Palm-Sized Laser Spectrometer with High Robustness and Sensitivity for Trace Gas Detection Using a Novel Double-Layer Toroidal Cell.

A palm-sized laser spectrometer has been developed for detecting trace gases based on tunable diode laser absorption spectroscopy in combination with a novel double-layer toroidal cell. With the benefit of a homemade electronic system and compact optical design, the physical dimensions of the sensor are minimized to 24 × 15× 16 cm3. A toroidal absorption cell, with 84 reflections in 2 layers for an effective optical path length of 8.35 m, was used to enhance the absorption signals of gaseous species. A homemade electronic system was designed for implementing a distributed feedback (DFB) diode laser controller, an analog lock-in amplifier, data acquisition, and communication. Calibration-free scanned wavelength modulation spectroscopy was employed to determine the concentration of the gas and reduce the random fluctuations from electronical noise and mechanical vibration. The measurement of CH4 in ambient air was demonstrated using a DFB laser at 1.653 µm. The rise time and fall time for renewing the gas mixture are approximately 16 and 14 s, respectively. Vibration and temperature tests have been carried out for verifying the performance of the spectrometer, and standard deviations of 0.38 ppm and 0.11 ppm for 20 ppm CH4 at different vibration frequencies and temperatures, respectively, have been determined. According to the Allan deviation analysis, the minimum detection limit for CH4 can reach 22 ppb at an integration time of 57.8 s. The continuous measurement of atmospheric CH4 for 2 days validated the feasibility and robustness of our laser spectrometer, providing a promising laser spectral sensor for deploying in unmanned aerial vehicles or mobile robots.

Implementation of the toroidal absorption cell with multi-layer patterns by a single ring surface.

We developed a type of toroidal multi-pass cell with multi-layer patterns based on the off-axis model. The effective path length of the original toroidal multi-pass cell is extended several roundtrips in comparison with the single-layer pattern, since the inner surface of the toroidal multi-pass cell is more efficiently utilized. The light pattern has been achieved by using the simple ring surface, which is easy to fabricate. The exact analytical equations for the design of the toroidal multi-pass cell were derived based on analytical vector calculations. A series of numerical ray tracing simulations is presented, and the maximum theoretical optical path length that can be reached is 30 m with a setup of 5 cm column radius. Furthermore, two practical spot patterns are demonstrated with a path length of 8.3 m for a two-layer pattern and 10 m for a three-layer pattern, with respective effective volumes of 63 mL and 94 mL. Furthermore, the fringe effect is substantially reduced to less than 0.5% by the usage of our designed mask.

High-speed multi-pass tunable diode laser absorption spectrometer based on frequency-modulation spectroscopy.

We report a multi-pass tunable diode laser absorption spectrometer based on the frequency-modulation spectroscopy (FMS) technique. It has the advantage of high scan speed and is immune to the etalon effect. A multi-pass Herriott-type cell was used in the spectrometer to increase the effective optical length to 17.5 m and compact the physical dimensions of the spectrometer to 60×30×30 cm3. Noise due to low-frequency fluctuation of the laser power and the 1/f noise in the rapid detection are sufficiently reduced by FMS. Interference fringes are effectively suppressed when the modulation frequency equals to integer or half-integer times of their free spectral range (FSR). An absorption line of C2H2 around 1.51 µm was recorded with the spectrometer to demonstrate its capabilities. The response frequency of the spectrometer is up to 100 kHz (10 µs) thanks to the high modulation frequency of FMS. The detection sensitivity of the spectrometer is about 240 ppb (3σ) at 100 kHz measurement repetition rate. The amplitude of the absorption signal is highly linear to the C2H2 concentration in the range of 300 ppb -100 ppm. Based on the Allan variation, the detection limit was determined to be 18 ppb with a detection time of 166 s.

Coke workers' exposure to volatile organic compounds in northern China: a case study in Shanxi Province.

