Comparison of Klinkenberg-corrected gas permeability and water permeability in sedimentary rocks

We measured intrinsic permeability of sedimentary rocks from the western foothills of Taiwan by using nitrogen gas and distilled water as pore fluids in effective-pressure cycling tests at room temperature. The observed difference in gas and water permeabilities was analyzed in view of the Klinkenberg effect. This effect is due to the slip flow of gases at pore walls, which enhances gas flow when pore sizes are very small. Our experimental results showed that (1) gas permeability was larger than water permeability by several times to one order of magnitude, (2) gas permeability increased with increasing pore pressure, and (3) water permeability increased slightly as the pore-pressure gradient across the specimen increased. Results (1) and (2) can be explained quantitatively by an empirical power law in relation to the Klinkenberg constant b that is applicable in low permeable range. This correlation enables us to estimate water permeability from gas permeability. The Klinkenberg effect is important when permeability is lower than 10^?18 m² and at low pore-pressure differentials, and correction for the effect is essential to estimate water permeability from gas permeability measurement data. A simplified Bingham flow model for water can partially explain the trend of result (3), although non-Darcy flow behavior or inertial forces of water–rock interaction are needed to account for the observed deviation from Darcy's law.     

In situ rock salt permeability measurement for long term safety assessment of storage

A field test was carried out in the Amelie Mine owned by Mines de Potasse d'Alsace (MDPA, France) for the purpose of measuring rock salt permeability away from underground facilities. The selected salt bed is about 1 m thick and located 16 m away from the gallery floor. The permeability was measured by means of nitrogen and saturated brine injection. Theoretical studies indicated that in order to control the `disturbing effects' (thermal effects, chemical reaction between halite and brine), the work should be done at constant temperature and pressure. The field experiment results confirm that rock salt is permeable to gas and brine, even relatively far from underground openings.The measurements of the tests with brine were interpreted satisfactorily by a model based on Darcy's law, with an intrinsic permeability value of 2×10⁻²¹ m² and an initial pore pressure value of 1 MPa. Interpretation of the measured gas flow rate shows that: (a) after brine percolation, the capillary pressure effect is significant and (b) gas migration in salt is not controlled by Darcy's law; the Knudsen effect and partial saturation may play an important role.     

Experimental research on water retention and gas permeability of compacted bentonite/sand mixtures

Highly compacted bentonite-based materials are often considered as buffer or sealing materials for deep high-level radioactive waste repositories. In situ, the initial state of bentonite-based materials is only partially saturated, which has a very high suction that will promote water absorption from the host rock. In addition, a gradient of water saturation will be formed between the external part and the central part of the compacted bentonite blocks. In this paper, water retention tests, under both constant-volume and free-swelling conditions, were performed to investigate the suction behavior of a compacted bentonite/sand mixture. In order to investigate the sealing ability of the partially saturated bentonite/sand mixture, gas permeability tests were also carried out under the in situ confining stress. It was found that the confining conditions have a limited effect on the water retention capacity of the compacted bentonite/sand mixture at lower levels of relative humidity (RH), while this influence is significant at higher RH levels. The results of gas permeability tests show that gas permeability is very sensitive to the water content and the confining pressure. When the sample (stable at RH=98%) was subjected to a in situ confining pressure (7–8 MPa), the gas permeability was very low (1.83×10^–14 m/s) which indicates that gas tightness can be obtained even though the sample is not fully saturated.     

Application of the gas tracer method for measuring oxygen transfer rates in subsurface flow constructed wetlands

The oxygen transfer rate (OTR) has a significant impact on the design, optimal operation and modelling of constructed wetlands treating wastewater. Oxygen consumption is very fast in wetlands and the OTR cannot be determined using an oxygen mass balance. This problem is circumvented in this study by applying the gas tracer method. Experiments were conducted in an unplanted gravel bed (dimensions L × W × d 125 × 50 × 35 cm filled with a 30-cm layer of 10-11-mm gravel) and a planted horizontal subsurface flow constructed wetland (HSSFCW) (L × W × d 110 × 70 × 38 cm filled with a 30-cm layer of 3.5-mm gravel with Phragmites australis). Tap water saturated with propane as gas tracer (pure or commercial cooking gas, depending on the test) was used. The mass transfer ratio between oxygen and commercial propane gas was quite constant and averaged R = 1.03, which is slightly lower than the value of R = 1.39 that is usually reported for pure propane. The OTR ranged from 0.31 to 5.04 g O₂ m⁻² d⁻¹ in the unplanted gravel bed and from 0.3 to 3.2 g O₂ m⁻² d⁻¹ in the HSSFCW, depending on the hydraulic retention time (HRT). The results of this study suggest that the OTR in HSSFCW is very low for the oxygen demand of standard wastewater and the OTR calculations based on mass balances and theoretical stoichiometric considerations overestimate OTR values by a factor that ranges from 10 to 100. The gas tracer method is a promising tool for determining OTR in constructed wetlands, with commercial gas proving to be a viable low-cost alternative for determining OTR.     

