Composition and Source Apportionment of Heavy Metals in Aerosols at the Great Wall Station, Antarctica

Abstract

To elucidate the compositional characteristics and sources of heavy metals in aerosols at China’s Great Wall Station in Antarctica, high-volume aerosol sampling was conducted from 4 January to 26 December 2022, on Fildes Peninsula, King George Island. Ten heavy metals (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb) in total suspended particulates (TSPs) were quantified via inductively coupled plasma mass spectrometry (ICP-MS). Enrichment factor (EF) analysis, correlation metrics, and backward trajectory clustering were integrated to identify potential sources. The results revealed pronounced enrichment (EF > 10) for Cr, As, Zn, Cd, and Pb, indicating dominant non-crustal contributions. Source apportionment identified three pathways: (1) long-range transported anthropogenic emissions, including Southern Hemisphere marine traffic (e.g., V and Ni from ship fuel combustion) and industrial pollutants from South America (Pb and Cd); (2) local anthropogenic sources, primarily diesel generators and tourism-related gasoline combustion (Cu and Zn); and (3) crustal inputs via glacial melt and weathering (Fe and Mn). This study pioneers the quantification of direct anthropogenic impacts (e.g., power generation and tourism) on aerosol heavy metals in Antarctic research zones, offering critical insights into transboundary pollutant dynamics and regional mitigation strategies.

1. Introduction

Antarctica, the remotest and least developed polar continent on Earth, boasts unique biodiversity and abundant mineral and freshwater resources, playing an irreplaceable role in maintaining global climate balance and ecosystem stability [1,2]. At present, the Antarctic ecosystem is facing a dual threat of global warming and human activities, such as research station construction, bio-resource exploitation, and tourism development. These activities aggravate the fragility of the Antarctic ecosystem by directly destroying habitats or indirectly altering material cycles [3,4,5].

Aerosol, a multiphase particulate system of solids and liquids suspended in the atmosphere, serves as a key tracer for studying pollutant transport and the impact of human activities, thanks to its long-range transport properties [6]. With its distance from industrial continents and protection from the westerlies, Antarctica has an extremely low natural pollution background, making it an ideal region for investigating aerosol source–sink processes and marine biogeochemical cycles [7,8]. Atmospheric particulate matter mainly consists of carbonaceous components, soluble ions, and trace heavy metals. Although heavy metals account for a small proportion (<5%) of atmospheric particulate matter [9,10], their non-degradability and bioaccumulation can disrupt polar ecosystem stability via dry and wet deposition into soil and water systems [11]. More significantly, Antarctic heavy metal pollution may stem from intercontinental industrial emissions, indicating that polar environments are no longer absolute “pristine lands.” Thus, analyzing the composition and sources of heavy metals in Antarctic aerosols is crucial for assessing human impact on polar regions.

Source apportionment of heavy metals in Antarctic aerosols has long been a core issue in polar environmental studies. Early research revealed a complex “natural–anthropogenic” mixture through multi-site observations. For example, size-segregated sampling at the Brazilian station, combined with an Absolute Principal Factor Analysis (APFA), showed that Antarctic Peninsula aerosols are mainly sea salt, soil dust, and sulfates [12]. A seasonal analysis of PM2.5 at South Korea’s Sejong Station further indicated that summer marine biotic activities (e.g., sulfide release) and penguin habitat emissions significantly increase sulfate and ammonium concentrations [13]. Recently, high-precision technologies (e.g., ICP-MS) have enhanced anthropogenic source identification. In Terra Nova Bay’s PM10 study, a high Cd soluble fraction implied contributions from marine aerosol chemical transformations or long-range transport [14], while Ni and Cr enrichment pointed to diesel generators or ship emissions [7]. Additionally, HYSPLIT trajectory model studies showed that South Atlantic shipping aerosols (e.g., Cu and Sn) can reach the Antarctic Peninsula via the Drake Passage [2].

