Particulate Pb Concentrations Research Articles

Geochemical identification of particulate lead pollution in shallow groundwater in inhabited areas in Kabwe, Zambia

The town of Kabwe has been exposed to the most severe lead pollution due to mining activities in the 20th century. A large tailing (slag) hill containing over 1% of Pb is still standing within the mine's licensed area. We analysed the chemical composition and lead isotope ratios in seventeen shallow wells, five deep wells in the inhabitants' area, three ponds and three borehole wells in the area of the mine, and in the surrounding areas, we examined two samples from the soil's surface and nineteen 1-m deep core samples at each of the 15 sites. We found low dissolved Pb (<0.04 μg/L) but high particulate Pb concentrations (2–100 μg/L) in seventeen shallow groundwater samples (aquifer depth of ca. 10 meters). Five shallow wells exceeded the World Health Organization (WHO) guideline (10 μg/L) for total-Pb concentration. However, three of the five shallow wells had low dissolved Zn and sulphate ion concentrations (<1 μg/L; <50 mg/L), suggesting a low amount of Pb transfers through the aquifer. The isotopic water and soil samples data clarified that the Pb pollution in the shallow groundwaters is derived from the tailings deposit.Most of the shallow groundwater samples had negative cerium (Ce) anomaly in the rare earth element (REE) pattern, indicating contributions of colloidal transport from the dolomite aquifer in this area. However, PHREEQC modelling shows that migration by hydroxide colloids from the mining area does not explain the high particulate lead concentrations in the well water. The positive correlation between Pb/Ce and Pb/Al ratios in the particulates exhibited that the lead pollutants were derived from the aluminosilicates on the land. The estimated Pb contents in particulates in most shallow-well water were 700–2800 mg/L, and they distributed geographically similar to the Pb bulk concentration contour map of the surface soil. The analysis of the grain-size fractions in a 2-km transect soil demonstrated that Pb was eight times enriched in the silt fraction (<53 μm) than a very coarse sand fraction (1–2 mm). Therefore, we hypothesized that the particulates in the well water were mainly derived from the aeolian dust (>0.45 μm) at the well site. Further studies are required to examine the hypothesis.

Using historical atmospheric pollution data to prioritize environmental sampling in urban areas

Even when atmospheric particulate matter (PM) pollution declines in urban settings, the residual effects of PM can still be felt by the community. Specifically, PM containing elevated levels of lead (Pb) can accumulate in soils and pose an ingestion/inhalation risk well after deposition because of the relatively immobile chemical nature of Pb. This short communication utilizes a case study of Memphis, TN, where particulate pollution has been reported at high levels. Through conducting time series analysis of atmospheric Pb concentrations, a Pb pollution hot spot in Southwest Memphis is identified as a location where urban soil Pb testing should be focused because of high particulate Pb concentrations in the past. Furthermore, residents in this area are predominantly low income and of ethnic minority (African-American), reiterating previous literature regarding uneven distribution of demographics exposed to pollution in Memphis. Although Pb PM pollution has decreased in recent decades throughout the United States, the use of past Pb air monitoring data in cities can help target specific areas where additional Pb testing may be needed by governments and researchers, particularly where blood Pb level or historical land use data may be limited.

Sampling in schools and large institutional buildings: Implications for regulations, exposure and management of lead and copper

Legacy lead and copper components are ubiquitous in plumbing of large buildings including schools that serve children most vulnerable to lead exposure. Lead and copper samples must be collected after varying stagnation times and interpreted in reference to different thresholds. A total of 130 outlets (fountains, bathroom and kitchen taps) were sampled for dissolved and particulate lead as well as copper. Sampling was conducted at 8 schools and 3 institutional (non-residential) buildings served by municipal water of varying corrosivity, with and without corrosion control (CC), and without a lead service line. Samples included first draw following overnight stagnation (>8h), partial (30 s) and fully (5 min) flushed, and first draw after 30 min of stagnation. Total lead concentrations in first draw samples after overnight stagnation varied widely from 0.07 to 19.9 μg Pb/L (median: 1.7 μg Pb/L) for large buildings served with non-corrosive water. Higher concentrations were observed in schools with corrosive water without CC (0.9–201 μg Pb/L, median: 14.3 μg Pb/L), while levels in schools with CC ranged from 0.2 to 45.1 μg Pb/L (median: 2.1 μg Pb/L). Partial flushing (30 s) and full flushing (5 min) reduced concentrations by 88% and 92% respectively for corrosive waters without CC. Lead concentrations were <10 μg Pb/L in all samples following 5 min of flushing. However, after only 30 min of stagnation, first draw concentrations increased back to >45% than values in 1st draw samples collected after overnight stagnation. Concentrations of particulate Pb varied widely (≥0.02–846 μg Pb/L) and was found to be the cause of very high total Pb concentrations in the 2% of samples exceeding 50 μg Pb/L. Pb levels across outlets within the same building varied widely (up to 1000X) especially in corrosive water (0.85–851 μg Pb/L after 30MS) confirming the need to sample at each outlet to identify high risk taps. Based on the much higher concentrations observed in first draw samples, even after a short stagnation, the first 250mL should be discarded unless no sources of lead are present. Results question the cost-benefit of daily or weekly flushing as a remediation strategy. As such, current regulatory requirements may fail to protect children as they may not identify problematic taps and effective mitigation measures.

