Temperature sensitivity of the turnover times of soil organic matter in forests.

Soils represent the largest carbon pool in the terrestrial biosphere, and climate change might affect the main carbon fluxes associated with this pool. These fluxes are the production of aboveground litter and root litter, and decomposition of the soil organic matter (SOM) pool by soil microorganisms. Knowledge about the temperature sensitivity of the decomposition of different SOM fractions is crucial in order to understand how climate change might affect carbon storage in soils. In this study, the temperature sensitivity of the turnover times of three different SOM fractions (labile, intermediate, and stabilized) was investigated for 11 forest sites along a temperature gradient. Carbon-14 isotope analyses of the SOM fractions combined with a model provided estimates of their turnover times. The turnover times of the labile SOM fraction were not correlated with mean annual soil temperature. Therefore it was not possible to estimate temperature sensitivity for the labile SOM fraction. Given considerable evidence elsewhere for significant temperature sensitivities of labile SOM, lack of temperature sensitivity here most likely indicates limitations of the applied methodology for the labile SOM fraction. The turnover times of the intermediate and the stabilized SOM fractions were both correlated with mean annual soil temperatures. The temperature sensitivity of the stabilized SOM fraction was at least equal to that of the intermediate SOM fraction and possibly more than twice as high. A correction for confounding effects of soil acidity and clay content on the temperature sensitivities of the intermediate and stabilized SOM fractions was included in the analysis. The results as observed here for the three SOM fractions may have been influenced by (1) modeling assumptions for the estimation of SOM turnover times of leaf and needle longevities, constant annual carbon inputs, and steady-state SOM pools, (2) the occurrence of summer drought at some sites, (3) differences between sites in quality of the SOM fractions, or (4) the relatively small temperature range. Our results suggested that a 1 degree C increase in temperature could lead to decreases in turnover times of 4-11% and 8-16%, for the intermediate and stabilized SOM fractions, respectively.     

Corporate waste accounting at PSE&G: Bringing a companywide system on-line

Waste accounting has become a necessary practice for companies endeavoring to track their wastes toward realizing discrete waste minimization and pollution prevention objectives. Measurement systems and program initiatives certainly must be tested to find out what will repeatedly work for and best serve a company. Public Service Electric and Gas Company (PSE&G) has committed to revolutionizing the processes of managing materials, wastes, and their associated information. In laying out their strategic plan, company representatives specified the need for a companywide waste accounting system to enable them to monitor progress toward achieving two important short-term waste management targets by the close of 1995. Together with the Electric Power Research Institute, PSE&G is implementing a four-year program to install such a system. The results of the first year-and-a-half's work are reported in this article. The purpose of this article is to discuss the results of implementing a waste accounting system on a utility companywide basis. We will address the experience of bringing such a system on-line at PSE&G. The Electric Power Research Institute (EPRI) previously developed a framework and approach for measuring the performance of utility pollution prevention programs called waste accounting, including the development of a software program called Accounting Software Application for Pollution Prevention or ASAPP.¹ These programs were devised to assimilate detailed information from the facility up through the corporate levels.     

AN INDEX OF STORED FINE SEDIMENT IN GRAVEL BEDDED STREAMS1

An index of sediments less than 0.3 mm stored in the top layer of small streams was estimated by disturbing a fixed area for 2 minutes and catching the resultant sediment drift in downstream traps. The method was used in 24 small northern California streams and was tested by releasing known amounts and sizes of sediments in controlled trails. Field use showed general agreement with an exponential model of decrease in sediment trapped vs. distance. Sites in distrubed reaches (watersheds logged with no streamside buffers or with buffers less than 30 m) had higher indices of stored sediment than control sites. Estimates from controlled trials averaged 7.5 percent higher than actual losses for composite size classes ≤ 0.3 mm, 19.7 percent higher than actual losses for just the ≤ 0.125 mm class, and 15.2 percent for all 14 trials. The method is relatively simple and suitable for remote locations, particularly in studies comparing many small streams.     

