Natural and Anthropogenic Factors Controlling the Dissolved Organic Carbon Concentrations and Fluxes in a Large Tropical River, India

Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO₂ emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3–12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans.     

Soil CO2 flux in relation to dissolved organic carbon, soil temperature and moisture in a subtropical arable soil of China

IntroductionCarbondioxide(CO2 ) ,concentrationofwhichinatmosphereisincreasingat 0 5%annually ,isthemostimportantgreenhousegascausingglobalwarming(Lal,1 995) .SoilCO2 evolutionfromsoilsisoneoftheimportantsourcesofatmosphericCO2 aswellasamainoutputpathwayofsoilorganiccarbonpool(SOC) (Eswaran ,1 993 ;Batjes,1 996;Mosier,1 998) .ApartfromcontributingCtotheatmosphere ,soilCO2 evolutioncanalsobeusedasanindexofunder groundprocesses,andoftheCcyclingcapacityofsoilecosystems.SoilCO2 evolutionge…     

UV/H_2O_2氧化处理水中去污剂

表面活性剂是一类特殊的有机污染物,在去污、洗衣、印染等废水中广泛存在.本文以某电厂实用的5种去污剂为研究对象,考察了UV/H2O2对5种去污剂的矿化能力,研究了H2O2和去污剂初始浓度、初始p H值、去污剂种类、辐照时间等因素对氧化效果的影响.结果表明,5种去污剂在254 nm处均无较强吸收,单独UV辐照对其降解效果不明显.当去污剂初始DOC浓度为50 mg·L-1,H2O2最佳投加量为1 m L·L-1,反应时间为90 min时,对5种去污剂的矿化率(即DOC去除率)在53%~87%,矿化率随去污剂种类的不同而不同.对去污剂的矿化率随着UV辐照时间的延长而增大,去除率曲线符合一级反应动力学方程.废水初始p H值对氧化效果的影响不显著,H2O2/DOC比值对氧化效果有显著影响.研究表明,UV/H2O2技术能高效矿化水中的去污剂,H2O2/DOC比值和UV辐照时间是影响氧化效率的关键因素.     

溶解性有机碳的主要组成对青鳉鱼铜急性毒性的影响

为揭示溶解性有机碳(DOC)的组成对生物配体模型(BLM)预测铜的生物毒性准确性的影响,研究了不同浓度黄腐酸(FA)、腐殖酸(HA)和两者不同浓度比例混合物影响铜对青鳉急性毒性。结果表明:在相同水质条件下,黄腐酸或腐殖酸浓度增加时,铜对青鳉的LC50均增加;两者共存时,当腐殖酸质量百分比从10%增至90%时,铜对青鳉的LC50也增加。当天然水中DOC的组成不确定时,可假设HA和FA的组成比例为1∶1,此时BLM预测铜对青鳉的LC50的偏差最小。     

The effects of temperature and resource availability on denitrification and relative N2O production in boreal lake sediments

Anthropogenic environmental stressors(like atmospheric deposition,land use change,and climate warming) are predicted to increase inorganic nitrogen and organic carbon loading to northern boreal lakes,with potential consequences for denitrification in lakes.However,our ability to predict effects of these changes is currently limited as northern boreal lakes have been largely neglected in denitrification studies.The aim of this study was therefore to assess how maximum potential denitrification and N_2O production rates,and the relationship between the two(relative N_2O production),is controlled by availability of nitrate(NO_3~-),carbon(C),phosphorus(P),and temperature.Experiments were performed using the acetylene inhibition technique on sediments from a small,nutrient poor boreal lake in northern Sweden in 2014.Maximum potential denitrification and N_2O production rates at 4°C were reached already at NO_3~-additions of 106–120 μg NO_3~-–N/L,and remained unchanged with higher NO_3 amendments.Higher incubation temperatures increased maximum potential denitrification and N_2O production rates,and Q10 was somewhat higher for N_2O production(1.77) than for denitrification(1.69).The relative N_2O production ranged between 13% and 64%,and was not related to NO_3~-concentration,but the ratio increased when incubations were amended with C and P(from a median of 16% to 27%).Combined,our results suggests that unproductive northern boreal lakes currently have low potential for denitrification but are susceptible to small changes in NO_3 loading especially if these are accompanied by enhanced C and P availability,likely promoting higher N_2O production relative to N_2.     