Immediate and long-term impacts of UV-C irradiation on photosynthetic capacity, survival and microcystin-LR release risk of Microcystis aeruginosa

In this study, the immediate and long-term impacts of shortwave ultraviolet (UV-C) irradiation on photosynthetic capacity, survival, and recovery of Microcystis aeruginosa were investigated. The risk of microcystin-LR (MC-LR) release during irradiation was also estimated. The cell density was determined by a flow cytometry, and typical chlorophyll fluorescence parameters, including the effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse amplitude modulated (PAM) fluorometer. Under various UV-C dosages (140-4200 mJ cm⁻²), photosynthetic capacities were reduced, to different degrees, accompanied by slight cytoclasis and complete degradation of extracellular MC-LR immediately after irradiation. In a 6-d cultivation following UV-C irradiation, cell density and extracellular MC-LR in the samples treated by 140 mJ cm⁻² UV-C irradiation increased from 4.0 × 10⁶ cells mL⁻¹ and 8 μg L⁻¹ to 5.1 × 10⁶ cells mL⁻¹ and 20 μg L⁻¹, respectively. Significant M. aeruginosa cytoclasis (cell density from 4.0 × 10⁶ to 1.0 × 10⁶ cells mL⁻¹) and MC-LR release (2-25 μg L⁻¹) occurred when the UV-C dosage reached 350 mJ cm⁻². Cell cytoclasis and MC-LR release were enhanced in the cultivated samples under higher UV-C dosages. Results revealed that photosynthetic parameters were useful tools to predict the recovery profiles of M. aeruginosa cells, and the MC-LR release risk should be considered after UV-C inactivation.     

A photoelectrocatalytic process that disinfects water contaminated with Mycobacterium kansasii and Mycobacterium avium

Nontuberculous mycobacteria are resistant to conventional water treatment; indeed, they have been recovered from a wide variety of environmental sources. Here, we applied the photoelectrocatalytic technique using a Ti/TiO₂–Ag photoanode to inactivate mycobacteria. For a mycobacteria population of 5 × 10⁸ CFU mL⁻¹, we achieved 99.9 and 99.8% inactivation of Mycobacterium kansasii and Mycobacterium avium with rate constant of 6.2 × 10⁻³ and 4.2 × 10⁻³ min⁻¹, respectively, after 240 min. We compared the proposed method with the photolytic and photocatalytic methods. Using a mycobacteria population of 7.5 × 10⁴ CFU mL⁻¹, the proposed Ti/TiO₂–Ag photoanode elicited total mycobacteria inactivation within 3 min of treatment; the presence of Ag nanoparticles in the electrode provided 1.5 larger degradation rate constant as compared with the Ti/TiO₂ anode (1.75 × 10⁻² for M. kansassi and 1.98 × 10⁻² for M. avium). We monitored the degradation of the metabolites released during cellular lysis by TOC removal, sugar release, chromatography, and mass spectrometry measurements; photoelectrocatalysis and Ti/TiO₂–Ag photoanodes furnished the best results.     

