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•HCB, p,p’-DDD and δ-HCH were the primary OCPs contaminants in soil.•DDTs and HCHs have undergone an aging process in Larsemann Hills.•Local station activities contributing to the ...organic pollutants are limited to specific areas.
Antarctica is widely regarded as a sink for persistent organic pollutants (POPs). However, there is a scarcity of data on the occurrence and spatial pattern of POPs in Antarctica, especially in the cold-xeric East Antarctica. Here, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in soils from the Larsemann Hills, the second-largest ice-free area along East Antarctica, were investigated. It is shown that the main OCP contaminants were HCB, p,p’-DDD and δ-HCH (3.7–1522.3 pg g−1, 38.2–2276.6 pg g−1 and < LOD–570 pg g−1, respectively). OCPs in soils were primarily caused by long-distance atmospheric transport, but local sources can be found in areas heavily impacted by local human activities. Among DDTs and HCHs, only p,p’-DDD and δ-HCH were detected, indicating that DDTs and HCHs have aged. For PCBs (14.1–993.4 pg g−1), low-chlorinated PCB congeners were found in soil samples far from the station areas (Zhongshan, Progress II, and Progress I), possibly due to long-range atmospheric transport, while high levels of high-chlorinated PCB were found in the soils inside the station area (Law Base) and close to the main road, possibly associated with local station activities. Among the measured PBDEs (81.8–695.5 pg g−1), BDE-209 was the most frequently observed species, and the low-BDE found in soil samples could be from BDE-209 photodegradation. The majority of samples containing high concentrations of BDE-209 are concentrated in the station areas, implying that its source may be related to local station activities.
A detailed investigation was conducted to understand the contamination characteristics of a selected set of potentially toxic metals in Shanghai. The amount of Pb, Zn, Cu, Cr, Cd and Ni were ...determined from 273 soil/dust samples collected within urban area. The results indicated that concentration of all metals except Ni in soils was significant, and metal pollution was even severer in roadside dust. A series of metal spatial distribution maps were created through geostatistical analysis, and the pollution hotspots tended to associate with city core area, major road junctions, and the regions close to industrial zones. In attempt of identifying the source of metals through geostatistical and multivariate statistical analyses, it was concluded as follows: Pb, Zn and Cu mainly originated from traffic contaminants; soil Ni was associated with natural concentration; Cd largely came from point-sourced industrial pollution; and Cr, Ni in dust were mainly related to atmospheric deposition.
Human activities have led to high accumulation of potentially toxic metals in urban soils and roadside dust of Shanghai.
Urban and suburban road dust samples were collected in the most populated city of China, Shanghai. Size fractions of dust particles were analyzed; metal levels of the dust were also measured. Human ...exposure to individual toxic metals through road dust was assessed for both children and adults. The results showed that dust particles from urban and suburban road were presented similar size distribution pattern, with most particles in the range of 100–400
μm. Urban road dust consisted of higher proportions of inhalable, thoracic and respirable particles with increased risk of adverse effects to human. In general, mean grain sizes of urban road dust were smaller than suburban dust. Total organic carbon contents and levels of Pb, Cd, Cu, Zn, Ni, Cr in urban dust were higher than those of suburban dust. But the concentrations of As and Hg from suburban dust were higher, indicting a different main source. The exposure pathway which resulted in the highest level of risk for human exposed to road dust was ingestion of this material, which was followed by dermal contact. Except for some locations, risk values of both cancer and non-cancer obtained in this study were in the receivable range on the whole. Children had greater health risks than adults. The overall risks of non-cancer in urban area were higher than those in suburban area, but the values of cancer in the two areas were comparable. As for the aggregate noncarcinogenic risk, Pb was of most concern regarding the potential occurrence of health impacts. Of the three carcinogenic metals As, Cr and Cd, the only mean risk higher than 10
−6 was Cr, accounting for a great percentage (95%) of the overall risk of cancer. Hence, potentially adverse health effects arising from Pb and Cr in road dust should arouse wide concern.
