Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment1

Crockett, Kris, Jonathan B. Martin, Henri D. Grissino-Mayer, Evan R. Larson, and Thomas Mirti, 2010. Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment. Journal of the American Water Resources Association (JAWRA) 1-13. DOI: 10.1111/j.1752-1688.2010.00464.x Abstract: Information about long-term variability of streamflow is important to allocate water resources, but few historical records extend more than 75 years into the past, requiring proxy records to evaluate flow prior to that time. Flow proxies have been found in tree-ring widths in temperate regions, but have rarely been used in humid subtropical environments because the relationship between tree growth and climate was believed to be weakened by limited seasonality and stress on tree growth from drought conditions. Tree-ring residual chronologies from two forests sampled from northern Florida correlate well with historical annual discharge (r² values as high as 0.47) from 3 of 15 river-gauging stations that were used to compare with the tree-ring chronologies. The best correlations occur where streamflow has little contribution from spring discharge or continuous flow from lakes and wetlands. Streams lack correlations with the tree-ring residual chronologies (r² values as low as 0.0002) where springs and continuous discharge from lakes mute variations in their flow. Tree-ring chronologies appear to be useful for reconstruction of prehistorical variations of some streamflow in humid subtropical regions, but interpretations of the reconstructions must consider the local hydrologic conditions.     

Effects of organic matter on the distribution of uranium in soil and plant matrices

This work studied interactions of uranium with pure organic compounds, such as glutathione, and more complex mixtures, such as humic acid and aqueous plant extracts. High performance liquid chromatography with UV absorption interfaced to inductively coupled plasma mass spectrometry sequential detection was used to detect organouranium complexes in a variety of soils and plant materials, indicating that nearly 100% of the uranium extracted from certain plant tissues was bound to organic ligands. In addition, soil sorption experiments indicated that humic acid generally decreased uranium sorption to soils and promoted subsequent desorption of uranium because of uranium partitioning to the organic phase. These experiments demonstrate that organic compounds influence the mobility and chemistry of uranium in the environment.     

A cost-effective weighing chamber for particulate matter filters

Particulate matter (PM) is a ubiquitous air pollutant that has been receiving increasing attention in recent years due in part to the association between PM and a number of adverse health outcomes, including mortality and increases in emergency room visits and respiratory symptoms, as well as exacerbation of asthma and decrements in lung function. As a result, the ability to accurately sample ambient PM has become important, both to researchers and to regulatory agencies. The federal reference method for the determination of fine PM as PM2.5 in the atmosphere recommends that particle-sampling filters be conditioned and weighed in an environment with constant temperature and relative humidity (RH). It is also recommended that vibration, electrostatic charges, and contamination of the filters from laboratory air be minimized to reduce variability in filter weight measurements. These controls have typically been maintained in small, environmentally controlled "cleanrooms." As an alternative to constructing an elaborate cleanroom, we have designed, and presented in this paper, an inexpensive weighing chamber to maintain the necessary level of humidity control.     

Environmental behavior of explosives in groundwater from the Milan Army Ammunition Plant in aquatic and wetland plant treatments. Removal, mass balances and fate in groundwater of TNT and RDX.