温度围压对低渗透砂岩孔隙度和渗透率的影响研究

 对低孔、高孔两组低渗透砂岩岩心孔隙度和渗透率在温度压力共同作用下的变化特征进行试验研究。在围压5 MPa、温度25 ℃的条件下,第一组砂岩的孔隙度变化范围为3.2%～4.6%,渗透率为0.098 8×10－3～0.191 9× 10－3 μm2;第二组砂岩的孔隙度变化范围为12.8%～14.2%,渗透率为0.176 7×10－3～0.301 3×10－3 μm2。研究结果表明,在试验采用的温度、压力变化范围(25 ℃～80 ℃,5～55 MPa)内,两组低渗透砂岩的孔隙度、渗透率都表现出了较强的压力、温度敏感性。随温度、围压升高,孔隙度、渗透率都减小,围压对渗透率的影响明显高于温度对渗透率的影响。总的趋势看,温度对孔隙度的影响高于围压对孔隙度的影响,恒定测量围压5 MPa,温度由25 ℃升高到80 ℃,低孔低渗砂岩孔隙度下降了34.7%,渗透率下降了75.1%;高孔低渗砂岩孔隙度降低了18.4%,渗透率下降了35.2%;恒定测量温度25 ℃,围压由5 MPa升高到55 MPa,低孔低渗砂岩孔隙度降低32.3%,渗透率下降了89.5%,高孔低渗砂岩孔隙度降低了4.6%、渗透率降低了77.4%。     

Influence of bacteria on the compressive strength, water absorption and rapid chloride permeability of fly ash concrete

This paper presents the results of an experimental investigation carried out to evaluate the influence of Sporoscarcina pasteurii bacteria on the compressive strength and rapid chloride permeability of concrete made without and with fly ash. Cement was replaced with three percentages (10, 20 and 30) with fly ash by weight. Three different cell concentration (0, 10³,10⁵,10⁷ cells/ml) of bacteria were used in making the concrete mixes. Tests were performed for compressive strength, water absorption and rapid chloride permeability at the age of 28 days. Test results indicated that inclusion of S. pasteurii in fly ash concrete enhanced the compressive strength, reduced the porosity and permeability of fly ash concrete. Maximum increase (22%) in compressive strength and four-times reduction in water absorption was observed with 10⁵ cells/ml of bacteria. This improvement in compressive strength was due to deposition on the bacteria cell surfaces within the pores.Calcite deposition in concrete observed nearly eight times reduction in chloride permeability of fly ash concrete. The present work highlights the influence of bacteria on the properties of concrete made with supplementing cementing material such as like fly ash. Usage of bacteria like S. pasteurii improves strength and durability and strength of fly ash concrete through self-healing effect.     

致密岩石气体渗流滑脱效应试验研究

由于致密结构和低的渗透率,气体在孔隙喉道小的致密岩石中流动会受到滑脱效应的影响。以湖南某试验场地致密砂岩为研究对象,对岩样进行了微观结构的SEM分析,通过一系列围压和孔隙压力作用下的砂岩气体流量和渗透率测试,研究气体在致密岩石中渗流特征,证明了致密砂岩气体流动存在滑脱效应现象,其渗流不符合Darcy定律。分析了孔压对滑脱效应的影响、滑脱效应对气测渗透率的影响以及滑脱因子与绝对渗透率的函数关系。研究结果表明,滑脱效应对气测渗透率的影响随着围压和气体孔隙压力的变化有所不同。同等围压下,孔隙压力越小,滑脱效应越明显,导致气测渗透率大于砂岩绝对渗透率。同等孔压下,当围压达到某一值后,其对滑脱效应的影响有限,同时也说明围压对岩石的压密是有限的。砂岩的平均气体孔隙压力与气测渗透率关系更加符合二次项曲线方程。计算获得的克努森数Kn说明了在相对高的围压和低的孔隙压力条件下,气体渗流过程位于滑脱流和过渡流之间,传统的N-S方程可能不再适用,应用Knudsen扩散方程更加合理,特别是当克努森数Kn比较高时。     

Level and source of 129I of environmental samples in Xi'an region, China

Iodine-129 is widely used as a tracer in various environmental practices such as monitoring of nuclear environmental safety, seawater exchange and transport, geochemical cycle of stable iodine and dating of geological events. The spatial distribution of ¹²⁹I concentration varies significantly on global scale because of anthropogenic input from nuclear activities coupled with scarcity of data on environmental ¹²⁹I variability in many parts of the world including Asia. Here we report new data on ¹²⁹I and ¹²⁷I concentrations in soil, vegetation, river water and precipitation collected from Xi'an area, China. The results indicate values for environmental ¹²⁹I/¹²⁷I ratios in the investigated area range from 1.1 × 10^− 10 to 43.5 × 10^− 10 with a mean of 20.6 × 10^− 10, which is 1-3 orders of magnitude lower than the ratios observed in Europe, but comparable with those observed in the locations far from direct effect of point release sources and at similar latitude. The main source of ¹²⁹I in the investigated area is attributed to the global fallout of both atmospheric nuclear weapons testing and long distance dispersion of fuel reprocessing releases.     

