Weekday-Weekend Pollutant Studies of the Los Angeles Basin

Pollutant data from the Los Angeles Basin were analyzed for weekday-weekend differences for the smog months of June through September 1972 and 1973. The pollutants investigated were oxidant, NO, NO₂, total hydrocarbons (HC), CO, and particulates. In order to maintain the diurnal variation, the concentration percentiles were calculated for each weekday and weekend hour.     

Variance Design and Air Pollution Control

Confronted with shortages of low sulfur content residual fuel oil and, consequently, faced with the threat of social and economic upheaval, several air pollution control authorities in the Northeastern states were forced to relax hard-won air quality standards during the winter of 1972. The authorities did so by granting variances to their sulfur content standards for residual fuel oil. This paper examines the institutional characteristics of these variance policies from an economic incentive standpoint. After setting up desirable structural criteria for institutional design of such crisis policies, the authors examine the experience of the winter of 1972 and arrive at policy guidelines which recommend themselves for consideration in future periods of fuel oil shortages.     

Interregional Exchanges of Air Pollution: Model Types and Applications

Regional scale air quality simulation models covering spatial scales of thousands of kilometers are finding increasing applications in studies of acid deposition and other air pollution problems. The purpose of this paper is to familiarize the nonexpert with the characteristics of the major types of interregional air quality models currently in use: Eulerian grid, statistical trajectory, and Lagrangian trajectory. The basic features, advantages, and disadvantages of each of these modeling approaches are summarized, as are the important limitations and problems associated with interregional modeling in general. Typical applications are illustrated using examples from the use of a representative Lagrangian trajectory model, ENAMAP, over the eastern North American area.     

Use of Energy Scenarios in Addressing the CO2 Question

A reference scenario for CO₂ emissions was developed using a model of world energy supply and demand. In the reference scenario, world GNP and world energy demand increase at average rates of 2.1 percent per year and 1.5 percent per year, respectively during the period 1975-2100. The corresponding annual CO₂ emissions rise to a maximum of 16 gigatons of carbon around 2050 and then decline as a result of a transition to nonfossil fuel energy systems. A modified scenario for high CO₂ emissions was obtained by assuming an abundant supply of low cost coal, thus eliminating the transition. A low case was developed in which the low cost of alternative energy (i.e., solar, nuclear) induces an earlier shift away from fossil fuels.

Annual emissions of the three scenarios were used as input to a global carbon cycle model and the CO₂ buildup in the atmosphere during the period 1980-2100 was determined by the model. All three scenarios showed continuous rises in atmospheric CO₂ concentration. The reference scenario reached 775 ppm by 2100. The high CO₂ case resulted in concentrations of over 1040 ppm, and for the low case the 2100 concentration was just under 700 ppm. If the climate theory is correct, even 700 ppm is sufficient to give significant climate warming, but by experiencing the change gradually over a century, adaptation may not be painful. An early transition to nonfossil fuel supplies makes the problem less severe but does not eliminate it.     

Parts-per-trillion LC-MS(Q) analysis of herbicides and transformation products in surface water

The goal of this study was to develop a robust method of analyzing surface water samples for S-triazine herbicides, chloroacetanilide herbicides, and their transformation products (TPs) using solid-phase extraction (SPE) followed by liquid chromatograph-mass spectrometry (LC-MS) with electrospray ionization (ESI) by in-source collision-induced dissociation (ISCID) capability of an orthogonal electrospray ionization probe on a single quadrupole LC-MS system. The method developed here met the goals of the study and yielded estimated method detection limits (EMDLs) averaging 0.3 ± 0.1 ng L(-1) for S-triazines and their TPs and 0.7 ± 0.4 ng L(-1) for chloroacetanilides and TPs. Spiked filtered river water yielded SPE recoveries ranging from 94.2 % ± 4.8 % for S-triazines and TPs after eliminating three compounds with less that 65 % recovery from analysis and 95.9 % ± 19 % for chloroacetanilides and their TPs. The method was field-tested with filtered water samples collected from four sites over a four-month period. Detectible values of S-triazines and TPs ranged from 0.3 to 1540 ng L(-1) with a mean of 79.3 and a median of 19.4 ng L(-1). Detectible values for chloroacetanilides and TPs ranged from 0.31 to 3780 ng L(-1) with a mean of 252 and a median of 25.6 ng L(-1). An additional goal was to determine if the method was useful for microbial degradation studies using native bacterial communities. The bacteria transformed atrazine (2-chloro-4-ethylamino-6-isopropylamino-S-triazine) solely into 2-hydroxy atrazine (2-hydroxy-4-ethylamino-6-isopropylamino-S-triazine) with concentrations of 78.4, 63.3 and 32.5 ng L(-1) after 12 days of incubation compared with 6.3 and 7.1 ng L(-1) for control dark and control sunlight respectively.     

