Photochemical model evaluation of the surface ozone impact of a power plant in a heavily industrialized area of southwestern Spain

The characterization and evaluation of the impact that an industry is likely to have on the surrounding ozone levels is one of many problems confronting air quality managers and should be taken into consideration when authorizing its installation. The correct management of an environment, in terms of monitoring existing industries and planning new activities, requires adequate knowledge of the processes sustained by the industrial emissions therein. This paper explores the improvements in air quality management arising from taking into account the uncertainties involved in the photochemical modeling of the impact of an industry on surface ozone levels. For this, we evaluate the impact on ozone levels of a power plant located in an industrial area of southwestern Spain (Huelva). The evaluation takes into account the effects of both emissions' uncertainty and the non-linear chemistry between ozone and its precursors, thus providing a probable range of increase over the normative values (hourly and 8-hourly maximums) defined in the European Directive. The proposed methodology is easily applicable by air quality managers. Advanced modeling techniques were used for the power plant assessment, MM5 atmospheric modeling system, and air quality model CAMx. The results from meteorology and ozone forecasts have shown acceptable agreement with the observations. The spatial distribution of the impact is found to be strongly determined by mesoscale meteorological processes, which are reinforced by the local orography; there is also a marked temporal evolution. The industrial plume is observed to induce a decrease (or maintenance) of the ozone levels near the emission source (0-10km), and an increase in the ozone concentrations farther away (with maximums between 10 and 50km). In fact, in the meteorological episodes with a predominance of local breeze circulations, impacts have been detected at distances of more than 100km from the emission source. Sensitivity of the power plant impact to variations in ozone precursor emissions is described, and the scenarios and the points in the domain presenting higher sensitivity and registering larger impacts are also identified. The results show that the largest impacts take place in emission scenarios where the NO(x) has been reduced with respect to the base case scenario. In contrast, in scenarios where the VOC emissions are reduced with respect to the base case scenario, the impact is smaller or remains unchanged. This is important in areas like the study case, where there is a high percentage of biogenic VOC emissions and the industrial areas are close to natural protected areas and agricultural fields.

Sensitivity analysis of surface ozone to modified initial and boundary conditions in both rural and industrial zones

Abstract. A three-dimensional air quality model based on a set of chemical species mass conservation equations describes the time evolution of chemical species in the atmosphere. In order to solve this set of equations, proper choices of initial and boundary conditions are needed. Ideally, initial and boundary conditions should be determined on the basis of observations. However, since such high-resolution observations are generally not available, it becomes necessary to use other information sources to specify the initial and boundary values. The fact that both the initial and the boundary conditions are specified with some degree of presumption makes it important to evaluate their influence in the model results. In this paper we present a study of the impact of initial and boundary concentrations on the modelled surface ozone concentration over two environments: Huelva and Badajoz, an industrial and a rural zone, respectively. The impacts are analysed for the same meteorological period (10–15 August 2003).

The impact of biogenic VOC emissions on photochemical ozone formation during a high ozone pollution episode in the Iberian Peninsula in the 2003 summer season

Abstract. Throughout Europe the summer of 2003 was exceptionally warm, especially July and August. The European Environment Agency (EEA) reported several ozone episodes, mainly in the first half of August. These episodes were exceptionally long-lasting, spatially extensive, and associated to high temperatures. In this paper, the 10$ndash;15 August 2003 ozone pollution event has been analyzed using meteorological and regional air quality modelling. During this period the threshold values of the European Directive 2002/3/EC were exceeded in various areas of the Iberian Peninsula. The aim of this paper is to computationally understand and quantify the influence of biogenic volatile organic compound (BVOC) emissions in the formation of tropospheric ozone during this high ozone episode. Being able to differentiate how much ozone comes from biogenic emissions alone and how much comes from the interaction between anthropogenic and biogenic emissions would be helpful to develop a feasible and effective ozone control strategy. The impact on ozone formation was also studied in combination with various anthropogenic emission reduction strategies, i.e., when anthropogenic VOC emissions and/or NOx emissions are reduced. The results show a great dependency of the BVOC contribution to ozone formation on the antropoghenic reduction scenario. In rural areas, the impact due to a NOx and/or VOC reduction does not change the BVOC impact. Nevertheless, within big cities or industrial zones, a NOx reduction results in a decrease of the biogenic impact in ozone levels that can reach 85 μg/m3, whereas an Anthropogenic Volatile Organic Compound (AVOC) reduction results in a decrease of the BVOC contribution on ozone formation that varies from 0 to 30 μg/m3 with respect to the contribution at the same points in the 2003 base scenario. On the other hand, downwind of the big cities, a decrease in NOx produces a minor contribution of biogenic emissions and a decrease in AVOCs results in greater contributions of BVOCs to the formation of ozone.

