水稻土中铁-氮循环耦合体系影响镉活性机理研究

关于铁-氮循环耦合体系对镉(Cd)活性影响的研究目前尚鲜见报道.本文采用淹水培养试验,研究不同硝酸根(NO_3~-)、铵根(NH_4~+)处理条件下,南方典型Cd污染水稻土中铁氧化还原与氮形态转化耦合关系及其对Cd活性影响的机理.结果表明:随着培养时间延长,不同处理的pH值逐渐向7.0靠拢,Eh值由273~321 mV持续下降至118~132 mV,pe+pH值(e-活度的负对数值与H+活度的负对数值之和)从10.62~11.19持续下降至8.55~8.83,土-水体系处于中度还原条件;化学反硝化(Chemodenitrification)和NO_3~-依赖的厌氧铁氧化过程(Microbial NO_3~--dependent FeIIoxidation,NDFO)生成无定形氢氧化铁(Fe(OH)_3(amorp)),其对Cd~(2+)专性吸附及与Cd~(2+)共沉淀降低了有效态Cd浓度,加之pH值上升增大Cd~(2+)在土壤固相表面的吸附量,导致水稻土中Cd活性下降;NH_4~+被Fe(OH)_3(amorp)厌氧氧化(Anaerobic NH_4~+oxidation coupled to FeIII reduction,Feammox)会消耗H+而提高体系的pH值,在一定程度上会降低Cd活性,但其自身与Cd~(2+)对土壤固相表面吸附位点的竞争,可能会更大程度地减少Cd~(2+)在土壤固相表面的吸附量,而导致Cd活性提高.本研究成果可为丰富和拓展水稻土中Cd的生物地球化学理论,并为南方Cd污染农田修复及治理提供科学依据.     

中亚热带典型农业小流域氮素输出特征及监测采样频率研究

以湖南省长沙县的脱甲小流域为例,研究了中亚热带典型农业小流域中氮素输出的规律,并采用统计学方法确定合理的氮素输出监测频率.研究结果表明,该地区农业小流域氮素输出过程受降雨-径流过程和农业管理活动的影响明显,除颗粒态氮(PN)外,流域出口水体中铵态氮(NH+4-N)、硝态氮(NO-3-N)、可溶性氮(DN)和全氮(TN)的浓度均与沟渠径流量显著相关(p0.01).降雨-径流过程和农业管理活动也会影响河道水体中氮素化学形态,但其对氮素化学形态的影响往往是短期的,因为在整个观测期间内,仅NH+4-N/TN比例与径流量有显著相关关系(p0.01).对于不同形态氮素采样频率计算结果表明,水体中氮素浓度变异系数越大,在允许的误差范围内需要的监测频率越高.按照平均值误差的20%控制,NH+4-N和PN的采样频率要达到每天2次才能满足要求,采样频率显著高于NO-3-N、DN和TN(1天1次).如果将典型小流域中的氮素输出监测频率定为每天1次,NH+4-N和PN的相对误差将达到30%.该研究为阐明中亚热带农业小流域氮素输出规律和制定氮素监测策略和规范提供了样本.     

臭氧组合工艺去除饮用水源水中有机物的效果

研究由臭氧氧化、生物处理、常规处理和活性炭吸附组成的臭氧组合工艺以及各单元工艺对饮用水源水中有机物的去除效果 .结果表明 ,由于预臭氧对有机物的氧化 ,减小了有机物的分子量 ,增加了可生物降解的有机物 ,从而强化了后续的生物处理和活性炭对有机物的去除 .整个工艺对有机物的控制能力很好 ,UV2 54、DOC、BDOC、AOC、THMFP和 HAAFP的去除率分别达到 95.1%、92.5%、98.4%、85.8%、63.1 %和 89.1% .预臭氧-生物陶粒的预处理对各有机物的去除效果在 50%左右 ,常规处理对各有机物的去除不尽相同 ,后臭氧 -活性炭对有机物的去除达到了 60 %左右 .     