Rapid Release and Changing Sources of Pb in a Mountainous Watershed during Extreme Rainfall Events

Although atmospheric Pb is known to accumulate in forest soils over time, little is known about the hydrologic Pb export from mountain forest soils. Short-term changes in Pb release and its sources during monsoon rainfall events were investigated in a mountainous watershed in the northern extreme of South Korea by combining intensive storm sampling with measurements of Pb concentrations and isotope ratios in soils and size-fractionated sediments. Biweekly monitoring of forest and agricultural streams showed relatively low dissolved Pb concentrations compared to those found in precipitation. Particulate Pb concentrations in both streams were higher than the dissolved concentrations and increased rapidly during rainfall events. Particulate Pb concentrations were substantially higher in the agricultural stream; the highest concentrations were associated with silt-size sediment followed by sand. A comparison of (206)Pb/(207)Pb and (208)Pb/(206)Pb among sediment fractions and source soils indicated that major sources for silt- and sand-associated Pb in the agricultural stream change between streambank and cropland soils, whereas Pb in the forest stream is primarily derived from forest floors. The results suggest that Pb isotopes can be efficiently applied to tracing short-term changes in sediment and Pb sources and that extreme rainfall events can significantly increase Pb mobilization from erosion-prone mountain soils.

Early diagenesis and isotopic composition of lead in Lake Laisan, northern Sweden

Water column (dissolved/suspended phase, sediment traps) and sediment data (pore-water, solid-phase sediment) were combined with stable Pb and 210Pb isotope data to trace the early diagenetic behaviour and geochemical cycling of Pb in Lake Laisan, a lake which has received large quantities of anthropogenic Pb since the early 1940s. Early diagenetic remobilisation of Pb is indicated by a subsurface pore-water Pb maximum (120 μg l −1) in the oxic surface layer of the sediment, where the solid-phase Pb concentration is 3400–4600 μg g −1. The remobilisation of Pb appears to be caused by a pH-controlled desorption of Pb from solid-phase sediment, which is consistent with a model describing surface complexation of Pb(II) on hydrous goethite surfaces. The diffusive Pb flux from the subsurface pore-water maximum towards the sediment surface (36 μg cm −2 year −1) exceeds the depositional Pb flux (8.6 μg cm −2 year −1) by approximately a factor of four, indicating that Pb is highly mobile in the sediment. Stable Pb isotope data and a mass balance calculation suggest that Pb diffusing upwards is, to a large extent, trapped in the surface sediment. Lead that may diffuse into the slightly alkaline lake water appears to be efficiently sorbed to suspended particulate matter, resulting in low dissolved Pb concentrations in the water column (0.040–0.046 μg l −1). Sorption of Pb to suspended particulate matter is consistent with the elevated suspended particulate Pb concentrations in the hypolimnion (3800–4000 μg g −1), and the fact that the stable Pb isotopic compositions of suspended matter and pore-water are similar.

Trace Metals in the Central and Southern North Sea

Measurements of both dissolved and particulate trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) were made on samples collected simultaneously in the central and southern North Sea (below 56°N), during four cruises covering the seasonal cycle. Analyses of trace metals in both phases were undertaken using similar analytical protocols, and the data subjected to rigorous quality controls. Clean techniques were used throughout sampling and analysis. Trace metal concentrations ranged from those characteristic of waters entering the shelf region from the North Atlantic Ocean to values which in some cases were two orders of magnitude higher. Marked increases in concentrations were often associated with waters directly influenced by riverwaters, but the results showed that the distributions could be influenced by processes other than fluvial inputs. The redox-sensitive metals, Fe and Mn, were influenced at some sites, including those overlying areas of fine-grained sediments, by benthic inputs associated with seasonal changes in oxidation-reduction conditions in the benthic interfacial zone. The behaviour of metals which are not redox-sensitive (Cd, Zn) in some cases paralleled those of Fe and Mn, suggesting an association with Mn-or Fe-rich solid phases, or with organic matter. However, seasonal variations in concentrations of Cd and Zn were not directly linked to the cycle of biological utilization and regeneration of nutrients, suggesting that their geochemistry is more influenced by boundary inputs. Resuspension of Pb-rich sediments, long-range transport of Pb-rich suspended particulate matter (SPM), and enhanced, though diffuse, atmospheric inputs of lead were considered to have contributed to the elevated concentrations of particulate Pb (mass metal/mass sediment) in the water column during winter. Estimates of partitioning (K D s) were derived from the dissolved and particulate data for each of the metals over the seasonal cycle. For the more particle-reactive metals (Co, Fe, Mn, Pb), transport in the suspended particulate phase is a significant, sometimes dominant factor. In contrast, for Cd, Cu and Zn, transport in solution will dominate under almost all conditions in the southern North Sea. Furthermore, the values of K D , for a particular metal, varied widely, partly in response to seasonal differences in the relative contributions of lithogenous and biogenous particles to the particles in suspension. Only for Cu and Zn during the winter could the partitioning be described by a narrow range of K D values covering the observed concentrations of SPM. The data from this study give unique information concerning the contemporaneous distribution of dissolved and particulate trace metals in the southers North Sea and they provide a baseline against which the effects of reductions of inputs into the North Sea may be more accurately assessed. Viewed in combination, the dissolved and particulate data have yielded new insights into mechanisms affecting trace metal cycling and transport, essential in the development of coupled hydrodynamic-geochemical models.

