Reduction of atmospheric emissions due to switching from fuel oil to natural gas at a power plant in a critical area in Central Mexico

ABSTRACT

A case study was conducted to evaluate the SO₂ emission reduction in a power plant in Central Mexico, as a result of the shifting of fuel oil to natural gas. Emissions of criteria pollutants, greenhouse gases, organic and inorganic toxics were estimated based on a 2010 report of hourly fuel oil consumption at the “Francisco Pérez Ríos” power plant in Tula, Mexico. For SO₂, the dispersion of these emissions was assessed with the CALPUFF dispersion model. Emissions reductions of > 99% for SO₂, PM and Pb, as well as reductions >50% for organic and inorganic toxics were observed when simulating the use of natural gas. Maximum annual (993 µg/m³) and monthly average SO₂ concentrations were simulated during the cold-dry period (152–1063 µg/m³), and warm-dry period (239–432 µg/m³). Dispersion model results and those from Mexico City’s air quality forecasting system showed that SO₂ emissions from the power plant affect the north of Mexico City in the cold-dry period. The evaluation of model estimates with 24 hr SO₂ measured concentrations at Tepeji del Rio suggests that the combination of observations and dispersion models are useful in assessing the reduction of SO₂ emissions due to shifting in fuels. Being SO₂ a major precursor of acid rain, high transported sulfate concentrations are of concern and low pH values have been reported in the south of Mexico City, indicating that secondary SO₂ products emitted in the power plant can be transported to Mexico City under specific atmospheric conditions.

Implications: Although the surroundings of a power plant located north of Mexico City receives most of the direct SO₂ impact from fuel oil emissions, the plume is dispersed and advected to the Mexico City metropolitan area, where its secondary products may cause acid rain. The use of cleaner fuels may assure significant SO₂ reductions in the plant emissions and consequent acid rain presence in nearby populated cities and should be compulsory in critical areas to comply with annual emission limits and health standards.     

Emergency drills for agricultural drought response: a case study in Guatemala

Drills are an important element of disaster management, helping to increase preparedness and reduce the risk of real‐time failure. Yet, they are not applied systematically to slow‐onset disasters such as a drought, which causes damage that is not instantly apparent and thus does not solicit immediate action. This case study evaluates how drills inform institutional responses to slow‐onset disasters. It spotlights Guatemala, a country where drought has severe impacts on livelihoods and the food security of small farmers. By implementing part of the Ministry of Agriculture, Livestock and Food's institutional response plan for drought, it explores how drills can help to detect issues in emergency response and to foster an institutional focus on improvements in preparedness. The results reveal that drills alone do not trigger institutional improvements if unsupported by a wider strategy that seeks to enhance capacities and protocols. These findings are valuable, however, in making problems transparent and in creating the space for discussion.     

Ground-Level Ozone in Eastern Canada: Seasonal Variations,Trends, and Occurrences of High Concentrations

Over the past few years, concern has increased in Canada over the health and environmental impacts of elevated concentrations of ground-level ozone. During the summer the most populated regions of Canada frequently record ozone concentrations that exceed the one-hour average maximum acceptable air quality objective of 32 parts per billion (ppb). In 1988 the Canadian Council of Ministers of the Environment agreed to develop a federal/provincial management plan to control nitrogen oxide and volatile organic compound emissions to reduce ozone concentrations in all affected regions of the country. In addition to the proposed interim control measures, the plan recommended that studies be undertaken to acquire the information necessary to develop sound control strategies. This report represents one of those studies and provides a summary of ground-level ozone measurements for eastern Canada for the 1980 to 1991 period with an emphasis on seasonal variations, trends, and occurrences of high concentrations.

Southwestern Ontario experiences the highest maximum hourly ozone concentrations and the greatest frequency of hours greater than the 82 ppb acceptable objective. Urban sites have the highest frequencies of ozone concentration measurements in the < 10 ppb range, while rural and remote sites show peaks in frequency distribution in the 20 to 30 ppb range. Trend analysis of summertime (May to September) average daily maximum ozone concentration showed no consistent pattern for eastern Canadian sites during 1980 to 1991. Sites in Montreal showed statistically insignificant downward trends while sites in Toronto showed small but statistically significant upward trends. These ozone-increasing trends are associated with reductions in nitric oxide concentrations. At all sites there was large year-to-year variability in peak ozone levels and in the frequency of hours with ozone concentrations above the maximum acceptable objective.     

Life cycle of the jellyfish <Emphasis Type="Italic">Rhizostoma pulmo</Emphasis> (Scyphozoa: Rhizostomeae) and its distribution,seasonality and inter-annual variability along the Catalan coast and the Mar Menor (Spain,NW Mediterranean)

Rhizostoma pulmo is one of the most abundant scyphomedusae along the Mediterranean coasts. To understand changes in the population densities of the medusa stage and its relationship with the benthic stage, we describe all developmental stages from the life cycle of R. pulmo, from the scyphistoma stage to young medusae reared in the laboratory. Mature scyphistomae showed a mean total body length of 1.7 mm and the average tentacle number was 16. Asexual reproduction occurred by lateral budding, podocyst and pedalocyst production. Each strobila released up to 8 ephyrae that had a mean total body diameter of 3.5 mm. Moreover, we also present data on the temporal and spatial distribution of the species in the Catalan Sea and the coastal lagoon on Mar Menor (NW Mediterranean) during the years 2007–2009. In the Catalan Sea, the presence of adult R. pulmo was recorded as extended along the whole coast, but most of the observation was concentrated in the central area; the highest abundances were recorded during the months of July and August. The highest number of observations was detected in 2008 in coincidence with the inter-annual variation observed in the Mar Menor lagoon.     

