History Of Metal Deposition Research Articles

Anthropogenic and lithogenic fluxes of atmospheric lead deposition over the past 3600 years from a peat bog, Changbai Mountains, China

Ombrotrophic peatlands are widely used to reconstruct atmospheric metal deposition histories. Here, we estimated the long-term atmospheric Pb deposition flux using ombrotrophic peatland data from the Changbai Mountains, northeast China. A peat profile of 320-cm depth was sampled and cut into 164 slices for measurement of Pb and other elements by ICP-MS and ICP-AES and radiometric dating by 210Pb, 137Cs and 14C. Pb concentration in the peat ranged from 2.18 to 68.33 mg kg−1, while the atmospheric Pb deposition flux ranged from 0.12 to 12.49 mg m−2 a−1. The Little Ice Age (cold and wet climate) led to low Pb concentration, Pb/Sc ratio, and Pb deposition flux (4.40 ± 0.70 mg kg−1, 2.04 ± 0.38, and 0.28 ± 0.09 mg m−2 a−1, respectively). On the other hand, intense volcanic eruptions resulted in high Pb concentration, Pb/Sc ratio, and P flux (54.48 ± 13.08 mg kg−1, 7.85 ± 2.09, and 8.15 ± 2.85 mg m−2 a−1, respectively). In addition, rapid economic development since the 1980s resulted in a gradual increase of anthropogenic Pb concentration from 1.54 mg kg−1 to 5.85 mg kg−1; thus, the anthropogenic Pb deposition flux (0.43 ± 0.21 mg m−2 a−1) was high during this period. In general, peat Pb concentration and atmospheric Pb deposition fluxes in this region have been affected by climate change, volcanic eruptions, and human activities. It was further demonstrated that atmospheric Pb emissions and deposition in China decreased since leaded gasoline was phased out in 2001. The results are critical to understand the geochemistry of Pb and to assess the effects of human activities on atmospheric Pb emissions and deposition in China.

Historical and contemporary metal budgets for a boreal shield lake

Metal concentrations in sediment cores are widely used to reconstruct metal deposition histories, but rarely have metal budgets based on measured inputs (atmospheric deposition and inflows) and lake outflows been compared with metal fluxes estimated from lake sediment cores. In this study, budgets for six metals (As, Cd, Co, Cu, Ni and Pb) were estimated by measuring inputs in bulk deposition, inputs in the major inflow and export in the lake outflow for one hydrologic year (2002−2003) at Plastic Lake, Ontario, Canada. Inputs in bulk deposition were between 0.03mgm−2y−1 (Co) and 0.69mgm−2y−1 (Cu), which represented between 2.5 and 80.7% of total metal inputs to the lake. The estimated budgets for Co, Cd and Ni, which exhibit similar geochemical behavior in the major inflow, were comparable to budgets estimated from the upper section of a sediment core taken in 2002, taking into account previously published correction factors for sediment focusing. For example, mass budgets for Co, Cd and Ni were 1.24, 0.28 and 1.89mgm−2y−1, compared with sediment budgets estimated to be 0.90, 0.19 and 4.72mgm−2y−1, respectively. In contrast, measured budgets for As, Cu and Pb, which also behave similarly in inflows (and different to Co, Cd and Ni), were between 3 (As) and 40 times lower than estimates from the upper sediment core. A possible explanation for the discrepancy is that sediment focusing transfers sediment from shallow to deep areas, which for metals like Pb, which have strong affinities for organic matter and where atmospheric deposition has decreased 15 fold since 1978 (4.31mgm−2y−1 in 1978 to 0.28mgm−2y−1 in 2013), leads to the transfer and accumulation of pollution metals to deeper parts of the lake long after a decrease in atmospheric deposition.

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

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 206Pb/207Pb of ∼1.20. The Pb concentration increased to 55 mg/kg in the 1990s, and correspondingly the 206Pb/207Pb decreased to less than 1.14. The 206Pb/207Pb in the core top sediment is concordant with the 206Pb/207Pb 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/m2 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-20th century.