Concentrations of dissolved and suspended particulate Cd, Cu, Mn, Ni, Pb and Zn in surface waters around the coasts of England and Wales and in adjacent seas

Trace metal concentrations in British coastal waters were determined during the summers of 1991 and 1992. The measured concentrations of Cd, Cu, Ni, Pb and Zn are in general agreement with those previously reported in the literature. Higher offshore dissolved Mn concentrations (mean = 1·2 μg l −1) are attributed to summertime increases in benthic Mn fluxes to the water column. Concentrations of all determinands were generally higher in the Irish Sea and North Sea than in the English Channel. This reflects the larger riverine component of the North and Irish Seas, and the stronger influence of North Atlantic water in the English Channel. Elevated dissolved and suspended particulate Pb concentrations in the Dogger Bank region are tentatively attributed to atmospheric inputs, and reduced removal by the lower concentrations of suspended particulate matter at these stations. Of the six major estuaries sampled, the Tweed was regarded as a reference site since it has a sparsely populated catchment area with little industry. Dissolved Mn concentrations in the Tweed were generally lower than those in the other estuaries, although the highest suspended particulate Mn (6600 μg g −1) and Ni (69 μg g −1) concentrations were found there. These high particulate concentrations are attributed to the oxidation of Mn(II) and the subsequent scavenging of Ni by the newly precipitated Mn-oxyhydroxides. Highest suspended particulate Cd (6·1 μg g −1), Cu (200 μg g −1), Pb (650 μg g −1) and Zn (1400 μg g −1), and dissolved Pb (1·1 μg g −1) and Zn (25 μg l −1) concentrations were observed in the Tyne. The Tees had the highest dissolved Cu (10 μg l −1) concentration, while the Humber and Mersey had the highest dissolved Cd (220 ng l −1) and Ni concentrations (9·4 μg l −1), respectively. The high concentrations are attributed to anthropogenic inputs.

The impact of scavenging on trace metal budgets in Puget Sound

The distributions of dissolved and particulate Mn, Pb, Cu and Zn in Puget Sound, its tributaries, and its sediments were determined to illustrate the impact of scavenging reactions on trace metal budgets of a large fjordlike estuary. About 75% of the dissolved Pb discharged into the main basin of Puget Sound was scavenged from the dissolved phase. The high particulate Pb concentrations in regions of high particulate Mn concentrations and the significant correlations between Pb and Mn concentrations on suspended particles demonstrate the importance of hydrous manganese oxide phases in scavenging dissolved Pb. Since particles are effectively retained within the main basin, scavenging results in the sedimentation of about 70% of the total Pb added to the main basin. Only isolated instances of scavenging of dissolved Cu and Zn were observed and the discharge rates of dissolved Cu and Zn from known sources were equal to their rates of advective removal within the errors of the budget. The remineralization of organically-bound particulate Cu is partly responsible for its quasi-conservative behavior within the main basin of Puget Sound. The fates of Cu and Zn are controlled mainly by physical processes such as advection and settling of particles. Advection removes about 60% of the total Cu and Zn added to the main basin while 40% is deposited in the sediments of Puget Sound.

Cadmium and Lead Cycling Between Water, Sediment, and Biota in an Artificially Contaminated Mud Flat on Borkum (F.R.G.)

A ‘Bremerhaven caisson' was used to investigate the interactions of cadmium (Cd) and lead (Pb) with sea water, particulate matter (SPM), sediments, and biota in an enclosed (13m2) tidal mud flat area on the island of Borkum (FRG). Artificial contamination was accomplished by injecting Cd as a chloride and Pb as a nitrate into the caisson so as to maintain metal concentrations of 100 µg/1 in the inflowing water of each tidal cycle for 25 days. Each component of the system was sampled at selected intervals inside and outside the caisson. The results show that most (85%) of the injected Cd remained in the soluble phase whereas most (90%) of the Pb was transferred to the particulate phase. Cyclic changes in particulate Cd and Pb concentrations occur and indicate that Cd is progressively taken up by the SPM over each tidal cycle, but after an initial rapid uptake, particulate Pb concentrations remain relatively constant in the system. In the sediments, Cd concentrations decrease with depth but increase with time, with the highest increases occurring in the surface sediment layers. Lead concentrations initially remain constant with depth, but eventually Pb becomes enriched in the top 3 cm of the sediments. Biota show an exponential increase in Cd and Pb during the experiment. Lead is enriched relative to Cd by a factor of 2 in mussels despite its low level in the dissolved phase. Infaunal benthic species have lower metal concentrations than the filter feeders.