Effect of lipoic acid on biliary excretion of glutathione and metals

Several metals are excreted in bile as glutathione complexes, and their biliary excretion is facilitated by increased hepatobiliary transport of glutathione. The present study analyzed the effect of lipoic acid (LA; thioctic acid; 37.5-300 mumol/kg, iv), an endogenous disulfide which can be reduced in vivo to a dithiol, on the hepatobiliary disposition of glutathione-related thiols and the biliary excretion of metals (10 mumol/kg, iv) in rats. Administration of LA enhanced the biliary excretion of reduced glutathione in a dose-dependent fashion. Despite increasing glutathione output, LA (150 mumol/kg, iv) did not increase, but rather decreased, the biliary excretion of methylmercury, cadmium, zinc, and copper, which are transported into bile in a glutathione-dependent manner, as indicated by a marked reduction in their biliary excretion after diethyl maleate-induced glutathione depletion. In contrast, biliary excretion of inorganic mercury, which is minimally affected by glutathione depletion, was dramatically enhanced (12- to 37-fold) by LA administration. Following injection of LA, the concentrations of endogenous disulfides in arterial blood plasma (e.g., cystine, glutathione disulfide, cysteine-glutathione, protein-cysteine, and protein-glutathione mixed disulfides) were considerably diminished, while the levels of endogenous thiols (e.g., glutathione and cysteine) were increased. This finding indicates that LA, probably after enzymatic conversion to dihydrolipoic acid, can reduce endogenous disulfides to thiols. It appears that LA induces the transport of glutathione into bile by the temporary formation of dihydrolipoic acid-glutathione mixed disulfide, which after being translocated into bile is cleaved to LA and reduced glutathione. Because the glutathione molecule thus transported into bile cannot complex metals at the thiol group, this might be the mechanism for the observed failure of the LA-induced increase in biliary excretion of glutathione to enhance the hepatobiliary transport of metals that are transported into bile as glutathione complexes (i.e., methylmercury, cadmium, zinc, and copper). The observations also raise the possibility that endogenous dihydrolipoic acid, by forming a stable complex with mercuric ion, may play the role of a carrier molecule in the hepatobiliary transport of inorganic mercury.

Species variations in biliary excretion of glutathione-related thiols and methylmercury

The biliary excretion of methylmercury is thought to be related to the biliary excretion of nonprotein thiols in rats. Species differences in biliary excretion of glutathione (GSH) and related thiols are unknown; therefore, the relationship between the biliary excretion of GSH-related thiols and methylmercury in five species was studied. The biliary excretion rate of GSH-related thiols and disulfides was 369, 192, 94, 50, and 19 nmol/min/kg for mice, rats, hamsters, guinea pigs, and rabbits, respectively. The main thiol in mouse, hamster, and rat bile was GSH, whereas guinea pig and rabbit bile contained mainly cysteinylglycine (Cys-Gly). The larger percentage of Cys-Gly in guinea pig and rabbit bile was correlated with their greater hepatic gamma-glutamyltranspeptidase (GGT) activity than that observed in the other species. The biliary excretion rate (nmol/min/kg) of methylmercury was approximately 0.8 in mice, rats, and hamsters compared to significantly lower rates in guinea pigs and rabbits (0.15 and 0.03, respectively). It is concluded that the species-specific composition of GSH-related thiols and disulfides in bile is related to species variations in hepatic GGT activity, and that the species variation in biliary excretion of GSH-related thiols does not entirely account for the species variation in methylmercury excretion, indicating other factors are also apparently involved in determining the rate of biliary excretion of methylmercury.