Causes of Poor Sealant Performance in Soil-Gas-Resistant Foundations

Sealants for radon-resistant foundation construction must seal the gap between concrete sections. Modern sealants have such low permeability that seal performance depends only on the permeability of the material that contacts the sealant. The surface permeability of concrete walls and floors was measured by a specially designed permeameter, which measures the airflow induced by a pressure difference across a temporary test seal applied to the surface. The permeability of bulk concrete is about 10^?16 m². Areas free of the surface defects had surface permeability ranging from 10^?14 to 10^?16 m². However, surface defects are common on concrete wall surfaces, which increase the permeability to > 10^?12 m², too high for standard seal designs to be adequate as the only method of soil gas and radon exclusion. Radon-resistant seals require either extended contact widths or mechanical removal of the surface layer and defects.     

基于结构异性比的含瓦斯煤渗透各向异性研究

渗透率是煤层气生产中的重要参数,而原煤的结构异性导致其渗透率具有明显的方向性。假设煤体结构各向异性,建立基于结构异性比的煤体各向异性渗透模型,再进一步推导出瓦斯煤各向异性气–固耦合控制方程,并植入Comsol计算平台,系统研究了煤体各向异性对气体扩散和渗透的影响。理论和数值研究结果表明:煤体结构异性比和平行层理方向渗透率与垂直层理方向渗透率的比值之间存在指数关系,结构异性比越大,则渗透率比值越大;恒定围压条件下,结构异性比随压力的增大而增大,平行层理方向的渗透率与垂直层理方向的渗透率比值也在增大;恒定围体积条件下,结构异性比随压力的增大而减小,平行层理方向的渗透率与垂直层理方向的渗透率比值也在减小;本文模型计算数据与渗透各向异性试验数据吻合度高,验证了本文模型的合理性,可适用恒定围岩应力、恒定储层体积等多种条件的渗透各向异性研究。     

基于优势流及各向异性随上覆压力变化的填埋体饱和渗流模型

生活垃圾由于组成成分的多样性及分层填埋,其孔隙呈不均匀分布,并且水平向多于竖向。填埋体中的渗流存在明显的优先流效应,各向异性显著并受上覆压力等因素影响。基于Poiseuille方程,根据上覆压力作用下生活垃圾孔隙形状、孔隙尺寸分布及孔隙排列方向分布特征,提出了基于优先流及各向异性的饱和渗流模型。揭示了新鲜生活垃圾分布变化规律,0~200 k Pa,大孔隙逐渐消失,平均孔隙直径与可排水孔隙率呈指数下降,孔隙排列角度逐渐水平向倾斜。采用新建饱和渗流模型进行分析计算,确定采用可排水孔隙率可比总孔隙率更好地模拟垃圾孔隙渗流特性。渗流由大孔隙优先流主导,0~600 k Pa内计算获得新鲜垃圾水平向饱和渗透系数变化范围为10~(-2)~10~(-5)cm/s。给出了渗流各向异性值的计算公式,渗流各向异性值大体随上覆压力增加而增大,并与初始孔隙排列角度相关;0~600 k Pa内计算得新鲜垃圾渗流各向异性值变化范围为1~10。     

Free-radical-induced oxidative and reductive degradation of N,N′-diethyl-m-toluamide (DEET): Kinetic studies and degradation pathway

N,N′-Diethyl-m-toluamide (DEET) is widely used as an insect repellent and has therefore been detected as a contaminant in numerous waste and surface waters. In this study we have determined the absolute reaction rate constants of DEET with the hydroxyl radical and the hydrated electron in aqueous solution as (4.95 ± 0.18) × 10⁹ and (1.34 ± 0.04) × 10⁹ M⁻¹ s⁻¹, respectively, using pulse radiation. To provide additional information on the radicals formed upon oxidation, transient spectra were measured from 1 to 150 μs, with transient decay rates determined from the time-dependence of the maximum absorption at 330 nm. These data suggest simple decay of the initially formed radical to stable products. Radical-based destruction mechanisms for destruction of DEET are proposed based on the LC-MS determination of the stable compounds produced by ⁶⁰Co γ-irradiation of DEET solutions. These data will be useful in evaluating potential advanced oxidation/reduction processes for the control of DEET and understanding its fate and transport in surface water where analogous radical chemistry is operative.     

