[Optical Characteristics and Source Analysis of Dissolved Organic Matter in Hypersaline Lakes in Cold and Arid Regions].
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The composition and source information of the aquatic dissolved organic matter （DOM） in the Daihai Lake, a typical saline lake at the ecologically fragile agro-pastoral area, were explored with three-dimensional excitation and emission matrix fluorescence （3DEEM）, parallel factor analysis （PARAFAC）, and fluorescence peaks （B, T, A, M, C, D, and N）. Further, the relationship between aquatic DOM fluorescence characteristics and environmental factors were analyzed using correlation analysis in the Daihai Lake. The results showed that the water of Daihai was weakly alkaline, with high nutrient salt concentration and serious organic pollution. Two protein-like substances （C1 and C3） and one humic-like substance （C2） were identified using PARAFAC. The sum of C1 + C2 accounted for 80% of DOM. The results of fluorescence peaks showed that the total percentage of protein-like fluorescence absorption peaks （B, T, and N） was 49.67%. Aquatic DOM of Daihai demonstrated both terrigenous and endogenous characteristics. Terrestrial inputs were mainly from intensive agricultural activities and rapid ecological degradation of the watershed leading to large amounts of organic matter entering the lake. The environmental behavior of DOM was highly correlated with the metabolic activity of organisms and nutrient status of lakes. NHKeywords:
Water source
Abstract The sources, transport, and transformation of terrestrial dissolved organic matter (DOM) in large river systems are of great interest due to their importance in the regional and global carbon cycles. However, knowledge of these factors is limited, especially for different DOM compositions coupling with hydrodynamics at the basin scale. To investigate the dynamics of different DOM compositions in a large river system, we characterized the dissolved organic carbon (DOC), chromophoric DOM (CDOM), and dissolved lignin at both moderate (September–October 2009) and high (August 2012) discharges in the Changjiang River basin. We found that extensive soil erosion resulted in the increased DOC concentration in the middle to lower reaches in 2012. In 2009, the transformation of DOM was dominated by flocculation and photo degradation due to the low flow velocity and depressed particle suspension. In 2012, the degradation of CDOM and dissolved lignin was coupled and dominated by microbial degradation and photo degradation. In 2012, CDOM (absorbance and fluorescence) and dissolved lignin concentrations were positively correlated, demonstrating the potential of using CDOM to quantitatively estimate dissolved lignin. Mass balance estimations of the DOM fluxes further confirmed that 17.0% (6.1%) of DOC, 24.2% (32.3%) of dissolved lignin, and 14.5% (0.8%) of CDOM were degraded at high (moderate) discharge. This study reveals contrasting transformation processes of DOM compositions with different sources and reactivities along the Changjiang River under different hydrological conditions, and it provides new insights into the linkage between the chemical and optical properties of DOM in large river systems.
Spectral slope
Absorbance
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Biogeochemical Cycle
Carbon fibers
Total inorganic carbon
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Abstract Absorbance at 360 nm was measured on 44 filtered streamwater samples of different dissolved organic matter (DOM) contents. A regression equation of DOM on absorbance predicted DOM with a standard error of estimate of 1.26 mgl −1 , Use of a published equation relating dissolved organic carbon (DOC) to absorbance gave DOC values for the samples which were consistent with measured DOM. The method offers considerable potential for rapid quantification of dissolved organic matter concentrations in streamwater.
Absorbance
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Climatic characteristics of broadband solarradiation (Rs) in Chinese arid and semi-arid areas are reported in this study. The annual average daily Rs in thearid and semi-arid areas is 16.3 ± 5.77 and 15.3 ± 5.16 MJm-2 d-1, respectively. The highest value (17.2 ± 5.84 MJm-2 d-1) appears in an arid area at Linze. The lowest valueappears in the semi-arid area of Ansai. Pronounced seasonal variation of Rs is observed with the highest value insummer and the lowest in winter. The clearness indexshowed similar seasonal pattern at most sites, with theminimum observed in the summer and the highest valuesin winter at both arid and semi-arid areas. The seasonalvariation of the ratio of Rs to its extraterrestrial value Kt inthe arid area is more significant than that observed in thesemi-arid region, and it is caused by the different range ofvariation of water vapor between arid and semi-arid areasThe seasonal fluctuations in Rs and Kt are mainly controlled by the water vapor content in these areas. Theaerosol particles have significant influence on Rs and Kt atstations with higher aerosol burden.
Seasonality
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This article introduced a series of environment problems caused in the long- term exploitation of arid and half arid desert mine area. The strategy of environment problem is put forward, so that the environment of arid and half arid desert mine site should be improved persistendy, realize sustainable development.
