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Spatial outlier detection in the PM10 monitoring network of Normandy (France) Full text
2015
Michel, Bobbia | Michel, Misiti | Yves, Misiti | Jean-Michel, Poggi | Bruno, Portier
We consider hourly PM10 measurements from 22 monitoring stations located in Basse–Normandie and Haute–Normandie regions (France) and also in the neighboring regions. All considered monitoring stations are either urban background stations or rural ones. The paper focuses on the statistical detection of outliers of the hourly PM10 concentrations from a spatial point of view. The general strategy uses a jackknife type approach and is based on the comparison of the actual measurement with some robust spatial prediction. Two spatial predictions are considered: the first one is based on the median of the concentrations of the closest neighboring stations which directly consider weighted concentrations while the second one is based on kriging increments, instead of more traditional pseudo–innovations. The two methods are applied to the PM10 monitoring network in Normandy and are fully implemented by Air Normand (the official association for air quality monitoring in Haute–Normandie) in the Measurements Quality Control process. Some numerical results are provided on recent data from January 1, 2013 to May 31, 2013 to illustrate and compare the two methods.
Show more [+] Less [-]Integrating dispersion modelling and lichen sampling to assess harmful heavy metal pollution around the Karabash copper smelter, Russian Federation Full text
2015
Pollard, Adam S. | Williamson, Ben J. | Taylor, Mark | Purvis, William O. | Goossens, Marc | Reis, Stefan | Aminov, Pavel | Udachin, Valery | Osborne, Nicholas J.
Cu smelting has had a severe impact on the environment around the town of Karabash, Russia. Dispersion modelling has been carried out to estimate atmospheric fallout of metals and metalloids (henceforth termed metals for brevity) from the copper smelter, calibrated and ground-truthed using metal concentrations in transplanted and naturally growing lichens.Lichens (Hypogymnia physodes) were transplanted in June 2011 from a relatively little impacted ‘reference site’ to stations in NE–SW and W–E transects centred on the smelter at Karabash. The transplants were removed during September 2011 and then analysed for As, Cu and Pb. The results were compared with deposition loads estimated using TAPM modelling which was carried out for particles of various sizes, and with simple chemistries, and with the smelter conceptualised as a continuously emitting point source.Variation in the ratio of lichen divided by modelled concentrations was lowest for Pb, ranging from 30.3 to 939.9 and 4.9–107.8 for PM2.5 and PM10, respectively, across eight sample points.The TAPM modelling is in agreement with previous studies that smelter emissions are the major source of environmental Pb deposition around Karabash. Further modelling will be required to determine whether the Pb in the lichens is largely sourced from current smelter airborne emissions or windblown soil particles containing historic additions of Pb.
Show more [+] Less [-]The NET effect of dispersants — a critical review of testing and modelling of surface oil dispersion Full text
2015
Zeinstra-Helfrich, Marieke | Koops, Wierd | Murk, Albertinka J.
Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and transport of the oil.We aim to identify how natural, chemical and mechanical dispersion could be quantified in oil spill models. For each step in the dispersion process, we review available experimental data in order to identify overall trends and propose an algorithm or calculation method. Additionally, the conditions for successful mechanical and chemical dispersion are defined.Two commonly identified key parameters in surface oil dispersion are: oil properties (viscosity and presence of dispersants) and mixing energy (often wind speed). Strikingly, these parameters play a different role in several of the dispersion sub-processes. This may explain difficulties in simply relating overall dispersion effectiveness to the individual parameters.
