Occurrence and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Urban Residential Soils from National Capital Region,Uttar Pradesh,India

This study aims to investigate the level of priority polycyclic aromatic hydrocarbons (PAHs) and identification of their potential sources in residential soils. During the study, a total 36 soil samples collected from twelve residential locations at Sahibabad-Ghaziabad area of western Uttar Pradesh, India, a constituted part of the National Capital Region of India. Samples extracted using ultrasonication, cleaned with silica and analyzed by diode array detector–high-performance liquid chromatography using acetonitrile/water as mobile phase. The 25th and 75th percentile concentration of ∑PAHs was 264 μg kg^?1 and 584 μg kg^?1, respectively, with mean and median of 445 μg kg^?1 and 421 μg kg^?1. The detection frequency of PAHs in all samples was lower for low molecular weight PAHs (19%) than high molecular weight PAHs (81%). The concentration of seven probable carcinogenic PAHs accounted for 67% of the ∑PAHs. PAHs toxicity potential as benzo(a)pyrene toxicity equivalent ranged between 2.52–253 μg BaP_TEQ kg^?1. Composition profile of PAHs with different aromatic rings and selected diagnostic molecular ratios suggested the local pyrogenic sources of PAHs from vehicular emissions, diesel engines, biomass combustion, gasoline, and coal combustions.     

Evaluation of polyaromatic hydrocarbon removal from aqueous solutions using activated carbon and hyper‐crosslinked polymer (Macronet MN200)

BACKGROUND: Sorption of polycyclic aromatic hydrocarbons (PAHs) on activated carbon and the Macronet polymeric sorbent MN200 was investigated to determine the effectiveness of each sorbent for removal of pollutants from aqueous solution and their possible use as sorbent materials for groundwater. Experiments were carried out to determine the loading capacities of a family of PAHs (acenaphthene, anthracene, fluoranthene, fluorene, naphthalene and pyrene). RESULTS: Activated carbon was the more effective sorbent, with maximum loadings of PAHs between 90 and 230 g kg^?1, while MN200 resin showed values of 25–160 g kg^?1. Loading isotherms based on the Langmuir, Freundlich and Redlich–Peterson models were determined. The hydrophobic character of the pollutants appeared as an important parameter related to the sorption process. Equilibrium and kinetic parameters were used to determine the retardation factors for each PAH. CONCLUSION: The calculated values for the simulation of barrier thickness using both sorbents, taking into account EU requirements for PAHs in groundwater effluent, were perfectly reasonable as a first estimate. The better kinetic properties of MN200 are evident in lower hydraulic residence times and consequently in a lower barrier thickness. Copyright © 2008 Society of Chemical Industry     

Determination of Polycyclic Aromatic Hydrocarbons in Water- and Gin-Based Tea Infusions of Selected Tea Brands in Nigeria

The concentrations of the 16 priority polycyclic aromatic hydrocarbons (PAHs) in tea infusions made of water and local gin (alcohol) were investigated with a view to providing information on the profiles and health hazards associated with these two common Nigerian methods for tea consumption. The water-based tea infusion was prepared by submerging 4 g of tea in boiling water and allowing it to stand for 15 min, while the gin-based infusion was simply prepared by submerging 4 g of tea in gin at room temperature and allowing it to stand for 15 min. The concentrations of the ∑16 PAHs in the infusions were measured by using gas chromatography equipped with a flame ionization detector (GC-FID) after ultrasound-assisted extraction and clean-up. The concentrations of the ∑16 PAHs ranged from 24.9–623.4 μg kg^?1 with a mean value of 177 μg kg^?1 and 36.8–438.3 μg kg^?1 with a mean of 189 μg kg^?1 for water- and local gin-based infusions, respectively. The concentration of the ∑16 PAHs in the water- and local gin-based infusions of these teas were high when compared with levels reported in the literature for tea infusions. The local gin-based infusions had a higher mean level of the ∑16 PAHs than the water-based infusions. Four- and five-ring PAH compounds were dominant in these tea infusions.     