A Fenton-like degradation mechanism for 1,4-dioxane using zero-valent iron (Fe) and UV light

In this study, the degradation mechanism of 1,4-dioxane using zero-valent iron (Fe⁰) in the presence of UV light was investigated kinetically. The degradation of 1,4-dioxane in Fe⁰-only, photolysis, and combined Fe⁰ and UV reactions followed the kinetics of a pseudo-first-order model. The degradation rate constant (19 × 10⁻⁴ min⁻¹) in the combined reaction with UV-C (4.2 mW cm⁻²) and Fe⁰ (5 mg L⁻¹) was significantly enhanced compared to Fe⁰-only (4.8 × 10⁻⁴ min⁻¹) and photolytic reactions (2.25 × 10⁻⁴ min⁻¹), respectively. The removal efficiency of 1,4-dioxane in combined reaction with Fe⁰ and UV within 4 h was enhanced by increasing UV intensity at UV-C region (34% at 4.2 mW cm⁻² and 89% at 16.9 mW cm⁻²) comparing with the removal in the combined reaction with Fe⁰ and UV-A (29% at 2.1 mW cm⁻², and 33% at 12.6 mW cm⁻²). It indicates that 1,4-dioxane was degraded mostly by OH radicals in the combined reaction. The degradation patterns in both Fe⁰-only and combined reactions were well fitted to the Langmuir-Hinshelwood model, implying that adsorption as well as the chemical reaction occurred. The transformation of Fe⁰ to Fe²⁺ and Fe³⁺ was observed in the Fe⁰-only and combined reactions, and the transformation rate of Fe⁰ was improved by UV irradiation. Furthermore, the reduction of Fe³⁺ was identified in the combined reaction, and the reduction rate was enhanced by an increase of UV energy. Our study demonstrated that the enhancement of 1,4-dioxane removal rate occurred via an increased supply of OH radicals from the Fenton-like reaction induced by the photolysis of Fe⁰ and H₂O, and with producing less sludge.     

Research on gas migration properties in a saturated bentonite/sand mixture under flexible boundary conditions

Gas migration/breakthrough in saturated bentonite is an important issue for the evolution of the sealing ability of the engineered barrier in deep geological repositories. The main contribution of our study is to provide insights into the water and gas transport properties in a compacted bentonite/sand mixture, which was wrapped by a flexible Viton? membrane directly before being put into a triaxial cell. The experimental results indicate that the water permeability is very low and the magnitude is in the order of 10^?20?m². Gas breakthrough tests show that no continuous gas flow was detected during the entire gas breakthrough test (until the gas pressure of 10?MPa), which indicates that the compacted bentonite/sand mixture has a good sealing ability after full saturation. Another important finding is that the gas migration properties are closely related to the stress state around the sample, the internal pore fluid pressure, and the creep effects caused by the two factors.     

Oxidation kinetics of two pesticides in natural waters by ozonation and ozone combined with hydrogen peroxide

The oxidation of bromoxynil and trifluralin was investigated using ozone (O₃) and O₃ combined with hydrogen peroxide (H₂O₂) in natural waters using batch reactors. The results indicated that these pesticides could not be completely degraded during ozonation, achieving degradation levels lower than 50%. An enhancement of the level of degradation was observed using O₃/H₂O₂ process. A biphasic behaviour of O₃ was also observed. Depending on the experimental conditions, the rate constant for O₃ decomposition was estimated to be between 7.4 × 10⁻⁴ s⁻¹ to 5.8 × 10⁻² s⁻¹, and 3.2 × 10⁻³ s⁻¹ to 4.2 × 10⁻² s⁻¹ for bromoxynil and trifluralin samples, respectively. Acute toxicity analysis performed using Microtox^® showed a decrease in the toxic effects of the samples on the luminescent bacteria during the first few minutes of treatment, followed by an increase of the toxic effects at the end of the reaction for both pesticides. The quantification of oxidation by-products generated during treatment was also addressed. The total molar balances of the degradation by-products versus the initial pesticide concentrations ranged from 60 to 103% under different experimental conditions.     

