Permanent URI for this collection
Browsing Articles by Issue Date
Now showing 1 - 20 of 265
Results Per Page
- ItemMechanistic studies on Diels-Alder [4þ2] cycloaddition reactions ofa,b-substituted cyclobutenones: Role of substituents in regio- andstereoselectivity(Elsevier Ltd., 216-11-03) Fosu, Evans; Tia, Richard; Adei, EvansDiels-Alder reactions of substituted cyclobutenones with 6-methoxy-1-vinyl-3,4-dihydronaphthaleneand methoxy-substituted-1,3-butadiene have been studied with DFT. In the reactions of 6-methoxy-1-vinyl-3,4-dihydronaphthalene with cyclobutenone anda-bromocyclobutenone, the formation of themetaandorthoisomers have the same barriers, indicating that the two isomers might be formed in equalproportions, contrary to earlier reports. The regiochemistry of the reaction is mainly controlled by theketone functionality at C1 on the dienophiles. In the reactions of methoxy-substituted-1,3-butadienewith cyclobutenone anda,b-substituted cyclobutenones theortho/endoandpara/endostereo-isomericpathways are the most favorable pathways, changing toexoselectivity when OH, Br, CH3are placedon theb-carbon of the cyclobutenone, but still withorthoandpararegioselectivity. The stereoselectivityis independent of the bulkiness of substituents. The stability of substituted cycloadducts are lowercompared to unsubstituted adducts and this explains why thea-cyanoketones anda-bromoketoneproducts readily undergotrans-methylation and angular-alkylation as electrophiles.
- ItemHypertension and renal failure in Kumasi, Ghana(Human Hypertension, 1999-01-13) Plange-Rhule, J; Phillips, Richard Odame; Acheampong, JW; Saggar-Malik, AK; Cappuccio, FP; et.alHypertension is common in West Africa and likely to become more common as urbanisation increases. There are at present few facilities for the detection and management of hypertension so the influence it has on overall morbidity and mortality in the population is not clear. The objectives of the study were to assess: (a) renal disease and blood pressure related admissions and deaths among acute medical admissions to Komfo Anokye Teaching Hospital, Kumasi, during an 8-month period; and (b) the burden of renal disease among out-patient hypertensives at the same hospital. Ward admission books were examined in the four acute medical wards to ascertain admission diagnosis and cause of death (two 4-month periods in 1995 and 1996). Clinical assessment (blood pressure, plasma creatinine, proteinuria) was also made of 448 consecutive out-patient hypertensives seen between March 1995 and April 1996. Five Keywords: hypertension; renal disease; plasma creatinine; Ghanaians; West Africans Introduction Hypertension is an increasing problem in people of West African descent living in the western world.1,2 Studies in the United States3,4 and Britain5,6 have shown hypertension to be very common and its complications (stroke, heart failure, renal failure) a major cause of morbidity and mortality in black subjects in these countries. There are few data on the prevalence of hypertension in West Africa. Studies suggest that the prevalence of hypertension is higher in urban than rural areas.7–9 Increasing urbanisation in West Africa is associated with an increasing prevalence of hypertension9 so the burden of hypertension and its related complications on morbidity and mortality will rise. Indeed, hypertensive renal damage is the main cause of end-stage renal failure in black populations both in the UK10 and in West Africa.11,12 There is a lack of primary care facilities for the detection of hypertension in West Africa and clinics Correspondence: Dr JB Eastwood, Department of Renal Medicine, St George’s Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK Received 27 March 1998; revised 25 July 1998; accepted 31 July 1998 hundred and ninety-three (17.9%) of 3317 acute medical admissions were ascribable to a cardiovascular cause (hypertension, heart failure, stroke); 171 (28.8%) of these died. One hundred and sixty-six (5.0%) had renal disease of whom 45 (27.1%) died, usually of end-stage renal disease. Among the 448 hypertensive out-patients, 30.2% (110 out of 365) had a plasma creatinine .140 mmol/l (48 > 400 mmol/l) and 25.5% (96 out of 376) had proteinuria. Eighty-nine of the 448 had a diastolic blood pressure >115 mm Hg; in this group 38 (42.7%) had a plasma creatinine of .140 mmol/l (and 18 or 20.2% >400 mmol/l). In conclusion, cardiovascular and renal disease are important contributors to morbidity and mortality among acute medical admissions to a large city hospital in Ghana. Among out-patient hypertensives renal disease is an important complication, especially in those with the more severe hypertension.