Polycyclic Aromatic Hydrocarbons in Residential Soils from an Indian City near Power Plants Area and Assessment of Health Risk for Human Population

This article deals with the distribution, composition profiles, and possible sources of sixteen priority polycyclic aromatic hydrocarbons (PAHs) in residential soils from Korba district in Chhattisgarh State, India. Sixteen priority PAHs in soils were analyzed after ultrasonic extraction, silica gel column chromatographic cleanup, and quantitation was performed using HPLC-DAD. The concentrations of ∑16PAHs were within acceptable limits of soil quality guidelines and the study area got classified as weakly contaminated. The concentration of probable human carcinogenic PAHs in soils accounted for 10% of ∑16PAHs. The concentration of Benzo(a)Pyrene (BaP) accounted 1% to total PAHs. Benzo(a)pyrene Toxicity Equivalency (BaP_TEQ) for 16 PAHs was 30 ± 12 μg BaP_TEQ kg^?1. The composition profiles and molecular ratios of PAHs suggested mixed pyrogenic sources of PAHs from combustion of coal, wood, and vehicular exhaust emissions. Human health risk was assessed by calculating the lifetime average daily dose (LADD) and incremental life time cancer risk (ILCR) for human adults and children. Estimated ILCR was within safe limit (10^?6?10^?5), indicating low risk to human population. Potential risk to contaminated ground water from leaching of carcinogenic PAHs was assessed by estimating the Index of Additive Cancer Risk (IACR).     

Spatial and temporal nitrogen applications for winter wheat in a loamy soil in south-eastern China

Split application of nitrogen (N), applied by broadcasting, is both time consuming and inconvenient; yet it is widely practised for wheat. Simplified N fertilization is necessary for wheat in south-eastern China. One-time band application was compared with split application using three doses of N (150, 195, and 240 kg ha^?1) in 2014/2015 and 2015/2016. Grain yield and N-use efficiency of winter wheat were determined over two consecutive seasons. A corresponding micro-plot trial using ¹⁵N-labelled urea was conducted only in 2015/2016 to measure the fate of urea-¹⁵N. The two methods showed no difference in grain yield, except at 240 kg ha^?1 of N in 2014/2015. The average grain N concentration (18.2 g kg^?1) was slightly lower in band application than that in broadcast application (19.2 g kg^?1), but there was no significant difference (P > 0.05). In 2014/2015, N apparent recovery efficiency ranged from 33.1 to 49.9%; N agronomic efficiency, from 8.9 to 38.9 kg kg^?1; and N partial factor productivity, from 23.6 to 38.4 kg kg^?1. In 2015/2016, the corresponding values were 29.4–38.6%, 13.5–38.6, and 24.3–33.9 kg kg^?1. In the micro-plot trial, compared to split application, fertilizer N recovery in winter wheat in one-time band application was lower by 26.5% and increased the unaccounted-N loss by 21.7%. Thus, considering environmental impacts, one-time band application of N at sowing is not a suitable alternative to broadcast application in split doses for winter wheat in the loamy soils of south-eastern China.     

Nitrous oxide and methane emissions from cultivated seasonal wetland (dambo) soils with inorganic,organic and integrated nutrient management

In many smallholder farming areas southern Africa, the cultivation of seasonal wetlands (dambos) represent an important adaptation to climate change. Frequent droughts and poor performance of rain-fed crops in upland fields have resulted in mounting pressure to cultivate dambos where both organic and inorganic amendments are used to sustain crop yields. Dambo cultivation potentially increases greenhouse gas (GHG) emissions. The objective of the study was to quantify the effects of applying different rates of inorganic nitrogen (N) fertilisers (60, 120, 240 kg N ha^?1) as NH₄NO₃, organic manures (5,000, 10,000 and 15,000 kg ha^?1) and a combination of both sources (integrated management) on GHG emissions in cultivated dambos planted to rape (Brassica napus). Nitrous oxide (N₂O) emissions in plots with organic manures ranged from 218 to 894 µg m^?2 h^?1, while for inorganic N and integrated nutrient management, emissions ranged from 555 to 5,186 µg m^?2 h^?1 and 356–2,702 µg m^?2 h^?1 respectively. Cropped and fertilised dambos were weak sources of methane (CH₄), with emissions ranging from ?0.02 to 0.9 mg m^?2 h^?1, while manures and integrated management increased carbon dioxide (CO₂) emissions. However, crop yields were better under integrated nutrient management. The use of inorganic fertilisers resulted in higher N₂O emission per kg yield obtained (6–14 g N₂O kg^?1 yield), compared to 0.7–4.5 g N₂O kg^?1 yield and 1.6–4.6 g N₂O kg^?1 yield for organic manures and integrated nutrient management respectively. This suggests that the use of organic and integrated nutrient management has the potential to increase yield and reduce yield scaled N₂O emissions.     