Assessment of water pollution in different bleaching based paper manufacturing and textile dyeing industries in India

Paper industries using different raw materials such as hard wood, bamboo, baggase, rice-straw and waste papers and bleaching chemicals like chlorine, hypochlorite, chlorine dioxide, hydrogen peroxide, sulphite and oxygen were studied to estimate organic pollution load and Adsorbable Organic Halides (AOX) per ton of production. The hard wood based paper industries generate higher Chemical Oxygen Demand (COD) loads (105–182 kg t⁻¹) and Biochemical Oxygen Demand (BOD) loads (32.0–72 kg t⁻¹) compared to the agro and waste paper based industrial effluents. The bleaching sequences such as C–EP–H–H, C–E–H–H, C–E–Do–D1 and O–Do–EOP–D1 are adopted in the paper industries and the molecular elemental chlorine free bleaching sequence discharges low AOX in the effluent. The range of AOX concentration in the final effluent from the paper industries was 0.08–0.99 kg t⁻¹ of production. Water consumption was in the range of 100–130 m³ t⁻¹ of paper production for wood based industries and 30–50 m³ for the waste paper based industries. Paper machine effluents are partially recycled after treatment and pulp mill black liquor are subject to chemical recovery after evaporation to reduce the water consumption and the total pollution loads. Hypochlorite bleaching units of textile bleaching processes generate more AOX (17.2–18.3 mg l⁻¹) and are consuming more water (45–80 l kg⁻¹) whereas alkali peroxide bleaching hardly generates the AOX in the effluents and water consumption was also comparatively less (40 l kg⁻¹ of yarn/cloth).     

Precipitation Chemistry and Occurrence of Acid Rain Over Dhanbad, Coal City of India

The present study investigated the chemical composition of wet atmospheric precipitation over Dhanbad, coal city of India. The precipitation samples were collected on event basis for three years (July 2003 to October 2005) at Central Mining Research Institute. The precipitation samples were analyzed for pH, conductivity, major anions (F, Cl, NO₃, SO₄) and cations (Ca, Mg, Na, K, NH₄). The pH value varied from 4.01 to 6.92 (avg. 5.37) indicating acidic to alkaline nature of rainwater. The pH of the rainwater was found well above the reference pH (5.6), showing alkalinity during the non-monsoon and early phase of monsoon, but during the late phase of monsoon, pH tendency was towards acidity (<5.6~pH) indicating the non-availability of proper neutralizer for acidic ions. The observed acidic events at this site were 91, (n = 162) accounting 56% for the entire monitoring months. The (NO₃ + Cl)/SO₄ ratio in majority of samples was found below 1.0, indicating that the acidity is greatly influenced by SO₄. The calculated ratio of (Ca + NH₄)/(NO₃ + SO₄) ranges between 0.42–5.13 (average 1.14), however in most of the samples, the ratio is greater than unity (>1.0) indicating that Ca and NH₄ play an important role in neutralization of acidic ions in rainwater. Ca and SO₄ dominate the bulk ionic deposition and these two ions along with NH₄ accounts 63% of the annual ionic deposition.     

Eutrophication Status of Marine Environment of Mumbai and Jawaharlal Nehru Ports

The marine environment of Mumbai and Jawaharlal Nehru ports was monitored for some environmental and biological parameters during three different periods between 2001 and 2002. The results are compared with the records available since 1960s. With the passage of time the environmental status underwent changes, probably due to the increase in anthropogenic activities in the metropolis. The nutrient level especially the nitrate concentration has increased gradually over the years with a simultaneous decrease in dissolved oxygen, indicating increase in the biological activity. Characterization of this environment based on Assessment of Estuarine Trophic Status (ASSETS) model indicates that the current status is poor and may get worsen in future if no appropriate management policies are put into place.     