Synthesis of polychlorinated [14C]alkanes (PCA) of high specific activity

The synthesis of certain ¹⁴C-labelled polychlorinated alkanes is described. The compounds used as starting material were [1-¹⁴C]lauric acid, [1-¹⁴C]hexadecane and [U-¹⁴C]palmitic acid. The carboxylic acids were reduced with lithium aluminium hydride. The alcohol obtained was treated with triphenylphosphine dichloride which gave the corresponding 1-chloroalkane. The chlorination of the alkanes was performed in tetrachloromethane by use of sulphuryl chloride with benzoyl peroxide or UV-light as initiators. Three mixtures of polychlorinated dodecanes (45.9%, 55.9% and 68.5% chlorine) and two polychlorinated hexadecanes (34.1% and 69% chlorine) were synthesized. The products of higher chlorine content prepared were only available via the photoinduced chlorination.     

Mass balance modelling of contaminants in river basins: a flexible matrix approach

A novel and flexible approach is described for simulating the behaviour of chemicals in river basins. A number (n) of river reaches are defined and their connectivity is described by entries in an n x n matrix. Changes in segmentation can be readily accommodated by altering the matrix entries, without the need for model revision. Two models are described. The simpler QMX-R model only considers advection and an overall loss due to the combined processes of volatilization, net transfer to sediment and degradation. The rate constant for the overall loss is derived from fugacity calculations for a single segment system. The more rigorous QMX-F model performs fugacity calculations for each segment and explicitly includes the processes of advection, evaporation, water-sediment exchange and degradation in both water and sediment. In this way chemical exposure in all compartments (including equilibrium concentrations in biota) can be estimated. Both models are designed to serve as intermediate-complexity exposure assessment tools for river basins with relatively low data requirements. By considering the spatially explicit nature of emission sources and the changes in concentration which occur with transport in the channel system, the approach offers significant advantages over simple one-segment simulations while being more readily applicable than more sophisticated, highly segmented, GIS-based models.     

Microbial relationships in surface-mine revegetation

The establishment and interrelationships of microorganisms with soil and plant processes during reclamation are greatly influenced by the composition of the planting medium and vegetation practices. While in some instances the parent material may be used as the vegetation medium, the practice of topsoiling, particularly the direct haul method, may be beneficial in introducing microorganisms and improving the quality of the plant growth medium of spoils that are chemically or physically less desirable than the native soils. The influence of different vegetation types on soil development on surface mines may be a reflection of physioiogical differences that affect microbial development in the rhizosphere. Such differences include levels of carbohydrate translocated to the root system and/or released into the surrounding soil; the plant's effectiveness as a mycorrhizal host; and the rate of degradation of plant residues. It has become apparent that microbial interactions are an important part of plant and soil processes in reclamation. While some of the microorganisms important in plant growth and soil development can be introduced readily by management practices, the majority usually are disseminated by natural means and only gradually become a part of the microbial population. More research is needed on developing new methods or refining current procedures for early introduction of these microorganisms in reclamation practices.     

Analysis of heavy metals in foliage near a modern refuse incinerator

Heavy metals such as cadmium and lead are typically found at high levels in fly ash from refuse incinerators. In two earlier studies it was found that such heavy metals on grass or tree foliage in the vicinity of old refuse incinerators with relatively low stacks and limited or no emission control devices showed a high degree of correlation between diminishing foliar concentration and the logarithm of sampling distance from the incinerator. In the study reported here of the concentration of cadmium and lead on foliage near a modern refuse incinerator with a high stack and efficient emission controls, the foliar concentrations of the metals showed no significant diminution with sampling distance from the incinerator. Factors affecting heavy metal emissions from refuse incinerators and contamination of nearby areas are discussed.     

Collectivism,propensity to trust and self-esteem as predictors of organizational citizenship in a non-work setting

This study examined organizational citizenship of residents in a housing cooperative setting where roles were not influenced by traditional employee–employer work relationships. Results demonstrate that the individual differences of collectivism and propensity to trust predicted organizational citizenship (assessed six months later). In addition, organizational-based self-esteem fully mediated the effects of collectivism and propensity to trust on organizational citizenship, and tenure moderated the trust—self-esteem relationship. We discuss the implications of these results given the changing nature of work and the increasing importance of non-work organizations. Copyright © 2000 John Wiley & Sons, Ltd.