Desert (philosophy)
Desert climate
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Desert climate
Aridity index
Semi-arid climate
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The reasons and existing problems of water source shortages in the arid area of Ningxia were analyzed,and the environmental protection measures were proposed,so as to provide reference for the protection of water source in the arid area of Ningxia.
Economic shortage
Water source
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خشکسالی به عنوان پیامد اجتنابناپذیر نوسانات آب وهوایی، یکی از عوامل مهم در کاهش تولید محصولات کشاورزی به ویژه در شرایط دیم میباشد. در این پژوهش از شاخص مرجع کشاورزی برای خشکسالی (ARID) در دو رهیافت شامل مدلهای تک لایه و دولایهی توازن آب خاک جهت مدلسازی توابع تولید گندم و جو دیم در سطح استان گلستان استفاده شده است. بدین منظور دادههای هواشناسی روزانه برای 12 ایستگاه تبخیرسنجی و سینوپتیک موجود در سطح استان گلستان اخذ و مقدار شاخص ARID بر اساس دو رهیافت مورد نظر در دورهی رشد محصولات گندم و جو محاسبه گردید. همچنین آمار عملکرد گندم و جو در زراعتهای دیم و آبی در سطح 8 شهرستان استان گلستان طی دورهی متناظر جمعآوری و با آنالیز نقطهی جهش مقادیر سری نسبت عملکرد (R) در هر شهرستان برآورد گردید. با انتخاب 6 دورهی فنولوژیک رشد برای محصولات مورد بررسی، مقدار متوسط شاخص ARID در هر مرحله طی سالهای مختلف محاسبه و با حل غیرخطی رابطهی بین نسبت عملکرد و شاخص ARID، ضرایب حساسیت هر مرحله تعیین و مدل برآورد عملکرد مشخص گردید. در پایان با مقایسهی مقادیر عملکردهای محاسبه شده و مشاهده شده بر اساس معیارهای آماری، توانایی شاخص ARID در دو رهیافت مورد بررسی ارزیابی گردید. بر اساس این مقایسه نتایج شاخص ARID در رهیافت مبتنی بر مدل دولایهی توازن آب و خاک در شبیهسازی مقادیر عملکرد محصولات گندم و جو دیم از دقت بالاتری برخوردار بود. علاوه بر این دقت توابع تولید استخراج شده برای محصول جو نیز به مراتب بیشتر از گندم بوده است. بررسی ضرایب حساسیت تنش نسبی محصولات مورد ارزیابی نشان میدهد که به ازای محصولات گندم و جو دیم دوره ساقهرفتن حساسترین مرحله نسبت به تنش آبی در تمامی ایستگاهها به جز ایستگاههای واقع در شهرستان رامیان میباشد. اهمیت نسبی حساسیت مراحل رشد اولیه، خوشه رفتن و گلدهی نسبت به تنش آبی با توجه به نوع محصول در ایستگاههای مختلف، متفاوت بدست آمد. با این وجود کمترین میزان حساسیت به ازای دورههای رویشی اولیه و رسیدگی بدست آمد.
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琵琶湖北湖湖水および流入河川水を対象として,疎水性―親水性,酸性―塩基性の違いに基づいた溶存有機炭素(DOC)分画手法を適用し,湖水および河川水溶存有機物の特性や起源について検討した。湖水と河川水,および流域特性の異なる河川水ではDOC分画分布および紫外部吸光度(UV):DOC比に有意な違いが認められた。琵琶湖北湖湖水および流入河川水ともに,DOC成分として有機酸(疎水性酸(フミン物質)+親水性酸)が卓越していた。湖水では親水性酸(フミン物質:25-27%,0.37-0.41mg Cl-1;親水性酸:40-48%,0.58-0.78mg Cl-1),河川水ではフミン物質が優占した(フミン物質:37-73%,0.32-0.71mg Cl-1;親水性酸:23-35%,0.11-0.45mg Cl-1)。特に,森林自然系河川でフミン物質の存在比が最大となった。湖水のUV:DOC比は親水性酸,湖水DOC,フミン物質の順に高くなった。湖水DOCおよび湖水フミン物質のUV:DOC比は既報の藻類由来とする値とほぼ同じ低い値を示し,琵琶湖北湖水中の溶存有機物は主に藻類由来ではないかと推測された。河川水DOCのUV:DOC比は湖水よりも約60%高く,土壌由来DOCの影響が大きいと考えられた。しかしながら,分離された河川水フミン物質のUV:DOC比は河川水フミン物質としてはかなり低く,湖水フミン物質のUV:DOC比より顕著に高いものではなかった。特に都市系河川のフミン物質のUV:DOC比は湖水フミン物質より低かった。
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Degradation
Carbon fibers
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