Show more [+] Less [-]Detection of water quality parameters in Hangzhou Bay using a portable laser fluorometer Full text
2015
Chen, Peng | Pan, Delu | Mao, Zhihua | Tao, Bangyi
A field, light-weight laser fluorometer based on the method of laser induced fluorescence was developed for water quality monitoring. The basic instrument configuration uses a high pulse repetition frequency microchip laser, a confocal reflective fluorescent probe and a broadband hyperspectral micro spectrometer; it weights only about 1.7kg. Simultaneous estimates of three important water quality parameters, namely, chlorophyll a (chl-a), colored dissolved organic matter (CDOM), and total suspended matter (TSM) measured by the laser fluorometer were observed to agree well with those measured by traditional methods (0.27–0.84μgL−3 chl-a, R2=0.88; 0.104–0.295m−1 CDOM absorption, R2=0.90; and 59.8–994.9mgL−3 TSM, R2=0.86) in Hangzhou Bay water. Subsequently, distribution and characteristics of CDOM and chl-a laser fluorescence in Hangzhou Bay were analyzed, which will enhance our understanding of biogeochemical processes in this complex estuarine system at high-resolution, high-frequency and long-term scale.
Show more [+] Less [-]Studies on crude oil removal from pebbles by the application of biodiesel Full text
2015
Oil residues along shorelines are hard to remove after an oil spill. The effect of biodiesel to eliminate crude oil from pebbles alone and in combination with petroleum degrading bacteria was investigated in simulated systems. Adding biodiesel made oil detach from pebbles and formed oil–biodiesel mixtures, most of which remained on top of seawater. The total petroleum hydrocarbon (TPH) removal efficiency increased with biodiesel quantities but the magnitude of augment decreased gradually. When used with petroleum degrading bacteria, the addition of biodiesel (BD), nutrients (NUT) and BD+NUT increased the dehydrogenase activity and decreased the biodegradation half lives. When BD and NUT were replenished at the same time, the TPH removal efficiency was 7.4% higher compared to the total improvement of efficiency when BD and NUT was added separately, indicating an additive effect of biodiesel and nutrients on oil biodegradation.
Show more [+] Less [-]A spatial–seasonal analysis of the oiling risk from shipping traffic to seabirds in the Aleutian Archipelago Full text
2015
Renner, Martin | Kuletz, Kathy J.
Some of the largest seabird concentrations in the northern hemisphere are intersected by major shipping routes in the Aleutian Archipelago. Risk is the product of the probability and the severity incidents in an area. We build a seasonally explicit model of seabird distribution and combine the densities of seabirds with an oil vulnerability index. We use shipping density, as a proxy for the probability of oil spills from shipping accident (or the intensity chronic oil pollution). We find high-risk (above-average seabird and vessel density) areas around Unimak Pass, south of the Alaska Peninsula, near Buldir Island, and north of Attu Island. Risk to seabirds is greater during summer than during winter, but the month of peak risk (May/July) varies depending on how data is analyzed. The area around Unimak Pass stands out for being at high-risk year-round, whereas passes in the western Aleutians are at high risk mostly during summer.
Show more [+] Less [-]Highly recyclable superhydrophobic sponge suitable for the selective sorption of high viscosity oil from water Full text
2015
Wang, Jintao | Geng, Guihong
Inspired by the adhesion of marine mussels, a kind of superhydrophobic oil sorbent was successfully fabricated by robustly immobilizing the micro/nanostructure layer onto the sponge skeleton. The as-prepared sponges possess excellent hydrophobicity with the water contact angle of 154°, which enables the sponge to selectively absorb various oils floating on water surface. The oil sorption capacities of as-prepared sponge for a series of oils can reach 18.3–46.8g/g. The absorbed oil can be recovered by mechanical squeezing and the resulting sponge can be recycled more than 70 cycles while still keeping high oil sorption capability. More importantly, the obtained sponge has excellent affinity to the high viscosity oils. Therefore, the as-prepared sponge might find practical applications in the large-scale removal of oils especially high viscosity oils from water surface.
Show more [+] Less [-]Celebration-induced air quality over a tropical urban station, Pune, India Full text
2015
Devara, Panuganti C.S. | Vijayakumar, Katta | Safai, Pramod D. | Made, P Raju | Rao, Pasumarti S.P.