China is the largest coke producer and exporter in the world, and it has been a major concern that large populations of coke workers are exposed to the associated air pollutants such as volatile organic compounds (VOCs). This study aimed to preliminarily quantify the potential exposure to VOCs emitted from two representative coking plants and assess the potential health risks. Air samples from various stages of coking were collected from the topside of coke ovens and various plant areas and then analyzed for benzene, toluene, ethylbenzene, and xylene (BTEX). The time-weighted average (TWA) concentrations were used to quantify the coke oven emission (COE). The TWA concentrations for benzene were 705.6 and 290.4 µg m(-3) in plant A and plant B, respectively, which showed a higher exposure level than those reported in other countries. COE varied on the topside of coke ovens during charging and pushing processes, from 268.3 to 1197.7 µg m(-3) in plant A and 85.4-489.7 µg m(-3) in plant B. Our results indicate that benzene exposure from the diffusion of tar distillation also exerts significant health risks and thus should also be concerned. Charging and pushing activities accounted for nearly 70 % of benzene dose at the topside, and the benzene exposure risks to the coke oven workers in China were higher than those reported by US EPA. Compared to the reported emission sources, the weight-based ratios of average benzene to toluene, ethylbenzene, and xylene in different COE air samples showed unique characteristic profiles. Based on the B/T ratios from this work and from literatures on several major cities in northern China, it was evident that COE contributes significantly to the severe pollution of VOCs in the air of northern China. Future more rigorous studies are warranted to characterize VOC emission profiles in the stack gas of the coking processes in China.

Comparison of three source apportionment methods based on observed and initial HCHO in Taiyuan, China.

Identifying the sources of formaldehyde (HCHO) is key to reducing the pollution of HCHO and ozone (O3) on the ground level. Using the same datasets applied to the positive matrix factorization (PMF) model by (Hua et al., 2023), the initial concentrations of HCHO were estimated using the photochemical age and the sources of observed and initial HCHO were apportioned based on multiple linear regression (MLR) and photochemical age-based parameterization (PCAP) methods. These results suggest that the source of the initial HCHO can better reflect its contribution. The secondary formation contributed to 49.3-69.1 % of initial HCHO at four sites in Taiyuan based on MLR, which was higher (7.4-36.2 %) than the contributions of secondary formation from observed HCHO. The HCHO was mainly affected by anthropogenic secondary (10.8-34.4 %) and background sources (17.4-78.7 %) based on the PCAP method. We compared the results of the HCHO sources from the MLR, PCAP, and PMF models under photochemical loss. There was good agreement among the emission ratios of acetylene-based HCHO obtained by the different methods at the four sites. The correlation analysis of different source apportionment methods illustrated that primary emissions from the PCAP and the MLR model had the greatest correlation (0.22-0.60). Secondary formations from the PMF and MLR models showed good correlations at all four sites, with R values ranging from 0.42 to 0.83. The HCHO peak of diurnal variation simulated by MLR appeared late compared to the other methods, and the difference in daily variation of HCHO from the PMF model was significantly higher than that of PCAP and MLR. The overlapping conclusions of different source apportionment methods should be considered and used to guide efforts to improve air quality.

Urbanization and agriculture intensification jointly enlarge the spatial inequality of river water quality.

Rivers are severely polluted by multiple anthropogenic stressors. An unevenly distributed landscape pattern can aggravate the deterioration of water quality in rivers. Identifying the impacts of landscape patterns on the spatial characteristics of water quality is helpful for river management and water sustainability. Herein we quantified the nationwide water quality degradation in China's rivers and analyzed its responses to spatial patterns of anthropogenic landscapes. The results showed that the spatial patterns of river water quality degradation had a strong spatial inequality and worsened severely in eastern and northern China. The spatial aggregation of agricultural/urban landscape and the water quality degradation exhibits high consistency. Our findings suggested that river water quality would further deteriorate from high spatial aggregation of cities and agricultures, which reminded us that the dispersion of anthropogenic landscape patterns might effectively alleviate water quality pressures.

Spatial characterization of HCHO and reapportionment of its secondary sources considering photochemical loss in Taiyuan, China.