Source Allocation of Aliphatic and Polycyclic Aromatic Hydrocarbons in Particulate-Phase (PM10) in the City of Valdivia,Chile

The concentration and signature of n-alkanes (n-C₁₀ to n-C₃₃) and 18 PAHs were determined in air filters across a year period (2010) in an urban area of the city of Valdivia, Chile. Filter samples were extracted using sohxlet apparatus and analyzed by GC-MS techniques. Concentrations of total hydrocarbons ranged from 45–352 ng.m^?3 and total PAHs ranged from 2.93–78.01 ng.m^?3. Concentrations of hydrocarbons during the summer were high (288–352 ng.m^-3) and reduced when the autumn began (45–79 ng.m^?3) to then increase almost linearly to the next summer. The drop in concentration was attributed in part to the significant reduction of traffic when summer ends as tourists leave the city (about 9–15% of the total cars circulating). Results from the chemometric technique of Polytopic Vector Analysis (PVA) indicated three main sources for the alkanes: biogenic (terrestrial plants), signatures of oil combustion, and an unconfirmed source which is thought to come from non specific organic matter degradation. Total PAHs correlated well with total particulate matter with a R² = 0.94. Levels of PAHs in the atmosphere were higher during the winter (6.85–78.01 ng.m^?3) period than the rest of the year (2.93–36.30 ng.m^?3). PVA results indicate three key sources of PAHs and two of those sources derived from oil combustion and biomass burning.     

Reactive separation of p-nitro phenol (PNP) from aqueous solution using tri-n-butyl phosphate: equilibrium and COSMO-RS studies

ABSTRACT

The present study is aimed to optimized diluent type, tri-n-butyl phosphate (TBP) composition and temperature for the reactive extraction of p-nitro phenol (PNP) in two different PNP concentration ranges [(0.00036–0.00646) kmol·m^?3 and (0.00646–0.01437) kmol·m^?3] as found in industrial effluents. 1-Octanol is investigated as the best diluent with TBP based on COSMO-RS theory. Equilibrium study based on mass action law is performed to find the insights of extraction mechanisms, equilibrium constant (K = 295.12 k·mol^?1) and stoichiometry (m:n = 1:1) as also confirmed by FTIR. Thermodynamic parameters, enthalpy (ΔH°), and entropy (ΔS°) are determined 27.51 K J mol^?1 and ?50.21 J mol^?1 K^?1, respectively.     

Olive response to potassium applications under different water regimes and cultivars

Although potassium (K) is a macronutrient few studies have evaluated the response of olive tree to K fertilization. In this work results of two field and two pot K fertilizer experiments are presented. One of the field trials was conducted in a commercial young olive grove. The second was conducted in a plantation purposely established for this study. In the two field and the first pot experiment, the K supply was the single variation factor. The second pot experiment was arranged as a factorial with two K rates, two water regimes and two cultivars (‘Arbequina’ and ‘Cobrançosa’). K supply did not increase olive tree growth or yield. Accumulated olive yield in the first field experiment, for instance, varied from 2.46 and 2.84 kg tree^?1, respectively in K treated and untreated plants. K supply increased the shoot/root ratio (1.6–2.0 from the control to the most fertilized treatment) and the concentration of K in roots (2.9–11.2 g kg^?1) to a greater extent than in leaves (7.0–11.9 g kg^?1), suggesting that shoots are a priority sink for K and roots may store the nutrient as a reserve. Plant water status and chlorophyll a fluorescence were not significantly affected by K applications. Plants suffering from water stress yielded less phytomass (40.2–56.4 g pot^?1, respectively in control and well-watered plants) and showed higher K concentrations in leaves (14.2–11.6 g kg^?1) and lower in roots (4.9–6.8 g kg^?1) which is probably due to the reduction of K uptake from the dry soil. ‘Cobrançosa’ appeared to be more tolerant to water stress than ‘Arbequina’. These experiments showed a poor response of olive tree to K fertilization. Considering that K is usually applied by farmers every year, it seems that further studies on K fertilization in olive are needed in order to adjust K fertilizer rates to crop needs.     

