Possible Sources Of Contamination Research Articles

A Complete mtDNA Genome of an Early Modern Human from Kostenki, Russia

The recovery of DNA sequences from early modern humans (EMHs) could shed light on their interactions with archaic groups such as Neandertals and their relationships to current human populations. However, such experiments are highly problematic because present-day human DNA frequently contaminates bones [1, 2]. For example, in a recent study of mitochondrial (mt) DNA from Neolithic European skeletons, sequence variants were only taken as authentic if they were absent or rare in the present population, whereas others had to be discounted as possible contamination [3, 4]. This limits analysis to EMH individuals carrying rare sequences and thus yields a biased view of the ancient gene pool. Other approaches of identifying contaminating DNA, such as genotyping all individuals who have come into contact with a sample, restrict analyses to specimens where this is possible [5, 6] and do not exclude all possible sources of contamination. By studying mtDNA in Neandertal remains, where contamination and endogenous DNA can be distinguished by sequence, we show that fragmentation patterns and nucleotide misincorporations can be used to gauge authenticity of ancient DNA sequences. We use these features to determine a complete mtDNA sequence from a approximately 30,000-year-old EMH from the Kostenki 14 site in Russia.

Risk factors at slaughter associated with presence of Salmonella on hog carcasses in Canada.

Despite the application of hazard analysis and critical control point systems at slaughter and during processing, Salmonella contamination is still a significant biological hazard associated with pork products. A better understanding of risk factors in slaughterhouses and of contamination sources is therefore critical to improve control of this bacterium in the abattoirs. The objectives of this study were to identify the risk factors at slaughter that are associated with the presence of Salmonella on hog carcasses and to assess possible sources of contamination. A questionnaire on potential risk factors was developed. Over 7,400 hogs originating from 312 randomly selected production lots were tested. The lots were from 10 different abattoirs located in five different Canadian provinces. At slaughter, blood was collected for serological analysis, and mesenteric lymph nodes (MLN) and carcass swabs were collected for Salmonella analysis. Furthermore, pulsed-field gel electrophoresis was conducted to establish the genetic profiles of selected isolates from carcasses and MLN and to compare these profiles with those recovered from the slaughter environment. Multivariate regression analysis results indicated that the cleanliness of the hogs and the status of the scald water were factors significantly associated with the Salmonella status of the carcasses at the end of the slaughter process. Pulsed-field gel electrophoresis analysis showed that most isolates from carcasses were similar to those from animals (MLN) or the preevisceration environment.

Legionella in industrial cooling towers: monitoring and control strategies

Legionella contamination of industrial cooling towers has been identified as the cause of sporadic cases and outbreaks of legionellosis among people living nearby. To evaluate and control Legionella contamination in industrial cooling tower water, microbiological monitoring was carried out to determine the effectiveness of the following different disinfection treatments: (i) continuous chlorine concentration of 0.01 ppm and monthly chlorine shock dosing (5 ppm) on a single cooling tower; (ii) continuous chlorine concentration of 0.4 ppm and monthly shock of biocide P3 FERROCID 8580 (BKG Water Solution) on seven towers. Legionella spp. and total bacterial count (TBC) were determined 3 days before and after each shock dose. Both strategies demonstrated that when chlorine was maintained at low levels, the Legionella count grew to levels above 10(4) CFU l(-1) while TBC still remained above 10(8 )CFU l(-1). Chlorine shock dosing was able to eliminate bacterial contamination, but only for 10-15 days. Biocide shock dosing was also insufficient to control the problem when the disinfectant concentration was administered at only one point in the plant and at the concentration of 30 ppm. On the other hand, when at a biocide concentration of 30 or 50 ppm was distributed throughout a number of points, depending on the plant hydrodynamics, Legionella counts decreased significantly and often remained below the warning limit. Moreover, the contamination of water entering the plant and the presence of sediment were also important factors for Legionella growth. For effective decontamination of outdoor industrial cooling towers, disinfectants should be distributed in a targeted way, taking into account the possible sources of contamination. The data of the research permitted to modify the procedure of disinfection for better reduce the water and aerosol contamination and consequently the exposure risk.