Antarctica’s unique geographical isolation and pristine environment position it as a critical region for studying long-range atmospheric transport and deposition of pollutants. Heavy metals, due to their non-degradable nature and bioaccumulative potential, are of particular concern in polar environmental research. They can undergo transcontinental migration via atmospheric circulation and oceanic currents, accumulating in polar ecosystems and posing latent risks to biota. Understanding the sources and distribution of heavy metals in Antarctic aerosols is essential for assessing anthropogenic impacts on this remote region and formulating targeted environmental protection strategies.

Despite advancements in previous studies, significant gaps persist in our understanding of heavy metal sources in Antarctic aerosols, particularly around the Great Wall Station. Existing research has predominantly focused on isolated natural or anthropogenic sources, with limited integration of multi-method source identification approaches. Furthermore, the relative contributions of local human activities (e.g., research station operations and tourism) and long-range pollution transport remain unresolved. This study addresses these gaps by employing an integrative framework that combines aerosol heavy metal concentration measurements with advanced statistical and modeling techniques, including principal component analysis (PCA), correlation heatmaps, enrichment factors (EFs), and air mass back-trajectory clustering. This multi-method approach enables precise source apportionment and elucidates the complex interplay between natural and anthropogenic drivers of aerosol composition in the Great Wall Station area.

By expanding the regional heavy metal baseline dataset and refining source resolution, this work provides robust scientific evidence to disentangle the “local–remote” contribution ratio of pollution sources. The findings directly inform Antarctic environmental management initiatives, such as optimizing ship emission controls and transitioning research stations to green energy alternatives. These advancements represent a critical step toward reconciling polar environmental preservation with sustainable development goals.

2. Materials and Methods

2.1. Site Description

The Chinese Antarctic Great Wall Station (Figure 1) is located on the Fildes Peninsula of King George Island, South Shetland Islands, Antarctica (geographic coordinates: 62°12′ 59″ S, 58°57′52″ W). The station extends 2 km north–south and 1.26 km east–west, covering a total area of approximately 2.52 km². The terrain is characterized by volcanic hills, with an average elevation of 10 m. The climate exhibits distinct seasonal variations: extreme summer temperatures reach 11.7 °C, winter minima drop to −27.7 °C, and the multi-year average temperature is −2.1 °C. Annual precipitation averages 589.6 mm, predominantly as snow, with a monthly maximum of 173.4 mm. Influenced by a maritime climate, the station experiences high annual relative humidity (89%) and elevated airborne salt content. Strong winds (≥Beaufort scale 6) occur over 129 days annually, with maximum sustained wind speeds of 33.0 m/s (equivalent to a Category 1 hurricane) and instantaneous gusts up to 38.1 m/s.

2.2. Sampling and Analysis

From 4 January to 26 December 2022, aerosol samples were continuously collected at the Great Wall Station using a KB-1000 high-volume particulate sampler (Qingdao Genstar Electronic technology Co. LTD., Qingdao, China; flow rate: 1.05 m³/min). The sampler, installed 1.5 m above ground, utilized 20 cm × 25 cm Whatman 41 cellulose filters, yielding 101 valid samples annually.

