We evaluated both the spatial distribution of gadolinium (Gd) and other rare earth elements (REE) in surface waters collected in a transect of San Francisco Bay (SFB) and their temporal variations ...within the Bay over two decades. The REE were preconcentrated using the NOBIAS PA-1 resin prior to analysis by high-resolution inductively coupled plasma mass spectrometry. Measurements revealed a temporal increase in the Gd anomaly in SFB from the early 1990s to the present. The highest Gd anomalies were observed in the southern reach of SFB, which is surrounded by several hospitals and research centers that use Gd-based contrast agents for magnetic resonance imaging. Recent increases in that usage presumably contributed to the order of magnitude increase in anthropogenic Gd concentrations in SFB, from 8.27 to 112 pmol kg–1 over the past two decades, and reach the northeast Pacific coastal waters. These measurements (i) show that “exotic” trace elements used in new high-tech applications, such as Gd, are emerging contaminants in San Francisco Bay and that anthropogenic Gd concentrations increased substantially over a 20 year period; (ii) substantiate proposals that REE may be used as tracers of wastewater discharges and hydrological processes; and (iii) suggest that new public policies and the development of more effective treatment technologies may be necessary to control sources and minimize future contamination by REE that are critical for the development of new technologies, which now overwhelm natural REE anomalies.
Communities in low-income and middle-income countries (LMIC) are disproportionally affected by industrial pollution compared to more developed nations. This study evaluates the dispersal and ...associated health risk of contaminant-laden soil and dust at a copper (Cu) smelter in Tsumeb, Namibia. It is Africa’s only smelter capable of treating complex Cu ores that contain high arsenic (As) contents (<1%). The analyses focused on the primary trace elements associated with ore processing at the smelter: As, Cu, and lead (Pb). Portable X-Ray fluorescence spectrometry (pXRF) of trace elements in soils (n = 83) and surface dust wipes (n = 80) showed that elemental contamination was spatially associated with proximity to smelter operations. Soil concentrations were below US EPA soil guidelines. Dust wipe values were elevated relative to sites distal from the facility and similar to those at other international smelter locations (As = 1012 μg/m2 (95% CI 687–1337); Cu = 1838 μg/m2 (95% CI 1191–2485); Pb = 1624 μg/m2 (95% CI 862–2385)). Source apportionment for Pb contamination was assessed using Pb isotopic compositions (PbIC) of dust wipes (n = 22). These data revealed that the PbIC of 73% (n = 16/22) of these wipes corresponded to the PbIC of smelter slag and tailings, indicating contribution from industrial emissions to ongoing exposure risk. Modeling of carcinogenic risk showed that dust ingestion was the most important pathway, followed by inhalation, for both adults and children. Dermal contact to trace elements in dust was also determined to pose a carcinogenic risk for children, but not adults. Consequently, contemporary smelter operations remain an ongoing health risk to the surrounding community, in spite of recent efforts to improve emissions from the operations.
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•Smelter related contamination of soil and dust in a Namibian city.•Toxic dust is elevated in residential areas—As, Cu, Pb (934, 1874, 1687 μg/m2).•Pb isotopic compositions link smelter materials to toxic dust exposures.•Ingestion of As and Cu in dust poses carcinogenic risk to adults and children.
Environmental contamination (As, Cu and Pb) in soil and dust from Cu smelting poses a significant health risk, particularly to children in Tsumeb, Namibia.
We report the continued lead (Pb) contamination of the Northwest Pacific Ocean in 2002 and present the first comprehensive Pb isotope data set for that region. In the upper ocean, a Pb concentration ...maxima (64-113 pmol kg
) extended throughout the entire North Pacific Subtropical Gyre (NPSG). We determined most of the Pb in this feature was from industrial emissions by many nations in the 1980s and 1990s, with the largest contributions from leaded gasoline emissions. In contrast, the deep water (>1000 m) Pb concentrations were lower (6-37 pmol kg
), and constituted a mix of background (natural) Pb and anthropogenic Pb inputs from preceding decades. Deep water below the Western Subarctic Gyre (WSAG) contained more industrial Pb than below the NPSG, which was attributed to a calculated 60-fold greater flux of particulate Pb to abyssal waters near the Asian continent. Assuming Pb isotope compositions in the North Pacific Ocean were homogeneous prior to large-scale 20th century anthropogenic inputs, this evidence suggests a relatively faster change in Pb isotope ratios of North Pacific deep water below the WSAG versus the NPSG.
