Chemical mass balance source apportionment for combined PM2.5 measurements from U.S. non-urban and urban long-term networks

The Minnesota Particulate Matter 2.5 (PM_2.5) Source Apportionment Study was undertaken to explore the utility of PM_2.5 mass, element, ion, and carbon measurements from long-term speciation networks for pollution source attribution. Ambient monitoring data at eight sites across the state were retrieved from the archives of the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Speciation Trends Network (STN; part of the Chemical Speciation Network [CSN]) and analyzed by an Effective Variance – Chemical Mass Balance (EV-CMB) receptor model with region-specific geological source profiles developed in this study. PM_2.5 was apportioned into contributions of fugitive soil dust, calcium-rich dust, taconite (low grade iron ore) dust, road salt, motor vehicle exhaust, biomass burning, coal-fired utility, and secondary aerosol. Secondary sulfate and nitrate contributed strongly (49–71% of PM_2.5) across all sites and was dominant (≥60%) at IMPROVE sites. Vehicle exhausts accounted for 20–70% of the primary PM_2.5 contribution, largely exceeding the proportion in the primary PM_2.5 emission inventory. The diesel exhaust contribution was separable from the gasoline engine exhaust contribution at the STN sites. Higher detection limits for several marker elements in the STN resulted in non-detectable coal-fired boiler contributions which were detected in the IMPROVE data. Despite the different measured variables, analytical methods, and detection limits, EV-CMB results from a nearby IMPROVE-STN non-urban/urban sites showed similar contributions from regional sources – including fugitive dust and secondary aerosol. Seasonal variations of source contributions were examined and extreme PM_2.5 episodes were explained by both local and regional pollution events.     

Distribution of radionuclides in the guano sediments of Xisha Islands, South China Sea and its implication

Several natural and anthropogenic radionuclides (²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs) in guano-phosphatic coral sediments and pure guano particles collected from Ganquan, Guangjin, Jinqing and Jinyin Islands of the Xisha archipelago, South China Sea, were analyzed. The Constant Initial Concentration (CIC) model and the Constant Rate of Supply (CRS) model were applied for age calculation. The average supply rate of ²¹⁰Pb was 126 Bq m⁻² a⁻¹, very close to the flux of northern hemisphere average (125 Bq m⁻² a⁻¹). The activities of anthropogenic radionuclides in the sediments were very low, indicating that human nuclear tests did not notably impact this region. The main source of radionuclides in the sediments was from atmospheric precipitation, and the organic matter derived from plant and produced by nutrient-rich guano could further enhance them.     

Concentration and characterization of plutonium in soils of Hubei in central China

To study the Pu concentration and isotope ratio distributions present in China, the ^239+240Pu total activities and ²⁴⁰Pu/²³⁹Pu atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBq g⁻¹ and the ^239+240Pu inventories of 45 and ∼55 Bq m⁻² agree well with that expected from global fallout. The ²⁴⁰Pu/²³⁹Pu atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar ²⁴⁰Pu/²³⁹Pu ratio to that of global fallout. The top 10 cm layer of the soil contributes ∼90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil.     

Distributions of radionuclide sorption coefficients (Kd) in sub-surface sediments and the implications for transport calculations

The effect of the spatial variability of K_d on calculations of contaminant travel time in the vadose zone was determined. Depth discrete measurements of K_d were made for a suite of radionuclides (¹⁰⁹Cd, ⁵⁷Co, ⁶⁰Co, ⁸⁵Sr, ¹³⁷Cs, and ⁸⁸Y) utilizing a sediment core from the E-Area at the Savannah River Site. The K_d’s were ordered as ⁸⁵Sr²⁺ < ¹³⁷Cs⁺ < ¹⁰⁹Cd²⁺ < ⁵⁷Co²⁺ = ⁶⁰Co²⁺ << ⁸⁸Y³⁺ and the values generally fell below or near the lowest quartile of values reported in the literature. Correlations were generally weak between soil properties and K_d values. Most importantly, all of the K_d distributions could be reasonably approximated as log-normal. Deterministic and stochastic calculations of contaminant travel time to the water table were made. The deterministic calculations were based on each of three conceptual models of the vadose zone: complete stratification (17 strata, each with a different K_d), two strata (two sections of the vadose zone, each characterized by a single, average K_d), and unstratified (a single zone with an average K_d). Stochastic calculations were based on log-normal fits to the K_d data. The two strata model generally yielded travel times 2× greater than those in the completely stratified model. The unstratified model yielded travel times that were between 3 and 5 times greater than the completely stratified model. The stochastic mean travel times were comparable to those of the two strata model.     