Effect of inhibition of gamma-glutamyltranspeptidase on biliary and urinary excretion of glutathione-derived thiols and methylmercury

Acivicin (AT-125; 6.25-200 mumol/kg i.v.) inhibited hepatic, biliary and renal gamma-glutamyltranspeptidase (GGT) activity up to 88, 99 and 97%, respectively, in 4-week-old rats. This inhibition of GGT by acivicin resulted in a 10- to 12-fold increase in the biliary excretion of reduced (GSH) and oxidized glutathione. Because the biliary excretion of cysteinylglycine (Cys-Gly), Cys-Gly disulfide, cysteine (Cys) and cystine concomitantly decreased (63-99%), the biliary excretion rate of total glutathione-derived thiols and disulfides did not change. In contrast, acivicin treatment dramatically elevated the urinary excretion rate of glutathione-derived thiols in a dose-dependent fashion, resulting in a 390-fold increase at the highest dosage. This mainly originated from enhancement of urinary excretion of GSH (up to 7200-fold), although the excretion of Cys and Cys-Gly into urine was also increased. Acivicin treatment did not affect hepatic and renal levels of GSH but, at high dosages, reduced the concentration of Cys in these organs. GSH and oxidized glutathione concentrations in serum were increased, whereas cystine was diminished in acivicin-treated rats. Inhibition of GGT by acivicin (100 mumol/kg i.v.) failed to influence the biliary excretion of methylmercury but increased urinary excretion 34-fold. Even though the urinary thiol excretion was much higher than the biliary thiol excretion in the acivicin-treated rats, methylmercury was preferentially excreted into bile rather than urine, indicating the importance of the liver as an excretory organ for methylmercury.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-dependent biliary excretion of glutathione-related thiols in rats: role of gamma-glutamyltransferase

The role of gamma-glutamyltransferase (GGT) in the biliary excretion of glutathione (GS) was studied in rats during postnatal development. Between 2 and 10 wk of age the biliary excretion of GS-related sulfur increased ninefold. During this period, alterations were observed in both hepatic GGT and the composition of GS-related thiols and disulfides in bile. For instance, between 3 and 4 wk of age, GGT activity and the biliary excretion of GS hydrolysis products (Cys-Gly and Cys) increased markedly, and the latter became the predominant sulfhydryls in bile. However, by 10 wk of age, the excretion rate of GS increased and exceeded the rate of excretion of Cys-Gly and Cys. The parallelism between hepatic GGT activity and the biliary excretion of GS-hydrolysis products during development suggests a role for GGT in the formation of biliary Cys-Gly and Cys. Furthermore, in 4-wk-old rats, inhibition of hepatic GGT by acivicin markedly decreased the biliary excretion of Cys-Gly and Cys and increased that of GS without influencing the excretion of total GS-related sulfur in bile. The biliary excretion of GS-related thiols was less responsive to acivicin in 2- and 7- to 10-wk-old rats, suggesting that GGT plays a smaller role in influencing biliary thiol composition at those ages. In summary, GS transported into bile is hydrolyzed in an age-dependent manner, however, the GGT-initiated hydrolysis of GS does not affect the biliary excretion of total thiols in rats.

Utilization of methionine as a sulfhydryl source for metallothionein synthesis in rat primary hepatocyte cultures

