Environmental exposure to perchlorate, nitrate, and thiocyanate in relation to chronic kidney disease in the general US population, NHANES 2005-2016 / 中华医学杂志(英文版)

BACKGROUND@#Few studies have explored the impact of perchlorate, nitrate, and thiocyanate (PNT) on kidney function. This study aimed to evaluate the association of urinary levels of PNT with renal function as well as the prevalence of chronic kidney disease (CKD) among the general population in the United States.@*METHODS@#This analysis included data from 13,373 adults (≥20 years) from the National Health and Nutrition Examination Survey 2005 to 2016. We used multivariable linear and logistic regression, to explore the associations of urinary PNT with kidney function. Restricted cubic splines were used to assess the potentially non-linear relationships between PNT exposure and outcomes.@*RESULTS@#After traditional creatinine adjustment, perchlorate (P-traditional) was positively associated with estimated glomerular filtration rate (eGFR) (adjusted β: 2.75; 95% confidence interval [CI]: 2.25 to 3.26; P  < 0.001), and negatively associated with urinary albumin-to-creatinine ratio (ACR) (adjusted β: -0.05; 95% CI: -0.07 to -0.02; P  = 0.001) in adjusted models. After both traditional and covariate-adjusted creatinine adjustment, urinary nitrate and thiocyanate were positively associated with eGFR (all P values <0.05), and negatively associated with ACR (all P values <0.05); higher nitrate or thiocyanate was associated with a lower risk of CKD (all P values <0.001). Moreover, there were L-shaped non-linear associations between nitrate, thiocyanate, and outcomes. In the adjusted models, for quartiles of PNT, statistically significant dose-response associations were observed in most relationships. Most results were consistent in the stratified and sensitivity analyses.@*CONCLUSIONS@#Exposures to PNT might be associated with kidney function, indicating a potential beneficial effect of environmental PNT exposure (especially nitrate and thiocyanate) on the human kidney.

Pediatric patients head-up-tilt-test with pharmacological challenge, it is safe? / Mesa inclinada en pacientes pediátricos con reto farmacológico, ¿es seguro?

Abstract Syncope in pediatrics represents an important cause of visits to the emergency units. For this reason, excluding a cardiac or malignant origin is essential at the time of the initial approach to determine what is the next step in management, or if they need to be referred to a pediatric cardiologist and/or electrophysiologist. Vasovagal syncope is the most frequent cause of syncope in pediatrics, in which a detailed clinical history is enough to make the diagnosis. If no diagnosis is concluded by the history, or if it is necessary to define the hemodynamic response of the patients, the head-up-tilt-test is indicated; this will trigger syncope due to an orthostatic stress caused by the angulated table (passive phase). If a negative response remains, it can be followed by a pharmacologic challenge to trigger the hemodynamic response, which is still controversial in pediatrics. The pharmacologic challenge increases the sensitivity with a slight reduction in test specificity. Although there is not a specific drug for the challenge in pediatric patients yet, the most commonly drugs used are nitrates and isoproterenol, the latter related to a great number of adverse effects. Sublingual administration of nitrates in the challenge has been proven to be ideal, effective, and safe in this specific age group. The aim of this article is to make a literature search to demonstrate the effectiveness and safety of the pharmacologic challenge during the head-up-tilt-test in pediatrics, emphasizing a study conducted at the National Institute of Cardiology with isosorbide dinitrate.

Resumen El síncope en edades pediátricas representa una causa importante en las visitas a unidades de urgencias, por lo que excluir un origen cardíaco o maligno es fundamental al momento del abordaje inicial para determinar la conducta a seguir o la necesidad de derivar al cardiólogo pediatra o electrofisiólogo. El síncope vasovagal (SVV) es la causa más frecuente de síncope en pediatría, para cuyo diagnóstico basta una historia clínica detallada. Cuando ésta no es suficiente para determinar el diagnóstico de síncope reflejo o es necesario definir el tipo de respuesta que lo origina, está indicada una prueba de mesa inclinada que produce un estrés ortostático por la angulación y ello desencadena un síncope (fase pasiva). En pruebas no concluyentes está indicado un reto farmacológico para precipitar la respuesta hemodinámica, pero aún es un tema de controversia en edades pediátricas. El reto farmacológico incrementa la sensibilidad de la prueba, con una ligera reducción de la especificidad. Si bien no existe todavía un medicamento específico para la población pediátrica, los más empleados son los nitratos y el isoproterenol, este último relacionado con un mayor número de efectos adversos. La administración sublingual de los nitratos utilizados ha demostrado ser ideal, efectiva y segura en los pacientes pediátricos. El objetivo del artículo es realizar una revisión de las publicaciones médicas que demuestran la efectividad y seguridad del reto farmacológico durante la prueba de mesa inclinada en pacientes pediátricos, con énfasis en un estudio conducido en el Instituto Nacional de Cardiología con dinitrato de isosorbida (DNIS).

Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial

The study aimed to evaluate the effectiveness of in-office bleaching and associated tooth sensitivity on application of nano-calcium phosphate paste as desensitizing agent. Bleaching was performed with 35% hydrogen peroxide gel in 40 patients who were randomly divided into placebo and nano-calcium phosphate paste groups. Bleaching efficacy (BE) was evaluated using a value-oriented Vita shade guide. Tooth sensitivity was recorded using a numeric rating scale (0–4) during bleaching and up to 48 h after each session. The primary outcome of absolute risk of tooth sensitivity was compared using the Fisher’s exact test (α = 0.05). The intensity of tooth sensitivity and the efficacy of in-office bleaching were also statistically evaluated. No significant differences in absolute risk and intensity of tooth sensitivity were detected between the groups (p = 1.0 and p = 0.53, respectively). BE was also found to be similar between the groups (p = 0.67). Although the use of a nano-calcium phosphate paste associated with fluoride and potassium nitrate did not influence the whitening outcome, but it also did not reduce bleaching-induced tooth sensitivity.

Dietary nitrate may have a role in development of gastro-esophageal reflux disease

Gastro-esophageal reflux disease [GERD] has become very common in the past three decades. The reason for this, as well as its exact pathophysiologic mechanisms are yet unknown. In this ecologic study we assessed the relation between water nitrate content and prevalence of GERD in Tehran, Iran. We determined the prevalence of acid regurgitation [AR] heartburn or any of them occurring on a frequent [at least weekly] or infrequent basis in areas with different water nitrate. The areas for nitrate were defined as below: <50mg nitrate/L, 50 - 74 mg/L, 75-100 mg/L, and >100 mg/L. Frequency of each symptom was assessed in each area and compared. Adjustment for age, sex, education, NSAID-consumption, BMI, smoking, history of GERD in first degree relatives and spouse was done in a multivariate model. People living in areas with water nitrate content more than 100mg/L had a higher chance of suffering from frequent AR than those living in areas with water nitrate less than 100mg/L [25.5% vs. 12.0%, OR: 2.53, 95% Cl: 1.36 - 4.73, P=0.006]. After adjustment for the named factors, the relationship remained significant [OR: 3.65, 95% Cl: 1.32 - 10.09]. The relation for frequent heartburn or infrequent symptoms was not significant. In this ecologic study, we found relation between experiencing frequent AR and drinking or cooking with water containing more than 100mg nitrate/L. Considering our current knowledge, if we put dietary nitrate into the puzzle of increased prevalence and/or pathophysi-ology of GERD, it can theoretically answer several questions. Hence we propose a nitrate-hypothesis for GERD pathogenesis

Contaminación del agua por nitratos: significación sanitaria: [revisión] / Water pollution by nitrates: sanitary significance: [review]

Se realizó una revisión del reporte de contaminación del agua subterránea por nitratos, tanto en países del exterior como en el nuestro. Se hicieron señalamientos sobre el deterioro de la calidad de estas aguas y los efectos adversos que las mismas pueden tener para la salud. También se hizo referencia al origen de la contaminación de las mismas en la mayor parte de los casos. Con respecto a Cuba un informe emitido hace ya varios años por el Ministerio de Salud Pública y el entonces Instituto de Hidroeconomía, señaló las provincias de Camagüey, Las Tunas y en menor grado Cienfuegos y Holguín como las de mayor afectación en este sentido.

A review of the contamination report of underground water by nitrates was carried out, as much in other countries as in ours. Appoitments are made on the deterioration of the quality of these waters and the adverse effects that the same ones may have for health. Reference is also made to the origin of the contamination of the said waters in most of the cases. Concerning Cuba an emitted statement already several years ago for the Ministry of Public Health and the Institute of Hydroeconomy, points out Camagüey, Las Tunas and in smaller grade Cienfuegos and Holguín provinces as the most affected in this sense.