- ItemPrevalence, Detection, Management, and Control of Hypertension in Ashanti, West Africa(American Heart Association, 2004-05) Cappuccio, Francesco P.; Micah, Frank B.; Emmett, Lynsey; Kerry, Sally M.; Phillips, Richard Odame; et. alHypertension and stroke are important threats to the health of adults in sub-Saharan Africa. Nevertheless, detection of hypertension is haphazard and stroke prevention targets are currently unattainable. Prevalence, detection, management, and control of hypertension were assessed in 1013 men (n 385) and women (n 628), both aged 55 [SD 11] years, living in 12 villages in Ashanti, Ghana. Five hundred thirty two lived in semi-urban and 481 in rural villages. The participants underwent measurements of height, weight, and blood pressure (BP) and answered a detailed questionnaire. Hypertension was defined as BP 140 and/or 90 mm Hg or being on drug therapy. Women were heavier than men. Participants in semi-urban areas were heavier and had higher BP (129/76 [26/14] versus 121/72 [25/13] mm Hg; P 0.001 for both) than in rural areas. Prevalence of hypertension was 28.7% overall and comparable in men and women, but higher in semi-urban villages (32.9% [95% CI 28.9 to 37.1] versus 24.1% [20.4 to 28.2]), and increased with age. Detection rate was lower in men than women (13.9% versus 27.3%; P 0.007). Treatment and control rates were low in both groups (7.8% and 4.4% versus 13.6% and 1.7%). Detection, treatment, and control rates were higher in semi-urban (25.7%, 14.3%, and 3.4%) than in rural villages (16.4%, 6.9%, and 1.7%). Hypertension is common in adults in central Ghana, particularly in urban areas. Detection rates are suboptimal in both men and women, especially in rural areas. Adequate treatment of high BP is at a very low level. There is an urgent need for preventive strategies on hypertension control in Ghana. (Hypertension. 2004;43:1017-1022.)
- ItemPilot Randomized Double-Blind Trial of Treatment of Mycobacterium ulcerans Disease (Buruli Ulcer) with Topical Nitrogen Oxides(Antimicrobial Agents and Chemotherapy, 2004-08) Phillips, Richard Odame; Adjei, O.; Lucas, S.; Benjamin, N.; Wansbrough-Jones, MarkMycobacterium ulcerans disease (Buruli ulcer) is a serious ulcerating skin disease which is common in many tropical countries. Standard treatment, by extensive excision and skin grafting, is not available in rural communities where the disease is common. We evaluated the efficacy and safety of treatment with topical nitrogen oxides. Thirty-seven patients with a clinical diagnosis of Buruli ulcer caused by M. ulcerans disease were randomly assigned to one of two groups. In one group, two creams containing sodium nitrite (6%, wt/wt) or citric acid monohydrate (9%, wt/wt) were applied daily for 6 weeks, while the other group received a placebo. In the second 6 weeks, both groups received the nitrogen oxide-generating combination of creams. Treatment was continued for another 4 weeks for patients whose ulcers were not healed after 12 weeks. The ulcer surface area was monitored by weekly tracings made by assessors blinded to the treatment. In the first 6 weeks, patients on sodium nitrite and citric acid monohydrate (group I, active treatment) showed a rapid decrease in ulcer size from 28.6 5.6 cm2 (mean standard error) to 12.6 3.2 cm2, a decrease significantly greater than that in group II (from 15.3 3.1 to 11.7 3.7 cm2; P 0.03). Five ulcers in the placebo group enlarged during this period, compared with one in the active group. In the second 6 weeks (both groups on active treatment), the rates of healing were similar for the two groups and there was a significant reduction in ulcer size in group II (previously on placebo) compared to the first 6 weeks. Yellow pigmentation of the skin, which disappeared 3 days after treatment was stopped, was the only side effect to date. We conclude that creams releasing nitrogen oxides increase the healing rate of ulcers caused by M. ulcerans infection with minimal adverse events. This is the first controlled trial of any form of therapy which demonstrates efficacy in treating this disease.