PERFIL SOROLÓGICO E DE ISOLAMENTO DE Salmonella sp. EM SUÍNOS NO INÍCIO DA TERMINAÇÃO E AO ABATE

Studies assessing the Salmonella transmission chain in pig herds are the first step to start a control program. The aims of this study were to compare the prevalence of Salmonella positive pigs at the beginning of the finishing phase and at slaughter, and to identify the possible sources of contamination in the farms. In three finishing farms, environmental swabs from the barns and from the feed silos were collected during the sanitary emptiness. Furthermore, samples of feces and blood from the animals on the day of housing; and aliquots from all feed lots were taken. At slaughter, blood, mesenteric lymph nodes (LM) and intestinal content (CI) were sampled. Blood samples were submitted to a S. Typhimurium ELISA-LPS test. All other samples were submitted to a Salmonella isolation protocol. Feed samples were also submitted to Polymerase Chain Reaction (PCR) targeting the invA gene. Feces samples from all pigs were Salmonella negative at the beginning of the finishing phase, in two farms seropositive animals were found. In two farms, residual environmental contamination was detected, and, in the third farm, one of the feed batches was Salmonella positive on the PCR assay. At slaughter, over 90% of the animals were positive on the ELISA-LPS test and, in all cohorts, a variable number (12%-92%) of carriers in LM and CI was detected. From this on, it was concluded that the finishing phase was critical for the amplification of Salmonella infection, and the residual environmental contamination in the farms as well as Salmonella positive feed batches were the probable infection sources. KEY WORDS: Isolation, finishing and slaughter, Salmonella, serology, swine.

Endosulfan in Wind-Transported African Dust Depositions in Crete

The presence of endosulfan in samples of African dust after a typical red dust storm in May 2007 was investigated. The samples were collected from a remote and mountainous area of Crete (Greece) where olive groves are cultivated. Endosulfan I, endosulfan II and endosulfan sulphate were detected at concentrations of 2.7, 1.4 and 1.1 ng/g, respectively, indicating that long range aeolian dust transport could be a possible source of contamination of olive cultivations.

Assessment of Heavy Metal and Pesticide Levels in Soil and Plant Products from Agricultural Area of Belgrade, Serbia

This study was aimed to assess the levels of selected heavy metals and pesticides in soil and plant products from an agricultural area of Belgrade, Serbia and to indicate possible sources and risks of contamination. Soil, vegetable, and fruit samples from the most important agricultural city areas were collected from July to November of 2006. Metal contents were determined by atomic absorption spectrometry, whereas pesticide residues were analyzed by gas chromatography-mass spectrometry after extraction performed using solid-phase microextraction technique. Soil characterization based on the determination of selected physical and chemical properties revealed heterogeneous soils belonging to different soil groups. The concentrations of lead, cadmium, copper, and zinc in soil samples do not exceed the limits established by national and international regulations. Residues of the herbicide atrazine were detected in three soil samples, with levels lower than the relevant limit. The presence of other herbicides, namely prometryn, chloridazon, acetochlor, flurochloridone, and napropamide, was registered in some soil samples as well. Among the insecticides investigated in the soil, fenitrothion and chlorpyrifos were the only ones detected. In most of the investigated vegetable samples from the Obrenovac area, Pb and Cd contents are higher in comparison with the maximum levels, indicating the emission of coal combustion products from local thermal power plants as a possible source of contamination. Residue levels of some herbicides and insecticides (metribuzin, trifluralin, pendimethalin, bifenthrin, chlorpyrifos, and cypermethrin) determined in tomato, pepper, potato, and onion samples from Slanci, Ovca, and Obrenovac areas are even several times higher than the maximum residue levels. Inappropriate use of these plant protection products is considered to be the most probable reason of contamination. Because increased levels of heavy metals and pesticide residues found in plant products could pose a risk to consumers' health, their continual monitoring before product distribution to city markets is indispensable.