For heavy metal quantification, 25 mm × 80 mm filter sections were excised using ceramic scissors and digested in Teflon bombs. Sequential additions of 4 mL ultrapure nitric acid (HNO₃, double-distilled) and 1 mL hydrofluoric acid (HF, double-distilled) were followed by sealed digestion at 160 °C for 36 h. Residual acids were evaporated on a hotplate (120 °C), and 1 mL HNO₃ was added to eliminate residual HF. After redissolution in 3 mL Milli-Q water and 1 mL HNO₃, the samples were redigested at 160 °C for 12 h, cooled, and diluted to 40 mL. Concentrations of V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb were determined via inductively coupled plasma mass spectrometry (ICP-MS; Thermo Scientific iCAP RQ; No. 1806064S; Thermo Fisher Scientific, Waltham, MA, USA). The internal standards included Y (for V), Bi (for Pb), and Rh (for other elements). The method detection limits (LODs) were 0.01 ppt for V, Cd, and Pb; 1 ppt for As; and 0.1 ppt for remaining elements. Field blanks (unexposed Whatman 41 filters) and procedural blanks (acid digestion reagents) were processed in parallel with each batch of 10 samples to monitor background contamination. All blank values were consistently below 30% of the method detection limits (LODs), and sample concentrations were blank-corrected. Spiked recoveries were evaluated by adding certified standard solutions to 10% of randomly selected samples. Replicates were reanalyzed for any samples with initial recoveries outside the 80–120% range until acceptable recovery rates (88–115%) were achieved. Analytical accuracy was further validated using certified reference materials, with measured element concentrations deviating by <12% from certified values. Method precision was confirmed through duplicate analyses of 5% of samples, yielding relative standard deviations (RSDs) <10%. The ICP-MS performance was verified daily with multi-element calibration standards (0.1–100 ppb), ensuring instrumental stability and data validity throughout this study. The method detection limits (LODs) and limits of quantification (LOQs) are summarized in Table S1.

2.3. Data Processing

A correlation analysis and a principal component analysis (PCA) were performed using OriginPro 2025 (64-bit, v10.2.0.196). For the PCA, the input variables included log-transformed and standardized concentrations of 10 heavy metals. The principal components were extracted based on eigenvalues >1, with varimax rotation applied to maximize factor interpretability. The Pearson correlation coefficients (r) and their significance (p-values) were calculated for all element pairs, with p < 0.05 considered statistically significant. The PCA identified principal components (cumulative variance > 80%) to characterize pollution sources and environmental drivers [15]. An enrichment factor (EF) analysis distinguished anthropogenic from natural contributions [2].

2.4. Clustering Analysis of Backward Trajectories

The HYSPLIT model [16], integrated via MeteoInfo software [17], simulated 72 h back trajectories using NCEP GDAS reanalysis data (1° × 1° resolution; NOAA ARL FTP server). The parameters included a 50 m starting height, 6 h temporal resolution (00:00, 06:00, 12:00, 18:00 UTC), and Ward’s hierarchical clustering (Euclidean distance) to resolve dominant transport pathways. The trajectory lengths correlated positively with air mass velocity, with longer paths indicating rapid transboundary transport.

3. Results and Discussion

3.1. Heavy Metal Concentration Analysis

The present study conducted year-round aerosol sampling at the Great Wall Station in Antarctica, a region characterized by distinct bimodal seasonality with summer (November–March) and winter (April–October) periods. Ten heavy metal elements were quantitatively analyzed, including V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb. A comprehensive analysis revealed a characteristic hierarchy in annual mean concentrations: Fe exhibited the highest atmospheric loading, followed sequentially by Zn, Cr, Mn, Ni, Cu, Pb, V, As, and Cd. A notable seasonal pattern emerged, with all analyzed heavy metals demonstrating elevated mean concentrations during summer sampling campaigns compared to winter measurements. These inter-element concentration variations displayed significant element-specific characteristics, with detailed numerical data presented in

Table 1. Concentration of heavy metals in aerosols from Great Wall Station, China (ng/m³).

Element	Annual	Summer	Winter
V	0.103 ± 0.057	0.119 ± 0.072	0.086 ± 0.021
Cr	1.766 ± 0.906	1.830 ± 1.244	1.709 ± 0.409
Mn	1.360 ± 0.639	1.479 ± 0.841	1.248 ± 0.047
Fe	30.030 ± 19.43	35.639 ± 25.12	24.055 ± 0.333
Ni	0.811 ± 0.649	0.846 ± 0.662	0.774 ± 6.709
Cu	0.269 ± 0.177	0.299 ± 0.237	0.237 ± 0.065
Zn	3.014 ± 1.663	3.481 ± 2.199	2.557 ± 0.607
As	0.063 ± 0.030	0.081 ± 0.036	0.048 ± 0.006
Cd	0.013 ± 0.008	0.0131 ± 0.011	0.0130 ± 0.002
Pb	0.251 ± 0.139	0.273 ± 0.194	0.235 ± 0.069

.