Adsorption behavior of 2,4-dichlorophenol and pentachlorophenol in an allophanic soil

The adsorption of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) by a variable-charge soil from southern Chile was studied in a series of batch equilibration experiments. 2,4-DCP and PCP adsorption behavior was evaluated as a function of pH (pH values of 4.5, 6.0 and 7.5) in a 0.1M KCl (25 degrees C) background solution for soil material collected at three different depths (0-20 cm, 20-40 cm, and 40-60 cm). 2,4-DCP and PCP adsorption decreased with increasing soil pH, suggesting that the undissociated species were adsorbed more readily and that electrostatic repulsion may inhibit partitioning as pH increases. The PCP adsorption was greater than observed for 2,4-DCP and decreased with soil depth. Multiple regression analysis between K(d) and various soil properties indicated that the soil organic carbon content is a strong indicator of chlorophenol adsorption, and in addition to organic carbon, the soil pH is an important property controlling adsorption behavior.     

Degradation of organic pollutants in Mediterranean forest soils amended with sewage sludge

The degradation of two groups of organic pollutants in three different Mediterranean forest soils amended with sewage sludge was studied for nine months. The sewage sludge produced by a domestic water treatment plant was applied to soils developed from limestone, marl and sandstone, showing contrasting alkalinity and texture. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10–13 carbon alkylic chain, and nonylphenolic compounds, including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO + NP2EO). These compounds were studied because they frequently exceed the limits proposed for sludge application to land in Europe. After nine months, LAS decomposition was 86–96%, and NP + NP1EO + NP2EO decomposition was 61–84%, which can be considered high. Temporal trends in LAS and NP + NP1EO + NP2EO decomposition were similar, and the concentrations of both types of compounds were highly correlated. The decomposition rates were higher in the period of 6–9 months (summer period) than in the period 0–6 months (winter + spring period) for total LAS and NP + NP1EO + NP2EO. Differences in decay rates with regard to soil type were not significant. The average values of decay rates found are similar to those observed in agricultural soils.     

Improvement of coagulation-flocculation process using anionic polyacrylamide as coagulant aid

A physicochemical treatment (coagulation-flocculation) was applied to a slaughterhouse wastewater, using anionic polyacrylamide as coagulant aid to improve the settling velocity of the flocs formed with the coagulants used: ferric sulphate, aluminium sulphate and polyaluminium chloride. The optimum speed and stirring time for the flocculation stage were ascertained along with the optimum pH and coagulant and coagulant aid doses. The speed and coagulation time were initially set according to recommendations in the literature concerning the treatment of this type of water. Chemical oxygen demand (COD), biochemical oxygen demand at 5 days (BOD5) and total suspended solids (TSS) were recorded at the beginning and end of each experiment in order to monitor the process. Once the optimal conditions had been established, several parameters were measured in order to assess the coagulation-flocculation process: particle number and size, sludge volume, nutrients (ammonia nitrogen, total Kjeldahl nitrogen, albuminoid nitrogen, orthophosphate, total phosphorus) and the residual concentration of iron and aluminium in clarified water. Anionic polyacrylamide, when added with ferric sulphate or polyaluminium chloride led to a significant increase in the settling speed.     

Growth,mortality and disease susceptibility of oyster<Emphasis Type="Italic"> Ostrea edulis</Emphasis> families obtained from brood stocks of different geographical origins,through on-growing in the Ría de Arousa (Galicia,NW Spain)

Infection by Bonamia ostreae has caused extensive mortalities of oysters Ostrea edulis through European and United States coasts for at least 25 years. The development of a bonamiosis-resistant strain seems a promising strategy to fight against the disease. As a first step, evaluation of variability in productive traits and disease susceptibility of European populations was performed to identify favourable oyster populations with which to start selective breeding in Galicia (NW Spain). Oysters taken from Greece, Ireland, Ortigueira (Galicia) and Coroso (Galicia) were used as brood stock, and 19 seed families were produced (4–5 families from each origin). The oyster families were used to assess variability through on-growing in an area of the Ría de Arousa heavily affected by bonamiosis. Results showed significant differences in growth, mortality and susceptibility to bonamiosis and other diseases, both between origins and between families under origins. Bonamiosis was associated with mortality in the late stage of oyster on-growing. Indications of natural selection of bonamiosis less-susceptible oysters due to the long exposure of the Ortigueira population to bonamiosis were found. Other symbionts and pathological conditions were detected, of which herpes-like viral infections and disseminated neoplasia could also cause mortality. An index of the overall incidence of pathological conditions (OIPC) was estimated for each family. A significant correlation between the OIPC and the cumulative mortality of the families was noted. On average, oysters from autochthonous origins showed better performance. The results obtained with the best-performing families suggest that the profitability of oyster farming in Galicia would improve, even under bonamiosis pressure, by using appropriate oyster spat.Communicated by S.A. Poulet, Roscoff