洞庭湖湿地潜流带地下水中氮磷迁移转化过程及驱动机制分析

为了揭示洞庭湖湿地潜流带地下水中氮磷的迁移转化过程,以洞庭湖湘江入湖口附近湿地为研究区,定期采集地表水和地下水水样进行水化学参数测试,采用熵权指数法进行水质评价,运用相关性分析、结构方程模型等方法研究理化参数对氮磷迁移转化的驱动机制。结果表明:58.8%的地下水水样为Ⅳ类或Ⅴ类水, TN、NH⁺₄和TP是主要的超标因子,氮的迁移转化主要受矿化作用、反硝化作用和硝酸盐异化还原成铵等反应控制,磷的迁移富集与Fe/Mn氧化物或氢氧化物的还原性溶解密切相关;地下水中氮磷组分含量在丰水期和枯水期表现出明显差异,受潜流交换作用影响,除NH⁺₄、溶解有机氮和TN外,地下水中NO-₂、NO-₃、TP和溶解态活性磷含量随着河岸距离增加而减小;温度、氧化还原电位、溶解氧、总溶解固体和电导率均会影响微生物活性,是地下水中氮磷迁移转化的关键驱动因子。     

浦阳江中下游氮分布特征及来源解析

基于2022—2023年绍兴市浦阳江中下游水体中TN、NO-₃、NO-₂和NH⁺₄质量浓度数据,分析了氮污染的主要形态、质量浓度和负荷的空间分布,并通过正向溯源法(现场监测、产排污系数法、SWAT模型)及反向溯源法(氮氧稳定同位素方法)探析了氮污染来源。结果表明:地表水氮污染以硝态氮为主,旱季TN质量浓度显著高于雨季(p＜0.05),城镇及农业分布地区氮素指标质量浓度高于其他区域;2022年流域内TN负荷以生活源(58.7%)为主,其次为农业源(39.5%);TN高负荷地区主要分布在人口密集的浦阳江下游干流沿岸以及农田分布较多的子流域;TN负荷与降水量之间存在较强的正相关性(p＜0.01),并在雨季的6月达到最高值;城市化程度和生活区集群对δ¹⁵N-NO-₃值有较大影响,流域硝酸盐来源以生活污水为主(平均占比54.5%);不同支流的硝酸盐来源也存在差异,土地利用类型及城镇化水平是主要驱动因素。     

充氮欠平衡水平井技术

欠平衡压力钻井可大大减轻地层伤害,提高油气井产能,增强油气资源的勘探评价能力,显著地增加钻井速度,提高钻井效益。本文详细介绍了胜利油田黄河钻井三公司在墨西哥进行的欠平横钻井施工过程。     

南方丘陵山区湿地氮磷时空变化及影响因素分析

对陈墩库区湿地从2015年9月到2016年8月进行水质监测,通过方差分析和相关性分析归纳总结湿地氮磷浓度变化规律,探究不同植物与湿地氮磷的相互作用。结果表明:陈墩库区TN、TP浓度在不同湿地季节变化有所差异,各湿地TN浓度在春、夏、冬差异显著;TP在冬季有显著差异,其余季节均无明显差异,陈墩库区TN、TP浓度季节变化与进水氮磷浓度和湿地面积、植物类型及生长状况密切相关;不同植物与湿地TN、TP呈现不同的相关性,这与水生植物对氮磷的吸收能力不同有关;轮叶黑藻、再力花、芦苇对氮磷的去除效果较好。     

羰基合成法制取高纯纳米氧化铁工艺研究

纳米氧化铁是近年来研发的新型纳米材料,它具有良好的光学、磁性、催化性能,在涂料、磁性材料、医学磁介质和催化等方面有广泛的应用前景,采用传统技术生产的纳米氧化铁因其粒度分布宽,纯度低等问题无法用于生物医药等高端领域,本文通过实验的方法介绍了一种新型高纯纳米氧化铁生产技术,可为高纯纳米氧化铁的研究和生产提供参考。     

衡水湖水体氮磷变化规律及富营养化现状分析

衡水湖是华北平原具有独特自然景观的国家级湿地和鸟类自然保护区,富营养化是其面临的一个主要问题。通过对衡水湖水体的主要营养物质氮、磷的污染特征、来源、成因分析以及对水体的富营养化现状进行评价,表明衡水湖的水质状况近年来得到了一定程度的改善,但氮、磷的污染仍相当严重,污染程度冬春季较轻,夏秋季节较重,富营养化程度从中营养到轻度、中度富营养。     