This study reveals significant regional heterogeneity in aerosol heavy metal concentrations at Great Wall Station, Antarctica (

Table 2. Comparison of atmospheric metal concentrations measured at China’s Great Wall Station and different Antarctic research stations (Cd, Cu, Pb, and V are in pg/m³, and Fe, Cr, Mn, Ni, Zn, and As are in ng/m³).

Antarctic Research Stations	V	Cr	Mn	Ni	Cu	Zn	As	Cd	Pb	Fe	Reference Data
The Great wall	103	1.766	1.360	0.811	269	3.014	0.063	13	251	30.030
Gabriel de Castilla	864	-	1.051	-	548	4.576	0.398	-	193	-	[2]
King Sejong Station	36	0.114	-	0.083	143	0.13	-	1	41	-	[18]
Mario Zucchelli Station	22	0.059	0.147	-	394	0.109	-	-	15	6.58	[19]
Maitri	-	-	2.8	-	1300	5.5	-	-	120	45	[20]
Comandante Ferraz	-	1.06	0.13	0.088	230	1.07	-	-	250	1.11	[21]
Concordia Station	-	-	-	-	120	-	-	0.24	21	-	[22]
McMurdo (Hut Point Site)	363	0.278	2.478	-	189	1.516	-	-	851	129.536	[23]
McMurdo (Radar Sat Dome Sit)	528	0.396	3.463	-	200	0.863	-	-	470	164.404	[23]

). Vanadium (103 pg m⁻³) and zinc (3.014 ng m⁻³) reached 12% and 66% of the levels observed at the Antarctic Peninsula station Gabriel de Castilla, respectively, reflecting localized anthropogenic contributions from ship fuel combustion and zinc alloy abrasion. Chromium (1.766 ng m⁻³) and lead (251 pg m⁻³) exceeded concentrations at King Sejong Station and the remote Concordia Station by 15-fold and 12-fold, respectively, underscoring persistent impacts from diesel generator operations and aviation activities. In contrast, iron (30.03 ng m⁻³) and manganese (1.360 ng m⁻³) were markedly lower than those at wind erosion-dominated sites such as McMurdo (Fe: 23%; Mn: 55% of McMurdo values), suggesting that snow and ice coverage around Great Wall Station effectively suppressed mineral dust mobilization. Heavy metals at Antarctic Peninsula stations (Great Wall, Gabriel de Castilla) were predominantly attributed to ship-related emissions (V, Cu, and Zn), whereas inland and high-human-activity stations (McMurdo, Comandante Ferraz) exhibited combined regulation by mechanical wear (Pb and Cr) and local dust sources (Fe and Mn). These findings highlight divergent anthropogenic–natural source contributions across Antarctic regions, providing critical baseline data for polar environmental assessment.

3.2. Multivariate Analysis

A principal component analysis (PCA) was employed to analyze the heavy metal composition of atmospheric aerosols, successfully identifying two principal components that collectively explained 68.9% of the total variance (Figure 2a). The first principal component (PC1), accounting for 53.0% of the variance, was primarily characterized by high loadings of Mn, Cr, and Pb. This indicates that these three elements were the dominant contributors to the variance in the dataset. The second principal component (PC2) contributed an additional 15.9% to the total variance, with As exhibiting a loading of 0.54 and Fe demonstrating a loading of 0.35. The significant loadings of these elements on their respective components highlight Mn, Cr, Pb, Fe, and As as the key heavy metal components in the atmospheric aerosols under investigation.