Formaldehyde (HCHO) plays an important role in atmospheric ozone (O3) formation. To accurately identify the sources of HCHO, carbonyls and volatile organic compounds (VOCs) were measured at three urban sites (Taoyuan, TY-U; Jinyuan, JY-U; Xiaodian, XD-U) and a suburban site (Shanglan, SL-B) in Taiyuan during a high O3 period (from July 20 to August 3, 2020). The average mixing ratio of HCHO at XD-U (8.1 ± 2.8 ppbv) was comparable to those at TY-U (7.4 ± 2.1 ppbv) and JY-U (7.0 ± 2.3 ppbv) but higher (p < 0.01) than that at SL-B (4.9 ± 2.3 ppbv). HCHO contributed to 54.3-59.9 % of the total ozone formation potentials (OFPs) of non-methane hydrocarbons (NMHCs) at four sites. The diurnal variation of HCHO concentrations reached a peak value at 12:00-15:00, which may be attributed to the strong photochemical reaction. To obtain more accurate source results of HCHO under the condition of photochemical loss, the initial concentrations of NMHCs were estimated based on photochemical age parameterization and incorporated into the positive matrix factorization (PMF) model (termed IC-PMF). According to the IC-PMF results, secondary formation (SF) contributed the most to HCHO at XD-U (35.6 %) and SL-B (25.1 %), whereas solvent usage (SU) (40.9 %) and coking sources (CS) (36.0 %) were the major sources at TY-U and JY-U, respectively. Compared to the IC-PMF, the conventional PMF analysis based on the observed data underestimated the contributions of SU (100.5-154.2 %) and biogenic sources (BS) (28.5-324.7 %). Further reapportionment of secondary HCHO by multiple linear regression indicated that SU dominated the sources of HCHO at SL-B (28.3 %) and TY-U (41.7 %), while industrial emissions (IE) and CS contributed the most to XD-U (26.6 %) and JY-U (43.0 %) in Taiyuan from north to south, respectively.

[On-line Measurement of Trace Elements in PM2.5 in Winter in Urban Taiyuan, China: Levels and Source Apportionment].

In order to better identify the sources of PM2.5 in Taiyuan, hourly concentrations of 13 trace elements (K, Ca, Ba, Cr, Mn, Fe, Cu, Ni, Zn, As, Se, Pb, and Sr) in PM2.5 were monitored at an urban site in Taiyuan from January 1 to 29, 2022. The pollution characteristics of trace elements were analyzed and sources were apportioned using positive matrix factorization (PMF). The results showed that the average concentration of 13 total trace elements was (3901.6±2611.2) ng·m-3, which accounted for (7.1±7.7)% of PM2.5. The three dominant elements were Fe[(1319.5±1003.5 ng·m-3)], Ca[(1181.0±1241.6 ng·m-3)], and K[(883.3±357.3 ng·m-3)]. The average concentrations of Cr(Ⅵ) (4.6 ng·m-3) and As (11.2 ng·m-3) exceeded the guideline values of the Chinese National Ambient Air Quality Standard (GB 3095-2012) and the World Health Organization. Fugitive dust, vehicle emissions, industry, stainless-steel production, biomass burning and waste incineration, residential coal combustion, and industrial coal combustion were identified by the PMF model, which accounted for 45.5%, 1.4%, 15.8%, 23.7%, 5.5%, and 8.1%, respectively, of the total elements.Compared with those during the stages of pollution development and dissipation, the contributions of industrial coal combustion, residential coal combustion, and biomass burning and waste incineration to the total elements during the pollution maintenance stage of the PM2.5 pollution episode increased significantly, contributing 11.8%, 7.1%, and 28.1%, respectively, of the total elements. These results could provide scientific references for the refined source apportionment of PM2.5 in other areas.

Factors regulating interaction among inorganic nitrogen and phosphorus species, plant uptake, and relevant cycling genes in a weakly alkaline soil treated with biochar and inorganic fertilizer.