Abstract
In recent years, the emissions control in nitrogen oxides (NO
x
) was conducted across China, but how the concentrations of NO
x
and its product ozone (O
3
) in the atmosphere varied in ...space and time remains uncertain. Here, the spatial and temporal distributions of nitrogen dioxide (NO
2
) and O
3
in 348 cities of China based on the hourly concentrations data during 2015–2020 were investigated, and the relationships among NO
2
, O
3
and meteorological and socioeconomic parameters were explored. It is shown that higher NO
2
and O
3
concentrations were mainly distributed in North, East and Central China, which are economically developed and densely populated regions. The annual mean concentrations of NO
2
increased from 2015 to 2017 but decreased from 2017 to 2020. The annual variations in O
3
generally exhibited an upward trend in 2015–2019 but decreased by 5% from 2019 to 2020. About 74% and 78% of cities had a decline in NO
2
and O
3
in 2020, respectively, compared to 2019, due to the limits of the motorized transports and industrial production activities during COVID-19 lockdown. The monthly mean concentrations of NO
2
showed an unusual decrease in February in all regions due to the reduced emissions during the Chinese Spring Festival holidays. Compared to 2019, the mean concentrations of NO
2
in January, February and March, 2020 during COVID-19 lockdown decreased by 16%, 28% and 20%, respectively; O
3
increased by 13% and 14% in January and February, respectively, but decreased by 2% in March, 2020. NO
2
and O
3
concentrations are likely associated with anthropogenic and natural emissions. In addition, meteorological parameters can affect NO
2
and O
3
concentrations by influencing the production process, the diffusion and local accumulation, and the regional circulations.
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•Perchlorate between 31°N and 40°S contains terrestrial and atmospheric contribution.•Perchlorate in the southern high latitudes exhibits an obvious seasonal difference.•Elevated ...perchlorate levels between ~40°S and 80°S are linked to stratospheric inputs.
Perchlorate (ClO4−) is harmful to human health, and knowledge on the levels and sources of natural ClO4− in different environments remains rather limited. Here, we investigate ClO4− in aerosol samples collected along a cross-hemisphere ship cruise between China and Antarctica and on a traverse between coastal East Antarctica and the ice sheet summit (Dome Argus). Perchlorate concentrations range from a few to a few hundred pg m−3. A clear latitudinal trend is found, with elevated ClO4− concentrations near populated areas and in the southern mid-high latitudes. Spatial patterns of atmospheric ClO4− over oceans near the landmasses support that terrestrial ClO4− is not transported efficiently over long distances. In the southern mid-latitudes, higher ClO4− concentrations in March than in November-December may be caused by significant stratospheric inputs in March. Perchlorate concentrations appear to be higher in the warm half than in the cold half of the year in the southern high latitudes, suggesting seasonal difference in main atmospheric sources. ClO4− may be formed in the reactions between chlorine free radical (Cl·) and ozone (O3) in the stratosphere when Antarctic ozone hole occurs during September-October. And the stratosphere-produced ClO4− is moved to the boundary layer in several months and may be responsible for the high ClO4− concentrations in the warm half of the year. Perchlorate produced by photochemical reactions between O3 and Cl· in the Antarctic stratosphere is likely responsible for the higher ClO4− concentrations in Antarctica than in Arctic.
Abstract
In urban North China, nitrate (
NO
3
−
) is a primary contributor to haze formation. So far, the production processes and source apportionments of atmospheric
NO
3
−
during the heating ...season (i.e. the wintertime) have not yet been well understood. This study determined δ
15
N–
NO
3
−
, δ
18
O–
NO
3
−
, and Δ
17
O–
NO
3
−
of aerosol samples to compare the potential sources and formation pathways of atmospheric
NO
3
−
during heating (November to March) and non-heating (April to May) seasons. Combining stable isotope composition with the MixSIAR model based on Δ
17
O–
NO
3
−
showed that NO
3
+ DMS/HC (dimethyl sulfate/hydrocarbon) pathway was the dominant process of atmospheric nitrate formation during the heating season (mean = 52.88 ± 16.11%). During the non-heating season, the contributions of NO
3
+ DMS/HC (mean = 37.89 ± 13.57%) and N
2
O
5
+ H
2
O (mean = 35.24 ± 3.75%) pathways were comparable. We found that Δ
17
O–
NO
3
−
was negatively correlated with wind speed and positively correlated with relative humidity during the heating season, possibly associated with the sources and production of atmospheric
NO
3
−
. In specific, in a dust storm event, the very low Δ
17
O–
NO
3
−
is likely associated with particles from land surface. Under the premise of considering
15
N fractionation, the constraint-based on δ
15
N–
NO
3
−
illustrated that coal combustion was the major source of NO
x
emission during the heating season, and the relative contribution of coal combustion decreased rapidly from the heating season (mean = 42.56 ± 15.50%) to the non-heating season (mean = 21.86 ± 4.91%). Conversely, the proportion of NO
x
emitted by soil microbes rose significantly from the heating (mean = 9.67 ± 5.99%) to non-heating season (mean = 24.02 ± 11.65%). This study revealed differences in the sources and formation processes of atmospheric
NO
3
−
during the heating and non-heating seasons, which are of significance to atmospheric nitrogen oxide/nitrate pollution mitigation.