Urban Stream Vulnerability Toward PAHs and n-Alkanes and Their Source Identification

Monjolinho River is an important water body located in the central urban region of São Paulo State in southeast Brazil. The present work reports a 4-year study related to spatio-temporal distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in surface water and sediment samples of Monjolinho River. A total of 25 sampling campaigns for water, and 10 sampling campaigns for sediment collection, were performed from 2011 to 2014. In sediment samples, total PAHs were found in the range of 2.25 µg kg^?1–26,253.87 µg kg^?1, while n-alkane concentrations ranged from 0.01 to 165.64 µg kg^?1. Total PAHs' concentration in surface water was in the range of 0.17–1,348.35 ng L^?1, while n-alkanes were detected in the range of 6.17–316.15 µg L^?1. Principal component analysis was used as a statistical tool for summarizing and interpreting a huge quantity of data. It was observed that concentrations of contaminants increased along the river course in urban zone. Distribution indexes were calculated to identify possible sources of carbon pool that pointed towards petrogenic, pyrogenic, and biogenic sources. The overall concentrations of PAHs and n-alkanes were low compared to many previous studies done elsewhere and were mostly below the threshold effects level except in very few occasional cases, while probable effect level was violated in 1 sample during 4 years. Although adverse impacts are unexpected due to overall low contaminant concentrations, unexpected industrial, and sewage discharges make it risky for safer use as a drinking water resource, especially in dry conditions.     

Combined hot air convective drying and microwave-vacuum drying of blueberries (Vaccinium corymbosum L.): Drying kinetics and quality characteristics

The aims of this study were to: (1) evaluate the effect of each stage of HACD + MWVD on the drying kinetics and quality parameters of blueberries, including color, overall appearance, mechanical and physical attributes, and rehydration potential; (2) select proper combination order and conversion point of HACD + MWVD to minimize physicochemical changes and maintain high quality of blueberries. The results were compared with HACD and MWVD alone. A linear equation produced a good fit to data describing the drying kinetics of the constant or first falling rate period, whereas the Henderson and Pabis model was a good fit for the dataset describing the second falling rate period. The color changes induced in berries by HACD + MWVD were limited (ΔE* ranged from 3.08 ± 2.25 to 3.65 ± 2.28) in comparison with HACD (ΔE* ranged from 7.90 ± 2.29 to 8.21 ± 1.77). HACD + MWVD contributed to the achievement of significantly lower values of hardness, chewiness, and gumminess in blueberries, compared to HACD. Multi-stage HACD + MWVD with hot air predrying at 80°C until the achievement of the moisture content of 1.95 ± 0.05 kg · kg^?1 db caused the lowest shrinkage of blueberries. Blueberries dried by multi-stage HACD +MWVD with hot air predrying at 80°C until the achievement of moisture content of 1.95 ± 0.05 kg · kg^?1 db were characterized by the highest rehydration potential, in terms of moisture content, rehydration ratio, and water gain; i.e., 4.15 ± 0.02 kg · kg^?1 db, 4.02 ± 0.05 g · g^?1 db, 4.07 ± 0.01 g · g^?1 db, respectively.     

