Тренды содержания закисляющих и эвтрофирующих соединений в атмосферных осадках на урбанизированной территории

The trends in changing the content of sulfur and nitrogen in atmospheric precipitation in the territory of Minsk over an 18-year period are characterized on the basis of the analysis of the monitoring results of the chemical composition of atmospheric precipitation at the experimental site. A downtrend in the sulfur and nitrogen content combined with an uptrend in the precipitation acidity was identified. An average decrease (trend) in the content of sulfur in atmospheric precipitation for 2002–2019 was 0.019 mg S/dm3/year, of oxidized nitrogen – 0.008 mg/dm3, of reduced nitrogen – 0.019 mg/dm3. Over an 18-year period, the changes in the content of sulfur and nitrogen in atmospheric precipitation decreased the deposition of sulfur on average by 31.3 kg/km2/year, of oxidized nitrogen – by 15.4 kg/km2/year, of reduced nitrogen – by 25.6 kg/km2/year. It is shown that for the period from 2005 to 2012, the acidification potential of the natural environment decreased parallel to the reduction of the sulfur and nitrogen deposition; in the subsequent period, the trend of the acidification potential basically follows the trend of the precipitation of the main cations. It is revealed that the rates of average reduction in the content of oxidized sulfur and oxidized nitrogen in atmospheric precipitation in Minsk for the period from 2002 to 2017 are comparable to the rates of reduction of these compounds at the stations of the EMEP Program in Europe, and exceed those for reduced nitrogen.Охарактеризованы тенденции изменения уровней содержания серы и азота в атмосферных осадках на территории Минска за 18-летний период на основе анализа результатов мониторинга химического состава атмосферных осадков на экспериментальной площадке. Выявлен нисходящий тренд содержания серы и азота, сочетающийся с восходящим трендом величины рН осадков. Среднее сокращение (тренд) за 2002–2019 гг. содержания серы в атмосферных осадках составило 0,019 мг/дм3/год, окисленного азота – 0,008 мг/дм3, восстановленного азота – 0,019 мг/дм3. Изменение содержания серы и азота в осадках привело к сокращению выпадения серы за 18-летний период в среднем на 31,3 кг/км2/год, окисленного азота – на 15,4 кг/км2/год, восстановленного азота – на 25,6 кг/км2/год. Показано, что потенциал закисления природной среды снижался с 2005 по 2012 г. параллельно снижению выпадений серы и азота; в последующий период тренд потенциала закисления в основном следует тренду выпадения основных катионов. Выявлено, что средние за период с 2002 по 2017 г. темпы сокращения содержания окисленной серы и окисленного азота в атмосферных осадках в Минске сопоставимы с темпами сокращения этих соединений на станциях Программы ЕМЕП в Европе, и превышают – для восстановленного азота

Основные гидрохимические характеристики антарктических озер Холмов Тала

The article presents the results of measurements of the principal ions content, electrical conductivity and pH for 13 lakes and small (temporary) water ponds in the east part of the Thala Hills, Enderby Land, East Antarctica. Water sampling was carried out by participants of the seasonal Belarusian Antarctic expeditions in the period from 2011 to 2018. The purpose of the study is the evaluation of the hydrochemical composition of lakes and temporary ponds of the Thala Hills (on an example of the Vecherny Oasis), identification of natural and anthropogenic factors which determine the variability of the hydrochemical parameters for assessment of vulnerability of lakes and temporary ponds to anthropogenic impacts and climate change. It is shown that the waters of the lakes of this region are low mineralized with the sum of ions within the range of 10.6–87.5 mg/l (the average is 34.5 mg/l), electrical conductivity — 19.3–130.0 μS/cm (61.3 μS/cm). The water is characterized as slightly acidic and neutral. The waters of small (temporary) ponds are characterized by greater variability of hydrochemical parameters in comparison with lakes: the sum of ions is in the range of 6.7–915.0 mg/l (the average is 158.0 mg/l), the electrical conductivity is 4.6–1663.0 μS/cm (the average is 267.0 μS/cm). Coefficients of variation for most compounds in the waters of temporary ponds exceed 100 %. In most cases the predominance of sodium and chloride ions was established, which indicates the influence of marine aerosols on chemical composition of water lakes and temporary ponds. Elevated concentrations of mineral elements in the water of temporary ponds are caused by the lack of flow and, and as a consequence of thies, the accumulation of salts as a result of evaporation. Статья посвящена анализу гидрохимических показателей озер и временных водоемов восточной части Холмов Тала (Земля Эндерби, Восточная Антарктида). Впервые для данного региона охарактеризовано содержание основных ионов и других гидрохимических показателей по результатам опробования водоемов в период с 2011 по 2018 г. в рамках сезонных Белорус­ских антарктических экспедиций. Показано, что озера, являясь низкоминерализованными с диапазоном суммы ионов в пределах 10,6–87,5 мг/л, со слабокислой и нейтральной реакцией среды, близки между собой по химическому составу. Воды малых (временных) водоемов характеризуются большей вариабельностью гидрохимических параметров. Установлено пре­обладание в большинстве случаев ионов натрия и хлоридов, что свидетельствует о влиянии морских аэрозолей на химический состав водоемов. Полученные данные являются основой последующих оценок уязвимости озер и временных водоемов к антропогенным воздействиям и климатическим изменениям