To further explore the relationships between the elements, a Pearson correlation analysis was conducted (Figure 2b). The results revealed significant correlations among most elements, with correlation coefficients (r) exceeding 0.3 and p-values below 0.05. Particularly noteworthy were the strong correlations (r > 0.7, p < 0.001) observed between Mn and V, Cr, Fe, Cd, Pb, and As. Given that Mn is widely recognized as a crustal reference element, these correlations strongly suggest a shared crustal origin for these elements. This finding is consistent with previous studies conducted in remote regions of the southeastern Tibetan Plateau [8], where similar elemental associations were attributed to crustal sources.

Cr exhibited exceptionally high correlations with Pb and Cd, with correlation coefficients (r) exceeding 0.9 and p-values below 0.001. This degree of correlation implies that Cr, Pb, and Cd likely share a common anthropogenic source. Although Pb showed a significant association with Mn, it is primarily known to originate from anthropogenic activities. For instance, at Spain’s “Gabriel de Castilla” Station [2], local tourism cruises and generator operations have been identified as significant sources of Pb emissions. This underscores the complex interplay of natural and anthropogenic factors in the distribution of heavy metals in atmospheric aerosols.

Previous studies in the Arctic have identified V, Cu, Zn, Cd, and As as markers of anthropogenic influence [24]. V and Ni are often associated with ship fuel combustion [25], Cd is linked to fossil fuel combustion and industrial metallurgy [26], and Zn is commonly related to traffic emissions and biomass burning [27,28]. These established associations provide a valuable reference for interpreting the sources and pathways of heavy metals in atmospheric aerosols, helping to contextualize the findings of this study within the broader spectrum of environmental research.

3.3. Enrichment Factor

Enrichment factors (EFs) were calculated to evaluate the anthropogenic contribution of trace elements using the following formula:

$$\mathrm{EFc}={\displaystyle \frac{(\mathrm{X}/ \mathrm{Ref}) \mathrm{aerosol} \mathrm{sample}}{(\mathrm{X}/\mathrm{Ref}) \mathrm{crustal} }}$$

where X represents the target element concentration. Manganese (Mn) was selected as the crustal reference element based on two key considerations. Initial analyses of blank filters identified significant exogenous Al contamination (>120% of the MDL), attributed to the aluminum foil wrapping used in Antarctic sample transport. Therefore, Mn, a validated crustal tracer with minimal anthropogenic influence and stable crustal ratios in both urban [29] and Antarctic [30] atmospheric studies, was utilized for crustal normalization in this work. EFs < 10 indicate dominant natural sources (crustal dust or sea salt), 10–100 suggest mixed anthropogenic and natural contributions, and >100 reflect strong anthropogenic enrichment [11,31].

As shown in Figure 3, Pb exhibited extreme enrichment (EF > 100), followed by Cd, Zn, As, and Cr (EF = 10–100). Ni, Cu, V, and Fe had EFs < 10. Pb’s exceptionally high EF (>10,000) at the Great Wall Station, though lower than the values reported at Brazilian [12] and U.S. stations [32], underscores its anthropogenic origin, including local fuel combustion, waste incineration, tourism, and generator emissions. The enrichment of Cd is mainly related to vehicle wear (such as cadmium-containing tire wear) and the long-distance transmission of industrial emissions from South America. This conclusion is related to previous studies conducted at Zhongshan Station in Antarctica, which previously pointed out that the enrichment phenomena of Zn and Cr at Zhongshan Station are related to daily operation activities in the station area [16]. To further explore the sources of cadmium in depth, a backward trajectory clustering analysis was carried out using the HYSPLIT model in winter (Figure 4). The analysis results obtained strongly confirmed that the vehicle wear mentioned above and the long-distance transmission of industrial emissions from South America are the key mechanisms leading to cadmium enrichment in the Antarctic region. As may originate from crustal weathering or global industrial emissions [33]. These provide more comprehensive and powerful evidence support for revealing the sources and transmission paths of heavy metal pollution in the Antarctic region and also lay the foundation for subsequent related research and environmental governance work. While current concentrations of Pb, Cd, and Zn are unlikely to induce immediate harm, their pronounced enrichment (EF > 10) underscores the need for monitoring long-term bioaccumulation trends, particularly in species vulnerable to chronic exposure, such as krill and seabirds.

