthrene in different soil and different moisture content is significantly different. In the aquifer at the rate of 15 per cent, four soil-depth range is from 0.22 to 0.37 mm in between, the S2-A clay-depth solutions is the smallest, sand-S1-A solution is in the deepest depth and in the aquifer rate of 30%, clay and sand S3-A S1-A-depth are basically the same, but some slightly larger than the former, clay soil S4-A is of minimum depth ,the four types of soil samples in the depth range of the light is between 0.31 ~ 0.41mm, when the moisture content of soil samples is 30% ,the photolysis of water depth is more than the general rate of 15 per cent of the soil samples, the optical depth is 1.05,1.28,1.54,1.41 times respectively, among them, S3-A increases the highest multiples, S1-A remains as the minimum. Photodegradation rate of Phenanthrene soil samples in the soil has become increasingly low with the increase of initial concentration, clay soil samples of the two lower-rate is lower than the rate of the other two soil samples, clay S3-A-reduced rate is of the largest. As the light intensity increases, the rate of acceleration of the Phenanthrene soil in the light solution increases dramatically . The fastest rate of photolysis is S1-A sand, and clay-A S2, S3-A are slower in terms of the rate of photolysis.Simulation environment in the Phenanthrene in the ground biodegradation experiment shows that the biodegradation rate of the Phenanthrene in the S1, S2, S3, S4 point of the vadose zone (A level) were 10%, 32%, 29% , 23%, and vadose zone (B level) in the Phenanthrene followed by biodegradation rates were 15%, 26%, 23%, 20%; the number of micro-organisms can be seen intuitively from the charter , S1, S2, S3, S4 on the point of the vadose zone (A level) in the number of micro-organisms (×106/g-1) were 2.6,5.3,6.7,4.1, vadose zone (B level) in the number of micro-organisms (×106/g-1), respectively 3.68,4.6,4.0,4.6. In the first 30 days, both the Phenanthrene microbial and biodegradation rate are fast increasing, and the Phenanthrene degradation rate of is about 90% of the rate in the period of 120 days, the number of microbes is 85 percent in 120 days. Phenanthrene soil in the vadose zone is in accordance with the zero-biodegradable reaction kinetic equation. Four points in the aquifer samples show the biological degradation of the Phenanthrene Obviously, S1, S2, S3, S4 point of the aquifer and the Phenanthrene biodegradation rates were 43%, 52%, 44%, 48%, increase of microbiological speed is also very notable, the number of micro-organisms from the four points of the aquifer in 120 days is 5.1 times, 5.9 times, 5.2 times and 4.12 times the number of micro-organisms of the initial microbial volume. The Phenanthrene microbial degradation rate and the number of basic microbiological positively correlated. Monod kinetic parameter in the range between 0.000104 to 0.000255 shows that the microorganisms in the aquifer of the matrix is in strong affinity with the Phenanthrene, also can effectively promote the biodegradable process of the Phenanthrene in the aquifer.Through the soil column experiment of the Phenanthrene in migration and transformation in the underground environment, the experimental results showed that: Polycyclic Aromatic Hydrocarbons in the Phenanthrene are mainly distributed in high content of organic matter and clay in the soil, indicating the great concern between the Phenanthrene soil and organic matter and visco-related content. Pulse rainfall patterns in the Phenanthrene under water make the Phenanthrene more easily in the downward migration than the continuous rainfall. While entering the aquifer, the Phenanthrene significantly has higher concentrations of groundwater pollution. Under continuous rainfall patterns, microbial increases faster in soil column in the first 30 days, with the average daily increase of 2.2×105 micro-organisms, microbes may be in logarithmic growth phase at this stage, which was due to changes in soil column in environmental conditions, microbial growth speed decreased . Under the pulse mode rainfall, when the number of leaching at 25, there appears a small amount of micro-organisms, followed a relatively rapid growth, with the average daily increase of 5.3×104 microorganisms. The TOC attenuation studies in the soil column show that the Phenanthrene soil column in the degradation of the Phenanthrene in soil column can be roughly divided into two stages: namely the non-biological and biological decaying attenuation stage. Pollution in the early stage is mainly a non-biological effect,when the soil adsorption capacity reached saturation, it is mainly a biological effect. The study of the relationship between microbial decay and the Phenanthrene proved the contribution made by the microbial in the process of degradation.Application of leachate tank simulation aquifer in the Phenanthrene migration process suggests the principal of the Phenanthrene in in the groundwater movement.Through tracer experiments of NaCl, we observed that the extension of the sampling holes in the NaCl concentration increased gradually until stabilized. The time is different for different locations from the inlet to achieve stability. After 15 h of NaCl transport, the water inlet side reaches the largest concentration of density to 5.01mg/L respectively. Through the establishment and calculation of the mathematical model of environmental pollutants in the groundwater transforming ,the diffusion coefficient is D 1.08m/d. At the same time the pH value of the aquifer is more stable, and in the 7.7 to 8.1 range, conductivity remains basically stable in 0~12h.The experiments of the Phenanthrene in the aquifer migration found that if water trough was near the water inlet, the Phenanthrene was quicker to achieve faster stability.In the 50 cm hole, the concentration is about to achieve basic stable condition after 20 h. Retardation factor is 1.045 through calculation, the Phenanthrene migration rate is of 0.038m/h, the front migration rate is of 0.0325(m/h), migration rate and migration rate front is basically the same.When Phenanthrene migrates in the aquifer, the pH value is between 7.75~8.05 volatility. The final stability is 7.9, but Eh values simultaneously dropped from 35 to 20 after stabilizing, due to its larger impact on Eh in the reduction of the migration process.The establishment of Markov model in the soil - groundwater in the Phenanthrene environmental fate is based on the application of the Markov chain knowledge. When the Phenanthrene in the biogeochemical behavior in the underground environment, it is divided into six states by time units of days, the results of simulation and calculation from the Phenanthrene at different times in different states show that the Markov model has strong operational function, and can be a more accurate simulation of organic pollutants in the underground environment in the state of fate and migration process. This paper provides a theoretical basis to environmentalists .
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