Phytoremediation of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in groundwater using constructed wetlands is a potentially economical remediation alternative. To evaluate Explosives removal and fate was evaluated using hydroponic batch incubations of plant and substrate treatments with explosives-contaminated groundwater amended with [U-14C]-TNT or [U-14C]-RDX. Plants and substrates were collected from a small-scale wetland constructed for explosives removal, and groundwater originated from a local aquifer at the Milan Army Ammunition Plant. The study surveyed three aquatic, four wetland plant species and two substrates in independent incubations of 7 days with TNT and 13 days with RDX. Parent compounds and transformation products were followed using 14C and chemical (HPLC) analyses. Mass balance of water, plants, substrates and air was determined. It was demonstrated that TNT disappeared completely from groundwater incubated with plants, although growth of most plants except parrot-feather was low in groundwater amended to contain 1.6 to 3.4 mg TNT L-1. Highest specific removal rates were found in submersed plants in water star-grass and in all emergent plants except wool-grass. TNT declined less with substrates, and least in controls without plants. Radiolabel was present in all plants after incubation. Mineralization to 14CO2 was very low, and evolution into 14C-volatile organics negligible. RDX disappeared less rapidly than TNT from groundwater. Growth of submersed plants was normal, but that of emergent plants reduced in groundwater amended to contain 1.5 mg RDX L-1. Highest specific RDX removal rates were found in submersed plants in elodea, and in emergent plants in reed canary grass. RDX failed to disappear with substrates. Mineralization to 14CO2 was low, but relatively higher than in the TNT experiment. Evolution into 14C-volatile organics was negligible. Important considerations for using certain aquatic and wetland plants in constructed wetlands aimed at removing explosives from water are: (1) plant persistence at the explosives level to which it is exposed, (2) specific plant-mass based explosives removal rates, (3) plant productivity, and (4) fate of parent compounds and transformation products in water, plants, and sediments.     

Water management decision makers' evaluations of uncertainty in a decision support system: the case of WaterSim in the Decision Theater

Model-based decision support systems are increasingly used to link knowledge to action for environmental decision making. How stakeholders perceive uncertainty in models and visualisations affects their perceptions of credibility, relevance and usability of these tools. This paper presents a case study of water decision makers’ evaluations of WaterSim, a dynamic water simulation model presented in an immersive decision theatre environment. Results reveal that decision makers’ understandings of uncertainty in their evaluations of decision support systems reflect both scientific and political discourse. We conclude with recommendations for design and evaluation of decision support systems that incorporate decision makers' views.     

Cancer risk assessment of selected hazardous air pollutants in Seattle

The risk estimates calculated from the conventional risk assessment method usually are compound specific and provide limited information for source-specific air quality control. We used a risk apportionment approach, which is a combination of receptor modeling and risk assessment, to estimate source-specific lifetime excess cancer risks of selected hazardous air pollutants. We analyzed the speciated PM(2.5) and VOCs data collected at the Beacon Hill in Seattle, WA between 2000 and 2004 with the Multilinear Engine to first quantify source contributions to the mixture of hazardous air pollutants (HAPs) in terms of mass concentrations. The cancer risk from exposure to each source was then calculated as the sum of all available species' cancer risks in the source feature. We also adopted the bootstrapping technique for the uncertainty analysis. The results showed that the overall cancer risk was 6.09 x 10(-5), with the background (1.61 x 10(-5)), diesel (9.82 x 10(-6)) and wood burning (9.45 x 10(-6)) sources being the primary risk sources. The PM(2.5) mass concentration contributed 20% of the total risk. The 5th percentile of the risk estimates of all sources other than marine and soil were higher than 110(-6). It was also found that the diesel and wood burning sources presented similar cancer risks although the diesel exhaust contributed less to the PM(2.5) mass concentration than the wood burning. This highlights the additional value from such a risk apportionment approach that could be utilized for prioritizing control strategies to reduce the highest population health risks from exposure to HAPs.     

Remotely engaged? Towards a framework for monitoring the success of stakeholder engagement in remote regions

The importance of stakeholder engagement for the success of natural resources management processes is widely acknowledged, yet evaluation frameworks employed by administrators of environmental programmes continue to provide limited recognition of or insistence upon engagement processes. This paper presents a framework for monitoring and evaluation of engagement that aims to better incorporate community engagement into mainstream environmental programmes, in particular in remote regions such as arid and desert regions of the world. It is argued that successful monitoring of engagement should not only comprise a generic set of indicators but rather, in addition to the principles of good monitoring practice, should take into account a variety of the stakeholder interests as well as key regional drivers, addressing them at right geographic, institutional and time scale.