Atmospheric Metal Pollutants-Archives, Methods, and History

Pollution of the atmosphere with cadmium (Cd), mercury (Hg), and lead (Pb) is a consequence of human activities. Natural archives are necessary to reconstruct the long-term history of metal deposition because accurate measurement of atmospheric deposition is a recent accomplishment. Reconstructions require: (1) accurate determination of concentrations of elements and isotopes, (2) accurate chronology of archives, and (3) archives that faithfully record atmosphere deposition. The most useful long-term archives are accumulations of ice and snow, peat, and lake sediment. Quantification of Cd deposition is uncommon because of its low concentration and substantial chemical mobility. Nonetheless, trends in peat and lake sediment are similar to those of Hg and Pb since ca. 1800 a.d. Both Hg and Pb are relatively chemically immobile and thus the peat and lake archives are believed to record historic trends of atmospheric deposition. Isotopic and concentration studies of Pb indicate a history of northern hemisphere atmospheric pollution extending back prior to 0 a.d. Although measurements of Hg concentration are now routine, isotopic measurements are in their infancy. Some Hg pollution sources have unique isotopic ratios, thereby contributing unique signals to the total Hg. Maximum accumulation rates of Hg and Pb occur up to 10 years later than for Cd (1970s versus 1960s in eastern North America, perhaps slightly later in Europe). By 2004, deposition of Cd, Hg, and Pb had declined from peak values in eastern North America more than 75, 75, and 90%, respectively.

Simulating the long-term chemistry of an upland UK catchment: Heavy metals

CHUM-AM was used to investigate the behaviours of atmospherically-deposited heavy metals (Ni, Cu, Zn, Cd and Pb) in three moorland sub-catchments in Cumbria UK. The principal processes controlling cationic metals are competitive partitioning to soil organic matter, chemical interactions in solution, and chemical weathering. Metal deposition histories were generated by combining measured data for the last 30 years with local lake sediment records. For Ni, Cu, Zn and Cd, default parameters for the interactions with organic matter provided reasonable agreement between simulated and observed present-day soil metal pools and average streamwater concentrations. However, for Pb, the soil binding affinity in the model had to be increased to match the observations. Simulations suggest that weakly-sorbing metals (Ni, Zn, Cd) will respond on timescales of decades to centuries to changes in metal inputs or acidification status. More strongly-sorbing metals (Cu, Pb) will respond over centuries to millennia.

Comparison of Atmospheric Deposition of Copper, Nickel, Cobalt, Zinc, and Cadmium Recorded by Finnish Peat Cores with Monitoring Data and Emission Records

This study aims to determine the extent to which the accumulation rates of Cu, Ni, Co, Zn, and Cd in peat cores agree with established histories of atmospheric emission from local pointsources. Metals accumulating in three Finnish peat cores with known metal deposition histories have been measured using inductively coupled plasma-sector field mass spectrometry. Samples were age-dated using both 210Pb and 14C (bomb pulse curve). At the Outokumpu (OUT) site as well as the low-background site Hietajärvi (HIJ), 210Pb age dates are in excellent agreement with the 14C bomb pulse curve method results, and the precision is between 1 and 10 years for most of the samples; at the Harjavalta (HAR) site, precision is > 6 years. Mean regional "background" concentrations have been calculated from deeper peat layers of the HIJ site (microg g(-1)): Cu, 1.3 +/- 0.2 (n = 62); Co, 0.25 +/- 0.04 (n = 71); Cd, 0.08 +/- 0.01 (n = 23); and Zn, 4 +/- 2 (n = 40). For layers accumulated within the past 100 years, accumulation rates (ARs) have been calculated. At sites with < 0.06 g m(-2) cumulative Ni inventory (HIJ and OUT), ARs of Cu and Co trace the known metal deposition histories very well. At HAR, where metal inventories are much greater, Cu and Co are mobile. ARs of Zn were between 3 and 30 mg m(-2) year(-1) and those of Cd between 24 and 140 microg m(-2) year(-1) at all sites and are independent of the chronology of their inputs from the atmosphere.