Abstract
Airborne microplastics (MPs) can undergo long range transport to remote regions. Yet there is a large knowledge gap regarding the occurrence and burden of MPs in the marine boundary layer, ...which hampers comprehensive modelling of their global atmospheric transport. In particular, the transport efficiency of MPs with different sizes and morphologies remains uncertain. Here we show a hemispheric-scale analysis of airborne MPs along a cruise path from the mid-Northern Hemisphere to Antarctica. We present the inaugural measurements of MPs concentrations over the Southern Ocean and interior Antarctica and find that MPs fibers are transported more efficiently than MPs fragments along the transect, with the transport dynamics of MPs generally similar to those of non-plastic particles. Morphology is found to be the dominant factor influencing the hemispheric transport of MPs to remote Antarctic regions. This study underlines the importance of long-range atmospheric transport in MPs cycling dynamics in the environment.
While nitrate (NO3-) serves as a vital nutrient for soil organisms, the lack of knowledge on its sources and cycling in Antarctic soils does not allow to predict the possible effects of climate and ...environmental changes on the functioning of terrestrial ecosystems. Thus, the NO3- and its stable isotopes of Δ17ONO3, δ15NNO3, and δ18ONO3 were analyzed in Antarctic soils, collected in coastal ice-free areas of East Antarctica and the tip of the northern Antarctic Peninsula. The soil NO3- concentrations and isotopic values of Δ17ONO3, δ15NNO3, and δ18ONO3 were comparable across the latitudinal gradient except for soils collected beneath moss cushions in the Fildes Peninsula. The proportional calculation of Δ17ONO3 indicated that 93–97% of soil NO3- derived from nitrification process, whereas atmospheric deposition probably contributed to the NO3- budget for a fraction <10 %. The linear relationship between δ18ONO3 and δ15NNO3 suggested the occurrence in Antarctic soils of denitrification process and active cycling between NO3- and nitrite (NO2-). The NO3- assimilation in soil likely occurred, but at minimal rates. These findings provide new insights in the biogeochemical cycle of nitrogen (N) in Antarctic terrestrial ecosystems and seem to indicate that despite climatic and environmental changes along the wide latitudinal gradient, the sources and cycling of NO3- maintain a rather consistent pattern along coastal ice-free areas. The noteworthy increase of NO3- concentrations and δ15NNO3, δ18ONO3, and Δ17ONO3 values in soils collected under moss in the Fildes Peninsula could also suggest that the warming and the increased availability of liquid water will likely favor the developments of soil biotic communities and changes in the biogeochemical cycle of N in Antarctic terrestrial ecosystems.
Snow nitrate is vulnerable to photolytic loss that causes isotopic alteration, and thus its isotopes can potentially track the extent of snow nitrate photolysis and its impacts in environments where ...loss is significant. Large increases in δ15N‐NO3− below the snow surface have been attributed to photolysis and this behavior is generally consistent amongst theoretical as well as lab and field studies. Oxygen isotope ratios are thought to be influenced by photolysis as well as secondary condensed‐phase chemistry, but the competing effects have yet to be reconciled. Here we use a model that simulates nitrate burial, photolytic fractionation, and re‐oxidation in snow to quantitatively assess these processes with the aim of developing a consistent framework for interpreting the photolytic effects of the complete nitrate isotopic composition (δ15N, δ18O, and Δ17O). This study reveals that isotopic effects of nitrate photolysis and aqueous‐phase re‐oxidation chemistry are important sources of uncertainties in modeling δ18O‐NO3−.
Plain Language Summary
Nitrate is a major ion species in Antarctic snow, and often measured in snow and ice cores. Accurate interpretation of ice core nitrate records, however, remains challenging mostly due to uncertainties associated with nitrate photolysis, especially in low snow accumulation sites. Consequently, both nitrogen and oxygen stable isotopes of nitrate are altered via photolysis, but can serve as a useful diagnostic of these processes. Compared to nitrogen isotopes, which have been characterized in detail by both model simulations and observations, oxygen isotopic effects of nitrate photolysis are far from understood. Here, we present a model incorporating processes of snow burial, photolytic loss, and re‐oxidation to quantitatively assess the changes in the full isotopic parameters (δ15N, δ18O, and Δ17O) over the course of snow nitrate burial in central Antarctica. Model simulations show that about 25%–30% of the photoproducts will be re‐oxidized to form secondary nitrate within the snow. Major uncertainty of our model predicted δ18O is largely associated with limited knowledge on oxygen isotopic fractionation during nitrate photolysis and reformation in snow grains. This model will help diagnose the processes of nitrate burial, photolytic fractionation, and re‐oxidation in snow and allow for better interpretation of these tracers in snow and ice.
Key Points
We developed a model to quantify changes in NO3− isotopes based on burial, photolytic fractionation, and re‐oxidation in East Antarctic snow
The observed snow Δ17O profile is constrained by photolysis‐driven aqueous‐phase formation of secondary NO3− on the order of ∼25–30%
Isotopic effects of NO3− photolysis and aqueous‐phase re‐oxidation chemistry are important sources of uncertainties in modeling δ18O
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