A century long sedimentary record of anthropogenic lead (Pb), Pb isotopes and other trace metals in Singapore

Abstract

Reconstructing the history of metal deposition in Singapore lake sediments contributes to understanding the anthropogenic and natural metal deposition in the data-sparse Southeast Asia. To this end, we present a sedimentary record of Pb, Pb isotopes and eleven other metals (Ag, As, Ba, Cd, Co, Cr, Cu, Ni, Tl, U and Zn) from a well-dated sediment core collected near the depocenter of MacRitchie Reservoir in central Singapore. Before the 1900s, the sedimentary Pb concentration was less than 2 mg/kg for both soil and sediment, with a corresponding (206)Pb/(207)Pb of ∼1.20. The Pb concentration increased to 55 mg/kg in the 1990s, and correspondingly the (206)Pb/(207)Pb decreased to less than 1.14. The (206)Pb/(207)Pb in the core top sediment is concordant with the (206)Pb/(207)Pb signal of aerosols in Singapore and other Southeast Asian cities, suggesting that Pb in the reservoir sediment was mainly from atmospheric deposition. Using the Pb concentration in the topmost layer of sediment, the estimated atmospheric Pb flux in Singapore today is ∼1.6 × 10(-2) g/m(2) yr. The concentrations of eleven other metals preserved in the sediment were also determined. A principal component analysis showed that most of the metals exhibit an increasing trend towards 1990s with a local concentration peak in the mid-20(th) century.

Lead isotope exchange between dissolved and fluvial particulate matter: a laboratory study from the Johor River estuary

“…In this case, regardless of local or distal sources, none of the 206 Pb/ 207 Pb in aerosols in this region comes close to the 1.195 ± 0.004 (2σ ) ratio observed in Singapore Strait seawater (figure 3). Instead of reflecting the aerosol Pb isotope value, the high 206 Pb/ 207 Pb in Singapore water is similar to the 100-year-old natural soil we observe in this region ( 206 Pb/ 207 Pb ∼ 1.214, [44]), also in the same geological formation of the Johor River catchment [46]. In this case, the isotope differences between Singapore seawater and aerosols, (b) Mechanisms inferred from the closed-system isotope exchange experiment…”

“…There is almost no Pb isotope data in either of these regions, but neither the South China Sea water (one surface sample collected near Taiwan figure 3). Atmospheric deposition appears to be the main source of Pb to the Singapore region as suggested by the sedimentary record from the central catchment reserve [44]. Besides Singapore aerosols, the regional aerosols (Kuala Lumpur, Bangkok, Vietnam, Indonesia, Hong Kong) 206 Pb/ 207 Pb range from 1.097 to 1.167 (table 3, [30,45]).…”

Spatial Distribution and Ecological Risk Assessment of Potentially Harmful Trace Elements in Surface Sediments from Lake Dali, North China

“…The EFs of the PHTEs were generally higher than one in surface sediments from Lake Dali, suggesting that in the whole lake, As, Cd, Cr, Cu, Ni, Pb, and Zn were influenced by human activities. Atmospheric deposition, catchment industrial and domestic sewage discharge, and agrochemical inputs are main pathways of anthropogenic input of PHTEs to lake sediments [11,[15][16][17]33]. Lake Dali is located at the margin of Hunshandak Sandy Land, and no modern industry exists in the catchment.…”

The hydro-geomorphic status of Nee Soon freshwater swamp forest catchment of Singapore

“…According to Chen et al (2016) there are several possible sources contributing Pb to the nearby MacRitchie Reservoir in Singapore, including power generation-based coal combustion from nearby Indonesia (Lucarelli, 2010). Our isotope data are less variable than those of Chen et al (2016), but also appear to be enriched by external sources, although it is not possible to calculate a source budget at this time.…”