3.4. Air Mass Back Trajectories

To delve into the seasonal transport mechanisms of atmospheric aerosols over Antarctica, 72 h backward trajectories at 0 m above ground level were meticulously simulated utilizing the HYSPLIT model in conjunction with GDAS1 meteorological data. A cluster analysis was performed on both annual and monthly trajectories, with a specific focus on the months of August, November, and December. This analysis unveiled three predominant transport pathways, as depicted in Figure 4. Figure 4a shows that the northwest (NW) ocean transportation route accounts for 48.53% of the annual trajectory, the west (W) ocean transportation route accounts for 17.84% of the annual trajectory, and the southeast (SE) continental transportation route accounts for 33.64% of the annual trajectory. The 60° S latitude belt is governed by westerly circumpolar winds, which is consistent with the dynamics of the Antarctic Circumpolar Current. Wind rose diagrams (Figure 5) provided further confirmation of the dual wind regimes (NW and SE) that drive the transport of aerosols in this region.

In August (Figure 4b), an increase in NW trajectories (17.74%) was observed to coincide with elevated levels of Cd. This correlation implicates the long-range transport of industrial pollutants originating from mid-latitude regions of South America. For instance, an isotopic analysis of Pb in Dome F snow cores [34] has previously established a link between Pb in this region and industrial activities in South America. This serves as compelling evidence supporting the hypothesis that industrial emissions from South America can be transported over long distances to reach Antarctic regions.

During the period from November to December (Figure 4c,d), enhanced maritime transport was found to be correlated with higher concentrations of V, Cr, and Pb. This suggests that emissions from Southern Ocean shipping activities are a significant source of these pollutants. Shipping emissions are known to contain various heavy metals [2], and the increased maritime transport during these months likely contributes to the elevated levels of V, Cr, and Pb observed in the atmospheric aerosols.

The analysis revealed that the circumpolar westerlies were responsible for driving 66.37% of the marine-sourced aerosols, while the southeast winds contributed 33.64% of the continental inputs. This dual wind system underscores the complexity of aerosol sources in Antarctica and provides novel insights into the mechanisms governing pollutant transport to this remote region. Understanding these transport pathways is crucial for comprehending the environmental impact of both local and distant anthropogenic activities on the Antarctic environment.

4. Conclusions

This study systematically investigated the multi-dimensional sources and environmental impacts of 10 heavy metals (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, and Pb) in aerosol samples collected at China’s Great Wall Station, Antarctica, during 2022. The results revealed distinct seasonal variations, with higher summer concentrations (Fe > Zn > Cr > Mn > Ni > Cu > Pb > V > As > Cd), attributable to intensified release processes during ice melt. Multivariate source apportionment demonstrated that 38.2% of total variance was explained by natural sources, as evidenced by strong correlations between Mn and crustal elements (Fe; r > 0.72). Anthropogenic influences were predominant for Pb (EF > 10,000) and Cd (10 < EF < 100), linked to local station operations (fuel combustion and tourism) and transcontinental transport from South American industries, particularly evidenced by winter peaks of Cd synchronized with transoceanic air mass trajectories. Shipping emissions were identified as a critical pathway through characteristic V-Ni signatures from marine fuel combustion. Although current Pb, Cd, and Zn concentrations remain below acute toxicity thresholds, their bioaccumulation potential poses chronic risks to keystone species (e.g., krill and seabirds) via trophic transfer. The established “local emission–marine transport–intercontinental transmission” model underscores the necessity for integrated mitigation strategies, including shipping emission controls, clean energy transition, and international cooperation on pollution regulation. These findings provide quantitative support for environmental policymaking in Antarctic Specially Managed Areas.