Factorial Design Optimization of Solid-Phase Microextraction for High-Performance Liquid Chromatography−Ultraviolet Spectrometry Analysis of Polycyclic Aromatic Hydrocarbons in Cigarette Filter Tar

A simple and rapid procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using solid-phase microextraction (SPME) was developed. The analysis was carried out using high-performance liquid chromatography equipped with an ultraviolet detector. The effects of the SPME experimental parameters on the extraction recovery were studied simultaneously using a central composite design (CCD) after a 2^6?2 fractional factorial experimental design. The SPME variables of interest were the extraction temperature, the extraction time, and the stirring speed, as well as the pH and the concentrations of NaCl (%, w/v) and acetonitrile (ACN). The optimal SPME conditions were as follows: an extraction temperature of 65°C, an extraction time of 50 min, a stirring speed of 800 rpm, 0% NaCl (w/v), 10% ACN in the sample, and a source pH of 8.0. The extraction calibration plots were linear over the range of 0.25?20 ng mL^?1 (r² > 0.9912) and the limits of detection (LODs) for the 6 PAHs studied were from 0.17–5.02 ng cigarette^?1. The relative standard deviation (RSD) ranged from 7.1–13.5% for intra-day variation and from 8.5–18.4% for inter-day variation. The performance of the proposed method was evaluated for extraction and determination PAHs in real samples (various brands of cigarettes). The total amounts of all of the studied PAHs found in the filter tar of the three brands of cigarettes were 320.2, 17.9, and 66.7 ng cigarette^?1, respectively.     

Selective Competitive Biosorption of Au(III) and Cu(II) in Binary Systems by Magnetospirillum gryphiswaldense

The biosorption of Au(III) and Cu(II) ions in both single and binary systems by Magnetospirillum gryphiswaldense (MSR-1) was investigated. For comparison with the selective reinforced competitive biosorption process in a binary system, the experimental research first explored the biosorption of Au(III) and Cu(II) in a single system under various conditions. The biomass exhibited the highest single Au(III) and Cu(II) ion adsorption yields at room temperature (25°C), pH values of 2.5 and 5.0, respectively, and a biomass concentration of 10 g · L^?1 (3.83 g · L^?1, dry basis). The experimental data from the single component system for the two metallic ions fitted well to a Langmuir isotherm and a pseudo second-order kinetic models. In the Au(III)-Cu(II) binary system, the coexistence of Cu(II) cations promoted the adsorption of Au(III) within a certain range of ratios. A new sigmoidal Cu(II) biosorption isotherm was determined specifically to reveal the Cu(II) adsorption behavior in this case.     

Crop yields and soil organic carbon fractions as influenced by straw incorporation in a rice–wheat cropping system in southeastern China

In agro-ecosystems, the relationship between soil fertility and crop yield is mediated by manure application. In this study, an 8-year field experiment was performed with four fertilizer treatments (NPK, NPKM₁, NPKM₂, and NPKM₃), where NPK refers to chemical fertilizer and M₁, M₂, and M₃ refer to manure application rates of 15, 30, and 45 Mg ha^?1 year^?1, respectively. The results showed that the NPKM (NPKM₁, NPKM₂, and NPKM₃) treatments produced greater and more stable yields (4.95–5.45 Mg ha^?1 and 0.59–0.75) than the NPK treatment (4.01 Mg ha^?1 and 0.50). Crop yields under the NPKM treatments showed two trends, with a rate of decrease of 0.48–0.83 Mg ha^?1 year^?1 during the first 4 years and a rate of increase of 0.10–0.25 Mg ha^?1 year^?1 during the last 4 years. The soil organic carbon (SOC) significantly increased under all treatments. The estimated annual SOC decomposition rate was 0.35 Mg ha^?1 year^?1 and the equilibrium SOC level was 6.22 Mg ha^?1. Soil total nitrogen (N), available N, total phosphorus (P) and available P under the NPKM treatments increased by 0.15–0.26, 15–33, 0.17–0.66 and 45–159 g kg^?1, respectively, compared with the NPK treatment. Manure application mainly influenced crop yield by affecting the soil TN, available N, and available P, which accounted for up to 64% of the crop yield variation. Taken together, applying manure can determine or at least improve the effects of soil fertility on crop yield in acidic soils in South China.     

