Toxic Substances in the Atmospheric Environment Discussion

The Critical Review on Toxic Substances in the Atmospheric Environment was presented by Bernard D. Goldstein at the 76th Annual Meeting of the Air Pollution Control Association in Atlanta, Georgia. Dr. Goldstein summarized his paper, which had been published in the May 1983 issue of JAPCA. Prepared discussions presented at the Critical Review Session are reproduced here. In addition, comments made from the floor and through the mails have been formalized and are published along with closing remarks by Dr. Goldstein. Dr. Paul J. Lioy served as Moderator for the 1983 Critical Review Session.     

DYNAMIC RESPONSE OF AQUIFER SYSTEMS TO LOCALIZED RECHARGE1

ABSTRACT. The response of stream-unconfined aquifer systems to localized recharge is investigated by means of a two-dimensional finite element model. A variational approach is used in conjunction with the finite element method to solve the ground water flow equation. Linear approximated triangular elements are used to calculate the hydraulic head distribution in the flow region. The Crank-Nicholson centered scheme of numerical integration is employed to approximate the time derivative in the flow equation. A computer program is developed to calculate the hydraulic head distribution in the flow region. Solutions provided by the finite element model should prove useful in the evaluation of quantitative and qualitative changes in aquifer systems due to natural or artificial recharge. In addition, they should prove useful in the study of irrigation and drainage problems.     

Composting of vinasse and cotton gin waste by using two different systems

Two composts were obtained by co-composting of a concentrated depotassified beet vinasse and cotton gin waste using two different aeration systems: static aerated pile (forced aeration provided by a blower whom operated in the positive mode) and windrow (turned pile). The composting mixtures were cotton gin trash (55%) and vinasse (45%) (dry weight). In static pile, the total amount of vinasse was added at the beginning of the process whereas, in windrow two additions of vinasse were performed. Differences in temperature changes between both composting systems were found: a faster increase of temperature in the windrow (54 °C at 7 days) than in the static pile (45 °C at 21 days) was observed. Probably in the static pile system, the compaction of the substrates made difficult the correct distribution of the air inside the pile. Moreover, after the second addition of vinasse a new thermophilic phase was started in windrow. The different aeration systems and the way of addition of vinasse could cause differences in organic matter (OM) degradation and in weight (22.6% for the static pile and 26.7% for the windrow) and gas losses during the process. Nevertheless, the composts obtained by the two systems had a high fertilizer value (25.1 g kg⁻¹ N; 3.2 g kg⁻¹ P₂O₅; 21.4 g kg⁻¹ K₂O; C/N8) for compost obtained in static pile and (16.2 g kg⁻¹ N; 3.4 g kg⁻¹ P₂O₅; 16.1 g kg⁻¹ K₂O; C/N 12) for compost obtained in the windrow). A high degree of stability was reached in the final composts. Composting of vinasse with cotton gin waste serves two objectives, disposal of wastes and recycling of waste components.     

Trace elements in wild grasses: a phytoavailability study on a remediated field

There have been significant efforts to establish a widely usable method for the prediction of trace element bioavailability in soil. In this work, we used extraction with 0.01 M CaCl₂ and 0.05 M ethylenediaminetetraacetic acid (EDTA) to estimate bioavailable concentrations of As, Cd, Cu, Pb, and Zn in a soil moderately contaminated with trace elements 1 and 2 years after the application of three amendments. The experiment took place in a field plot of a soil affected by the toxic spill of the Aznalcóllar mine. Four treatments were established: three with amendments (biosolid compost, sugar beet lime, and a combination of leonardite plus sugar beet lime) and a control without amendment. Trace element concentrations of two representative species in each year (Lamarckia aurea and Poa annua in 2004 and Lamarckia aurea and Bromus rubens in 2005) were analyzed. The results showed a positive effect of the amendments both on soil and vegetation. Trace element concentrations in plants growing in the amended subplots were lower than those in plants from nonamended subplots. As a rule, concentrations of CaCl₂-soluble Cd, Cu, and Zn in soil were positively correlated with trace elements in plants, whereas EDTA extraction was scarcely correlated with plant concentration. For species of grasses, especially L. aurea, CaCl₂ seems to be a more suitable extractant to predict trace element bioavailability in this contaminated soil.     