- ItemIn Vitro Killing of Mycobacterium ulcerans by Acidified Nitrite(Antimicrobial Agents and Chemotherapy, 2004-08) Phillips, Richard Odame; Kuijper, S.; Benjamin, N.; Wansbrough-Jones, M.; Wilks, M.; et. alMycobacterium ulcerans, which causes Buruli ulcer, was exposed to acidified nitrite or to acid alone for 10 or 20 min. Killing was rapid, and viable counts were reduced below detectable limits within 10 min of exposure to 40 mM acidified nitrite. M. ulcerans is highly susceptible to acidified nitrite in vitro.
- ItemEfficacy of the Combination Rifampin-Streptomycin in Preventing Growth of Mycobacterium ulcerans in Early Lesions of Buruli Ulcer in Humans(American Society for Microbiology, 2005-04-29) Etuaful, S.; Carbonnelle, B.; Phillips, Richard Odame; Evans, M.; Ofori-Adjei, D.; et.alMycobacterium ulcerans disease is common in some humid tropical areas, particularly in parts of West Africa, and current management is by surgical excision of skin lesions ranging from early nodules to extensive ulcers (Buruli ulcer). Antibiotic therapy would be more accessible to patients in areas of Buruli ulcer endemicity. We report a study of the efficacy of antibiotics in converting early lesions (nodules and plaques) from culture positive to culture negative. Lesions were excised either immediately or after treatment with rifampin orally at 10 mg/kg of body weight and streptomycin intramuscularly at 15 mg/kg of body weight daily for 2, 4, 8, or 12 weeks and examined by quantitative bacterial culture, PCR, and histopathology for M. ulcerans. Lesions were measured during treatment. Five lesions excised without antibiotic treatment and five lesions treated with antibiotics for 2 weeks were culture positive, whereas three lesions treated for 4 weeks, five treated for 8 weeks, and three treated for 12 weeks were culture negative. No lesions became enlarged during antibiotic treatment, and most became smaller. Treatment with rifampin and streptomycin for 4 weeks or more inhibited growth of M. ulcerans in human tissue, and it provides a basis for proceeding to a trial of antibiotic therapy as an alternative to surgery for early M. ulcerans disease.
- ItemMycobacterium ulcerans disease(Bulletin of the World Health Organization, 2005-10) Phillips, Richard Odame; Werf, Tjip S. van der; Stienstra, Ymkje; Johnson, R. Christian; Adjei, Ohene; et. alMycobacterium ulcerans disease (Buruli ulcer) is an important health problem in several west African countries. It is prevalent in scattered foci around the world, predominantly in riverine areas with a humid, hot climate. We review the epidemiology, bacteriology, transmission, immunology, pathology, diagnosis and treatment of infections. M. ulcerans is an ubiquitous micro-organism and is harboured by fish, snails, and water insects. The mode of transmission is unknown. Lesions are most common on exposed parts of the body, particularly on the limbs. Spontaneous healing may occur. Many patients in endemic areas present late with advanced, severe lesions. BCG vaccination yields a limited, relatively short-lived, immune protection. Recommended treatment consists of surgical debridement, followed by skin grafting if necessary. Many patients have functional limitations after healing. Better understanding of disease transmission and pathogenesis is needed for improved control and prevention of Buruli ulcer.