Regression model,artificial intelligence,and cost estimation for phosphate adsorption using encapsulated nanoscale zero-valent iron

This study investigated the adsorption of PO₄^3? onto encapsulated nanoscale zero-valent iron (nZVI). At initial PO₄^3–: 10 mg · L^?1, the optimum condition was initial pH: 6.5, nZVI dosage: 20 g · L^?1, stirring-rate: 100 rpm, and time: 30 min, achieving PO₄^3? removal of 42%. The effect of pH and time on the PO₄^3? removal efficiency was quadratic-linear concave up, whereas the curve of nZVI dosage was quadratic-convex. Artificial neural network with a structure of 5?7?1 adequately predicted PO₄^3? removal (R²: 97.6%), and the sensitivity analysis demonstrated that pH was the most influential input. The cost of the adsorption unit was 3.15 $USD · m^?3.     

ENZYME-MEDIATED PRODUCTION OF SUGARS FROM SAGO STARCH: STATISTICAL PROCESS OPTIMIZATION

Glucoamylase (γ-amylase, EC 3.2.1.3) from Aspergillus niger was used to hydrolyze the soluble sago starch to reducing sugars without any major pretreatment of the substrate. A 2 L stirred tank reactor was used for the hydrolysis. The effects of pH, temperature, agitation speed, substrate concentration, and enzyme concentration on the reaction were investigated in order to maximize both the initial reaction velocity v and the final product yield Y_p/s. A response surface methodology central composite design was used for the optimization. A maximum Y_p/s of 0.58 g · g^?1 and a high v of 0.50 mmoles · L^?1 · min^?1 were predicted by the response surface at the identified optimal conditions (61°C, a substrate concentration of 0.1% (w/v, g/100 mL), an enzyme concentration of 0.2 U · mL^?1). The pH and agitation speed did not significantly affect the production of sugars. The subsequent validation experiments under the above-specified optimal conditions confirmed a maximum conversion rate and yield combination of 0.51 ± 0.07 mmoles · L^?1 · min^?1 and 0.60 ± 0.08 g · g^?1.     

Synthetic Cis-Jasmone Exposure Induces Wheat and Barley Volatiles that Repel the Pest Cereal Leaf Beetle, Oulema melanopus L.

The plant semiochemical cis-jasmone primes/induces plant resistance that deters herbivores and attracts natural enemies. We studied the induction of volatile organic compounds (VOCs) in winter wheat and spring barley after exposure of plants to three synthetic cis-jasmone doses (50 μl of 1, 100, and 1?×?10⁴ ng μl^?1) and durations of exposure (1, 3, and 6 h). Cereal leaf beetle, Oulema melanopus, adult behavioral responses were examined in a Y-tube olfactometer to cis-jasmone induced plant VOC bouquets and to two synthetic blends of VOCs (3 green leaf volatiles (GLVs); 4 terpenes?+?indole). In both cereals, eight VOCs [(Z)-3-hexanal, (Z)-3-hexanol, (Z)-3-hexanyl acetate, (Z)-β-ocimene, linalool, β-caryophyllene, (E)-ß–farnesene, and indole] were induced 100- to 1000-fold after cis-jasmone exposure. The degree of induction in both cereals was usually positively and linearly associated with increasing exposure dose and duration. However, VOC emission rate was only ~2-fold greater from plants exposed to the highest vs. lowest cis-jasmone exposure doses (1?×?10⁴ difference) or durations (6-fold difference). Male and female O. melanopus were deterred by both cereal VOC bouquets after plant exposure to the high cis-jasmone dose (1?×?10⁴ ng μl^?1), while females were also deterred after plant exposure to the low dose (1 ng μl^?1) but attracted to unexposed plant VOC bouquets. Both O. melanopus sexes were repelled by terpene/indole and GLV blends at two concentrations (25 ng?·?min^?1; 125 ng?·?min^?1), but attracted to the lowest dose (1 ng?·?min^?1) of a GLV blend. It is possible that the biologically relevant low cis-jasmone dose has ecological activity and potential for inducing field crop VOCs to deter O. melanopus.     