[Investigation of the source of nitrate contamination in ground waters of Gorgan, Iran [2005]]

One of the problems in urban areas is nitrate contamination of ground waters. High nitrate concentration can cause methemoglobinemia, appearing as a risk factor is provided by ground waters. More than 80% of drinking water of Gorgan, Iran. So this investigation was done to determine of nitrate level in ground waters in Gorgan. This study has been carried out for investigation of nitrate rate in drinking water supply networks and not drinking water ground water wells of Gorgan city. This discriptive study was done on 43 ground waters and surface water samples which collected in spring and winter, in Gorgan during 2005. K+, Cl-, NO21-, NO31- of samples were analyzed by spectrophotometery method. The chemical analysis of ground waters of drinking water resources of Gorgan city showed significant variation of nitrate between 3.52 to 69.52 mg/l. The rates of nitrate in certain ground waters wells in vicinity of landfills were between 84.48 to 145.2 mg/l which is more than drinking water standards. Nitrate concentration in agricultural lands such as Shast-kula and Garmabdasht aquifers is lower than Ziarate aquifer in vicinity of urban area. Nitrate contamination in aquifers in vicinity of urban area and unsanitary disposal of solid waste substance may result from house sewage effluents and infiltration of landfillleachs to ground water wells

effect of storage on the level of nitrite and nitrate in meat products available in Cairo market and effect of adding some antioxidants on one of the meat products

Meat is considered of high nutritional value as it contain protein, fat, vitamins and minerals. Nitrates and nitrites were used in meat products. The presence of nitrates and nitrites in foods may play a negative role in general health status. This study aimed to estimate the concentration levels of nitrite and nitrate in different meat and meat products that are available in Cairo Governorate markets and the effect of adding some antioxidant on the level of nitrates and nitrites in the products. The nitrate and nitrite contents were determined according to Griess methods. The results indicated that, sausage and kofta fresh samples tended to have the highest content of sodium nitrates, followed by burger. On contrast, luncheon fresh samples tended to have the lowest content of nitrates. As expected, after 30 and 60 days of storage, the level of nitrates has been significantly decreased, as compared to fresh samples. On contrast, the level of nitrites has been significantly increased, as compared to fresh samples. The investigated samples contained nitrite lower than the recommended safety limit proposed by Egyptian standards. With the exception of basterma samples the contained nitrites were higher than the recommended by Egyptian standard partially after storage. It should be noticed that, all investigated sausage samples treated with antioxidant [vitamin C, vitamin E and selenium] have nitrites in the amount lower than the recommended safety limit, even after storage for 60 days. All tested antioxidants had a good affect for lowering nitrate and nitrite contents for all investigated samples. It should be noted that vitamin C tended to have the most effect for reducing nitrites among all tested antioxidants followed by vitamin E

A questão do nitrato em alface hidropônica e a saúde humana / The nitrate issue in hydroponic lettuce and the human health

A alface (Lactuca sativa L.) destaca-se como a espécie mais produzida em sistema hidropônico. Nesse tipo de cultivo, a maior parte do nitrogênio é fornecida na forma de nitrato, o que pode acarretar acúmulo deste íon nos vacúolos celulares. O teor de nitrato nas plantas depende de fatores genéticos, da disponibilidade desse nutriente no sistema radicular e de fatores ambientais. Diversos estudos indicam que o consumo de nitrato pode ser nocivo à saúde humana, causando metahemoglobinemia e câncer gástrico. Porém, pesquisas recentes discorrem que não há ligação entre nitrato e as doenças citadas, destacando ainda o papel benéfico do nitrato à saúde humana, como protetor contra gastrenterites. Existem indícios de que a presença de certas vitaminas em vegetais inibe uma possível ação negativa do nitrato. Altas concentrações de nitrato em alface cultivada sob hidroponia em países do norte europeu causaram apreensão da comunidade científica e de consumidores brasileiros. Porém, as pesquisas realizadas no Brasil demonstram que, por haver maior disponibilidade de radiação solar, devido às menores latitudes, os teores de nitrato encontrados em alface produzida em hidroponia são bastante inferiores aos limites máximos preconizados pela união européia, indicando não haver risco à saúde humana.

