Purpose Methane biofiltration is based on gas transformation to carbon dioxide and water by methanotrophic microorganisms. Biofilter performance has been thoroughly investigated under climatic conditions of Western Europe, but not those of Russia. Therefore, this study was conducted to analyze methane biotransformation performance of soil and soil-like biofilters in Moscow. Materials and methods Biofilters were designed as threelayer systems (0.2×0.2×0.5 m) where methane (2.5 vol%) was injected daily. This system operated for 9 months. Five biofilters with different working layers have been investigated: a natural humic horizon of albeluvisol (AB); two soil-like types of media containing peat (PB) or compost (CB) as organic matter; and two soil-like types of media containing the reclamation additives vermiculite (CVB) and clayite (CCB). Methane and carbon dioxide were measured in hermetically covered biofilters immediately and 24 h after methane injection. These gases were collected through a six-tube system incorporated into the biofilters and analyzed by gas chromatography. Results and discussion The maximum methane biotransformation occurred in summer, while there was slightly less in autumn and much less in winter. The highest values of 99.7, 97.0, and 91.5 % were observed in AB, followed by 97. 8, 92.4, and 72.8 % in CB and 52.6, 43.2, and 23.8 % in PB during summer, autumn, and winter, respectively. Methane biotransformation rates were correlated with methanotroph pools in biofilter media. Summer carbon dioxide levels were lowest in AB (0.7 %) and highest in CB (2.6 %) due to difference in organic composition and its mineralization rates. Emission levels were highest in AB (0.2 %)
Статья посвящена актуальным вопросам эмиссии парниковых газов в атмосферу в городской среде и выявлению роли почв в регулировании этого процесса. Исследовано три типа потенциально газогенерирующих объектов: территории над погребенными стихийными свалочными телами, участки строительства на засыпанной переувлажненной речной пойме и рекультивированные поля фильтрации сточных вод. На каждом объекте определялись типы доминирующих почв, их физические, химические свойства, способность образовывать и окислять метан, продуцировать углекислый газ. Показано, что более развитые урбисерогумусовые техногенные почвы и урбаноземы техногенные, а также созданные в ходе благоустройства реплантоземы более эффективно утилизируют аллохтонные потоки метана, чем литостраты, органолитостраты и слаборазвитые почвы. Эмиссии метана в атмосферу из первой группы почв не наблюдается, но они служат более мощным источником углекислого газа в атмосферу по сравнению с литостратами и органолитостратами. Запечатывание, переуплотнение, засоление, подтопление городских почв снижают их окислительную способность и повышают вероятность эмиссии метана в атмосферу.В связи с ростом индустриализации города приобретают больший вес в естественном круговороте веществ в природе. Города являются источниками парниковых газов, выделяемых промышленностью, автотранспортом, полигонами ТБО, а также городскими почвами. В связи с увеличением плотности населения застраивается все больше территорий с неблагоприятными свойствами: переувлажненные поймы рек, засыпанные овраги и балки, погребенные несанкционированные свалки, рекультивированные поля фильтрации. Городские почвы над такими территориями являются источником и стоком метана и углекислого газа. Данное исследование важно для понимания вклада городских почв в выбросы парниковых газов в атмосферу. Полученные результаты могут быть задействованы при разработке более рациональных рекомендаций по рекультивации потенциально опасных в газогеохимическом отношении территорий, используемых под строительство.
Introduction. The use of chlorine-containing reagents for disinfection of water in swimming pools may lead to the formation of chloramines, both worsening the organoleptic properties of water and affecting the health of swimmers. To reduce the content of chloramines in pool water, UV radiation can be used. The aim of work is investigation of the effect of UV radiation on the transformation of mono- and dichloramines in water. Material and methods. The study was conducted on water samples from children’s pools, as well as in a model experiment on aquarium water with sodium hypochlorite added. Samples were irradiated with ultraviolet at doses of 40, 80 and 120 mJ/cm2. Before and after UV treatment, the content of chloramines was determined in all samples. Results. UV dose 40 mJ/cm2 was found to be insufficient for the destruction of mono- and dichloramine in water. During UV treatment with a dose 80 mJ/cm2 a decrease in the content of monochloramines and an increase in the content of dichloramines were observed. These processes were depended on the initial concentration of active chlorine in the samples. Conclusion. Thus, an effective UV dose to reduce the concentration of monochloramines in water with a concentration of active chlorine of 0.5 mg/l is 80 mJ/cm2. However, standard UV equipment used for disinfection of pool water cannot guarantee a reduction of chloramine concentration as it is usually designed for the minimum required UV dose (25-40 mJ/cm2). In addition, the effect of UV at this dose on water with a high content of active chlorine led to a significant increase in the content of dichloramines, which is supposedly associated with the destruction of proteins in water under the influence of UV radiation and the subsequent reaction of amino acids with active chlorine.
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