Metallothioneins (MT) contain a high concentration of cysteine which bind heavy metals. Exposure of liver cells to metals induces the synthesis of MT and thus causes the cells to draw upon their sulfhydryl (SH) pools. The utilization of methionine as compared with that of cysteine as a source of SH for the synthesis of MT has not been shown. Therefore, studies were designed to determine whether methionine, in addition to cysteine, serves as an SH donor for Zn-induced synthesis of MT in rat hepatocyte cultures. Hepatocytes were able to synthesize only low levels of MT when the concentration of both amino acids was extremely low; however, when either of the amino acids was present at a high concentration, production of MT was independent of the other amino acid concentration. Subsequently, induction of MT was compared in four media: complete (0.5 mM methionine, 0.5 mM cysteine), Met (0.5 mM methionine), Cys (0.5 mM cysteine), and SH free (-SH). Somewhat higher concentrations of MT were produced by the hepatocytes in the Met than in the Cys media and no differences were observed between the Met and the complete media. By contrast, GSH synthesis was much more dependent on methionine than on cysteine for its synthesis. Incorporation studies with 35S-labeled cysteine and methionine indicated that lower concentrations of MT found in hepatocytes in the Cys media may be due to less accumulation of cysteine by the hepatocytes. Cellular accumulation of cysteine was initially rapid and then reached a plateau, whereas the rate for methionine accumulation was more constant and eventually obtained higher cellular levels. To provide additional evidence for the role of methionine in MT production, a known inhibitor of the cystathionine pathway, DL-propargylglycine (PPG), was added to each of the four media. Reductions in MT levels were not observed in the cells cultured in the complete and Cys media; however, a 95% reduction was observed in the cells cultured in the Met media. In summary, the present results suggest that both cysteine and methionine can serve as a SH source for MT synthesis, and that the availability of SH in most culture mediums would not limit the synthesis of MT. Whereas methionine is a much better SH source than cysteine for GSH synthesis in hepatocyte cultures, it is only slightly better for MT synthesis.

High-performance liquid chromatographic analysis of glutathione and its thiol and disulfide degradation products

A rapid and sensitive high-performance liquid chromatographic method for quantitation of picomole levels of glutathione, glutathione disulfide, cysteine, cystine, cysteinylglycine, cysteinylglycine disulfide and cysteine glutathione-mixed disulfide in biological samples is described. The compounds were separated isocratically on a reversed-phase column by ion-pair chromatography. The mobile phase consisted of an aqueous buffer containing 0.1 M monochloroacetic acid and 3.3 mM 1-heptanesulfonic acid (pH 2.60)-methanol-N,N-dimethylformamide (96.5:3.0:0.5). After chromatographic separation, the disulfides were reduced by a potential (-1.0 V) from a battery, with subsequent detection of all thiols by electrochemical oxidation (+0.15 V) with a dual gold-mercury electrode. Thiol and disulfide concentrations were determined in tissue extracts (liver and kidney) and fluids (bile and plasma) from control rats and rats treated with acivicin, an inhibitor of gamma-glutamyltranspeptidase. A marked increase in biliary glutathione concentration was observed in treated animals with a corresponding decrease in cysteine and cysteinylglycine concentrations. The results demonstrate that this method is useful for measuring glutathione and its degradation products in tissues and fluids.

Renal tubular secretion and reabsorption as factors in ochratoxicosis: effects of probenecid on nephrotoxicity

Ochratoxin A (OA) is a food-borne fungal metabolite capable of producing nephrotoxicity. Renal clearance of [3H]OA and the effects of probenecid on clearance were compared in sham-operated and partially nephrectomized (surgical removal of 70% of the total renal mass), impaired renal function rats. Sham-operated and partially nephrectomized rats cleared OA at 0.109 and 0.078 ml/min, respectively. These values were significantly lower than glomerular filtration rate (GFR) determined by inulin clearance, indicating net tubular reabsorption. Clearance of a single dose of OA in both sham-operated and partially nephrectomized rats pretreated with probenecid was significantly diminished and provided evidence for the involvement of secretory processes in the elimination of OA. Probenecid (administered before OA or simultaneously with OA) failed to prevent nephrotoxicity in rats exposed to five daily doses of mycotoxin. On the contrary, enhanced nephrotoxicity was exhibited. Decreases in urine osmolality, Na+ and K+ concentrations, and body weight were prominent and, interestingly, renal levels of parent OA were increased (over OA treatment alone) in the presence of probenecid. These data suggest that renal tubular secretion and reabsorption are important factors in modulating the nephrotoxicity of OA and may facilitate the residual persistence of this mycotoxin in the kidneys (via renal recycling). Renal metabolism may contribute to the detoxification of OA.