Lettuce (Lactuca sativa L.) is the main vegetable crop produced hydroponically. In this kind of cropping, the majority of nitrogen is provided as nitrate, which may lead to the accumulation of this ion in cells. Nitrate amount in plants depends upon genetic factors, the availability of this nutrient in roots and environmental factors. Several studies have indicated that the consumption of nitrate may be harmful to human health, causing methaemoglobinaemia and gastric cancer. However, recent studies have proposed that there is no link between nitrate and these diseases, and that nitrate may be even good for human health as a protector against gastroenteritis. Some other studies have indicated that the presence of certain vitamins in plants is likely to inhibit possible negative effects of nitrate. High nitrate concentrations in lettuce grown hydroponically in northern European countries have been a matter of concern to the scientific community and Brazilian consumers. Nevertheless, studies have demonstrated that in Brazil, because of higher solar radiation at low latitudes, nitrate amounts found in lettuce produced hydroponically are much lower than the amounts given by the European community, indicating no risk to human health.

Nitratos, nitritos, nitrosaminas e seus efeitos sobre o organismo humano / Nitrates, nitrites, nitrosamines and their effects on the human body

Os nitratos e nitritos, na forma de sal de sódio e potássio, são largamente usados no processamento de derivados cárneos, originando produtos como presuntos, bacon e salsichas. São conservantes geralmente adicionados aos sais de cura, sendo responsáveis pela formação e estabilidade da cor de produtos cárneos, possuindo também atividade antimicrobiana. O nitrito pode ser adicionado diretamente na carne ou ser obtido através da redução do nitrato na própria carne, por ação de bactérias redutoras. Os nitratos são pouco tóxicos, a não ser em níveis elevados, porém, os nitritos possuem uma toxicidade maior, pois são capazes de se combinar com compostos presentes nos alimentos formando compostos nitrosos denominados nitrosaminas. Como a maioria desses compostos têm apresentado atividade cancerígena e mutagênica, a sua formação e ocorrência estão sendo cada vez mais estudadas com o propósito de se conhecer melhor esse tipo de contaminante e os riscos potencialmente envolvidos com a sua ingestão. A utilização destes conservantes em concentrações adequadas e rigorosamente controladas, associada com a avaliação da sua ingesta pela população, possibilita minimizar a possibilidade de ocorrência de problemas de toxidade pelo seu consumo. Com isso tem-se uma maneira de diminuir os riscos sofridos pelos consumidores de produtos cárneos curados.

Study on the effect of nitrogen fertilizer levels on chlorophyll concentration of grape leaves using FT-IR spectroscopy

Methods used to detect N deficiencies during the growing season include chlorophyll meter readings, destructive plant sampling, and soil sampling. Furthermore, diagnostic methods like FT-IR techniques that take advantage of the optical properties of leaves are another possibility to assess the nitrogen status of plants in a field and to assess nitrogen fertility effects on yield. The use of effective FT-IR techniques would eliminate the need for extensive field sampling. Fourier Transform Infrared [FT-IR] spectroscopic technique was used in the present work to study the effect of N-fertilization levels on the concentrations of chlorophyll and nitrogen in grape leaves. Ammonium nitrate [N-fertilizer] was applied after the beginning of vegetative growth by supplying 33.3%, 66.6%, 100%, 133.3%, and 166.6% of the recommended N-fertilizer level, according to the Ministry of Agriculture [50 units N which is considered the level of 100% for comparing during N application]. To establish a range of leaf chlorophyll levels, each treatment was applied to definite row; thus there were 5 different rows, three vines in each line were selected to make the application

A review of nitrates in drinking water: maternal exposure and adverse reproductive and developmental outcomes

In this review, we present an update on maternal exposure to nitrates in drinking water in relation to possible adverse reproductive and developmental effects, and discuss nitrates in drinking water in the United States. The current standard for nitrates in drinking water is based on retrospective studies and approximates a level that protects infants from methemoglobinemia, but no safety factor is built into the standard. The current standard applies only to public water systems. Animal studies have found adverse reproductive effects resulting from higher doses of nitrate or nitrite. The epidemiologic evidence of a direct exposure-response relationship between drinking water nitrate level and adverse reproductive effect is still not clear. However, some reports have suggested an association between exposure to nitrates in drinking water and spontaneous abortions, intrauterine growth restriction, and various birth defects. Uncertainties in epidemiologic studies include the lack of individual exposure assessment that would rule out confounding of the exposure with some other cause. We conclude that the current literature does not provide sufficient evidence of a causal relationship between exposure to nitrates in drinking water and adverse reproductive effects.

