Klopper et al. 2020 - Namibian coastal aerosol metals

Klopper and colleagues measured inorganic elements and water-soluble ions in PM10 aerosols at the Henties Bay Aerosol Observatory on the Namibian coast and used positive matrix factorisation to apportion sources. This is upstream atmospheric-deposition and source-attribution evidence: it does not measure bottled water or a finished product, but it identifies heavy-metal aerosol burdens and likely source classes that can deposit to coastal land and marine systems.

Key numbers

The study collected 385 PM10 filter samples over 26 non-consecutive weeks in 2016 and 2017. Table 1 reports mean elemental concentrations in ng m−3 with ranges across the full dataset: Al 478 ± 581, range 2-4739; Fe 367 ± 458, range 3-3687; Mn 13 ± 11, range 1-86; Zn 12 ± 7, range 1-42; Cr 8 ± 6, range 1-31; V 8 ± 5, range 1-38; Ba 9 ± 7, range 1-34; Co 8 ± 5, range 1-32; Cu 13 ± 9, range 1-48; Ni 8 ± 6, range 1-33; Cd 735 ± 1124, range 1-6776; As 191 ± 317, range 1-1092; and Pb 75 ± 89, range 1-509. Table 1 also reports Sr 77 ± 63 ng m−3 and Nd 15 ± 11 ng m−3, which are source-apportionment tracers in this paper but do not currently have HMI metal pages.

Positive matrix factorisation identified five PM10 components: sea salt 74.7 ± 1.9% of total estimated mass, mineral dust 15.7 ± 1.4%, ammonium-neutralised aerosol 6.1 ± 0.7%, fugitive dust 2.6 ± 0.2%, and industry 0.9 ± 0.7%. The authors state that the PMF fugitive-dust component was traced by V, Cd, Pb, Nd, and Sr, while the industry component was characterised by As, Zn, Cu, Ni, and Sr.

Section 4.2.3 reports annual mean V concentrations of 9 ± 5 ng m−3 in 2016 and 7 ± 6 ng m−3 in 2017, and annual mean Ni concentrations of 8 ± 7 ng m−3 in 2016 and 7 ± 4 ng m−3 in 2017. The authors interpret V as associated preferentially with mineral dust and fugitive dust, with mining activities and heavy-oil combustion as plausible contributors, while Ni is associated preferentially with the industry component and heavy-oil combustion.

For other heavy metals, Section 4.2.3 states that the mean Pb concentration was 75 ± 89 ng m−3 and that the PMF model separated the largest fractions of Zn and Pb into industry and fugitive-dust components, respectively. The mean Cd concentration was 1502 ± 1458 ng m−3 in 2016 and 219 ± 163 ng m−3 in 2017, with the 2016 elevation attributed mainly to high October 2016 concentrations that coincided with high concentrations of most other heavy metals except As. Section 4.2.5 reports annual mean As concentrations of 22 ± 16 ng m−3 in 2016 and 239 ± 344 ng m−3 in 2017.

The abstract attributes V, Cd, Pb, and Nd to fugitive dust emitted from bare surfaces or mining activities. It attributes As, Zn, Cu, Ni, and Sr to combustion of heavy oils in commercial ship traffic across the Cape of Good Hope sea route, power generation, smelting, and other regional industrial activities. The conclusion states that PMF identified mining activities, including road-construction-related mining, as a distinct contributor for most heavy metals and that atmospheric deposition of trace metals including Cr, Cu, Ni, Mn, and Zn could affect marine productivity in the Benguela Upwelling System.

Methods (brief)

PM10 samples were collected at HBAO, approximately 100 m from the shoreline, using a Thermo Fisher Scientific Partisol 2025i sampler with a certified PM10 inlet and 47 mm Whatman Nuclepore polycarbonate filters. Sampling used 9 h daytime and nighttime filters, yielding 385 samples. Elemental concentrations for 24 elements including Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Pb, Nd, Cd, and Ba were measured by wavelength-dispersive X-ray fluorescence. Water-soluble ions were measured by ion chromatography. Source apportionment used temporal correlations, HYSPLIT back trajectories, local wind data, and EPA PMF 5.0.

Implications

Certification: This source does not contribute mineral-water, bottled-water, or product occurrence values. It contributes atmospheric-deposition and source-attribution evidence for coastal Namibia, especially Cd-, Pb-, V-, As-, Ni-, Cu-, and Zn-bearing aerosols linked to fugitive dust, mining, shipping, smelting, power generation, and industrial activity.

Courses: The paper is a strong example of why upstream source-attribution belongs in the corpus. It helps distinguish an end-product contamination question from a shared environmental-burden question: the relevant claim here is not that a product contains a metal, but that regional aerosol pathways can carry metals from identifiable source classes toward land and marine receiving systems.

App: Context only for product thresholds. The aerosol concentrations are not product concentrations and should not enter bottled-water or mineral-water HMTc occurrence pools.

Wiki pages this source may touch

• atmospheric-deposition
• source-attribution-environmental-burden-apportionment
• aquatic-bioaccumulation
• cadmium
• lead
• arsenic-total
• nickel
• chromium
• copper
• manganese
• zinc
• iron
• cobalt
• barium
• aluminum
• vanadium

Verification notes

Recovered from skip:not-food-occurrence under the 2026-06-10 inclusion-by-default rule. The old skip reason was too narrow because the paper measures heavy metals in atmospheric aerosols and apportions them to upstream source classes relevant to atmospheric deposition and environmental burden sharing.

All key numbers were checked against the extracted PDF text, especially Table 1, Section 4.2.3, Section 4.2.5, the abstract, and the conclusion. Units are preserved as ng m−3 for elemental aerosol concentrations and percent mass contribution for PMF components. Arsenic is treated as total arsenic (tAs) because XRF elemental analysis did not speciate inorganic arsenic. Products and ingredients are intentionally empty; the filename’s mineral-water query label is not the paper’s matrix.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.