Prevalence of Cryptosporidium isolated from dromedary camels (Camelus dromedarius) in Qeshm Island, Southern Iran

This study was undertaken to assess the prevalence of Cryptosporidium in dromedary camels (Camelus dromedarius) on Qeshm Island, southern Iran. Sixty-five faecal samples were obtained from camels (age range 2–12 years) housed in ten privately owned herds from three equal-length areas (west, east and central) on Qeshm Island, southern Iran. All samples were analysed for Cryptosporidium oocysts by microscopic examination of smears stained by modified Ziehl-Neelsen technique. The parasite was detected in 11 camels (16.9%). The genus identity of the oocysts was confirmed by morphology and was similar to Cryptosporidium parvum. The mean (±SD) size of 225 oocysts was 5.1 (0.42) × 4.38 (0.27) µm (range 4.2–5.3 × 3.8–4.5 µm) with a shape index (length/width) of 1.17 (0.03; range 1.11–1.18). Data analyses indicated significant difference in prevalence of Cryptosporidium infection in western and central areas compared with the eastern area. Numerous reports indicate that water is a major vehicle for transmission of cryptosporidiosis. Geographical studies in western and eastern areas show that areas of vegetation, lagoons and seasonal rivers in these two regions are more frequent than the eastern part. Possible source of contamination of these waters by Cryptosporidium may be related to sewage from human and faeces of domesticated and wild animals. Therefore, it is possible that water may be a predisposing factor for transmission of cryptosporidiosis in these areas.

Anthropogenic Influences on Annual Flux of Cations and Anions at Meio Stream Basin, São Paulo State, Brazil

The chemical dynamics at Meio Stream Basin, Sao Paulo State, Brazil were evaluated using major elements as natural tracers. The surface water samples from Meio Stream were collected near the mouth of Meio Stream at the confluence with the Mogi-Guacu River on February 25, 2005, April 20, 2005, and July 8, 2005. Rainwater samples were collected (using a “bulk” collector) for 1 year at one sampling point located about 4 km from downtown Leme city and other possible sources of contamination. The analyses were performed by pH, temperature, dissolved oxygen, electrical conductivity, total solids, sulfate, nitrate, phosphate, alkalinity, chloride, sodium, calcium, potassium, and magnesium. This basin has serious environmental problems in terms of rainwater and surface water quality, which result in the negative annual flux of cations and anions at Meio Stream Basin, with the exception of chlorine. The Meio Stream, downstream from Leme city, receives several elements/compounds through anthropogenic activities, mainly related to the discharge of domestic effluents. Anthropogenic inputs (mining, fossil fuel burning, and agricultural activities) are responsible for the higher concentrations of cations and anions in the rainwater from this basin.

Factors affecting the attachment of micro-organisms isolated from ultrafiltration and reverse osmosis membranes in dairy processing plants

To identify the types of micro-organisms involved in the formation of biofilms on dairy ultrafiltration and reverse osmosis membranes and investigate factors affecting the attachment of those isolates. Micro-organisms isolated from industrial membranes following standard cleaning were identified using the API culture identification system. Thirteen different isolates representing eight genera were isolated and their ability to attach to surfaces was compared using a microtitre plate assay. Three Klebsiella strains attached best, while mixed strains of Pseudomonas and Klebsiella attached better than individual strains. Whey enhanced the attachment of the isolates. The micro-organisms were characterized according to cell surface hydrophobicity using the microbial adhesion to hydrocarbon (MATH) test, and cell surface charge by measuring the zeta potential. These cell surface characteristics did not show a clear relationship with the attachment of our strains. A variety of different micro-organisms is associated with dairy ultrafiltration and reverse osmosis membranes after cleaning, suggesting several possible sources of contamination. The cleaning of these membranes may be inadequate. The attachment of the different isolates is highly variable and enhanced in the presence of whey. Knowledge of persistent microflora colonizing dairy membrane systems will help develop strategies to mitigate biofilm development in this environment, improving hygiene in membrane processing plants.