The effect of pulsed electric field on drying kinetics,color, and microstructure of carrot

The aim of the study was to investigate the impact of pulsed electric field (PEF) treatment on the convective drying kinetics of a carrot and color and microstructure changes of the dried product. Samples were treated by PEF with the specific energy input equal to 5.63, 8 and 80 kJ · kg^?1. After PEF treatment, thermal conductivity and electrical conductivity were measured. Drying time of the PEF-treated samples was reduced up to 8.2% (W_s = 8 kJ · kg^?1, 5 kV · cm^?1; 10 pulses) in comparison to intact tissue. Statistical analysis showed that Midilli et al.’s model was considered to describe the kinetics of the process the most precisely. Pulsed electric field treatment increased the effective water diffusion coefficient up to 16.7%. Moreover, PEF treatment and drying caused the alteration of the sample color. After drying, the lightness and chroma were higher or unchanged in comparison to the intact tissue. The dried PEF-treated samples exhibited significantly higher redness (higher value of a^* parameter) in comparison to the untreated dried samples. Moreover, the visual inspection of scanning electron microscope images revealed that PEF pretreatment performed at high electric field intensity (5 kV · cm^?1, regardless of pulse number) provoked the material to form greater cavities during drying in comparison to the untreated material.     

Mangrove Oyster (Crassostrea belcheri) as a Biomonitor Species for Bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) from Sediment of the West Coast of Peninsular Malaysia

ABSTRACT

Rapid industrialization and urbanization in the west coast of Peninsular Malaysia has caused increasing pollution particularly of petroleum and petroleum by-products. Surface sediment and mangrove oyster (Crassostrea belcheri) were collected from five mangrove ecosystems in the west coast of Peninsular Malaysia and investigated for bioavailability of polycyclic aromatic hydrocarbons (PAHs). Sampling locations were selected from both remote areas with few or no previous records of petroleum pollution such as Pulau Merambong and polluted areas that are under international attention such as Klang mangrove ecosystem. PAH fractions were obtained through soxhlet extraction and two-step column chromatography and the fractions were injected to gas chromatography-mass spectrometry (GC-MS) for analysis. The concentrations of PAHs ranged from 151 to 4973 ng g^?1 dw in the sediments, while from 309 to 2225 ng g^?1 dw in the oysters. When tested for diagnostic ratios, a predominance of pyrogenic source PAHs was detected in the sediments, whereas PAHs in the oysters had mixed petrogenic and pyrogenic sources. A significant correlation (p < 0.05) was found between high molecular weight (HMW) PAHs in the sediments and oysters and biota accumulation factors (BAFs) of PAHs were approaching or exceeding unity indicating the ability of mangrove oyster in bioaccumulation of PAHs. Overall, this study indicates that mangrove oyster (C. belcheri) can be used as a biomonitor species for PAHs in an aquatic environment.     

The Effect of Polycyclic Aromatic Hydrocarbons on the Structure of Organotrophic Bacteria and Dehydrogenase Activity in Soil

The objective of this article was to determine the structure of microbial communities and the activity of dehydrogenases in soil samples contaminated with four polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, anthracene, and pyrene, in the amount of 0, 1000, 2000, and 4000 mg kg^?1soil DM. Organic substances—cellulose, sucrose, and compost—were added to the samples in the amount of 0 and 9 g kg^?1soil DM. The experiment was performed in a laboratory on samples of loamy sand. Indices of colony development (CD) and eco-physiological diversity (EP) of organotrophic bacteria, soil resistance (RS), and soil resilience (RL) were calculated. Soil contamination with PAHs differentiated the structure of organotrophic bacteria, and the lowest CD and EP values were noted in soil samples containing pyrene. PAHs inhibited the activity of dehydrogenases, and pyrene exerted the most inhibitory effect on enzyme activity. Dehydrogenase activity was determined mainly by the applied PAH dose, the date of analysis and the type of organic substance added to soil. Low RL values indicate that exposure to PAHs induces long-term changes in dehydrogenase activity.