The amounts of labile trace metals: Co (3 to 11 µg g-1), Cu (15 to 69 µg g-1), Ni (6 to 15 µg g-1), Pb (7 to 42 µg g-1), and Zn (65 to 500 µg g-1) in ash collected from the 2012 Williams Fire in Los ...Angeles, California attest to the role of fires in remobilizing industrial metals deposited in forests. These remobilized trace metals may be dispersed by winds, increasing human exposures, and they may be deposited in water bodies, increasing exposures in aquatic ecosystems. Correlations between the concentrations of these trace metals, normalized to Fe, in ash from the fire suggest that Co, Cu, and Ni in most of those samples were predominantly from natural sources, whereas Pb and Zn were enriched in some ash samples. The predominantly anthropogenic source of excess Pb in the ash was further demonstrated by its isotopic ratios (208Pb/207Pb: 206Pb/207Pb) that fell between those of natural Pb and leaded gasoline sold in California during the previous century. These analyses substantiate current human and environmental health concerns with the pyrogenic remobilization of toxic metals, which are compounded by projections of increases in the intensity and frequency of wildfires associated with climate change.
Photo-decomposition is among the most important mechanisms responsible for degrading monomethylmercury (MMHg) in aquatic systems, but this process is not fully understood. We investigated the ...relative importance of different factors in controlling the rate of MMHg photo-decomposition in surface waters in experiments using DOM isolated from natural waters. We found no evidence of net abiotic production of MMHg in any dark or light exposed treatments. The average (mean±s.d.) MMHg photo-decomposition rate constant for all light exposed samples using DOM concentrated from three coastal wetlands was 0.0099±0.0020E−1m2 (range of 0.006–0.015E−1m2) when expressed in photon flux from 330–700nm. This was roughly 3-fold higher than the average MMHg photo-decomposition rate constant in coastal seawater of 0.0032±0.0010E−1m2.
MMHg photo-degradation was highly wavelength dependent. The ratio of MMHg photo-decomposition rate constants, with respect to photon flux, was 400:37:1 for UVB:UVA:PAR. However, when integrated across the entire water column over which MMHg photo-demethylation occurs, PAR was responsible for photo-degrading more MMHg than UVB and UVA combined in the three wetland sites because of the more rapid attenuation of UV light with depth. MMHg half-lives in the wetlands were calculated for the upper 250cm where photo-degradation occurred, and ranged from 7.6 to 20days under typical summer sunlight conditions at 37°N.
Rates of MMHg photo-decomposition decreased with increasing salinity, and were 27% higher at a salinity of 5 than those at a salinity of 25. This difference could not be accounted for by changes in the complexation of MMHg by DOM and chloride. Differences in MMHg photo-degradation rate constants of up to 18% were measured between treatments using DOM concentrated from three different wetlands. Surprisingly, increasing DOM concentration from 1.5 to 11.3mgOCL−1 had only a small (6%) effect on MMHg photo-decomposition, which was much smaller than the 34% decrease predicted due to the attenuation of light at the higher DOM levels. This suggests that DOM plays an important role in MMHg photo-decomposition apart from mediating light levels and MMHg complexation.
Experiments employing various scavengers implied that singlet oxygen and hydroxyl radicals were not involved in the photo-degradation of MMHg in the natural waters used. Varying concentrations of Fe, Cu, and Mn had only small (⩽11%) effects on rates of MMHg photo-decomposition, and relatively high rates were measured in high purity water with no trace metals or DOM. These results demonstrate that MMHg photo-decomposition can occur via pathways not involving Fe, the photo–Fenton reaction, nitrate photolysis, or thiol complexation. Taken with previous studies, multiple reaction pathways appear to exist, and their importance varies as a function of water chemistry and light wavelength.
Recent trends of atmospheric lead deposition to the North Pacific were investigated with analyses of lead in aerosols and surface waters collected on the fourth Intergovernmental Oceanographic ...Commission Contaminant Baseline Survey from May to June, 2002. Lead concentrations of the aerosols varied by 2 orders of magnitude (0.1-26.4 pmol/m(3)) due in part to variations in dust deposition during the cruise. The ranges in lead aerosol enrichment factors relative to iron (1-119) and aluminum (3-168) were similar, evidencing the transport of Asian industrial lead aerosols across the North Pacific. The oceanic deposition of some of those aerosols was substantiated by the gradient of lead concentrations of North Pacific waters, which varied 3-fold (32.7-103.5 pmol/kg), were highest along with the Asian margin of the basin, and decreased eastward. The hypothesized predominance of Asian industrial lead inputs to the North Pacific was further corroborated by the lead isotopic composition of ocean surface waters ((206)Pb/(207)Pb = 1.157-1.169; (208)Pb/(206)Pb = 2.093-2.118), which fell within the range of isotopic ratios reported in Asian aerosols that are primarily attributed to Chinese industrial lead emissions.