Photoassisted reduction of metal ions and organic dye by titanium dioxide nanoparticles in aqueous solution under anoxic conditions

The photoassisted reduction of metal ions and organic dye by metal-deposited Degussa P25 TiO₂ nanoparticles was investigated. Copper and silver ions were selected as the target metal ions to modify the surface properties of TiO₂ and to enhance the photocatalytic activity of TiO₂ towards methylene blue (MB) degradation. X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the crystallinity, chemical species and morphology of metal-deposited TiO₂, respectively. Results showed that the particle size of metal-deposited TiO₂ was larger than that of Degussa P25 TiO₂. Based on XRPD patterns and XPS spectra, it was observed that the addition of formate promoted the photoreduction of metal ion by lowering its oxidation number, and subsequently enhancing the photodegradation efficiency and rate of MB. The pseudo-first-order rate constant (k_obs) for MB photodegradation by Degussa P25 TiO₂ was 3.94 × 10^− 2 min^− 1 and increased by 1.4-1.7 times in k_obs with metal-deposited TiO₂ for MB photodegradation compared to simple Degussa P25 TiO₂. The increase in mass loading of metal ions significantly enhanced the photodegradation efficiency of MB; the k_obs for MB degradation increased from 3.94 × 10^− 2 min^− 1 in the absence of metal ion to 4.64-7.28 × 10^− 2 min^− 1 for Ag/TiO₂ and to 5.14-7.61 × 10^− 2 min^− 1 for Cu/TiO₂. In addition, the electrons generated from TiO₂ can effectively reduce metal ions and MB simultaneously under anoxic conditions. However, metal ions and organic dye would compete for electrons from the illuminated TiO₂.     

Analysis of principal gas products during combustion of polyether polyurethane foam at different irradiance levels

This paper studies the release of the principal gas species produced during the combustion of a non-flame-retarded Polyether Polyurethane Foam (PPUF) of density of 20.9 kg m⁻³ in the cone calorimeter. Five irradiance levels are studied: 10, 20, 30, 40 and 50 kW m⁻². Heat release rate, mass-loss rate and bulk gas mass flow are measured. The mass flow and yields of gas species are measured as well. The analysis of release of gas species relative to time allowed the study of the different stages of PPUF kinetics and to quantify the gas composition. Of the twenty-two different gas species that were monitored simultaneously, the principal species found were CO₂, CO, H₂O, NO and total hydrocarbons. According to species release, two decomposition stages for PPUF are identified. In the first stage, the solid structure breaks down carrying the decomposition of isocyanate, and in the second stage the polyol decomposes. These two stages are in agreement with the decomposition mechanism proposed in the literature. However, the data presented here is the first experimental study of burning behavior of PPUF taking into account the release of gas species too. An elemental analysis was performed and the chemical formula of the virgin material was determined. This allows the mass balance of the elements in the virgin foam content with the gaseous product content. The effective heat of combustion and the ratio between heat release rate and CO₂ mass flow are calculated at each of the irradiance levels.     

Analysis of phenols and nitrophenols in rainwater collected simultaneously on an urban and rural site in east of France

The behaviour of phenols and nitrophenols in the atmosphere is of concern for environmental research as these are known to be toxic to humans and wildlife. To increase the knowledge about these compounds, the concentrations of 20 phenols and nitrophenols in rainwater were studied in an urban (Strasbourg) and a rural (Erstein) site in Eastern France.The wet rain samples were collected on a weekly basis between January 2002 and July 2003, and analyzed for phenols and nitrophenols using SPME and gas chromatography coupled to mass spectrometry. The compounds were derivatized with MDBSTFA directly in the injection port of the gas chromatograph.Total concentrations ranged from 0 to 1383 µg L^− 1 in Strasbourg and from 0 to 1215 µg L^− 1 in Erstein. These concentrations are in the same range than those measured in other studies, but considerably higher than the concentrations measured for pesticides (about 10 times) and polycyclic aromatic hydrocarbons (about 1000 times) on the same sites and at the same period.Phenols, except for o-cresol, were generally less concentrated than nitrophenols. o-Cresol was one of the major compounds, probably due to its role as raw material in pesticide production. The concentrations of phenols and nitrophenols were found to vary with time. No seasonal trend was observed, but significant correlations with rainfall amount were identified.