Nitrate Accumulation and Other Components of the Groundwater in Relation to Cropping System in an Aquifer in Southwestern Spain

Inappropriate farming techniques and 4 years of drought (1992–1995) produced conditions for high nitrate concentration in an aquifer located in the Province of Seville (Southwest Spain). The objectives of this study were to study groundwater components and to determine the relationship between the cropping system and nitrate concentrations in groundwater. From October 1994 to May 1996, 16 groundwater samples were obtained from a network of 35 sample points. Groundwater concentrations were analysed by multivariate statistical techniques (factor and cluster analysis). Two factors were found: firstly, agricultural pollution and secondly, salinization (from natural mineralization of groundwater and from anthropogenic effects). High levels of NO_3– were closely associated with intensive cotton (Gossypium herbaceum L.) and potato production (Solanum tuberosum L.). The salinization factor includes electrical conductivity, Cl_–, Na₊, Ca_{2 +}, Mg_{2 +}, SO_{42 –} and HCO_3–. Our study permits the impact of crops on groundwater to be determined. In comparison to the other crops, cotton (Gossypium herbaceum L.) and potato (Solanum tuberosum L.) made the greatest contribution to nitrate pollution and salinization. Use of the groundwater for human consumption in drought periods could represent a public health risk. Alternative farming techniques for these crops such as monitored fractional fertilization and controlled irrigation are recommended.     

Stream regulation and nitrogen dynamics in sediment interstices: comparison of natural and straightened sectors of a third‐order stream

Nitrogen dynamics were studied in the interstitial environment (i.e. hyporheic zone) of a sandy‐bottom stream in a rural landscape. A third‐order stream in Brittany (France) was studied at 11 stations (riffles) to evaluate spatial patterns of water exchange between surface and interstitial habitats. More intensive sampling was conducted in three riffles selected according to their hydrological characteristics. Chemical characteristics (especially nitrogen) and microbial denitrification were studied at 12.5 and 25 cm depth upstream, and 25 cm depth downstream of each riffle. This study confirms that the interstitial habitat of a N‐rich stream acts as a sink for the nitrate‐nitrogen. Experimental manipulation of sediment cores indicates that denitrification is limited by carbon in surface (i.e. benthic) and by nitrate in hyporheic sediments. River regulation increases inputs of fine sediments, modifies river channel location, and generates changes in the spatial patterns of biogeochemical processes, water origins, and hydrologic exchanges. Copyright © 2004 John Wiley & Sons, Ltd.     

Timing Nitrogen Fertilizer Application to Reduce Nitrogen Losses to the Environment

The advantage of using insurance to help a farmeradopt a best nitrogen management plan (BNMP) thatreduces the impact of agricultural production on theenvironment is analytically and empiricallydemonstrated. Using an expected value analysis, it isshown that an insurance program can be structured soas to reduce a farmer's cost of bearing the adoptionrisk associated with changing production practicesand, thus, to improve the farmer's certaintyequivalent net return thereby promoting the adoptionof a BNMP. Using the adoption of growing-season onlyN fertilizer application in Iowa as a case study, itis illustrated how insurance may be used to promotethe adoption of this practice to reduce N fertilizeruse. It is shown that it is possible for a farmer andan insurance company both to have an incentive todevelop an insurance adoption program that willbenefit both the farmer and the insurance company,increasing net social welfare and improvingenvironmental quality in Iowa.     

赣南红壤坡面不同措施径流泥沙及氮磷污染输出试验研究

选择赣南于都县左马小流域的典型红壤坡面,通过在研究区布设标准径流小区,进行了不同措施径流泥沙及氮磷污染输出的试验研究。通过径流小区的试验观测分析表明:水保林+水平竹节沟式综合水保措施实施初期,平均减流和减沙效果达到近73%,以植被增加地表覆盖度,以水平竹节沟坡面水保工程截短坡长,分段拦蓄径流泥沙,可实现保水保土目的;经果林+坡面工程或绿篱是坡地经济果业开发保持水土的重要措施,工程措施在初期发挥作用较绿篱更大;氮磷等面源污染随水土流失从坡面输出,试验区不同措施氮素输出多以径流携带为主,磷素输出均以泥沙携带为主;经果林+工程措施对径流携带氮磷拦截率较高,水保林+工程措施对泥沙携带氮磷的拦截率较高,都在75%以上。