Nesta revisão, apresentamos um estudo sobre exposição materna aos nitratos na água potável e possíveis reações adversas ao desenvolvimento reprodutivo, no caso dos Estados Unidos. O padrão de uso de nitratos na água potável é baseado em estudos retrospectivos e leva em conta níveis que protegem os bebês contra a metemoglobinemia. Mas nenhum fator de segurança foi construído a partir desse padrão, sendo que os níveis atuais foram construídos e exigidos apenas para os sistemas públicos de distribuição de água. Estudos com animais encontraram efeitos reprodutivos adversos e advindos das altas doses de nitrato ou nitrito na água. A evidência epidemiológica sobre a relação de exposição-resposta direta entre o nível de nitratos na água potável e efeitos adversos não está clara. No entanto, algumas notificações sugerem associação entre exposição a nitratos na água potável e abortos espontâneos, restrições ao crescimento intrauterino e vários defeitos de nascença. As incertezas nos estudos epidemiológicos incluem a falta de avaliação da exposição individual que excluiria confundir a exposição com outros fatores. Concluimos que a literatura atual não provê suficiente evidência de uma relação causal entre exposição a nitratos na água potável e efeitos reprodutivos adversos.

Avaliação da adição de nitrato de amônia para redução de odor nos esgotos de Pereira Barreto-SP: reflexos na qualidade da água do reservatório de Três Irmãos, após dez anos de aplicação / Evaluation of the addition of ammonium nitrate to the sewer system in Pereira Barreto-SP, in order to reduce the odor: reflections upon the quality of the water in the Três Irmãos reservoir, after ten years of application

Avalia a alteração da água da região de lançamento dos efluentes domésticos no reservatório de Três Irmãos, em virtude da aplicação de nitrato de amônia, para controle de odor, na rede coletora de esgotos do município de Pereira Barreto desde 1996. Foram realizadas 6 campanhas , com frequência bimestral, no período de outubro a agosto de 2005. As amostras foram coletadas em seis pontos, sendo cinco no reservatório, e um na ETE-Pereira Barreto. Em cada estação no reservatório, as amostras foram tomadas à superfície, à meia profundidade e fundo. Obtiveram-se amostras de água e esgoto para análise de parâmetros físicos, químicos e hidrobiológicos. Para melhor avaliar a qualidade da água, como também do efluente final da ETE, foram efetuados o Teste de Postos com Sinais de Wilcoxon para pares combinados (método não-paramétrico), análise de componentes principais (ACP) e Análise de Agrupamento (Cluster). Os resultados mostram que os níveis de nitrogênio nitrato na água e no efluente final situaram-se bem abaixo do limite máximo estabelecido pelo CONAMA 357/05 para águas da Classe 2 (10mg/L) Conclui-se que a prática da adição de nitrato de amônia para reduzir os odores em rede coletoras de esgotos sanitários, sob o ponto de vista ambiental, não apresentou potencial para acarretar impacto negativo no corpo receptor, e que a região de estudo no reservatório é um ambiente bem oxigênado, inclusive nas camadas mais profundas, com baixos teores de turbidez e pH levemente alcalino, entretanto, com alta condutibilidade elétrica e elevadas concentrações de nutrientes (fósforo e amônia), principalmente no Período de verão. Este fato é devido à influência principalmente do esgoto domético que é lançado nesta área.

