Determination of biomass burning emission factors: Methods and results

Biomass burning, in a broad sense, encompasses different burning practices, including open and confined burnings, and different types of vegetation. Emission factors of gaseous or particulate trace compounds are directly dependent both on the fuel type and the combustion process. Emission factors are generally calculated by stoichiometric considerations using the carbon mass balance method, applied either to combustion chamber experiments or to field experiments based on ground-level measurements or aircraft sampling in smoke plumes. There have been a number of experimental studies in the last 10 years to investigate wildfires in tropical, temperate, or boreal regions. This article presents an overview of measurement methods and experimental data on emission factors of reactive or radiatively active trace compounds, including trace gases and particles. It focuses on fires in tropical regions, that is, forest and savanna fires, agricultural burns, charcoal production, use of fuelwood, and charcoal combustion.     

Characterizing soils for hazardous waste site assessments

This paper provides a review and justification of the minimum data needed to characterize soils for hazardous waste site assessments and to comply with the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). Scientists and managers within the regulatory agency and the liable party need to know what are the important soil characteristics needed to make decisions about risk assessment, what areas need remediation and what remediation options are available. If all parties involved in characterizing a hazardous waste site can agree on the required soils data set prior to starting a site investigation, data can be collected in a more efficient and less costly manner. Having the proper data will aid in reaching decisions on how to address concerns at, and close-out, hazardous waste sites.This paper was prepared to address two specific concerns related to soil characterization for CERCLA remedial response. The first concern is the applicability of traditional soil classification methods to CERCLA soil characterization. The second is the identification of soil characterization data type required for CERCLA risk assessment and analysis of remedial alternatives. These concerns are related, in that the Data Quality Objective (DQO) process addresses both. The DQO process was developed in part to assist CERCLA decision-makers in identifying the data types, data quality, and data quantity required to support decisions that must be made during the remedial investigation/feasibility study (RI/FS) process. Data Quality Objectives for Remedial Response Activities: Development Process (US EPA, 1987a) is a guidebook on developing DQOs. This process as it relates to CERCLA soil characterization is discussed in the Data Quality Objective Section of this paper.     

Field scale variability of cadmium and zinc in soil and barley

CaCl₂-extractable soil Cd and Zn contents have been suggested as a measure of bioavailability. To investigate the ability of this measure to reflect spatial patterns of Cd and Zn concentrations in barley (Hordeum vulgare L.) in an arable field, plant and soil samples were taken from a 0.5 ha area sandy soil contaminated with Cd and Zn. Cd and Zn contents in barley and yield were spatially variable. Yield was low, which may have been caused by Zn toxicity or atrazine turnover. For Cd, CaCl₂-extractable soil contents explained only 17% of the variation in Cd contents in grain, and for Zn no significant correlation was observed. Nevertheless, surface plots of CaCl₂-extractable soil contents and contents of barley grain illustrated their corresponding spatial patterns. Despite the poor linear correlation between CaCl₂-extractable soil-Cd and grain-Cd, a stochastic model for long term behaviour of Cd in field soils predicted observed variability in Cd contents of barley grain well from spatial variability of soil pH and organic matter content. The probabilistic model predicted behaviour of Cd in terms of probability, and was more appropriate than the deterministic approach.     

Effects of exposure of aquatic snails to sublethal concentrations of waste drilling fluid

Static bioassays were carried out using two aquatic snails (Pilia sp. and Lanistes sp.) as test organisms in soft natural dilution water, with waste drilling fluid as the test material, at 28±2°C. Comparison of results for the control and different concentrations of the waste drilling fluid were made by means of the F-statistic method. The waste drilling fluid was practically non-toxic to the two aquatic snails.     

