Historical and Future Stream Temperature Change Predicted by a Lidar‐Based Assessment of Riparian Condition and Channel Width

Riparian forests attenuate solar radiation, thereby mediating an important component of the thermal budget of streams. Here, we investigate the relationship between riparian degradation, stream temperature, and channel width in the Chehalis River Basin, Washington State. We used lidar data to measure canopy opening angle, the angle formed between the channel center and trees on both banks; we assumed historical tree heights and calculated the change in canopy angle relative to historical conditions. We then developed an empirical relationship between canopy angle and water temperature using existing data, and simulated temperatures between 2002 and 2080 by combining a tree growth model with climate change scenarios from the NorWeST regional prediction. The greatest change between historical and current conditions (~7°C) occurred in developed portions of the river network, with the highest values of change predicted at channel widths less than ~40 m. Tree growth lessened climate change increases in maximum temperature and the length of river exceeding biologically critical thresholds by ~50%–60%. Moreover, the maximum temperature of channels with bankfull widths less than ~50 m remained similar to current conditions, despite climate change increases. Our findings are consistent with a possible role for the riparian landscape in explaining the low sensitivity of stream temperatures to air temperatures observed in some small mountain streams.     

Aerosol exposure assessment during reclaimed water utilization in China and risk evaluation in case of Legionella

• The Chinese population exposure habits were surveyed. • The risks of three scenarios of reclaimed water utilization were evaluated by QMRA. • The risks were markedly higher than the threshold (10⁻⁴ pppy) recommended by WHO. • The risks were age-, educational background-, region- and gender-specific. Reclaimed water utilization provides an effective way to alleviate water shortage. However, the residual pathogens in the recycled water like Legionella, could be spread into the air as aerosols through water-to-air transmission process. Inhaling the aerosols by the people nearby increases their susceptibility to diseases. For estimating the health risks associated with the potential exposure of airborne Legionella emitted from the urban use of reclaimed water in China, nationwide questionnaire was designed to investigate the exposure habits of Chinese population in different scenarios. Quantitative microbial risk assessment (QMRA) served as the suitable explanatory tool to estimate the risk. The results indicated that annual infection probability of populations exposed to Legionella for three scenarios, 0.0764 (95% CI: 0.0032–0.6880) for road cleaning, 1.0000 (95% CI: 0.1883–1.0000) for greenfield irrigation, 0.9981 (95% CI: 0.0784–1.0000) for landscape fountain, were markedly higher than the threshold recommended by WHO (10⁻⁴ per person per year (pppy)) according to the concentration distribution of Legionella in the reclaimed water. An age-, educational background-, region- and gender-specific data in annual infection probability also showed different tendencies for some subpopulations. This study provides some detailed information on the health risks from the water reuse in China and will be useful to promote the safe application of reclaimed water in water-deficient areas.     

Anthropogenic pollutants in the Russian Arctic atmosphere: sources and sinks in spring and summer

The 5-day forward and backward trajectories of air mass transport to three Russian Arctic points for each day in April and July over a 10-year period from 1986 to 1995 have been analyzed. The important features and seasonal differences in air exchange processes in various areas of the Arctic have been investigated. Taking into account seasonal variations in aerosol scavenging mechanisms and velocities, the average contributions of large highly industrialized regions of the Russian Arctic air pollution were estimated for April and July. Reasonable correspondence between the calculated mean concentrations for six anthropogenic chemical elements (As, Ni, Pb, V, Zn, Cd) and experimentally determined values have been obtained. The atmospheric pollution transport from the Arctic was studied as yet another way of cleaning the Arctic atmosphere, in addition to the traditionally considered wet and dry depositions onto the surface. The average apportionment of conservative contaminants after passing the observation points was estimated for spring and summer. The air masses passing through the observation points in spring may take about 20–40% of pollutants out of the Arctic. In summer, however, more than 90% of pollutants transported into the Russian Arctic deposit within 5 days onto the surface inside the Arctic region. The monthly average fluxes of six anthropogenic elements onto the surface in the Russian Arctic were estimated for April and July.     