Coagulation of micro-polluted Pearl River water with IPF-PACls

IntroductionThewaterqualityofnaturalriverisverycomplex,includingvariouskindsoforganic ,inorganicandbiologicalmatters,suchasthesolublemolecules,polymericmatters,colloids ,andsuspendedparticlessuchaslivebacteria ,algaeandalsoprotozoan (Tang,2 0 0 0 ) .Generally ,aquaticparticulatesaredispersivelysuspended ,ordepositintodiversesedimentsthroughadsorption ,aggregationandsedimentation.Furthermore ,theycanberesuspended ,transferredandconvertedundervariouswaterfluidconditions.Clearlydocumentedhistori…     

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

In this paper we investigate the seasonal autochthonous sources of dissolved organic carbon (DOC) and nitrogen (DON) in the euphotic zone at a station in the upper Chesapeake Bay using a new mass-based ecosystem model. Important features of the model are: (1) carbon and nitrogen are incorporated by means of a set of fixed and varying C:N ratios; (2) dissolved organic matter (DOM) is separated into labile, semi-labile, and refractory pools for both C and N; (3) the production and consumption of DOM is treated in detail; and (4) seasonal observations of light, temperature, nutrients, and surface layer circulation are used to physically force the model. The model reasonably reproduces the mean observed seasonal concentrations of nutrients, DOM, plankton biomass, and chlorophyll a. The results suggest that estuarine DOM production is intricately tied to the biomass concentration, ratio, and productivity of phytoplankton, zooplankton, viruses, and bacteria. During peak spring productivity phytoplankton exudation and zooplankton sloppy feeding are the most important autochthonous sources of DOM. In the summer when productivity peaks again, autochthonous sources of DOM are more diverse and, in addition to phytoplankton exudation, important ones include viral lysis and the decay of detritus. The potential importance of viral decay as a source of bioavailable DOM from within the bulk DOM pool is also discussed. The results also highlight the importance of some poorly constrained processes and parameters. Some potential improvements and remedies are suggested. Sensitivity studies on selected parameters are also reported and discussed.     

京密引水中天然有机物的形态

用改进的Ｌｅｅｎｈｅｅｒ分离方法，并引入最新的ＸＡＤ－８，ＸＡＤ－４树脂串联技术，将京密引水中有机物定量分离为悬浮和溶解态两大类。后者又进一步分离为憎水有机物、腐殖酸类，ＸＡＤ－４酸和亲水中性有机物等形成。溶解态有机物含量约为３ｍｇＣ／ｌ，其中一半左右为腐殖酸类。ＸＡＤ－４酸占溶解态有机１５－２０％，非极性憎水有机物所占比例很低。     

Keep swimming but stop peeing in the pools

正Swimming is excellent exercise and offers many health benefits.However,the"chlorine smell"in swimming pools may be a turn-off for some people.Although this smell is often thought to be of chlorine,it actually comes from volatile compounds that are produced from unintended reactions between disinfectants(e.g.,chlorine)and organic matter in     

淡水系统中4种塑料颗粒的老化过程及DOC产物分析

淡水系统中的微塑料污染及其生态效应已经引起国内外学者的广泛关注,但关于不同类型微塑料在自然环境中的老化研究较少.为探究不同类型微塑料的老化过程,分析老化产物,以4种水体中常见的微塑料聚丙乙烯(polystyrene,PS)、低密度聚乙烯(low-density polyethylene,LDPE)、聚丙烯(polypr...