Field application of cost-effective sensors for the monitoring of NH3, H2S, and TVOC in environmental treatment facilities and the estimation of odor intensity.

Odor is usually a complex mixture of various compounds. In many countries, odor complaints have been addressed using the air dilution olfactory method (ADOM) to reduce their malodor complaint. In this study, continuous monitoring of ammonia, hydrogen sulfide, and total volatile organic compounds (TVOC) using sensors was conducted in facilities for municipal and livestock wastewater treatment (LWT), and for food waste composting (FWC). Odor intensity was modeled by multivariate linear regression using sensor monitoring data with air dilution measured by the ADOM. In testing the performance of sensors in the lab, all three sensors showed acceptable values for linearity, accuracy, repeatability, lowest detection limit, and response time, so the sensors were acceptable for application in the field. In on-site real-time monitoring, the three sensors functioned well in the three environmental facilities during the testing period. Average ammonia and hydrogen sulfide concentrations were high in the LWT facility, while TVOC showed the highest concentration in the FWC facility. A longer sampling time is necessary for ammonia monitoring. Odor intensity from individual sensor data correlated well to complex odor measured by the ADOM. Finally, we suggest a protocol for field application of sensor monitoring and odor data reproduction.Implications: We suggest a protocol for the field application of sensor monitoring and odor data estimation in this study. This study can be useful to a policy maker and field operator to reduce odor emission through the determination of a more effective treatment technology and removal pathway for individual odorants.

Interference-Robust Transmission in Wireless Sensor Networks.

Low-power wireless sensor networks (WSNs) operating in unlicensed spectrum bands may seriously suffer from interference from other coexisting radio systems, such as IEEE 802.11 wireless local area networks. In this paper, we consider the improvement of the transmission performance of low-power WSNs by adjusting the transmission rate and the payload size in response to the change of co-channel interference. We estimate the probability of transmission failure and the data throughput and then determine the payload size to maximize the throughput performance. We investigate that the transmission time maximizing the normalized throughput is not much affected by the transmission rate, but rather by the interference condition. We adjust the transmission rate and the transmission time in response to the change of the channel and interference condition, respectively. Finally, we verify the performance of the proposed scheme by computer simulation. The simulation results show that the proposed scheme significantly improves data throughput compared with conventional schemes while preserving energy efficiency even in the presence of interference.

Tracing lead pollution sources in abandoned mine areas using stable Pb isotope ratios.

This study focused on Pb isotope ratios of sediments in areas around an abandoned mine to determine if the ratios can be used as a source tracer. For pretreatment, sediment samples were dissolved with mixed acids, and a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS, Nu plasma II) was used to investigate the Pb isotopic composition of the samples. The measured isotope ratios were then corrected for instrumental mass fractionation by measuring the (203)Tl/(205)Tl ratio. Repeated measurements with the NIST SRM 981 reference material showed that the precision of all ratios was below 104 ppm (±2σ) for 50 ng/g. The isotope ratios ((207)Pb/(206)Pb) found were 0.85073 ± 0.0004~0.85373 ± 0.0003 for the main stream, while they were 0.83736 ± 0.0010 for the tributary and 0.84393 ± 0.0002 for the confluence. A binary mixing equation for isotope ratios showed that the contributions of mine lead to neighboring areas were up to 60%. Therefore, Pb isotope ratios can be a good source tracer for areas around abandoned mines.

Development of a pretreatment system for the analysis of atmospheric reduced sulfur compounds.

A new pretreatment system was used to evaluate a technology to analyze reduced sulfur compounds (RSCs). To conduct this research, a self-developed custom dryer (Desolvator) and a thermal desorber system (TDS) were installed in the front of GC/PFPD. The syringe pump inside the TDS was devised in such a way that it can be desorbed in a relatively low desorption temperature and low vacuum (730 Pa). When comparing water removal efficiency of the Desolvator and frequently used Nafion dryer, the removal efficiency of the Desolvator stood between 94.6 and 96.1%, considerably higher and more stable than the Nafion dryer (81.3-94.5%). Moreover, analyses were made under various conditions in order to minimize the loss of samples when analyzing sulfur compounds using the TDS, and it was determined that adsorption temperatures less than -25 °C and a flow rate of 50 mL/min were appropriate for the efficient analysis of these sulfur compounds. Moreover, the desorption flow rate and the degree of a vacuum were found to be significant variables for the RSCs desorption. Besides, it was observed that a peculiar peak was formed by thermal decomposition when some sulfur compounds were rapidly desorbed at high desorption temperatures.

Comparison of compositional characteristics of amino acids between livestock wastewater and carcass leachate.

