Determination of o-phthalic acid in snow and its photochemical degradation by capillary gas chromatography coupled with flame ionization and mass spectrometric detection

Phthalic acid and its photochemical degradation has been determined in snow and rainwater samples collected during winters (2003-2010) in the Southeast of Massachusetts using capillary gas chromatography (GC) with flame ionization and mass spectrometric detection. Water samples were dried using a rotary evaporator and derivatized with a 14% BF₃/methanol reagent before GC analysis. The developed method proved simple and accurate. Phthalic acid was found in snow samples collected in a concentration range of 7.22-76.5 nM. The photodegradation of phthalate was carried out under 300 nm UV light. The direct photodecomposition of the acid is slow (5% h⁻¹). However, the addition of dissolved Fe(III) species at 2.0 μM accelerated the light-induced degradation of phthalic acid by 3.5 times in the atmospheric water samples. Photodegradation rates of phthalic acid increases with decreasing pH value of water samples in the range of pH 2.8-4.5.     

Photophysical and photochemical properties of the pharmaceutical compound salbutamol in aqueous solutions

Salbutamol is a potent β₂-adrenergic receptor agonist widely used in the treatment of bronchial asthma and chronic obstructive pulmonary disease. An increasing number of studies have detected salbutamol in natural water systems worldwide. Studies have shown that sunlight degrades salbutamol resulting in the formation of products; some showing higher toxicity to bacteria Vibrio fischeri than the parent compound. In this contribution, steady-state absorption and emission techniques, high-performance liquid chromatography, and transient absorption spectroscopy are used to investigate the photochemistry of salbutamol in aqueous buffer solutions at controlled pH values. Ground- and excited-state calculations that include solvent effects are performed to guide the interpretation of the experimental results. Salbutamol is sensitive to UVB light absorption in the pH range from 3 to 12, forming products that absorb light at longer wavelengths than the parent compound. Quantum yields of degradation reveal that the deprotonated species is 10-fold more photo-active than the protonated species. In line with this result, the fluorescence quantum yield of the protonated species is more than an order of magnitude higher than that of the deprotonated species. Transient absorption spectroscopy shows that population of the triplet state occurs with a rate constant of 7.1 × 10⁸ s⁻¹ in the protonated species, while a rate constant of 1.7 × 10¹⁰ s⁻¹ is measured for the deprotonated species. While degradation of the deprotonated species is not affected by the presence of molecular oxygen, a twofold increase in the photodegradation yield of the protonated species in air-saturated conditions is observed.     

Watershed factors affecting stream acidification in the White Mountains of New Hampshire,USA

The streams tributary to acidic Cone Pond, pH 4.5–4.8, and circumneutral Black Pond, pH 5.3–6.4, in the White Mountains of New Hampshire, USA, were monitored for a year. The watersheds of these two ponds were characterized in terms of geology and stream hydrology. Chemical gradients and patterns in rock weathering and groundwater discharge explain many of the differences in mineral content and acidity of the streams. The rocks of Black watershed produced an average of ten times the equivalent of basic cations as rocks from Cone watershed. This is on the same order as the difference in acidity of the two streams. Down-stream changes in stream chemistry follow differing patterns, but reflect the same principle of residence time and water path length controlling chemical evolution of streamwater. Watershed and aquatic managers may use these parameters in an inexpensive and simple assessment of the susceptibility of individual streams and ponds to acidification. A method is recommended to determine quickly the potential influence of bedrock type to aquatic chemistry.     

SENSITIVITY OF HIGH-ELEVATION STREAMS IN THE SOUTHERN BLUE RIDGE PROVINCE TO ACIDIC DEPOSITION1

ABSTRACT: The Southern Blue Ridge Province, which encompasses parts of northern Georgia, eastern Tennessee, and western North Carolina, has been predicted to be sensitive to impacts from acidic deposition, owing to the chemical composition of the bedrock geology and soils. This study confirms the predicted potential sensitivity, quantifies the level of total alkalinity and describes the chemical characteristics of 30 headwater streams of this area. Water chemistry was measured five times between April 1983 and June 1984 at first and third order reaches of each stream during baseflow conditions. Sensitivity based on total alkalinity and the Calcite Saturation Index indicates that the headwater streams of the Province are vulnerable to acidification. Total alkalinity and p11 were generally higher in third order reaches (mean, 72 μeq/θ and 6.7) than in first order reaches (64 μeq/θ and 6.4). Ionic concentrations were low, averaging 310 and 340 μeq/θ in first and third order reaches, respectively. A single sampling appears adequate for evaluating sensitivity based on total alkalinity, but large temporal variability requires multiple sampling for the detection of changes in pH and alkalinity over time. Monitoring of stream water should continue in order to detect any subtle effects of acidic deposition on these unique resource systems.     