Teratogenic effects of Ochratoxin A in rats with impaired renal function

The teratogenic potential of Ochratoxin A (OA), was compared in impaired renal function (IRF) and sham-operated (SO) female rats. Surgical removal of approximately 70% of the total renal tissue was accomplished utilizing unilateral ligation/electrocoagulation procedures. Control animals were sham-operated. All animals were allowed a period of 27 days to recover post surgery. IRF rats exhibited normal mating tendencies and the pregnancy rate was 100%. A single, subcutaneous teratogenic dose of OA (1.75 mg/kg) on gestation day 7 resulted in significantly increased fetal resorptions, decreased fetal body weights and increased fetal malformations in both IRF and SO animals, although the incidence of gross malformations was greater in IRF rats. A subthreshold teratogenic dose (i.e. 1 mg/kg) did not produce any significant increase in embryotoxicity or fetal malformations in IRF animals compared to SO rats.

Effects of ochratoxin A in the partially nephrectomized rat

The effects of ochratoxin A (OA), a nephrotoxic mycotoxin, were investigated in partially nephrectomized (PN) rats (approximately 70% reduction in renal mass) following compensatory hypertrophy of the renal remnant. Renal function stabilized 27 d after surgery. PN rats compensated for the initial loss of renal function except for glomerular filtration rate (GFR, inulin clearance); this remained significantly impaired. Sham-operated (SO) rats cleared inulin and p-aminohippurate (PAH) at rates of 3.84 and 7.49 ml/min, respectively, while compensated PN rats cleared inulin at 2.51 and PAH at 8.84 ml/min. Daily administration of low levels of OA produced decreased urine osmolality and body weight with a modest increase in urinary protein of PN versus SO rats. OA-treated rats cleared inulin, creatinine, and PAH at rates significantly lower than nontreated controls: 0.89 and 1.96 ml/min for inulin, 0.35 and 0.56 ml/min for creatinine, and 2.29 and 6.23 ml/min for PAH. Histopathological findings indicated a considerable increase in renal tubular necrosis and subcellular damage (i.e., loss of cytoplasmic ground substance, vacuolization, degeneration of mitochondria, and reorganization of endoplasmic reticulum) in PN animals versus controls, concurrent with alteration in renal function. These results verify that the nephrotoxic action of OA is elicited mainly in renal proximal tubules and is enhanced in the PN rat.

High pressure liquid chromatographic determination of an O-methyl,methyl ester derivative of ochratoxin A

The mycotoxin ochratoxin A (OA) was derivatized to an O-methyl,methyl ester (Me2) with diazomethane and then determined by high pressure liquid chromatography (HPLC). Both OA and OA-Me2 were chromatographed by reverse phase HPLC with a mobile phase of acetonitrile-water (60 + 40). An increase in retention time of 309 s was observed with OA-Me2 which was detectable at 254 nm at levels as low as 3 ng. Recovery of OA as OA-Me2 from chicken kidney homogenates and human plasma was quantitative following simple extraction and cleanup procedures, reaction with diazomethane, and HPLC analysis. The novel method described should prove useful for measuring and confirming OA in tissues and in further studies on the biological fate of this mycotoxin.

Vanadium-induced inhibition of renal Na+, K+-adenosinetriphosphatase in the chicken after chronic dietary exposure

Recent work has shown that V accumulates in the kidney and is a potent inhibitor of Na+, K+-adenosinetriphosphatase (ATPase) in vitro. Thus, as a nutritionally required element, V may regulate cation transport. The effect of chronic intake of the metal on Na+, K+-ATPase in vivo has not been reported. In this study laying strain chickens were fed calcium orthovanadate for 15 mo from d 1 of age at levels of 0, 25, 50, and 100 ppm in the diet. Whole tissue homogenates and 13,000 X g fractions were analyzed for ATPase activities. Concentrations of V producing 50% inhibition of Na+, K+-ATPase activity ranged from 1.0 X 10(-5) M in liver to 1.8 X 10(-6) M in kidney, which was the most sensitive tissue tested in vitro. Mg2+ -ATPase was more resistant to V than Na+, K+-ATPase. Studies in vivo suggested a V-dependent inhibition of renal Na+, K+-ATPase. Correlation of enzyme specific activity and levels of V in kidneys suggested V-ATPase mediated alteration in renal function.