Modeling particle loss in ventilation ducts

Empirical equations were developed and applied to predict losses of 0.01–100 μm airborne particles making a single pass through 120 different ventilation duct runs typical of those found in mid-sized office buildings. For all duct runs, losses were negligible for submicron particles and nearly complete for particles larger than 50 μm. The 50th percentile cut-point diameters were 15 μm in supply runs and 25 μm in return runs. Losses in supply duct runs were higher than in return duct runs, mostly because internal insulation was present in portions of supply duct runs, but absent from return duct runs. Single-pass equations for particle loss in duct runs were combined with models for predicting ventilation system filtration efficiency and particle deposition to indoor surfaces to evaluate the fates of particles of indoor and outdoor origin in an archetypal mechanically ventilated building. Results suggest that duct losses are a minor influence for determining indoor concentrations for most particle sizes. Losses in ducts were of a comparable magnitude to indoor surface losses for most particle sizes. For outdoor air drawn into an unfiltered ventilation system, most particles smaller than 1 μm are exhausted from the building. Large particles deposit within the building, mostly in supply ducts or on indoor surfaces. When filters are present, most particles are either filtered or exhausted. The fates of particles generated indoors follow similar trends as outdoor particles drawn into the building.     

Characterization of aerosol optical properties, chemical composition and mixing states in the winter season in Shanghai, China

Physical and chemical properties of ambient aerosols at the single particle level were studied in Shanghai from December 22 to 28, 2009. A Cavity-Ring-Down Aerosol Extinction Spectrometer（CRD-AES） and a nephelometer were deployed to measure aerosol light extinction and scattering properties, respectively. An Aerosol Time-of-Flight Mass Spectrometer（ATOFMS）was used to detect single particle sizes and chemical composition. Seven particle types were detected. Air parcels arrived at the sampling site from the vicinity of Shanghai until mid-day of December 25, when they started to originate from North China. The aerosol extinction,scattering, and absorption coefficients all dropped sharply when this cold, clean air arrived.Aerosol particles changed from a highly aged type before this meteorological shift to a relatively fresh type afterwards. The aerosol optical properties were dependent on the wind direction.Aerosols with high extinction coefficient and scattering Angstrom exponent（SAE） were observed when the wind blew from the west and northwest, indicating that they were predominantly fine particles. Nitrate and ammonium correlated most strongly with the change in aerosol optical properties. In the elemental carbon/organic carbon（ECOC） particle type, the diurnal trends of single scattering albedo（SSA） and elemental carbon（EC） signal intensity had a negative correlation. We also found a negative correlation（r =-0.87） between high mass-OC particle number fraction and the SSA in a relatively clean period, suggesting that particulate aromatic components might play an important role in light absorption in urban areas.     

Chemical characteristics of size-resolved aerosols in winter in Beijing

Size-resolved aerosols were continuously collected by a Nano Sampler for 13 days at an urban site in Beijing during winter 2012 to measure the chemical composition of ambient aerosol particles. Data collected by the Nano Sampler and an ACSM(Aerodyne Aerosol Chemical Speciation Monitor) were compared. Between the data sets,similar trends and strong correlations were observed,demonstrating the validity of the Nano Sampler. PM10 and PM2.5concentrations during the measurement were 150.5 ± 96.0 μg/m3(mean ± standard variation)and 106.9 ± 71.6 μg/m3,respectively. The PM2.5/PM10 ratio was 0.70 ± 0.10,indicating that PM2.5dominated PM10. The aerosol size distributions showed that three size bins of 0.5–1,1–2.5 and 2.5–10 μm contributed 21.8%,23.3% and 26.0% to the total mass concentration(TMC),respectively. OM(organic matter) and SIA(secondary ionic aerosol,mainly SO42-,NO3-and NH4+) were major components of PM2.5. Secondary compounds(SIA and secondary organic carbon) accounted for half of TMC(about 49.8%) in PM2.5,and suggested that secondary aerosols significantly contributed to the serious particulate matter pollution observed in winter. Coal burning,biomass combustion,vehicle emissions and SIA were found to be the main sources of PM2.5. Mass concentrations of water-soluble ions and undetected materials,as well as their fractions in TMC,strikingly increased with deteriorating particle pollution conditions,while OM and EC(elemental carbon) exhibited different variations,with mass concentrations slightly increasing but fractions in TMC decreasing.     