Efficiency of cleaning procedure of milking equipment and bacterial quality of milk

The cleaning and sanitation of milking equipment could be consider a critical point in the milking procedure because a cleaning failure could influence the level of bacteria contamination of bulk tank milk. Aim of the study is to monitor the cleaning procedures of milking systems in 7 dairy cows farms in Lombardy and to find a relation between efficacy of cleaning system and the bacterial quality of bulk tank milk, remaining washing water through milking equipment and teat cup surface. Cleaning procedures were monitored with Lactocorder, that measured: duration, water temperature, turbulence, percentage of water in pipes, water conductivity of pre- and post-rinse and detergent phases. Results showed that the monitored farms the most of the cleaning parameters were lower than recommendations, in particular maximum water temperature (42.1±9.9°C) and percentage of water during detergent phase (76.1±13.9 %). A maximum temperature of detergent phase <40°C determined a high Standard Plate Count (SPC), thermoduric bacteria and Coliform Count (CC) of bulk tank milk, SPC and CC of teat cup surface. The research indicated that monitoring the efficiency of cleaning milking equipment with proper tools provide useful information about possible sources of contamination of bulk tank milk. Improving cleaning milking efficiency allow to improve milk quality.

Assessment of the chemical contamination in home-produced eggs in Belgium: General overview of the CONTEGG study

This overview paper describes a study conducted for the Belgian Federal Public Service of Health, Food Chain Safety and Environment during 2006–2007. Home-produced eggs from Belgian private owners of hens were included in a large study aiming to determine concentration levels of various environmental contaminants. By means of the analyses of soil samples and of kitchen waste samples, obtained from the same locations, an investigation towards the possible sources of contaminants was possible. Eggs, soils, faeces and kitchen waste samples were checked for the presence of dioxins, PCBs (including dioxin-like PCBs), organochlorine pesticides, trace elements, PAHs, brominated flame retardants and mycotoxins. The study design, sampling methodology and primary conclusions of the study are given. It was found that in some cases dioxin-like compounds were present at levels that are of concern for the health of the egg consumers. Therefore, measures to limit their contamination in eggs, produced by hens of private owners, were proposed and deserve further attention.

Studies of an improved system for the radial implantation of radio-isotopes

We report on experiments undertaken to clarify the implantation process of a coaxial plasma-based ion implanter designed for the implantation of radio-isotopes into small, cylindrical metal surfaces. Mapping the distribution of the radioactive fragments on the reactor's surfaces allows us to verify several aspects that impact the implantation efficiency. First, by a careful design of the radioactive deposit support, we eliminated the generation of radioactive ‘flakes’, thus removing a source of possible contamination. Second, we verified that the material is ejected from the radioactive source (RS) in a cosine distribution. Third, we clearly demonstrated that the ionization mean free path of the radioactive fragments is only a few centimetres, much shorter than our original estimates based on an electron impact ionization model. From these results, we believe that the dominant ionization process is Penning ionization. The measurements undertaken in this study were only possible through the use of radioactive atoms and the associated radiographic mapping techniques that we developed. We have also studied a new configuration, with the RS situated on the reactor's axis, and where the implantation process depends explicitly on the potential barrier generated by the plasma. Using this new configuration with optimized parameters we believe an implantation efficiency of the order of 20% is achievable.