- ItemRetrieval of stratospheric NO3 vertical profiles from SCIAMACHY lunar occultation measurement over the Antarctic(Journal of Geophysical Research, 2005-10-26) Amekudzi, L. K.; Sinnhuber, B.-M.; Sheode, N. V.; Meyer, J.; Rozanov, A.; Lamsal, L. N.; Bovensmann, J. P. Burrows NO3 vertical profiles have been retrieved over the Antarctic (60 –90 S) from the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) lunar occultation spectra, using the visible spectral band (610–680 nm) containing NO3 absorption bands at 623 and 662 nm. The retrieved NO3 profiles agree well with calculations from a photochemical model constrained by retrieved O3 and analyzed temperatures in the altitude range between 24 and 45 km. Below about 35–40 km, observed NO3 is well reproduced by photochemical steady state calculations. Differences between observed and modeled NO3 are within the estimated accuracy of 20–35%, demonstrating the consistency of the NO3 retrieval and model.
- ItemBoosting of Cellular Immunity against Mycobacterium tuberculosis and Modulation of Skin Cytokine Responses in Healthy Human Volunteers by Mycobacterium bovis BCG Substrain Moreau Rio de Janeiro Oral Vaccine(American Society for Microbiology, 2006-01-23) Cosgrove, Catherine A.; Castello-Branco, Luiz R. R.; Hussell, Tracy; Sexton, Amy; Giemza, Rafaela; et.alOral immunization of healthy adults with 107 CFU BCG Moreau Rio de Janeiro was well tolerated and significantly boosted gamma interferon responses to purified protein derivative, Ag85, and MPB70 from previous childhood intradermal BCG immunization. Oral BCG offers the possibility of a needle-free tuberculosis vaccine and of boosting the protective immunity from intradermal tuberculosis vaccines.
- ItemCytokine Response to Antigen Stimulation of Whole Blood from Patients with Mycobacterium ulcerans Disease Compared to That from Patients with Tuberculosis(American Society for Microbiology, 2006-02) Phillips, Richard Odame; Horsfield, C.; Kuijper, S.; Sarfo, Fred Stephen; Obeng-Baah, J.; et.alMycobacterium ulcerans disease (Buruli ulcer) is a skin-ulcerating infection common in some parts of the tropics. We have investigated cytokine secretion after stimulation of whole blood from Buruli ulcer (BU) patients in a region of endemicity in Ghana with M. ulcerans sonicate or culture filtrate antigens to investigate the development of the response over time and its specificity by comparison with the response to Mycobacterium tuberculosis sonicate in human immunodeficiency virus-negative tuberculosis patients. Significant gamma interferon (IFN- ) production in response to whole-blood stimulation with M. ulcerans sonicate was detected in patients with ulcers, which was higher than that in patients with nodules but similar to subjects with healed BU. The mean IFN- response in household contacts of BU patients was not significantly different from that in healthy control subjects from an area of nonendemicity. Results in patients with untreated, smear-positive pulmonary tuberculosis and tuberculosis patients on treatment for more than 2 weeks showed that BU patients responded better to M. ulcerans antigens than tuberculosis patients. In contrast, interleukin-10 results were higher in patients with active M. ulcerans disease than in those with healed lesions, but the pattern of response was similar to that seen in tuberculosis. A similar pattern of cytokine secretion was found using M. tuberculosis sonicate as an antigen. Neither of the two culture filtrate antigens of M. ulcerans appeared to be more specific than M. ulcerans sonicate. In the early stages of M. ulcerans disease there was a mixed Th1 and Th2 cytokine response, but the Th1 response emerged as the dominant type.