To highlight how biochar affects the interaction between inorganic nitrogen species (ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen: NH4+-N, NO3¯-N, and NO2¯-N) and phosphorus species (calcium phosphate, iron phosphate, and aluminum phosphate: CaP, FeP and AlP) in soil and plant uptake of these nutrients, walnut shell (WS)- and corn cob (CC)-derived biochars (0.5 %, 1 %, 2 %, and 4 %, w/w) were added to a weakly alkaline soil, and then Chinese cabbages were planted. The results showed that the changes in soil inorganic nitrogen were related to biochar feedstock, pyrolysis temperature, and application rate. For soil under the active nitrification condition (dominant NO3¯-N), a significant decrease in the NH4+-N/NO3¯-N ratio after biochar addition indicates enhanced nitrification (excluding WS-derived biochars at 2 % and 4 %), which can be explained by the most positive response of ammonia-oxidizing archaeal amoA to biochar addition. The CC-derived biochar more effectively enhanced soil nitrification than WS-derived biochar did. The addition of 4 % of biochars significantly increased soil inorganic phosphorus, and the addition of CC-derived biochars more effectively increased Ca2P than WS-derived biochars. Biochars significantly decreased plant uptake of phosphorus, while generally had little influence on plant uptake of nitrogen. Interestingly, NO2¯-N in soil significantly positively correlated with total phosphorus in both soil and plant, and significantly negatively correlated with phoC, indicating that a certain degree of NO2¯-N accumulation in soil slightly facilitated plant uptake of phosphorus but inhibited phoC-harboring bacteria. The NO3¯-N in soil significantly positively correlated with Ca2P and Ca8P, while the NH4+-N/NO3¯-N ratio significantly negatively correlated with Ca10P and FeP, indicating that the enhanced nitrification seemed to facilitate the change in phosphorus to readly available ones. This study will help determine how to scientifically and rationally use biochar to regulate inorganic nitrogen and phosphorus species in soil and plant uptake of these nutrients.

Emission Characteristics and Health Risks of Volatile Organic Compounds (VOCs) Measured in a Typical Recycled Rubber Plant in China.

The continued development of the automotive industry has led to a rapid increase in the amount of waste rubber tires, the problem of "black pollution" has become more serious but is often ignored. In this study, the emission characteristics, health risks, and environmental effects of volatile organic compounds (VOCs) from a typical, recycled rubber plant were studied. A total of 15 samples were collected by summa canisters, and 100 VOC species were detected by the GC/MS-FID system. In this study, the total VOCs (TVOCs) concentration ranged from 1000 ± 99 to 19,700 ± 19,000 µg/m3, aromatics and alkanes were the predominant components, and m/p-xylene (14.63 ± 4.07%-48.87 ± 3.20%) could be possibly regarded as a VOCs emission marker. We also found that specific similarities and differences in VOCs emission characteristics in each process were affected by raw materials, production conditions, and process equipment. The assessment of health risks showed that devulcanizing and cooling had both non-carcinogenic and carcinogenic risks, yarding had carcinogenic risks, and open training and refining had potential carcinogenic risks. Moreover, m/p-xylene and benzene were the main non-carcinogenic species, while benzene, ethylbenzene, and carbon tetrachloride were the dominant risk compounds. In the evaluation results of LOH, m/p-xylene (25.26-67.87%) was identified as the most key individual species and should be prioritized for control. In conclusion, the research results will provide the necessary reference to standardize the measurement method of the VOCs source component spectrum and build a localized source component spectrum.

Heavy metals removal from sewage sludge with mixed chelators of N, N-bis(carboxymethyl) glutamic acid and citric acid.

The mixed chelators (MC) of N, N-bis(carboxymethyl) glutamic acid (GLDA) and citric acid (CA), which were biodegradable chelating ligand, were employed to remove heavy metals from sewage sludge. The extraction of Cd, Cu, Zn, Mn, and Cr from sludge was studied under different experimental conditions. Results showed that the removal efficiencies of heavy metals from both sludges were the highest with MC of GLDA and CA at the molar ratio of 1:5. For the sludge of plant A, the extraction efficiencies increased with increasing contact time, but only slowly increase was observed after 24 h. However, for the sludge of plant B, the removal efficiencies were significantly decreased after 16 h, and sharply decreased after 24 h. The removal efficiencies of heavy metals decreased with the increase of the solution pH, while they increased with the increase of the solution concentration. For the sludge of plant A, single washing with 200 mmol·L-1 MC might be favourable to remove heavy metals. However, for the sludge of plant B, duplicate washing with 100 mmol·L-1 MC could remove much more heavy metals. The concentration of Cu in sludge of plant B decreased from 695.79-139.16 mg·kg-1, which was conformed to the standard (GB 4284-2018). These results suggested that MC may be useful and environmentally friendly chelators in the removal of heavy metals from sewage sludge.

Substantial changes of chemical composition and sources of fine particles during the period of COVID-19 pandemic in Taiyuan, Northern China.