Пространственные особенности химического состава снежного покрова Холмов Тала, Восточная Антарктида

Despite the great interest in the study of the chemical composition of the surface snow cover in Antarctica, the knowledge of the Enderby Land area remains extremely limited. In the Vecherny Oasis, where the construction of the Belarusian Antarctic Research Station has been carried out since 2015, the study of the chemical composition of the surface snow began in 2012 in preparation for the Comprehensive Environmental Evaluation. Its continuation is due to the need to assess the consequences of the construction and operation of the station in accordance with the requirements of the Antarctic Treaty Protocol on Environmental Protection.Snow samples were taken from 2012 to 2019 during the seasonal Belarusian Antarctic expeditions. Sampling was carried out from the surface horizons, which characterize the annual snow fallout. Chemical analytical studies were performed using standard methods. A total of 144 samples of snow water were analyzed.The aim of the study is to characterize the chemical composition of the surface snow of the Vecherny Oasis (and of the Thala Hills as a whole) to identify the areas of anthropogenic impact and trends in its change.The data on the main ions content in the surface snow, the value of pH and electrical conductivity, as well as the variabilities of the main indicators are presented. It is shown that the snow water of the Vecherny Oasis is very low-mineralized, with the sum of ions in the range of 1,04–57,3 mg/l (average — 7,4 mg/l), the values of electrical conductivity — 2,7–85,1 µS/cm (10,7 µS/cm). The snow water in most cases is characterized as slightly acidic. The chemical composition of the snow water and its mineralization is determined mainly by the content of chlorides and sodium ions. The high variability of the indicators of snow water hydrochemical composition within the areas of former and current human activities, as well as the increased content of sulfate ions, is considered to be indicative of anthropogenic impact.Статья посвящена пространственному анализу химического состава снежного покрова восточной части Холмов Тала (Земля Эндерби, Восточная Антарктида). Впервые на примере оазиса Вечерний детально охарактеризовано содержание основных ионов, величины рН и электропроводности для различных участков мониторинга, заложенных с учетом природных особенностей и антропогенного воздействия. Показано, что снеговые воды оазиса в период с 2012 по 2019 г. характеризовались как очень низкоминерализованные с диапазоном суммы ионов 1,04–57,3 мг/л (среднее — 7,4 мг/л), величины удельной электропроводности — 2,7–85,1 µСм/см (10,7 µСм/см); в 87 % случаев реакция среды снеговых вод оазиса характеризуется как слабокислая. Наиболее широким диапазоном измеренных концентраций хлоридов, сульфатов, ионов кальция и натрия характеризуются участки мониторинга, в пределах которых осуществлялась ранее и осуществляется в настоящее время хозяйственная деятельность. Полученные данные будут использованы для выявления трендов изменения химического состава снежного покрова в результате антропогенной деятельности и в связи с климатическими изменениями

Tetra-2,3-pyrazinoporphyrazines with externally appended thienyl rings: Synthesis, UV-visible spectra, electrochemical behavior, and photoactivity for the generation of singlet oxygen

A series of pyrazinoporphyrazine macrocycles carrying externally appended 2-thienyl rings, represented as [Th 8TPyzPzM], where Th 8TPyzPz = tetrakis-2,3-[5,6-di(2-thienyl)pyrazino]porphyrazinato anion and M = Mg II(H 2O), Zn II, Co II, Cu II, or 2H 1, were prepared and isolated as solid air-stable hydrated species. All of the compounds, completely insoluble in water, were characterized by their UV-visible spectra and electrochemical behavior in solutions of dimethylformamide (DMF), dimethyl sulfoxide, and pyridine. Molecular aggregation occurs at concentrations of ca. 10 -4 M, but monomers are formed in more dilute solutions of 10 -5 M or less. The examined octathienyl compounds [Th 8TPyzPzM] behave as electron-deficient macrocycles, and UV-visible spectral measurements provide useful information about how the peripheral thienyl rings influence the electronic distribution over the entire macrocyclic framework. Cyclic voltammetric and spectroelectrochemical data confirm the easier reducibility of the compounds as compared to the related phthalocyanine analogues, and the overall redox behavior and thermodynamic potentials for the four stepwise one-electron reductions of the compounds are similar to those of the earlier examined octapyridinated analogues [Py 8TPyzPzM]. Quantum yields (Φ Δ) for the generation of singlet oxygen, 1O 2, the cytotoxic agent active in photodynamic therapy (PDT), and fluorescence quantum yields (Φ F) were measured for the Zn II and Mg II complexes, [Th 8TPyzPzZn] and [Th 8TPyzPzMg(H 2O)], and the data were compared to those of corresponding octapyridino macrocycles [Py 8TPyzPzZn] and [Py 8TPyzPzMg(H 2O)] and their related octacations [(2-Mepy) 8TPyzPzZn] 8+ and [(2-Mepy) 8TPyzPzMg(H 2O)] 8+. These measurements were carried out in DMF and in DMF preacidified with HCl (ca. 10 -4 M). All of the examined Zn II compounds behave as excellent photosensitizers (Φ Δ = 0.4-0.6) both in DMF and DMF/HCl solutions, whereas noticeable fluorescence activity (Φ F = 0.36-0.43) in DMF/HCl solutions is shown by the Mg II derivatives; these data might provide perspectives for applications in PDT (Zn II) and imaging response and diagnosis (Mg II). © 2011 American Chemical Society