The Effects of Stress on Respiratory Disease and Transient Colonization of Turkeys with Listeria monocytogenes Scott A

Listeria monocytogenes contaminates poultry processing plants due to its ubiquitous nature and high resistance to disinfection. The sources of the persistent, biofilm-forming strains that colonize processing plants are unknown. The purpose of this study is to determine if intrinsic colonization of turkeys is a possible source of contamination. Male poults were subjected to cold stress from 4-12 days of age; poults were unchallenged or were exposed to an aerosol and oral challenge of either an avian pathogenic strain of Escherichia coli (Ec), the Scott A strain of L. monocytogenes (Lm), or to a combination (Ec-Lm). At 7 wk, all cold-stressed poults were treated with an immunosuppressive dose of dexamethasone (Dex) and exposed to the same bacterial challenges. Birds were necropsied at 1 wk and 2 wk post-Dex treatment. Percent mortality, body and organ weights, and airsacculitis scores were determined. Liver and knee synovial tissues were sampled, using transport swabs, and cultured by direct plating, pre-enrichment, and Taqman real-time PCR. There were no significant differences in cumulative mortality, and airsacculitis scores were variable but tended to be decreased by cold stress. Relative weights of liver and heart were increased, whereas body weights, and spleen and bursa relative weights, were decreased following all challenges. Listeria monocytogenes was isolated from up to 50% of liver or knee synovial tissues, using pre-enrichment followed by culturing methods, and from up to 67% of knee synovial tissues using pre-enrichment followed by real-time PCR at 1 wk post-challenge. The higher percentages of positive birds, detected by real-time PCR rather than by culture, and the negative results at 2 wk post-challenge suggest that the birds experienced a transient infection that was cleared by the immune system. These results suggest that environmentally acquired L. monocytogenes can transiently colonize the liver and synovial tissues of stressed turkeys and may be a sporadic source of contamination of processing plants.

Occurrence of mycoplasmas in semen samples of birds of prey

Mycoplasmas are well-known pathogens in a variety of animals. In poultry it is known that some species can be transmitted by semen and infect the uterus of females. As the prevalence of mycoplasmas in birds of prey is very high and artificial insemination is a commonly used technique for reproduction, the possibility of transmission Mycoplasma spp. by contaminated semen in birds of prey was investigated. Isolation of mycoplasmas was possible in five out of 32 (15.6%) semen samples of different bird of prey species. Two additional semen samples were positive for mycoplasma DNA using a Mycoplasma-genus-specific polymerase chain reaction. The isolation of mycoplasmas from a testicular sample indicates the testis as the possible source of contamination. Sequencing of large parts (>90%) of the 16S rRNA gene of the isolated mycoplasmas suggests that all isolates belong to the same species. Alignment of the sequenced products with the 16S rRNA gene of Mycoplasma species in GenBank demonstrated a similarity of 97% to Mycoplasma verecundum, but serological testing by immunobinding assay failed to identify it as such. It is recommended that the semen of donor birds of prey is examined for mycoplasmas before its use in artificial insemination.

Ionic outgassing from photoacid generators upon irradiation at 13.5 nm

Photoresist outgassing is considered a possible source of contamination of optics in extreme ultraviolet (EUV) lithography at 13.5 nm. We measured the relative proportions of ionic outgassing from 18 commercially available photoacid generators (PAG), which is a key component of chemically amplified photoresists, upon irradiation at 13.5 nm. These PAG include 17 triarylsulfonium or diaryliodonium salts, which contain CF 3 SO 3 - or C 4 F 9 SO 3 - as the anion, and one PAG of molecular type. The overall outgassed ions in the range 10–200 u were counted in relative proportions. Outgassing of F + is found to be dominant, and for most PAG the extent of F + outgassing shows a satisfactory correlation with the ratio of F atomic photoabsorption to the overall PAG photoabsorption. Outgassed ions F +, CF +, CF 2 + and CF 3 + from PAG containing the CF 3 SO 3 - anion and additional C x F y + such as C 2 F 4 + , C 2 F 5 + and C 3 F 5 + from those containing C 4 F 9 SO 3 - are identified. Triphenylsulfonium perfluoro-1-butanesulfonate is one PAG to emit the most abundant F + and total ionic fragments, and a PAG of molecular type ( N-hydroxy-5-norbornene-2,3-dicarboximide perfluoro-1-butanesulfonate) also emits abundantly both hydrocarbon ions and F +. Ionic outgassing of PAG cations includes (C 6H 5) 2S + from R(C 6H 5) 2S + salts and I + from diaryliodonium salts. For PAG containing t-C 4H 9, significantly less F + outgassing is observed; additional outgassing pathways are proposed. The pressure rise caused by PAG shows no dependence on the anion identity, but is correlated with cation photoabsorption, and ascribed to neutral aryl outgassing. Other minor outgassing species include HSO 2 + from sulfonates; C 11 H 9 + and ‘photostable’ PAH cations C 12 H 8 + are identified for the first time and provide evidence of concurrent outgassing from, and polymerization of, PAG upon irradiation at 13.5 nm.