To better understand the effects of COVID-19 on air quality in Taiyuan, hourly in situ measurements of PM2.5(particulate matter with an aerodynamic diameter less than 2.5 mm) and chemical components (water-soluble ions, organic carbon (OC), elemental carbon (EC), and trace elements) were conducted before (P1: 1 January-23 January 2020) and during (P2: 24 January-15 February 2020) the coronavirus disease 2019 (COVID-19) outbreak. The average concentrations of PM2.5 dropped from 122.0 µg/m3 during P1 to 83.3 µg/m3 during P2. Compared with P1, except for fireworks burning-related chemical components (K+, Mg2+, K, Cu, Ba), the concentrations of other chemical components of PM2.5 decreased by14.9-69.8%. Although the large decrease of some emission sources, fireworks burning still resulted in the occurrence of pollution events during P2. The analysis results of positive matrix factorization model suggested that six PM2.5 sources changed significantly before and during the outbreak of the epidemic. The contributions of vehicle emission, industrial process, and dust to PM2.5 decreased from 23.1%, 3.5%, and 4.0% during P1 to 7.7%, 3.4%, and 2.3% during P2, respectively, whereas the contributions of secondary inorganic aerosol, fireworks burning, and coal combustion to PM2.5 increased from 62.0%, 1.8%, and 5.5% to 71.5%, 9.0%, and 6.2%, respectively. The source apportionment results were also affected by air mass transport. The largest reductions of vehicle emission, industrial process, and dust source were distinctly seen for the air masses from northwest. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11869-021-01082-y.

Spatial Distribution, Potential Sources, and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Soils under Different Land-Use Covers of Shanxi Province, North China.

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment and pose a serious threat to the soil ecosystem. In order to better understand the health risks for residents exposed to PAH-contaminated soil, 173 surface soil samples were collected in Shanxi Province, China, to detect the levels of 16 priority PAHs. The spatial distribution patterns of PAHs were explored using interpolation and spatial clustering analysis, and the probable sources of soil PAHs were identified for different land-use covers. The results indicate that the soil Σ16 PAH concentration ranged from 22.12 to 1337.82 ng g-1, with a mean of 224.21 ng g-1. The soils were weakly to moderately contaminated by high molecular weight PAHs (3-5 ring) and the Taiyuan-Linfen Basin was the most polluted areas. In addition, the concentration of soil PAHs on construction land was higher than that on other land-use covers. Key sources of soil PAHs were related to industrial activities dominated by coal burning, coking, and heavy traffic. Based on the exposure risk assessment of PAHs, more than 10% of the area was revealed to be likely to suffer from high carcinogenic risks for children. The study maps the high-risk distribution of soil PAHs in Shanxi Province and provides PAH pollution reduction strategies for policy makers to prevent adverse health risks to residents.

Distribution of the Soil PAHs and Health Risk Influenced by Coal Usage Processes in Taiyuan City, Northern China.

The quality of urban soil is closely related to the safety of public places and the guarantee of food quality. This study investigated the level, distribution, source, and carcinogenic risk of 16 U.S. EPA (Environmental Protection Agency) priority polycyclic aromatic hydrocarbons (PAHs) in urban, agricultural, and montane soil in Taiyuan. The ∑16PAHs level varied from 104.78 to 6594.63 ng g-1 with a mean of 922.93 ng g-1, and 47.73% of the soil samples were severely contaminated, with a concentration higher than 600 ng g-1. PAHs with higher molecular weight (≥4 rings) were dominant in PAHs profiles accounting for 80.92%. In the spatial distribution of PAHs, hotspots of ∑16 PAHs were observed near the industries, indicating pollutants emitted by the industries directly affect the surrounding soil quality. The sources identified by positive matrix factorization (PMF) indicated: coal combustion (40.77%), vehicle exhausts (32.94%), biomass combustion (14.89%), and coking source (11.40%). Coal-related sources (coal and coking sources) were the major contributors (52.17%) to PAHs and carcinogenic risk (46.48%) assessed by BaP toxic equivalent concentration in total soils. Therefore, the extensive usage of coal was the leading factor for PAH pollution and health risk in Taiyuan soil.

The investigation of nematocidal activity in Stenotrophomonas maltophilia G2 and characterization of a novel virulence serine protease.