This study was purposed to examine the use of amino acids as an indicator to determine whether groundwater around carcass burial sites is polluted by livestock wastewater (LW) or carcass leachate (CL). The analysis of samples showed that the average amino acid concentration of carcass leachate (531.897 mg/L; 4341.784 µmol/L) was about 300 times as high as that of livestock wastewater (1.755 mg/L; 16.283 µmol/L). To identify distinct characteristics between LW and CL, six amino acids were paired with one another to calculate their relative composition ratios, which were found to be Leu/Trp (CL 8.39∼98.6, LW 0.89∼4.77), Val/Trp (CL 11.95∼175.38, LW 0.73∼3.62), Lys/Leu (CL 0.01∼0.72, LW 0.96∼8.44), Lys/Ile (CL 0.02∼1.55, LW 1.64∼10.99), Met/Lys (CL 0.14∼0.45, LW 0.03∼0.14), and Ile/Val (CL 0.38∼0.73, LW 0.40∼0.97). The hierarchical clustering result showed that the similarity was 0.617 among the seven LW samples and 0.563 among the seven CL samples, while the similarity between LW and CL samples was 0.198, presenting that these two sources are distinct from each other. All these results indicate that amino acids can be used as a tracer to evaluate if the contamination source is livestock wastewater or carcass leachate. To apply amino acids to tracing pollutants more effectively, however, further studies are needed to understand whether the relative abundance ratios of amino acids are maintained as they are transporting through soils as a medium.

Seasonal variations of monoterpene emissions from Pinus densiflora in East Asia.

The emission rates and compositions of monoterpene from Pinus densiflora were investigated in the Gumsung (GM) and Worak (WM) mountains. The standard emission rates (ERs: ERs is the monoterpene emission rate at standard temperature, 30 degrees C) from P. densiflora ranged from 0.817 to 1.704 (microgC/gdw-h). The ERs and beta-values of total monoterpene were measured at the two study sites (GM and WM). In the spring and summer, the ERs were the highest, while relatively low values (<0.058microgC/gdw-h) were measured in the autumn and winter. In GM and WM sites the beta-value obtained for the different seasons ranged from 0.047 to 0.179, with an average of 0.09. The major monoterpene compounds from P. densiflora were alpha-pinene, myrcene, beta-phellandrene, d-limonene and alpha-terpinene. The fractional compositions of individual monoterpene compounds were significantly different between the two test sites in the summer and winter. The ERs of the older group (31-40 years) were higher than those in the younger group (21-30 years). However, the monoterpene compositions were similar between the two age groups.

Characteristic behavior of peroxyacetyl nitrate (PAN) in Seoul megacity, Korea.

We measured the concentrations of peroxyacetyl nitrate (PAN) and other photochemically reactive species, including O3, NO2, and non-methane hydrocarbons (NMHCs), in the Seoul Metropolitan area (SMA) during May through June in 2004 and 2005. PAN was determined using a fast chromatograph with luminol-based chemiluminescence detection. Mixing ratios of PAN ranged from below the detection limit (0.1ppbv) to 10.4ppbv with an average of 0.8ppbv. O3 concentrations ranged from 0 to 141ppbv. The average PAN/O3 ratio of 0.07 was higher than that observed in cities of Europe and North America (0.02) where control strategies have been enforced to reduce hydrocarbon emissions through extensively reformulated gasoline programs. Strong positive correlations between daily PAN and O3 maxima during the day demonstrate that similar photochemical factors controlled the production of these two chemicals. However, relationships between PAN and its precursors, NO2 and NMHCs, suggest that PAN production was more sensitive to NO2 than NMHCs levels whereas O3 production was limited by the overall availability of NMHCs. It is likely that the compositions of NMHCs in SMA were favorable for PAN production because of the low fractions of oxygenated compounds in automobile fuels. PAN maxima were observed around noon, which was 2-3h earlier than the much broader O3 maxima that occurred in the midafternoon. After reaching the maximum, PAN concentrations rapidly dropped within a few hours, which could be largely due to thermal destruction and to limited production under the typically low NO2 levels that occurred in the early afternoon. The heterogeneous destruction of particulate matter could be an additional sink for PAN in SMA.

Seasonal variations of monoterpene emissions from coniferous trees of different ages in Korea.

Seasonal variations of emission rates and compositions from coniferous species were measured under controlled conditions using a vegetation enclosure method. Total emission rates and compositions of monoterpene compounds from young and adult trees in different seasons were compared. It was found that the total emission rates and the components of monoterpene varied significantly with tree species, age, and season. Total emissions from C. japonica and P. koraiensis were higher for older trees than for younger trees; however, significantly higher emissions were found from younger trees for C. obtusa. Higher monoterpene emission rates from each plant were found in spring and summer compared with autumn and winter emissions.