Relation of nitrate contamination of groundwater with methaemoglobin level among infants in Gaza

A descriptive, cross-sectional and analytical study was carried out in 3 areas of the Gaza Strip, Palestine, in 2002, to determine the factors associated with high methaemoglobin [Met-Hb] levels in infants and the relationship with nitrate concentration in drinking water wells. Drinking water sources were likely to be the main factor for high levels of Met-Hb. Out of 338 infants attending for vaccination, having supplemental feeding, use of boiled water and age 3-6 months were associated with high Met-Hb levels. The highest mean Met-Hb level was in Khan-Younis, where the highest mean nitrate concentration was recorded in drinking water. The results emphasize the importance of exclusive breastfeeding for infants < 6 months old, and the choice of a suitable source of water for these infants

Toxicopathological impact of sub-lethal concentration of lead nitrate on the aerial respiratory organs of [Murrel] Channa striata [Bloch, Pisces]

Sub-lethal toxicity of lead nitrate solution [46.25mg/L, 5% of 96h LC[50] value] on the air-breathing organ [suprabranchial chamber] of Channa striata was analysed for 60 days. Because air-breathing organs of C. striata remain in direct contact with waterborne xenobiotics, any change in the aquatic ecosystem was directly reflected in them. Concentration of lead accumulation in the air-breathing organ fluctuated at different stages of exposure. Due to extensive secretory activity, the mucous cells very often got exhausted and disappeared followed by their regeneration. This causes periodic fluctuations in the density of the mucous cells. A significant increase in the gross DNA contents in relation to the respective control is noticed at many stages of exposure. Increases in the RNA and protein contents with simultaneous increase in the mucogenic activity of the mucous cells were also observed. The total lipid contents also showed a periodic fluctuation in their concentration

Efeito do uso de nitrato e nitrito na inibição de Clostridium perfringens tipo A em linguiça bovina curada / The effect of the use of nitrate and nitrite on the inibition of Clostridium perfringnes type on the bovine cured sausage

O presente trabalho teve como objetivo verificar a eficiência dos conservantes nitrato e nitrito na inibição do Clostridium perfringens tipo A, (responsável por toxinfecção alimentar) durante a vida útil de linguiças de carne bovina curadas. As amostras foram elaboradas partindo-se de massa subdividida em grupo controle e grupo tratamento (adicionado de sal de cura), ambos inoculados com a cultura de C. perfringens (6 x 10 UFC). Efetuaram-se análises microbiológicas para quantificação da bactéria e a determinação dos níveis residuais de nitrato e nitrito. Os resultados demonstraram que durante o período de vida útil do produto( 44 dias) não houve desenvolvimento do microorganismo nas linguiças que receberam tratamento , mesmo em níveis baixos de nitrato e nitrito. Já no grupo controle verificou-se crescimento do microorganismo, embora enquadrado no limite exigido pela legislação brasileira (3 x 10 UFC). As quantidades de nitrato e nitrito de sódio adicionadas (200ppm) indicaram período de redução dos níveis de no mínimo quatro dias após o processo de elaboração, permanecendo então abaixo dos limites permitidos pela legislação (150ppm). Os resultados obtidos evidenciaram a efici~encia dos conservantes nitrato e nitrito na inibição do microorganismo Clostridium perfringens tipo A em linguiça

Determinações espectrofotométricas de nitrito e nitrato em sais de cura / Spectrophotometrics determination of nitrite and nitrate in curing salts

Este trabalho objetivou desenvolver um método para determinar espectrofotométricamente nitrito e nitrato em sais de cura. Foram estudados espectros de absorção do nitrato em faixa do ultravioleta, comparação de medidas no ultravioleta de nitrato e nitrito, usando cubetas de quartzo e metacrilato, e determinações de nitrito e nitrato em sais de cura nas regiões visível e ultravioleta. Com relação às determinações no ultravioleta, máxime no que diz respeito ao nitrato, verificou-se máxima absorção do nitrato na faixa de 301 nm; as cubetas de quartzo e de metacrilato apresentam as mesmas respostas espectofotométricas; e não existem diferenças estatísticas significativas nos métodos espectrofotométricos nas regiões visível e ultravioleta ás determinações de nitrito e de nitrato em sais de cura (P<0,0001). Com base nesses ensaios, concluímos que o método espectrofotométrico visível para determinação de nitrato possui inúmeras etapas que podem gerar erros, além do manuseio do cádmio metálico que é um produto altamente tóxico para o ser humano e para o meio ambiente; entretanto, o método espectrofotométrico direto (UV) é rápido e preciso.