The Gram-negative bacterium Stenotrophomonas maltophilia G2 was isolated from a soil sample and was found to have high nematotoxic activity against a free-living nematode, Panagrellus redivivus, and a plant-parasitic nematode, Bursaphelenchus xylophilus. The analysis of virulence factors revealed that although the small molecular metabolites participated in nematode killing, the crude extracellular protein extract from the bacterial culture supernatant contributed significantly to its nematocidal activity. An extracellular protease was purified by chromatography, and its effects on degrading purified nematode cuticle and killing living nematodes were confirmed experimentally. Characterization of this purified protease revealed that the application of phenylmethylsulphonyl fluoride, an inhibitor of serine proteases, could completely abolish its proteolytic activity. The results from N-terminal amino acid sequencing showed no similarity with any known serine protease in S. maltophilia, suggesting a novel virulence serine protease was obtained. Our study is the first to show the nematocidal activity of S. maltophilia, and we identified a novel serine protease as an important pathogenicity factor.

Bioaccumulation and biomagnification of short-chain chlorinated paraffins in marine organisms from the Pearl River Estuary, South China.

Short-chain chlorinated paraffins (SCCPs) are a series of new persistent organic pollutants, posing a risk of significant adverse effects to biota. Increasing attention has been paid to SCCP pollution in China as large amounts of chlorinated paraffin (CP) products containing SCCPs have been produced and used there. However, knowledge of the bioaccumulation of SCCPs in marine organisms from the Pearl River Estuary (PRE), Southern China, is still scarce. In this study, SCCP concentrations were measured in seawater, sediments, and marine organisms from the PRE. SCCP concentrations ranged from 180 to 460 ng/L in seawater, from 180 to 620 ng/g dry weight (dw) in sediments, and from 870 to 36,000 ng/g lipid weight (lw) in marine biota samples. C10-11 SCCPs were the predominant homologues in all the samples, with an average abundance of 68% in seawater, 57% in sediments, and 56-77% in marine organisms. However, chlorine patterns of SCCPs in seawater, sediments, and marine organisms were different. Cl8-10 SCCPs dominated in sediments, whereas Cl5-7 SCCPs were the predominant SCCP homologues in water and most organism species. The logarithm bioaccumulation factors (BAFs) of SCCPs ranged from 1.6 to 3.0, and increased significantly with the increase of Kow values for most marine biota species, indicating that Kow was the major factor controlling the bioaccumulation of SCCPs and that SCCPs with higher lipophilicity were more prone to being bioaccumulated from water. Opposite to that observed for log BAFs, biota-sediment accumulation factors of specific SCCPs (range: 0.01-30) decreased significantly with the increase of Kow values. The biomagnification factor of total SCCPs for oyster-mangrove crab was 2.40, implying the potential biomagnification of SCCPs for benthos in the PRE.

Short-chain chlorinated paraffins in fish from two developed regions of China: Occurrence, influencing factors and implication for human exposure via consumption.

The risk associated with human exposure to short-chain chlorinated paraffins (SCCPs) via dietary intake are of great concern because of the bioaccumulation potential of SCCPs in biota and adverse effects. Fish are an important food source for human beings. However, there is a paucity of studies on human exposure to SCCPs via fish consumption. In this study, SCCPs were measured in frequently consumed river fish from the Pearl River Delta, and farmed freshwater fish and wild sea fish from the Yangtze River Delta. Lipid-normalized SCCP levels in river fish ranged from 3000 to 41,000 ng/g lipid weight (lw), with an average of 16,000 ±â€¯12,000 ng/g lw. SCCP concentrations in farmed fish were significantly lower than those in river fish (p < 0.05), but significantly higher than those in sea fish (p < 0.05). Homologue patterns of SCCPs in river fish, farmed fish and sea fish were similar, with C10-11Cl6-7 SCCPs being the predominant homologues. SCCP concentrations in river fish increased significantly with increasing lipid content (p < 0.01), indicating that lipid content was a controlling factor influencing SCCP concentrations. Body length and weight also played important roles in SCCP concentrations in river fish, as SCCP concentrations decreased with the increase of body length and weight of breams, keeled mullets and tilapias. Although risk assessment implied no significant risk for human exposure to SCCPs via consuming fish collected in this study, the estimated daily intakes indicated that the consumption of sea fish was safer than farmed freshwater fish.