California's Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) was designed to protect the state's populace from exposures to toxic levels of chemicals in consumer products, ...including foods, by requiring businesses to warn the public about any of those hazards. There is, however, one qualification in the legislation, which is that warnings are not required if the source of that contamination is natural, as opposed to industrial. That qualification is especially problematic for lead because "natural" and "industrial" lead have a common origin and behave the same in the environment and industrial lead contamination has been pandemic for millennia. As a result of that historic and ongoing contamination, ambient lead levels in the biosphere may be orders of magnitude above natural levels, limiting comparisons of "natural" versus "industrial" lead concentrations in products. Further complicating those comparisons are reports of erroneously high measurements of lead concentrations in the biosphere as a result of sample contamination during collection, storage, and analysis. Some of those problems may be addressed with measurements of lead concentrations using rigorous trace metal clean techniques. These techniques often yield lead concentrations that are below the Act's maximum exposure in foods and non-foods of 0.5 μg/day, eliminating the need for a public alert. Those techniques have also been used to derive natural lead concentrations in a few organisms (marine fish, humans, rats, and dandelions), which range from 2- to 100-fold below ambient levels. However, extrapolating from those few determinations to establish natural lead levels in other organisms is complicated and often inappropriate. Complementary stable lead isotopic composition measurements have also been used to estimate the percent of natural and industrial lead in some consumer products, including foods, wine, and dietary supplements. These measurements, however, require the isotopic compositions of both the "natural" and "industrial" lead end members, which may be poorly defined. In addition, the global market has further complicated identification of the "industrial" lead end member, because lead contamination of foods can occur during production, harvesting, storage, shipping, processing, and packaging, which can happen in different locales within a country, different countries, and even different continents.
Relatively high levels (4.3 to 51 μg/g) of labile lead (Pb) in ash from the 2009 Jesusita Fire in Santa Barbara County, California attest to the pyrogenic remobilization of historic industrial lead ...depositions in this relatively pristine area in Southern California, USA. The primarily industrial origin of that lead was evidenced by its poor correlations (simple linear regressions) with lithogenic aluminum (r = 0.18, p = 0.354, n = 30) and iron (r = 0.21, p = 0.270, n = 30) concentrations and by its associated enrichment factors (EFs): EF using aluminum as conservative element (f-Al) vs lead concentration Pb (r = 0.79, p < 0.001, n = 30), and EF using iron as conservative element (f-Fe) vs Pb (r = 0.83, p < 0.001, n = 30). The industrial origins of much of that lead were corroborated by its isotopic compositions ((206)Pb/(207)Pb and (208)Pb/(207)Pb), which fell between those of natural lead in the Santa Barbara Basin and previous leaded gasoline emissions in Southern California. This apparent pyrogenic remobilization of legacy lead pollution indicates that it-and other persistent pollutants-will increase with the projected increase in the frequency and intensity of forest fires in the Southwest U.S. and elsewhere as a consequence of climate change.
Groundwater from the Mocorito River aquifer in Mexico has been historically employed for both human consumption and irrigation of its overlaying agriculture fields. The aim of this research was to ...investigate the levels and distribution of potentially toxic elements (PTEs) in the aquifer to determine their sources and to assess their potential health risks. Groundwater samples were collected from wells at eighteen sites in two climatic seasons. In the dry season, mean dissolved concentrations (µg L
−1
) of As, Pb, Cd, and Cr were 3.19, 0.05, 0.02, and 0.15, respectively, and their total (unfiltered) concentrations were 4.10, 0.47, 0.05, and 0.52, respectively. While in the rainy season, their dissolved concentrations were 4.60, 0.03, 0.01, and 0.06, respectively, and their total concentrations were 5.58, 0.25, 0.01, and 0.12, respectively. On average, concentrations of the four PTEs were below national and international guidelines for drinking water. Concentrations of As exceeded the WHO (2007) guidelines (10 µg L
−1
) at three sites and had yielded relatively high values of both chronic daily intake and hazard quotient. Lifetime cancer risk for As indicated the probability for developing this disease of 1 in 10, 000 inhabitants. Pearson’s correlation and principal component analysis (PCA-Varimax) were carried out. According to these, all the PTE concentrations were mainly derived from natural lithogenic sources. Arsenic concentrations constitute potential human health concerns for both direct consumption and its bioaccumulation in local crops. Finally, due to high As concentrations in some sites in the aquifer, the implementation of a sustainable groundwater management plan in the MORCA, that include a monitoring of PTE levels, is recommended.
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