- ItemCytokine mRNA Expression in Mycobacteriam ulcerans-Infected Human Skin and Correlation with Local Inflammatory Response(American Society for Microbiology, 2006-05) Phillips, Richard Odame; Horsfield, C.; Mangan, J.; Laing, K.; Etuaful, S.; et.alCytokine mRNA expression in biopsies of Mycobacterium ulcerans-infected human tissue was investigated using real-time PCR, and the findings were correlated with the clinical stages of disease and histopathologies. A broad range of cytokine mRNAs were detected in 16 early nodules and 28 late-stage ulcers, including those for the Th1 cytokines tumor necrosis factor alpha (TNF- ) and gamma interferon (IFN- ) and the Th2 cytokine interleukin 10 (IL-10). IFN- was strongly expressed in both nodules and ulcers, suggesting that a Th1 response begins early in the disease. There was a significantly higher expression of IL-8 and other proinflammatory cytokines in results from 32 biopsies with neutrophilia than in those from 12 biopsies without acute inflammation. Ten tissue samples containing granulomas showed high mRNA expression for IFN- , IL-1 , IL-12p35, IL-12p40, IL-15, and TNF- relative to 34 tissue samples without granulomas. These results suggest that the human immune response to M. ulcerans is similar to that seen with some other mycobacteria despite the presence of the toxin mycolactone in the tissues.
- ItemNighttime nox from sciamachy lunar occultation measurements(Proc. of the First ‘Atmospheric Science Conference’, ESRIN, 2006-05) Amekudz, L. K.; Bracher, A.; Bramstedt, K.; Bovensmann, H.; Burrows, J. PVertical profiles of stratospheric NO2 and NO3 have been retrieved from moderately resolution atmospheric lunar transmission spectra measured by SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) on board the ENVISAT (Environmental Satellite). The measurements were taken over the high Southern latitude (50o S–90o S). The global spectra fitting method by differential optical depth approach were used to fit NO2 and NO3 using the spectral window of 430–460 nm and 615–680 nm respectively. To assess the accuracy of the retrieved NO2 profiles the SCIAMACHY nighttime NO2 profiles were compared with daytime NO2 profiles measured by Halogen Occultation Experiment (HALOE), using photochemical correction model. The validation results show that the quality of SCIAMACHY nighttime NO2 is high within 5–20% in the altitude range of 24–39 km. Our current understanding of NO3 chemistry and the internal consistency of the retrieved NO3 profiles were verified with a complex and a relatively simple model scheme. The complex model uses a comprehensive photochemistry of the stratosphere and the simple model uses only SCIAMACHY ozone and ECMWF temperature and pressure analyses as input. We found that the retrieved NO3 profiles are in very good agreement with the model calculations within the expected accuracy of 20–35 %.
- ItemSciamachy solar and lunar occultation: validation of ozone, No2 and No3 profiles(ESRIN, 2007-02) Amekudzi, L. K.; Bramstedt, K.; Bracher, A.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.Using a global spectra fitting method by the differential optical depth within the radiative transfer and retrieval code SCIATRAN 2.1, vertical profiles of stratospheric traces gases are derived from SCIAMACHY solar and lunar occultation transmission spectra. From solar occultation observations ozone and NO2 profiles have been retrieved, from lunar occultation measurements ozone, NO2, and NO3 profiles have been derived. To access the quality of the SCIAMACHY occultation retrieved products a validation study was carried out, by comparing the retrieved ozone and NO2 profiles to correlative observations of other satellite instruments. These instruments are the Halogen Occultation Experiment (HALOE), the second Stratospheric Aerosol and Gas Experiment (SAGE II), and The third Polar Ozone and Aerosol Measurement (POAM III) . The NO3 profiles are compared with results from a photochemical model scheme. The validation show good results for SCIAMACHY occultation products. In solar occultion, the deviation of ozone is mostly within 0 % to +10 % for ozone and within 20 % for NO2 over a wide altitude range. In lunar occultation, the agreement is +10% to +20 % for ozone and within 20 % ˙ for NO2 in the main part of the profiles. The NO3 results show good agreement with the model outputs within the accuracy of 35 %.