Typical atmospheric haze during crop harvest season in northeastern China: A case in the Changchun region

This study presents the mass concentrations of PM_(2.5),O_3,SO_2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM_(2.5)at the four sites were daily sampled and analyzed. Most of daily concentrations of SO_2(7–82 μg/m~3),O_3(27–171 μg/m~3) and NOx(14–213 μg/m~3) were below the limits of the National Ambient Air Quality Standard(NAAQS)in China. However,PM_(2.5)concentrations(143–168 μg/m~3) were 2-fold higher than NAAQS.Higher PM_(2.5)concentrations(~ 150 μg/m~3) were measured during the pre-harvest and harvest at the urban site,while PM_(2.5)concentrations significantly increased from 250 to400 μg m~(-3) at suburban and rural sites with widespread biomass burning. At all sites,PM_(2.5)components were dominated by organic carbon(OC) and followed by soluble component sulfate(SO_4~(2-)),ammonium(NH_4~+) and nitrate(NO_3~-). Compared with rural sites,urban site had a higher mineral contribution and lower potassium(K~+and K) contribution to PM_(2.5).Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions(e.g.,biomass burning) and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization(PMF) analysis indicated five important emission contributors in the Changchun region,as follows: secondary aerosol(39%),biomass burning(20%),supply heating(18%),soil/road dust(14%) and traffic(9%).     

Synergetic analysis of springtime air pollution episodes over Gwangju, Korea

The characteristics of springtime aerosols,including their optical and microphysical properties,were analyzed for the months of March to May of 2009 in Gwangju(35.23°N,126.84°E),Korea.A high Light Detection and Ranging(LIDAR)-derived aerosol depolarization ratio(δ) of 0.25 ± 0.04 was determined on dust particles during the observation period.The?ngstr?m exponent values of the 440–870 nm wavelength pair(?_(440–870)) and single-scattering albedo at 675 nm(Ω_(675)) measured by a CIMEL sun/sky radiometer were 0.77 ± 0.19 and 0.95 ±0.01,respectively.The elevated dust layers reached a maximum elevation of 4 km above sea level.Anthropogenic/smoke particles that originated from highly populated/industrialized regions could be distinguished by their relatively smaller particle size(?_(440–870) ranged between1.33 and 1.36) and higher light-absorbing(Ω_(675) of 0.92 ± 0.01) characteristics.These aerosols are mostly distributed at altitudes 1.2 km.The root-mean-square deviation(RMSD) between the aerosol optical depth(AOD,τ) derived from LIDAR_((τ_(LIDAR))) and from the CIMEL sun/sky radiometer_((τ_(CIMEL))) varied with respect to the surface PM10 concentration.The RMSD between τ_(LIDAR) and τ_(CIMEL) was as low as 13% under lower PM_(10) concentration levels( 100 μg/m~3).In contrast,the RMSD between τ_(LIDAR) and τ_(CIMEL) increased three times(~31%) under high surface PM_(10) concentration levels(100 μg/m~3).These results suggest that the accuracy of τ_(LIDAR) is influenced by specific atmospheric conditions,regardless of its uncertainty.     

Characteristics of major secondary ions in typical polluted atmospheric aerosols during autumn in central Taiwan

In autumn of 2008, the chemical characteristics of major secondary ionic aerosols at a suburban site in central Taiwan were measured during an annually occurring season of high pollution. The semicontinuous measurement system measured major soluble inorganic species, including NH(4)(+), NO(3)(-), and SO(4)(2-), in PM(10) with a 15 min resolution time. The atmospheric conditions, except for the influences of typhoons, were dominated by the local sea-land breeze with clear diurnal variations of meteorological parameters and air pollutant concentrations. To evaluate secondary aerosol formation at different ozone levels, daily ozone maximum concentration (O(3,daily max)) was used as an index of photochemical activity for dividing between the heavily polluted period (O(3,daily max) ≧80 ppb) and the lightly polluted period (O(3,daily max)<80 ppb). The concentrations of PM(10), NO(3)(-), SO(4)(2-), NH(4)(+) and total major ions during the heavily polluted period were 1.6, 1.9, 2.4, 2.7 and 2.3 times the concentrations during the lightly polluted period, respectively. Results showed that the daily maximum concentrations of PM(10) occurred around midnight and the daily maximum ozone concentration occurred during daytime. The average concentration of SO(2) was higher during daytime, which could be explained by the transportation of coastal industry emissions to the sampling site. In contrast, the high concentration of NO(2) at night was due to the land breeze flow that transport inland urban air masses toward this site. The simulations of breeze circulations and transitions were reflected in transports and distributions of these pollutants. During heavily polluted periods, NO(3)(-) and NH(4)(+) showed a clear diurnal variations with lower concentrations after midday, possibly due to the thermal volatilization of NH(4)NO(3) during daytime and transport of inland urban plume at night. The diurnal variation of PM(10) showed the similar pattern to that of NO(3)(-) and NH(4)(+) aerosols. This indicated that the formatted secondary aerosols in the inland urban area could be transported to the coastal area by the weak land breeze and deteriorated the air quality in the coastal area at night.