Calibration of polyurethane foam (PUF) disk passive air samplers for quantitative measurement of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs): Factors influencing sampling rates.

PUF disk passive air samplers are increasingly employed for monitoring of POPs in ambient air. In order to utilize them as quantitative sampling devices, a calibration experiment was conducted. Time integrated indoor air concentrations of PCBs and PBDEs were obtained from a low volume air sampler operated over a 50d period alongside the PUF disk samplers in the same office microenvironment. Passive sampling rates for the fully-sheltered sampler design employed in our research were determined for the 51 PCB and 7 PBDE congeners detected in all calibration samples. These values varied from .57 to 1.55m(3)d(-1) for individual PCBs and from 1.1 to 1.9m(3)d(-1) for PBDEs. These values are appreciably lower than those reported elsewhere for different PUF disk sampler designs (e.g. partially sheltered) employed under different conditions (e.g. in outdoor air), and derived using different calibration experiment configurations. This suggests that sampling rates derived for a specific sampler configuration deployed under specific environmental conditions, should not be extrapolated to different sampler configurations. Furthermore, our observation of variable congener-specific sampling rates (consistent with other studies), implies that more research is required in order to understand fully the factors that influence sampling rates. Analysis of wipe samples taken from the inside of the sampler housing, revealed evidence that the housing surface scavenges particle bound PBDEs

Penerapan Metode Passive Sampler Untuk Analisa No2 Udara Ambien Di Beberapa Lokasi Di Jakarta Dan Sekitarnya

Analisa polutan udara ambien seperti NO2, SO2, O3 dan lain-lain denganmenggunakan Metode Passive Sampler telah banyak digunakan di negara-negara maju seperti Jepang, Thailand, China, USA. Sedangkan di Indonesia, metode ini masih belum dikenal luas. Metode ini memiliki banyak kelebihan dibanding dengan metode lain, antara lain mudah dibawa dan mempunyai tingkat mobilitas yang tinggi, dapat digunakan untuk menganalisa udara pada kondisi cuaca yang berbeda dll.Dalam paper ini, penulis bekerja sama dengan Universitas Tokushima, Jepang telah mencoba menerapkan metode Passive Sampler yang dikembangkan oleh Yanagisawa(1) untuk menganalisa konsentrasi NO2 dalam udara ambien di beberapa lokasi di Jakarta dan sekitarnya dari bulan Januari 1997 sampai Agustus 1997. Hasil analisa menunjukkan bahwa kandungan NO2 udara ambien di wilayah Jakarta dan sekitarnya belum melebihi nilai ambang batas yang ditentukan

Aplikasi Passive Air Sampler Untuk Persistent Organic Pollutants Di Udara Ambien

Aplikasi passive air sampler (PAS) untuk pengukuran persistent organic pollutants (POPs) di udara ambien di Indonesia penting dipertimbangkan mengingat masih terbatasnya informasi POPs di udara ambien. Pengambilan sampel POPs dengan pasif ini lebih mudah dan efisien dibandingkan secara aktif. POPs sudah dilarang penggunaannya, namun karena sifatnya yang persisten POPs masih ditemukan di lingkungan. Tujuan penulisan ini untuk menyampaiakan hasil worskhop yang dilakukan di KORDI kerjasama AMETEC-UNU dalam aplikasi PAS untuk pengukuran POPS di udara ambien. PAS yang berisi poliurethan foam (PUF) dipaparkan selama 63 hari di daerah rural Citeko-Puncak dan di urban Cawang Jakarta untuk mengambil sampel gas secara pasif. Hasil pengukuran menunjukkan bahwa beberapa senyawa POPs masih terdeteksi di udara ambien dengan konsentrasi di urban Jakarta lebih tinggi dibandingkan di rural Citeko Bogor. POPs yang terdeteksi di udara ambien adalah HCB, trans-chlordane, cis-chlordane, trans-nonachlor, PCBs, DDT dan turunannya yaitu pp'-DDT, op'-DDT, pp'-DDD, pp'-DDE, dengan kisaran konsentrasi 0.012-0.167 ng/m3. HCB di rural area cenderung berasal dari global transportasi. Total DDT di urban lebih tinggi dibandingkan dengan di rural namun rasio DDT/ DDE>1 yang ditemukan di rural area menunjukkan adanya indikasi terjadi masukan baru senyawa DDT. Rasio t rans chlordan/cis chlordane (TT/CC)>1,2 di urban juga menunjukkan indikasi terjadinya masukan baru senyawa chlordane. PCB di urban area terdeteksi lebih tinggi dan variasi lebih banyak dibandingkan di rural area, sehingga masih dimungkinkan adanya sumber pencemar lokal. Identifikasi lebih lanjut senyawa POPs yang sudah dilarang penting dilakukan untuk mendukung upaya pengawasan keberadaan senyawa POPs secara ilegal