Organochlorine contaminant concentrations in caddisfly adults (Trichoptera) collected from great lakes connecting channels

Pennsylvania-style light traps were used to capture adult Trichoptera from the St. Marys, St. Clair, Detroit and Niagara rivers, Canada. Adequate biomass was acquired in single, 2-h collections to permit triplicate gas chromatographic analyses of 1–4 g samples for 36 organochlorine contaminants. Contaminant levels varied unpredictably but relatively little among samples taken at monthly intervals over the summer. Samples collected simultaneously from the two sides of the Detroit R. reflected local sediment contaminant patterns, suggesting limited dispersal by adults. Genus-specific differences in contaminant concentrations within the Hydropsychidae and Leptoceridae probably reflect differences in larval habitats and manner of feeding. Contaminant concentrations and relative composition paralleled published reports of contaminants in sediments from collection locations. St. Marys R. caddisflies contained contaminant levels indistinguishable from samples collected at reference sites. St. Clair R. samples contained high levels of compounds associated with petrochemical industries located in the river's upstream reaches. High levels of polychlorinated biphenyls (PCBs) and most other contaminants in Detroit R. samples reflected industrial loadings near Detroit, Michigan. Niagara R. samples contained elevated concentrations of PCBs and pesticides. Cluster analysis grouped samples into five clusters each with unique contaminant composition. These also corresponded to geographic origin: St. Marys, St. Clair, Detroit and upper and lower Niagara rivers. The relative ease of collection and consistent results obtained render adult Trichoptera potentially valuable candidates for surveys of aquatic contamination over a broad range of geographical and ecological conditions.     

Matrix diffusion effects in the cleanup of heterogeneous aquifers

Simple mathematical models are developed to account for the rather slow mass transport of nonaqueous phase liquid (NAPL) into aqueous solution in groundwater during flushing operations. The models are based on the assumption that this bottleneck in the process is associated with diffusion in the aqueous phase in the porous medium from the location of the NAPL drops/ganglia in a region of relatively low permeability out into a region of substantially higher permeability, somewhat analogous to diffusion from a block of porous rock into a nearby fracture, where the fracture system overwhelmingly dominates the overall permeability. The models include batch flushing, flushing in a laboratory column, and a one-dimensional model for flushing by means of a single recovery well.     

Patchy distributions: Optimising sample size

A method for estimating sample size which does not require an a priori definition of desired precision, or the assumption that the population is normally distributed with constant variance, has recently been proposed. This paper discusses this method and presents five modifications which make the method easier to use and reduce the probability of estimating a larger sample size than is actually required. The method is extended and used to estimate the mean abundance of patchily distributed benthic organisms. The technique can be used to guide the design of any environmental sampling programme, be it physical, chemical or biological, where comparisons between times and/or locations are required. Trade-offs between numbers of replicates and numbers of levels/sites are discussed.     

Chemical monitoring and evaluation of the water quality of the Douro River at the Crestuma-Lever dam

Water taken from the Crestuma-Lever dam on the Douro River was evaluated considering the Portuguese Decree-law no. 236/98 of 1st August, 1998. This paper presents the metrological characteristics, validation of analytical methodologies and the data obtained from seasonal samplings. The test parameters selected are: temperature, pH, chloride, conductivity, carbon dioxide, alkalinity, hardness, oxidability, dissolved oxygen, BOD5, total suspended solids, sulfide, phosphate, silica, ammonium, nitrite, nitrate, sulfate, sodium, potassium, calcium, magnesium, iron, manganese, copper and zinc. From data analysis we can conclude that the water presented the following characteristics: a pH situated in the neutral zone; a median mineralization; a medium hardness; well oxygenated water; and a carbonate hardness exclusively due to bicarbonates. The temperature, pH, dissolved oxygen, ammonia, chlorides, sulfates, copper, zinc and BOD5 were compared with the legal limits presented in annexes XXI and I of Decree-law 236/98. The results relating to total hardness, nitrites, calcium, magnesium, sodium, potassium, aluminium, sulfides and oxidability were compared with the legal values in annex VI as there are no limits relating to these parameters in annexes XXI and I.