Agroforest’s growing role in reducing carbon losses from Jambi (Sumatra), Indonesia

This paper examines the size and intensity of changes among five land categories during the two time intervals in a region of Indonesia that is pioneering negotiations concerning reducing emissions from deforestation and forest degradation (REDD). Maps at 1973, 1993, and 2005 indicate that land-cover change is accelerating, while carbon loss is decelerating in Jambi Province, Sumatra. Land dynamics have shifted from Forest loss during 1973–1993 to Agroforest loss during 1993–2005. Forest losses account for most reductions in aboveground carbon during the both time intervals, but Agroforest plays an increasingly important role in carbon reductions during the more recent interval. These results provide motivation for future REDD policies to count carbon changes associated with all influential land categories, such as Agroforests.     

The use of nanovermiculite catalyst in the study of removal of the organic load and degradation of atrazine via ozone process in RPB reactor

Abstract

The main objective of this study is the degradation of a synthetic solution of atrazine by a modified vermiculite catalyzed ozonation, in a rotating packed bed (RPB) reactor. A 0.5?L RPB reactor was used to perform the experiments, using a Central Composite Design (CCD) response surface to construct the quadratic model based on the factors: pH, catalyst concentration and reactor rotation frequency. The response variable was the removal of the organic load measured in terms of Chemical Oxygen Demand (COD). After the complete quadratic model was constructed through the response surface, the COD degradation process had an optimal removal of 41% under the following conditions: pH 8.0, rotation of 1150?rpm and catalyst concentration 0.66?g L^?1.     

Contamination status and potential release of trace metals in a mangrove forest sediment in Ho Chi Minh City,Vietnam

Can Gio district is located in the coastal area of Ho Chi Minh City, southern Vietnam. Discharge of wastewater from Ho Chi Minh City and neighboring provinces to the rivers of Can Gio has led to concerns about the accumulation of trace metals (As, Cu, Cr, Ni, Pb, and Zn) in the coastal sediments. The main objective of this study was to assess the distribution of As, Cu, Cr, Ni, Pb, and Zn in surface and core sediments and to evaluate the contamination status in relation to local background values, as well as the potential release of these selected trace metals from sediments to the water environment. Sediment characteristization, including determination of fine fraction, pH, organic matter, and major elements (Al, Fe, Ca, K, Mg, and S), was carried out to investigate which parameters affect the trace metal enrichment. Fine fraction and Al contents were found to be the controlling proxies affecting the distribution of trace metals while other sediment characteristics did not show any clear influence on trace metals’ distribution. Although As concentrations in the sediments were much higher compared to its reference value in other areas, the enrichment factor based on local background values suggests minor contamination of this element as well as for Cr, Cu, and Pb. Risk assessment suggested a medium to very high risk of Mn, Zn, and Ni under acidification. Of importance is also that trace metals in sediments were not easily mobilized by organic complexation based on their low extractabilities by ammonium-EDTA extraction.

     

The response of Lemna trisulca L. to cadmium

Lemna trisulca was grown, using aseptic culture techniques in a filter-sterilized medium, a portion of which was replaced regularly during experiments. L. trisulca responded to the addition of 0.64 microM Cd with a reduction in multiplication rate (MR) 2 +/- 1 days after exposure. The internal Cd content reached 1000 +/- 140 microg Cd/g (dry wt) within 2 days exposure to 0.64 microM Cd. The final yield was reduced by an average of c.8% for each day of exposure to 0.64 microM Cd in a 14 day experiment. This implies that an equilibration period should be used for short-term bioassay tests before the effect of a toxicant is determined. Pretreating L. trisulca with 0.08 or 0.32 microM Cd for 6 weeks had no significant effect on MR or Cd uptake when plants were subsequently exposed to a range of Cd concentrations or grown in a control medium. This suggests that L. trisulca does not become acclimated to elevated Cd concentrations. The MR of L. trisulca fluctuated over a period of almost 600 days and the doubling time ranged from 1.6 to 2.4 days. This produced more than a fivefold difference in final yield in experiments of 14 days duration. The reduction in MR in response to 0.32 microM Cd during this same 600 days period averaged 24% with a coefficient of variation of 38%, and varied with the MR of control cultures. Fluctuations in the intrinsic growth rate and the effect of a toxicant on L. trisulca could potentially confound the assessment of toxicity and must be carefully considered when designing test protocols for aquatic plants.