Laboratory Development of a Passive Proportional Sampler for Overland FlowStudies in Agricultural Fields

peer-reviewedWater-quality in many rivers remains poor and needs to be improved. Diffuse pollution continues to cause difficulties. Some instruments are available which can monitor pollution of rivers from land. They allow measurement and sampling of overland flow (OLF), but they do not offer the precision required (proportional sampling and samples 0.1% of OLF). A laboratory unit was constructed to mimic instrument performance in the field. This was used to test three sampler designs. A V-notch weir was used in the first sampler and a Sutro weir in the second and third as this unit possessed a proportional discharge to head ratio, which the Vnotch weir did not have. Other parameters investigated included ground slope, sampler slope, pipe size and port location. The remaining issues of nozzle size (0.7, 1.0 and 2.0 mm), the number of 1.0 mm nozzles and the effect of aspiration were investigated. The arrangement with the Sutro weir and three 1.0 mm nozzles in series gave proportional discharge and the target low sampling rate of 0.1%. This will allow the calculation of sediment and chemical losses for the monitored area and will put the loss in context with other losses in a catchment

Speeding up Glauber Dynamics for Random Generation of Independent Sets

The maximum independent set (MIS) problem is a well-studied combinatorial optimization problem that naturally arises in many applications, such as wireless communication, information theory and statistical mechanics. MIS problem is NP-hard, thus many results in the literature focus on fast generation of maximal independent sets of high cardinality. One possibility is to combine Gibbs sampling with coupling from the past arguments to detect convergence to the stationary regime. This results in a sampling procedure with time complexity that depends on the mixing time of the Glauber dynamics Markov chain. We propose an adaptive method for random event generation in the Glauber dynamics that considers only the events that are effective in the coupling from the past scheme, accelerating the convergence time of the Gibbs sampling algorithm

Annual variability in the radiocarbon age and source of dissolved CO2 in a peatland stream

Radiocarbon dating has the capacity to significantly improve our understanding of the aquatic carbon cycle. In this study we used a new passive sampler to measure the radiocarbon (14C) and stable carbon (δ13C) isotopic composition of dissolved CO2 for the first time in a peatland stream throughout a complete year (May 2010 – June 2011). The in-stream sampling system collected time-integrated samples of CO2 continuously over approximately one month periods. The rate of CO2 trapping was proportional to independently measured streamwater CO2 concentrations, demonstrating that passive samplers can be used to estimate the time-averaged dissolved CO2 concentration of streamwater. While there was little variation and no clear trend in δ13CO2 values (suggesting a consistent CO2 source), we found a clear temporal pattern in the 14C concentration of dissolved CO2. The 14C age of CO2 varied from 707±35 to 1210±39 years BP, with the youngest CO2 in the autumn and oldest in spring/early summer. Mean stream discharge and 14C content of dissolved CO2 were positively correlated. We suggest that the observed pattern in the 14C content of dissolved CO2 reflects changes in its origin, with older carbon derived from deeper parts of the peat profile contributing proportionally more gaseous carbon during periods of low stream flow

Targeted monitoring for human pharmaceuticals in vulnerable source and final waters

A range of pharmaceuticals has been detected in soils, surface waters and groundwaters across the world. While the reported concentrations are generally low (i.e. sub μg l-1 in surface waters), the substances have been observed throughout the year across a variety of hydrological, climatic and land-use settings. As a result, questions have been raised over the potential for pharmaceuticals in surface waters to enter drinking water supplies and to affect consumers. In a previous Drinking Water Inspectorate (DWI) funded study, results from a simple exposure model were used alongside information on therapeutic doses of pharmaceuticals to identify pharmaceuticals that are likely to be of most concern in UK drinking water sources. However, this previous study was entirely desk-based and did not involve any experimental measurements of pharmaceutical concentrations. The current study was therefore performed to generate actual measurements on the occurrence of pharmaceuticals in source and treated waters in England. The study considered a range of pharmaceutical compounds and their metabolites that have either a) high predicted exposure concentrations; b) toxicological concerns; or c) a low predicted exposure to therapeutic dose ratio. An illicit drug and its major metabolite were also investigated. The study compounds (in total 17) covered a range of chemical classes and varied in terms of their physico-chemical properties. The study was done at four sites where concentrations in source water at the drinking water treatment abstraction point were predicted to be some of the greatest in England. The study therefore is likely to provide a ‘worst case’ assessment of potential human exposure to pharmaceuticals in drinking water in England and Wales. Ten of the 17 study compounds were detected in untreated source waters at sub-μg/l concentrations. Six of these compounds (namely, benzoylecgonine (a metabolite of cocaine), caffeine, carbamazepine (an antiepileptic medicine), carbamazepine epoxide (a metabolite of carbamazepine), ibuprofen and naproxen (both non-steroidal anti-inflammatory drugs) were also detected in treated drinking water. With the exception of carbamazepine epoxide, concentrations in treated drinking water were generally significantly lower than in source water. Even though England is a densely populated country and in some regions there is limited dilution of wastewater effluents, these observations, made at sites that were predicted to have some of the highest concentrations of pharmaceuticals in England and Wales, are in line with results from similar studies performed in other countries. Comparison of measured concentrations of the study compounds in drinking waters with information on therapeutic doses demonstrated that levels of these compounds in drinking water in England are many orders of magnitude lower than levels that are given to patients therapeutically. It would therefore appear that the low or non-detectable levels of pharmaceuticals and illicit drugs present in drinking waters in England and Wales do not pose an appreciable risk to human health