In this paper, we studied the regional aerosol and air quality over an urban location, Pune, India during the period from 8 to 18 November 2012, encompassing a major Indian celebration, namely, Diwali Festival (12–14 November 2012) and also a clean (control) day (9 November 2012). A suit of ground–based measurements, employing solar radiometers (Microtops II and Cimel Sun–sky radiometer), Nephelometer, and satellite observations carried out over the study region have been applied for these investigations. The study revealed many interesting results which include (i) almost four–fold enhancement in AOD and fine mode dominated aerosol size distribution (ASD) during Diwali compared to clean day conditions; (ii) higher columnar water vapor (H2O), nitrogen dioxide (NO2), and lower ozone (O3) during Diwali period; (iii) higher cooling at bottom (–117W m−2) and top of the atmosphere (–33W m−2) and warming (+82W m−2) in the atmosphere during the festival period, (iv) abundance of fine mode anthropogenic scattering particles associated with greater real part and smaller imaginary part of refractive index, and higher single scattering albedo, (v) higher backscattering coefficient revealing intrusion of more aerosol particles, higher depolarization ratio indicating particles of non–spherical nature, presence of water–phase particles, more polluted smoke and dust particles, (vi) greater attenuation and poor horizontal/vertical visibility, and (vii) dominance of urban industrial/biomass burning aerosols among other aerosol types. These results have been compared with concurrent satellite products and found to be consistent. The results have been further explained with local meteorology, back–trajectory analysis and satellite rapid response images.
Show more [+] Less [-]Influence of dissolved organic nitrogen on Ni bioavailability in Prorocentrum donghaiense and Skeletonema costatum Full text
2015
Huang, Xu-Guang | Li, Hao | Huang, Bang-qin | Liu, Feng-Jiao
Dissolved organic nitrogen (DON) is an important nutrient in the aquatic environment. This study examined the influence of DON addition on the adsorption, absorption, and distribution in macromolecular forms of environmentally deleterious trace metal (Ni) in Prorocentrum donghaiense and Skeletonema costatum over eight days. Ni adsorption and absorption of two species increased with the addition of urea, while Ni adsorption and absorption of two species in the presence of humic substances (HS) decreased. Meanwhile, Ni adsorption and absorption of P. donghaiense were higher than that of S. costatum. Furthermore, Ni contents in the protein fraction of the cells, both in P. donghaiense and S. costatum, were increased with both urea and HS addition. Thus, urea and HS input could impact Ni biogeochemistry and bioavailability, and then affect the biodynamics thereafter.
Show more [+] Less [-]Secondary organic aerosol over an urban environment in a semi–arid region of western India Full text
2015
Sudheer, Athiyarath K. | Rengarajan, Ramabadran | Varun Sheel,
Carbonaceous species in PM10 and PM2.5 samples, collected from an urban location at Ahmedabad in India during summer, were analyzed to study variability in water-soluble organic carbon (WSOC) and secondary organic carbon (SOC) along with atmospheric water vapor content. A significant correlation between WSOC and SOC was found indicating major contribution of soluble organic compounds by secondary organic aerosol formation. A strong inverse dependence of WSOC and SOC on atmospheric water vapor content is observed in both PM10 and PM2.5 (at <45% relative humidity, RH) during daytime; whereas data collected during monsoon season at higher RH conditions do not exhibit such relation. Aerosol liquid water content (LWC) calculated from thermodynamic equilibrium model suggests that the decrease in secondary organic aerosol (SOA) with increase in RH occurs when LWC is absent or insignificant amount. The inverse correlation in summertime indicates possible decrease in the extent of heterogeneous photochemical oxidation of precursor volatile organic compounds on mineral aerosol surface with increase in ambient water vapor. These results have implications for SOA estimations on regional scales especially in arid and semi-arid regions where significant amount of fine mineral dust is present.
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