Trace metal dynamics in an industrialized Brazilian river: A combined application of Zn isotopes, geochemical partitioning, and multivariate statistics

The Paraiba do Sul (PSR) and Guandu Rivers (GR) water diversion system (120 km long) is located in the main industrial pole of Brazil and supplies drinking water for 9.4 million people in the metropolitan region of Rio de Janeiro. This study aims to discern the trace metals dynamics in this complex aquatic system. We used a combined approach of geochemical tools such as geochemical partitioning, Zn isotopes signatures, and multivariate statistics. Zinc and Pb concentrations in Suspended Particulate Matter (SPM) and sediments were considerably higher in some sites. The sediment partition of As, Cr, and Cu revealed the residual fraction (F4) as the main fraction for these elements, indicating low mobility. Zinc and Pb were mostly associated with the exchangeable/carbonate (F1) and the reducible (F2) fractions, respectively, implying a higher susceptibility of these elements to being released from sediments. Zinc isotopic compositions of sediments and SPM fell in a binary mixing source process between lithogenic (δ^66/64Zn_JMC ≈ + 0.30‰) and anthropogenic (δ^66/64Zn_JMC ≈ + 0.15‰) end members. The lighter δ^66/64Zn_JMC values accompanied by high Zn concentrations in exchangeable/carbonate fraction (ZnF1) enable the tracking of Zn anthropogenic sources in the studied rivers. Overall, the results indicated that Hg, Pb, and Zn had a dominant anthropogenic origin linked to the industrial activities, while As, Cr, and Cu were mainly associated with lithogenic sources. This work demonstrates how integrating geochemical tools is valuable for assessing geochemical processes and mixing source effects in anthropized river watersheds.     

采空区亚自燃状态及其向自燃转化研究

针对高危自燃采空区遗留煤发生自燃问题,提出采空区亚自燃状态的概念.开采推进过程中的采空区自燃,都可理解为是从亚自燃状态向自燃状态转化的结果,且其转化过程时间很短,小于最短自然发火期.在不同条件下的自燃过程满足叠加组合原理,采空区亚自燃状态向自燃转化过程是两种以上过程的叠加.转化受亚自燃状态程度(稳定温度)、工作面推进度、漏风供氧、煤堆积状态及防灭火措施(注氮)等因素影响.亚自燃状态理论能够解释生产实践中一旦某一不利因素出现,能在短时间内导致自燃发生的现象(自燃突发性).亚自燃状态概念的提出,将有助于从理论上正确认识实际采空区自燃状态的演变过程,实现早期预防采空区自燃的发生.     

抗生素抗性基因在生活及工业混合废水处理系统中的分布和去除

抗生素抗性基因(ARGs)由于其广泛的传播与转移,成为日益严峻的环境问题。污水处理厂(WWTP)被公认为ARGs的主要来源之一。膜生物反应器(MBR)是一种新型污染物去除工艺。在一个具有传统生物处理和膜系统处理的城镇污水处理系统的进水中,检出17种ARGs,并首次检出甲氧苄啶类ARGs。进水中sulΙ基因的绝对丰度最高,随后依次是tet C、sulⅡ、tet W、dfr A1、flo R和dfr A13基因。不同的处理系统去除同一种ARGs效果各不相同,MBR对ARGs去除效果显著优于传统生物处理工艺,同一个处理系统处理不同类ARGs,四环素类ARGs被去除的效果显著优于其他ARGs被去除的效果,绝对丰度下降了3.8个数量级。ARGs没有真正意义上的去除,只是从水体转移到污泥中,污泥中的ARGs不断积累。     

Emerging electrochemical processes for materials recovery from wastewater: Mechanisms and prospects

• Mechanisms for selective recovery of materials in electrochemical processes are discussed. • Wastewaters that contain recoverable materials are reviewed. • Application prospects are discussed from both technical and non-technical aspects. Recovering valuable materials from waste streams is critical to the transition to a circular economy with reduced environmental damages caused by resource extraction activities. Municipal and industrial wastewaters contain a variety of materials, such as nutrients (nitrogen and phosphorus), lithium, and rare earth elements, which can be recovered as value-added products. Owing to their modularity, convenient operation and control, and the non-requirement of chemical dosage, electrochemical technologies offer a great promise for resource recovery in small-scale, decentralized systems. Here, we review three emerging electrochemical technologies for materials recovery applications: electrosorption based on carbonaceous and intercalation electrodes, electrochemical redox processes, and electrochemically induced precipitation. We highlight the mechanisms for achieving selective materials recovery in these processes. We also present an overview of the advantages and limitations of these technologies, as well as the key challenges that need to be overcome for their deployment in real-world systems to achieve cost-effective and sustainable materials recovery.