Localization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene (TNT) in poplar and switchgrass plants using phosphor imager autoradiography

Phosphor imager autoradiography is a technique for rapid, sensitive analysis of the localization of xenobiotics in plant tissues. Use of this technique is relatively new to research in the field of plant science, and the potential for enhancing visualization and understanding of plant uptake and transport of xenobiotics remains largely untapped. Phosphor imager autoradiography is used to investigate the uptake and translocation of the explosives 1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6-trinitrotoluene within Populus deltoides × nigra DN34 (poplar) and Panicum vigratum Alamo (switchgrass). In both plant types, TNT and/or TNT-metabolites remain predominantly in root tissues while RDX and/or RDX-metabolites are readily translocated to leaf tissues. Phosphor imager autoradiography is further investigated for use in semi-quantitative analysis of uptake of TNT by switchgrass.     

Deposition of reactive nitrogen during the Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study

Increases in reactive nitrogen deposition are a growing concern in the U.S. Rocky Mountain west. The Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study was designed to improve understanding of the species and pathways that contribute to nitrogen deposition in Rocky Mountain National Park (RMNP). During two 5-week field campaigns in spring and summer of 2006, the largest contributor to reactive nitrogen deposition in RMNP was found to be wet deposition of ammonium (34% spring and summer), followed by wet deposition of nitrate (24% spring, 28% summer). The third and fourth most important reactive nitrogen deposition pathways were found to be wet deposition of organic nitrogen (17%, 12%) and dry deposition of ammonia (14%, 16%), neither of which is routinely measured by air quality/deposition networks operating in the region. Total reactive nitrogen deposition during the spring campaign was determined to be 0.45 kg ha⁻¹ and more than doubled to 0.95 kg ha⁻¹ during the summer campaign.     

Effects of elevated atmospheric CO2 and tropospheric O3 on tree branch growth and implications for hydrologic budgeting

The forest hydrologic budget may be impacted by increasing CO₂ and tropospheric O₃. Efficient means to quantify such effects are beneficial. We hypothesized that changes in the balance of canopy interception, stem flow, and through-fall in the presence of elevated CO₂ and O₃ could be discerned using image analysis of leafless branches. We compared annual stem flow to the results of a computerized analysis of all branches from the 2002, 2004, and 2006 annual growth whorls of 97 ten-year-old trees from the Aspen Free-Air CO₂ and O₃ Enrichment (Aspen FACE) experiment in Rhinelander, WI. We found significant effects of elevated CO₂ and O₃ on some branch metrics, and that the branch metrics were useful for predicting stem flow from birch, but not aspen. The results of this study should contribute to development of techniques for efficient characterization of effects on the forest hydrologic budget of increasing CO₂ and tropospheric O₃.     

Biological and chemical assessments of zinc ageing in field soils

As zinc (Zn) is both an essential trace element and potential toxicant, the effects of Zn fixation in soil are of practical significance. Soil samples from four field sites amended with ZnSO₄ were used to investigate ageing of soluble Zn under field conditions over a 2-year period. Lability of Zn measured using ⁶⁵Zn radioisotope dilution showed a significant decrease over time and hence evidence of Zn fixation in three of the four soils. However, 0.01 M CaCl₂ extractions and toxicity measurements using a genetically modified lux-marked bacterial biosensor did not indicate a decrease in soluble/bioavailable Zn over time. This was attributed to the strong regulatory effect of abiotic properties such as pH on these latter measurements. These results also showed that Zn ageing occurred immediately after Zn spiking, emphasising the need to incubate freshly spiked soils before ecotoxicity assessments.     

Effect of water treatment residuals on soil phosphorus, copper and aluminium availability and toxicity

Water treatment residuals (WTRs) are produced by the treatment of potable water with coagulating agents. Beneficial recycling in agriculture is hampered by the fact that WTRs contain potentially toxic contaminants (e.g. copper and aluminium) and they bind phosphorus strongly. These issues were investigated using a plant bioassay (Lactuca sativa), chemical extractions and an isotopic dilution technique. Two WTRs were applied to an acidic and a neutral pH soil at six rates. Reductions in plant growth in amended soils were due to WTR-induced P deficiency, rather than Al or Cu toxicity. The release of potentially toxic Al from WTRs was found to be mitigated by their alkaline nature and pH buffering capacity. However, acidification of WTRs was shown to release more soluble Al than soil naturally high in Al. Copper availability was relatively low in all treatments. However, the lability of WTR-Cu increased when the WTR was applied to the soil.     

Reagenzienfreie Bestimmung von Quecksilberspuren in Wasserproben

Routinef?hige, kostengünstige analytische Messverfahren sind die Grundlage für ein fl?chendeckendes Umweltmonitoring von Schadstoffen und somit für die Sicherung unserer Gesundheit und natürlichen Lebensgrundlagen. Hierbei kann die Analytik zur nachhaltigen Nutzung und zur Schonung unserer Umweltressourcen beitragen, indem auf den Einsatz umweltgef?hrdender Reagenzien verzichtet wird.