- ItemChemical analysis of drinking water from some communities in the Brong Ahafo region(Springer-Verlag, 2007-03-01) Akoto, O.; Adiyiah, J.This study consisted of the determination of the trace metals and some physiochemical properties in drinking water samples from the Brong Ahafo region of the Republic of Ghana, where drinking water samples are not treated before it is consumed. The purpose was to ascertain the quality of water from these sources. Samples were taken from fifteen sampling points and analyzed for the following parameters Fe, Cu, Mn, Zn, Al, NO3 -, NO2 -, SO4 2, PO4 2-, and F- using the procedure outline in the palintest photometer method. The data showed the variation of the investigated parameters in samples as follows: pH 5.57-7.54, conductivity (EC) 35-1216 μs/cm, turbidity 3.25-72.50 NTU, PO4 2- 1 0.32-9.30 mg/L, F- 0.32-1.05 mg/L, NO3 - 0.09-0.99 mg/L, NO2 - 0.006-0.114 mg/L, SO4 2- 3.33-8.02 mg/L, Cu 1.19-2.75 mg/L Fe 0.05-0.85mg/L, Zn 0.04-0.15 mg/L, Mn 0.003-0.011 mg/L and Al 0.05-0.15 mg/L. The concentrations of most of the investigated parameters in the drinking water samples from Brong Ahafo region were within the permissible limits of the World Health Organization drinking water quality guidelines. There were no correlations between metal concentrations in the drinking water samples.
- ItemChemical analysis of drinking water from some communities in the Brong Ahafo region(Springer-Verlag, 2007-03-01) Akoto, O.; Adiyiah, J.This study consisted of the determination of the trace metals and some physiochemical properties in drinking water samples from the Brong Ahafo region of the Republic of Ghana, where drinking water samples are not treated before it is consumed. The purpose was to ascertain the quality of water from these sources. Samples were taken from fifteen sampling points and analyzed for the following parameters Fe, Cu, Mn, Zn, Al, NO3 -, NO2 -, SO4 2- , PO4 2-, and F- using the procedure outline in the Palintest Photometer Method. The data showed the variation of the investigated parameters in samples as follows: pH 5.57-7.54, conductivity (EC) 35-1216 μs/cm, turbidity 3.25-72.50 NTU, PO4 2- 1 0.32-9.30 mg/L, F- 0.32-1.05 mg/L, NO3 - 0.09-0.99 mg/L, NO2 - 0.006-0.114 mg/L, SO4 2- 3.33-8.02 mg/L, Cu 1.19-2.75 mg/L Fe 0.05-0.85mg/L, Zn 0.04-0.15 mg/L, Mn 0.003-0.011 mg/L and Al 0.05-0.15 mg/L. The concentrations of most of the investigated parameters in the drinking water samples from Brong Ahafo region were within the permissible limits of the World Health Organization drinking water quality guidelines. There were no correlations between metal concentrations in the drinking water samples.
- ItemSciamachy solar occultation: ozone and No2 profiles 2002-2006(ENVISAT, 2007-07) Bramstedt, K.; Amekudzi, L. K.; Bracher, A.; Rozanov, A.; Bovensmann, H.; Burrows, J. P.The spectrometer SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on-board ENVISAT is measuring solar irradiances and Earthshine radiances from the UV to the NIR spectral region in nadir, limb and lunar/solar occultation geometry. Solar occultation measurement are performed during sunrise at northern latitudes (49N to 69N, depending on season). Using an optimal estimation approach with the radiative transfer and retrieval code SCIATRAN 2.1, these measurements are used to derive vertical profiles of ozone and NO2. Precise tangent height information is derived from the scanning over the solar disk. Here we present an almost complete dataset from August 2002 to December 2006, including validation results with independent measurements from other satellites.