COMPARATIVE WATER CHEMISTRY OF FOUR LAKES IN ROCKY MOUNTAIN NATIONAL PARK1

ABSTRACT: The inorganic chemistry of two pairs of lakes in Rocky Mountain National Park was studied to determine reasons for their similarities and differences. The pairs were located on differing geologic units. It was expected that weathering from the different types of parent material would cause differing cation concentrations between the pairs. This was verified by dissimilar concentrations of those cations which are products of primary weathering. Unexpected was a significant difference in anion concentrations between members of one pair having the same bedrock geology. This difference has been attributed to the presence of a wet sedge meadow above one of the lakes which serves as a biological filter for anions, particularly nitrate and sulfate. It is shown that small scale drainage characteristics which can alter regional atmospheric contributions are important contributors to lake chemistry.     

Patterns of Streamwater Acidity in Lye Brook Wilderness,Vermont, USA

Under the United States Clean Air Act Amendments of 1977, a class I designation safeguards wilderness areas from the negative effects of new sources of air pollution. We monitored streamwater chemistry in the class I Lye Brook Wilderness in southwestern Vermont from May 1994 through August 1995. Stream samples were collected biweekly at nine sampling locations throughout the wilderness and were analyzed for major cations and anions, dissolved organic carbon, pH, and acid-neutralizing capacity. Eight of nine sites sampled had mean annual acid neutralizing capacity values below zero. During the study period, decreases in streamwater acid neutralizing capacity values were caused primarily by SO₄ ²⁻. At some sites, however, NO₃ ⁻ and naturally occurring, weak organic acids were seasonally important. During high discharge, the low pH and high concentrations of inorganic monomeric Al were at levels that are toxic to acid-sensitive aquatic species. Watershed mass balances were calculated to determine annual gains or losses for measured ions. These budgets indicate that S inputs and outputs were nearly equal, there was a net loss of base cations, and a net gain in N. How long these watersheds can continue to assimilate additional N inputs is unknown.     

Chemical Changes in Sediment Pore-Waters of an Acidic Mining Lake After Addition of Organic Substrate and Lime for Stimulating Lake Remediation

In the past five years, enclosures have beeninstalled in an acidic mining lake in Lusatia to investigate insitu remediation processes. They were treated with straw, withstraw and Carbokalk, or with Carbokalk alone, where Carbokalkis a by-product of the sugar industry (solid precipitate ofnon-sugars after lime clarification of extracted sugar beetjuice). Sediment samples were taken as cores to get informationabout the behaviour of organic and inorganic components insediment pore-water with depth. Vertical distributions of pH,soluble reactive phosphate, nitrate, ammonium, silica,aluminium, iron, manganese, calcium, magnesium, sodium,potassium, sulphate, and DOC were measured. The resultingprofiles, each consisting of 15 data points at differentdepths, were compared by cluster analysis. The similarities ofsediment cores from different treated enclosures relating toprofiles of chemical components were discussed. Increasedconcentrations of potassium and sulphate were found in pore-water after substrate treatment. The data imply dissolution ofpotassium iron sulphate hydroxide minerals (jarosite) after anincrease of pH caused by dissolution of lime and by sulphatereducing processes which were stimulated by organic substrateaddition.     

Trends in the Water Chemistry of High Altitude Lakes in Europe

Here we present the chemical trends of seven high altitude lakes, analysed within the AL:PE and MOLAR Projects of the EU (1999) and selected on the basis of the availability of complete and reliable data for the period 1984–1999. The lakes are representative of the Scandinavian Alps, the Cairngorm Mountains in Scotland, the Alps and the Pyrenees. Significant trends were identified for some indicators of acidification, for instance pH and alkalinity, but not all lakes reacted similarly to decreasing depositions of sulphate and base cations. Differences in lake response are discussed in relation to recent variations of atmospheric deposition chemistry and associated changes in climatic conditions. Beside individual variations of the studied lakes, depending, among other things, on altitude and morphology, catchment characteristics and climate trends play a major role for the reaction of high altitude lakes on changes in atmospheric depositions.     

中学化学教育中的可持续发展教育

本文阐述了中学化学教育中实施可持续发展教育的意义，认为化学教师作为可持续发展教育的实施者应努力更新知识结构、转变观念，承担起可持续发展教育的责任。着重介绍了在中学化学教育中结合实际如何对学生进行环保、可持续发展教育。     

环境化学进展动态

本文概述了近年来环境化学包括环境分析化学、环境污染化学、环境污染控制化学、生态化学等方面研究的一些新进展