POTENTIAL FOR CONTAMINATION OF ORTHOPAEDIC IMPLANTS USING INDIVIDUALLY WRAPPED SCREWS

There has been an anecdotal shift away from screw banks in orthopaedic surgery in preference for individually wrapped screws. Our hypothesis is that opening individually wrapped items introduces a possible source of contamination of the surgical set-up and repeated opening compounds this potential. Theoretically, this could pose a greater infection risk to the patient than the alternative of a screw bank. One hundred screws were double wrapped in an identical fashion to the standard practice at our hospital. We used Glitterbug (Glitterbug cream is a commercially available product available from Brevis Corporation, Salt Lake City, Utah, USA) cream, which is designed to be near invisible to the naked eye but visible under ultraviolet light. After bathing their hands in the cream, 5 theatre nurses opened 20 screws as if being carried out during an operation. Ultraviolet light was used to evaluate transfer of the cream. Samples were considered positive if there was any evidence of fluorescence under ultraviolet light. Five screw banks were also opened and inspected using the same methods for comparison. We identified contamination in one of the 100 screws. No contamination of the inner packaging of the screw banks was observed. At no stage did any participants believe that contamination had occurred. This study has shown that the opening of individually wrapped items increases the risk for potential contamination of an operative field, suggesting that the move towards using individually wrapped components for surgery warrants further investigation. We believe that orthopaedic operating theatres should consider the use of screw banks to minimize the risk of contamination.

Preen oil as the main source of external contamination with organic pollutants onto feathers of the common magpie ( Pica pica)

We investigated the possible sources of contamination with organic pollutants, such as polychlorinated biphenyls (PCBs), p,p′-dichlorodiphenyltrichloroethane (DDT) and metabolites, and polybrominated diphenyl ethers (PBDEs), in and onto tail feathers of a large songbird, the common magpie ( Pica pica). Although feathers are potentially useful as a non-destructive biomonitor for organic pollutants, concentrations may be influenced by external contamination onto the feather surface. In a first approach, a group of magpies was captured after the completion of moult. The third tail feather was pulled out and a blood sample was taken. Most PCBs, DDTs and some PBDEs could be quantified in one single tail feather, indicating that the applicability of feathers goes beyond monitoring with predatory birds, as shown previously. Nevertheless, correlations between levels in serum and feathers were found significant in three cases only (i.e. CB 170, CB 180 and CB 187). This finding may be attributed to different factors, such as varying diet, condition, sample size or external contamination. In a second approach, cadavers of magpies were collected throughout Flanders. The preen gland was removed and the first, third and fifth tail feathers were pulled out at both sides. No significant differences were found among tail feathers within an individual. We compared three washing procedures to remove external contamination with organic pollutants from these feathers: deionised water, acetone and a surfactant/acetone solution. Right feathers were washed and left feathers were kept as control. Concentrations in the resulting washes were found highest in the acetone solutions. Furthermore, feathers washed with acetone or with a surfactant/acetone solution had significantly lower mean concentrations than the control feathers. Highest correlations with levels in preen gland were obtained for the control feathers. Consequently, the source of external contamination with organic pollutants onto feathers seems to be endogenous, originating from the preen gland. This is in great contrast to the extensive airborne pollution that has been reported for most heavy metals. In summary, the results of the current study highlight the usefulness of feathers for non-destructive biomonitoring of organic pollutants.