Simultaneous detection of atmospheric CO and CH4 based on TDLAS using a single 2.3 µm DFB laser.

A laser-based spectrometer with a physical size of 60× 30 ×25 cm3 has been developed to continuously monitor CO and CH4 in atmosphere based on tunable diode laser absorption spectroscopy (TDLAS). Two neighboring lines of CO and CH4 around 2.3 µm were selected as candidates for simultaneous measurement by a single diode distributed feedback (DFB) laser. A special Herriott-type multipass absorption cell, with a 72 m optical path length, was designed and used to enhance the absorption signals of sample gases. Normalized wavelength modulation spectroscopy was applied to improve the sensitivity and robustness of the spectrometer and it was implemented on a home-made electronic system based on field programmable gate array (FPGA). Meanwhile, the electronic system controlled the temperature and current of DFB laser with the precision of 0.01 °C and 40 ppm. The 2nd-harmonic signals normalized by the corresponding 1st-harmonic signals for both CO and CH4 are of high linear response to their concentrations in the range of 0.046-4.6 ppm and 0.487-48.7 ppm, respectively. According to the Allan variance, respective minimum detection limits for CO and CH4 are 0.73 ppb and 36 ppb at 122 s and 137 s. As an application example, the spectrometer has been validated through real-time and in-situ measurement of atmospheric CO and CH4 for 48 h.

[Characteristics and Sources of Dissolved Heavy Metals in Summer Precipitation of Taiyuan City, China].

To investigate the characteristics and sources of dissolved heavy metals in precipitation of Taiyuan, 61 precipitation samples were collected using an automated dry and wet sampler from 2013 to 2015 during summertime. The concentrations of 12 dissolved heavy metals were detected using ICP-MS, and wet deposition fluxes and sources were analyzed. The results showed that the pH ranged from 4.34 to 7.95, with a volume-weighted mean of 5.37. The mean concentration of the dissolved heavy metals was 236.931 µg·L-1, with a range of 66.324 to 1029.212 µg·L-1. Zn and Fe were the major components, together accounting for 53.39% of the total concentrations. The wet deposition fluxes of the 12 dissolved heavy metals reached 1.735 mg·(m2·d)-1. The enrichment factors of Ba, Cu, Sr, Zn, As, Cd, and Pb were all in excess of 100, suggesting that these metals were seriously influenced by anthropogenic activities. Results from positive matrix factorization (PMF) indicated that steel smelting emissions, coal combustion, vehicle emissions, and crustal dusts were the major sources of heavy metals in the precipitation of Taiyuan City, with average contributions of 38.34%, 23.06%, 20.45%, and 18.15%, respectively. According to backward trajectory analysis, air masses from the southwest and southeast directions contributed the most to precipitation during summer in Taiyuan, with percentages of 38 and 35, respectively. The southern industrial areas located in the Yuncheng-Linfen-Jinzhong and Jincheng-Changzhi-Jinzhong regions should be paid more attention.

Effect of mixed chelators of EDTA, GLDA, and citric acid on bioavailability of residual heavy metals in soils and soil properties.

Soil washing is an effective technology for the remediation of multi-metal contaminated soils. However, bioavailability of residual heavy metals in soils and soil properties could be changed during washing processes. This study investigated the effects of EDTA, FeCl3 and mixed chelators (MC) on bioavailability of residual heavy metals in soils and soil biological properties after soil washing. The results showed that soil washing by chelators successfully decreased the total concentration of heavy metals in soils, while it did not effectively decrease the exchangeable fraction of heavy metals, especially for calcareous contaminated soil. The toxic effects of the washed soils seemed to exhibit higher correlations with the changes in the soil properties such as soil pH and nutrient concentrations. As compared with FeCl3 and EDTA, MC tended to moderately change soil properties (e.g., pH, total N, available N, available P, and exchangeable K, Ca, and Mg). Additionally, MC-washed soil had the least influence on the soil enzymes activities, and had the highest germination and growth of Chinese cabbage. Accordingly, MC is a moderate washing solution in the removal of heavy metals from multi-metal contaminated soils, and had minimal negative effects on soil qualities.