Determinações espectrofotométricas de nitrito e nitrato em sais de cura / Spectrophotometrics determination of nitrite and nitrate in curing salts

Este trabalho objetivou desenvolver um método para determinar espectrofotométricamente nitrito e nitrato em sais de cura. Foram estudados espectros de absorção do nitrato em faixa do ultravioleta, comparação de medidas no ultravioleta de nitrato e nitrito, usando cubetas de quartzo e metacrilato, e determinações de nitrito e nitrato em sais de cura nas regiões visível e ultravioleta. Com relação às determinações no ultravioleta, máxime no que diz respeito ao nitrato, verificou-se máxima absorção do nitrato na faixa de 301 nm; as cubetas de quartzo e de metacrilato apresentam as mesmas respostas espectofotométricas; e não existem diferenças estatísticas significativas nos métodos espectrofotométricos nas regiões visível e ultravioleta ás determinações de nitrito e de nitrato em sais de cura (P<0,0001). Com base nesses ensaios, concluímos que o método espectrofotométrico visível para determinação de nitrato possui inúmeras etapas que podem gerar erros, além do manuseio do cádmio metálico que é um produto altamente tóxico para o ser humano e para o meio ambiente; entretanto, o método espectrofotométrico direto (UV) é rápido e preciso.

The aim of this work was to develop a method of measuring spectrophotometrically nitrite and nitrate in curing salts.The folowing parameters have been studied: nitrate absorption spectra in the ultraviolet range, comparison of the nitrate and nitrite measures at the ultraviolet range using quartz and methacrylate cuvettes, and the nitrite and nitrate determinations in curing salts at the visible and ultraviolet ranges. With regard to the ultraviolet range determinations,it has been verified that the maximum nitrate absorption occurred in the 301nm zone, quartz and methacrylate cuvettes showed similar spectrophotometrics values, and there are no significant statistical differences in spectrophotometrics methods between the visible and ultraviolet ranges concerning nitrite and nitrate determinations in curing salts (P<0,0001). Based on these assays, it has been concluded that the visible spectrophotometric method to determine nitrate has severa1 steps that might lead the analyst to make mistakes, in addition there is the fact that the metallic cadmium handling can be harmful, due to its toxic properties to human beings and to theenvironment as well. Nevertheless, the direct (UV) spectrophotometric method proved to be fast and accurate.

Study on ground water characteristics and the effects of discharged effluents from textile units at Karur District.

A study was made on the physico-chemical characteristics of water samples mixed with effluent discharged from textile industries at Chellandipalayam (Site--I), Senaparatti (Site--II) and Pasupathipalayam (Sites--III and IV) revealed the elevated levels of Ca, Mg, Na, Cr, K, Ni, Cu, Zn, CO3, SO4, NO3 and Cl- . The concentrations of these ions exceeded the limit prescribed by ISI. The increase in the concentrations of ions was revealed by higher values of electrical conductivity (EC). Water at these sites was found to be hard, brackish and unsuitable for drinking purpose. In all these sites, the seed germination of rice alone was significantly affected among the other crops tested. Irrigation of crops with ground water notably lowered the quantity of reserve food in rice, wheat (starch), and sugarcane (sugar), indicating the interference of their metabolic pathway by polluted ground water.

Discretization of flow contain nitrate in porous media by finite volume technique

One of the most important pollutants of groudwaters is nitrate. Different human activities including the application of chemical fertilizers in agriculture, causes the emission of nitrate into groudwaters. In this paper, the dynamic effect of soil moisture on carbon and nitrogen cycles has been analyzed by presenting a connection between soil moisture sample and nonlinear differential equations. At present, wide researches are carried out on modeling soil moisture control in solution flows contain nitrate. In order to do so, separation of energy conservation law equations is carried out by a particular method. The mathematical model governing the nitrate containing current in non-isotropic environment has been presented in the form of combined equations. Equation for distribution in multiple environments and Darcy rule has been considered in this model. Then, using finite volume method, separation of flows contain nitrate in porous media is carried out. The current flux is obtained from central difference approximations or upwind approximation. Mashad plain has been considered for case study at this research. Carrying out calibration operation, the measured results have been contrasted with numerical results of finite volume method. After testing the model, it is possible to foresee the way of nitrate changes in other nodes of calculation network. Using these forecasts, the quality of drinking water for several next years is determined. Carrying out numerical modeling by finite volume method, it is found out that the quality of drinking water of Mashad plain would be suitable for the next ten years