Relationship between soil test phosphorus and phosphorus in runoff: effects of soil series variability

Phosphorus loss in runoff from agricultural fields has been identified as an important contributor to eutrophication. The objective of this research was to determine the relationship between phosphorus (P) in runoff from a benchmark soil (Cecil sandy loam; fine, kaolinitic, thermic Typic Kanhapludult) and Mehlich III-, deionized water-, and Fe(2)O(3)-extractable soil P, and degree of phosphorus saturation (DPS). Additionally, the value of including other soil properties in P loss prediction equations was evaluated. Simulated rainfall was applied (75 mm h(-1)) to 54 1-m(2) plots installed on six fields with different soil test phosphorus (STP) levels. Runoff was collected in its entirety for 30 min and analyzed for total P and dissolved reactive phosphorus (DRP). Soil samples were collected from 0- to 2-, 0- to 5-, and 0- to 10-cm depths. The strongest correlation for total P and DRP occurred with DPS (r(2) = 0.72). Normalizing DRP by runoff depth resulted in improved correlation with deionized water-extractable P for the 0- to 10-cm sampling depth (r(2) = 0.81). The STP levels were not different among sampling depths and analysis of the regression equations revealed that soil sampling depth had no effect on the relationship between STP and P in runoff. For all forms of P in runoff and STP measures, the relationship between STP and runoff P was much stronger when the data were split into groups based on the ratio of oxalate-extractable Fe to Al. For all forms of P in runoff and all STP methods, R(2) increased with the inclusion of oxalate-extractable Al and Fe in the regression equation. The results of this study indicate that inclusion of site-specific information about soil Al and Fe content can improve the relationship between STP and runoff P.     

Phosphorus and ammonium concentrations in surface runoff from grasslands fertilized with broiler litter

Application of broiler (Gallus gallus domesticus) litter to grasslands can increase ammonium (NH4-N) and dissolved reactive phosphorus (DRP) concentrations in surface runoff, but it is not known for how long after a broiler litter application that these concentrations remain elevated. This long-term study was conducted to measure NH4-N and DRP in surface runoff from grasslands fertilized with broiler litter. Six 0.75-ha, fescue (Festuca arundinacea Schreb.-)bermudagrass [Cynodon dactylon (L.) Pers.] paddocks received broiler litter applications in the spring and fall of 1995-1996 and only inorganic fertilizer N in the spring of 1997-1998. Surface runoff from each paddock was measured and analyzed for NH4-N and DRP. Broiler litter increased flow-weighted NH4-N and DRP concentrations from background values of 0.5 and 0.4 mg L(-1), respectively, to values > 18 mg L(-1) in a runoff event that took place immediately after the third application. Ammonium concentrations decreased rapidly after an application and were not strongly related to time after application or runoff volume. In contrast, DRP concentrations tended to decrease more slowly, reaching values near 1 mg L(-1) by 19 mo after the last application. Dissolved reactive P concentrations decreased linearly with the natural logarithm of days after application (p<0.03), and increased linearly with the natural logarithm of runoff volume (p<0.0001).     

Exergoeconomic and exergoenvironmental analyses of a combined cycle power plant with chemical looping technology

CO₂ capture and storage from energy conversion systems is one option for reducing power plant CO₂ emissions to the atmosphere and for limiting the impact of fossil-fuel use on climate change. Among existing technologies, chemical looping combustion (CLC), an oxy-fuel approach, appears to be one of the most promising techniques, providing straightforward CO₂ capture with low energy requirements.This paper provides an evaluation of CLC technology from an economic and environmental perspective by comparing it with to a reference plant, a combined cycle power plant that includes no CO₂ capture. Two exergy-based methods, the exergoeconomic and the exergoenvironmental analyses, are used to determine the economic and environmental impacts, respectively. The applied methods facilitate the iterative optimization of energy conversion systems and lead towards the improvement of the effectiveness of the overall plant while decreasing the cost and the environmental impact of the generated product. For the plant with CLC, a high increase in the cost of electricity is observed, while at the same time the environmental impact decreases.     

California Statewide Assessment of the Effects of Ozone on Crop Productivity

Six properties appear desirable for any set of ozone attainment criteria: (1) sufficient stringency to protect public health, (2) simplicity and understandability, (3) sensitivity to real changes in air quality, (4) stability against meteorological fluctuations, (5) use of as much data as possible, and (6) equivalence between the stringency the criteria appear to mandate, and what they actually mandate. We consider how the federal attainment criteria might be improved with respect to Properties 4 through 6 while being equally strong on 1 through 3. Whether the federal standard meets Property 1 has been the subject of debate, but our analysis would apply also to a modified standard. We show that there are subtleties in how improvements might be made. In particular, basing the attainment status on a statistic with low variance may not lead to a more stable criterion, and although it is easy to find a criterion that makes it hard for a district with bad air to reach attainment, or a district with good air to get out of attainment, it is hard to find a criterion that does both. This suggests using different criteria for districts that are out of attainment from districts that are in attainment. Initially the burden of proof would be on the district to prove that its air is of attainment quality. However, once the district has achieved attainment the burden of proof would shift; the district would remain in attainment unless there was strong evidence to the contrary. An evaluation of a set of criteria based on this idea showed improvements over the federal criteria with respect to the last three desirable properties-stability, use of data, and equivalent stringency-with some sacrifice in simplicity and sensitivity.