Oestrogenic activity using a recombinant yeast screen assay (RCBA) in South African laboratory water sources

Many chemicals released into the environment are believed to disrupt normal endocrine functions in humans and animals. These endocrine disrupting chemicals (EDCs) affect reproductive health and development. A major group of EDCs that could be responsible for reproductive effects are those that mimic natural oestrogens, known as xeno-oestrogens. A number of in vivo and in vitro screening strategies are being developed to identify and classify xeno-oestrogens, in order to determine whether they pose a health risk to humans and animals. It is also important to be able to apply the assays to environmental samples for monitoring purposes. In South Africa information on the levels of EDCs in water is limited. While establishing the recombinant yeast screen bioassay (RCBA) using the yeast strain Sacchyromyces cerivisiae for oestrogenic activity, problems were experienced with contamination. Four South African laboratory water sources were assessed. From the results it was clear that the water used in the preparation of the medium for the assay was the source of oestrogenic contamination. Care should be taken to eliminate all possible sources of contamination in the test procedures to eliminate the reporting of false positive results. The fact that South African laboratory and surface waters tested positive for estrogenic activity has far reaching implications regarding reproductive and general health. Water SA Vol. 31 (2) 2005: pp.253-256

Conditioned backward probability modeling to identify sources of groundwater contaminants subject to sorption and decay

If contamination is observed in an aquifer, a backward probability model can be used to obtain information about the former position of the observed contamination. A backward location probability density function (PDF) describes the possible former positions of the observed contaminant particle at a specified time in the past. If the source release time is known or can be estimated, the backward location PDF can be used to identify possible source locations. For sorbing solutes, the location PDF depends on the phase (aqueous or sorbed) of the observed contamination and on the phase of the contamination at the source. These PDFs are related to adjoint states of aqueous and sorbed phase concentrations. The adjoint states, however, do not take into account the measured concentrations. Neupauer and Lin (2006) presented an approach for conditioning backward location PDFs on measured concentrations of non‐reactive solutes. In this paper, we present a related conditioning method to identify the location of an instantaneous point source of a solute that exhibits first‐order decay and linear equilibrium or non‐equilibrium sorption. We derive the conditioning equations and present an illustrative example to demonstrate important features of the technique. Finally, we illustrate the use of the conditioned location PDF to identify possible sources of contamination by using data from a trichloroethylene plume at the Massachusetts Military Reservation.

Source characterization using compound composition and stable carbon isotope ratio of PAHs in sediments from lakes, harbor, and shipping waterway

Molecular compositions and compound specific stable carbon isotope ratios of polycyclic aromatic hydrocarbons (PAH) isolated from sediments were used to characterize possible sources of contamination at an urban lake, a harbor, a shipping waterway, and a relatively undisturbed remote lake in the northwest United States. Total PAH concentrations in urban lake sediments ranged from 66.0 to 16,500 μg g − 1 dry wt. with an average of 2600 μg g − 1 , which is ∼ 50, 100, and 400 times higher on average than PAH in harbor (48 μg g − 1 on average), shipping waterway (26 μg g − 1 ), and remote lake (7 μg g − 1 ) sediments, respectively. The PAH distribution patterns, methyl phenanthrene/phenanthrene ratios, and a pyrogenic index at the sites suggest a pyrogenic origin for PAHs. Source characterization using principal component analysis and various molecular indices including C2-dibenzothiophenes/C2-phenanthrenes, C3-dibenzothiophenes/C3-phenanthrenes, and C2-chrysenes/C2-phenanthrenes ratios, was able to differentiate PAH deposited in sediments from the four sites. The uniqueness of the source of the sediment PAHs from urban lake was also illustrated by compound specific stable carbon isotope analysis. It was concluded that urban lake sediments are accumulating PAH from sources that are unique from contamination detected at nearby sites in the same watershed.