- ItemRetrieval of Trace Gas Concentrations from Lunar Occultation Measurements with SCIAMACHY on ENVISAT(ENVISAT, 2007-09-17) Amekudzi, L. K.; Bramstedt, K.; Rozanov, A.; Bovensmann, H.; Burrows, J. P
- ItemHeavy metals pollution profiles in streams serving the Owabi reservoir(Academic Journals, 2008) Akoto, O.; Bruce, T. N.; Darko, G.Water samples from five sampling points on four rivers, Owabi, Akyeampomene, Pumpunase and Sukobri, representing the main streams serving the Owabi reservoir were analysed for some pollution indicators using standard methods. Heavy metals (Zn, Cu, Mn, Cu, Pb and As) concentrations and some physical parameters of the water samples were determined. Electrical conductivity and pH of waters from all the streams were found to be within the acceptable limits of the World Health Organization (WHO). All the streams showed high turbidity values above WHO limits. Of the heavy metals determined in the water samples, Fe, Mn, Zn and Cu concentrations in all the streams were within the acceptable WHO limits, whiles Pb and As appeared to be higher than the acceptable limits in all the streams. The highest concentrations of most of the heavy metals were recorded at the Kronum site on Owabi stream. There was a statistically significant positive correlation between pH and some metals at all the sample points (p = 0.05). The results showed that all the streams were polluted and must be treated before consumption. It was also recommended that, human activities within the catchments should be monitored closely to minimise their polluting impacts on the water quality.
- ItemDissolved nitrogen in drinking water resources of farming communities in Ghana(Academic Journals, 2008) Akoto, Osei; Adiyiah, JacksonA water quality study was carried out on streams and boreholes which serve as drinking water sources in farming communities in the Brong Ahafo region of the Republic of Ghana. The objective of this research was to determine concentrations of different forms of nitrogen in drinking water samples. Water samples were collected from these sources every three months (from January – December 2005) and analyzed for ammonia, nitrate and nitrite using the Palintest Photometer Method. Results indicated the annual mean concentration of nitrate, nitrite and ammonia varied from 0.09 - 1.06 mg/l, 0.006 - 0.36 mg/l and 0.008 - 0.179 mg/l respectively. An important observation is that, in general, higher nitrate and nitrite concentrations were found during the rainy season compared to the dry season. Concentrations of these potentially toxic substances were below WHO acceptable limits for surface and groundwaters, indicating these water resources appear safe for drinking from a dissolved nitrogen perspective.
- ItemValidation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)(Atmos. Chem. Phys., 2008-10-08) Kerzenmacher, T.; Wolff, M. A.; Strong, K.; Dupuy, E.; Walker, K. A.; Amekudzi, L. K.; et.alVertical profiles of NO2 and NO have been obtained from solar occultation measurements by the Atmospheric Chemistry Experiment (ACE), using an infrared Fourier Transform Spectrometer (ACE-FTS) and (for NO2) an ultraviolet-visible-near-infrared spectrometer, MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). In this paper, the quality of the ACE-FTS version 2.2 NO2 and NO and the MAESTRO version 1.2 NO2 data are assessed using other solar occultation measurements (HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY), stellar occultation measurements (GOMOS), limb measurements (MIPAS, OSIRIS), nadir measurements (SCIAMACHY), balloon-borne measurements (SPIRALE, SAOZ) and ground-based measurements (UV-VIS, FTIR). Time differences between the comparison measurements were reduced using either a tight coincidence criterion, or where possible, chemical box models. ACE-FTS NO2 and NO and the MAESTRO NO2 are generally consistent with the correlative data. The ACE-FTS and MAESTRO NO2 volume mixing ratio (VMR) profiles agree with the profiles from other satellite data sets to within about 20% between 25 and 40 km, with the exception of MIPAS ESA (for ACE-FTS) and SAGE II (for ACE-FTS (sunrise) and MAESTRO) and suggest a negative bias between 23 and 40 km of about 10%. MAESTRO reports larger VMR values than the ACE-FTS. In comparisons with HALOE, ACE-FTS NO VMRs typically (on average) agree to ±8% from 22 to 64 km and to +10% from 93 to 105 km, with maxima of 21% and 36%, respectively. Partial column comparisons for NO2 show that there is quite good agreement between the ACE instruments and the FTIRs, with a mean difference of +7.3% for ACEFTS and +12.8% for MAESTRO.