Sorption and desorption of diuron on Typic Argiudoll,Oxic Argiudoll and on their clay fractions: environmental aspects

Abstract

The sorption and desorption of diuron by soil samples from Horizons A and B (HA and HB) and by their different clay fractions were investigated, using two soil samples, classified as Typic Argiudoll and Oxic Argiudoll. The sorption and desorption curves were adjusted to the Freundlich model and evaluated by parameters K_f, K_d and K_oc. Based on the data of groundwater ubiquity score (GUS), leachability index (LIX) and hysteresis index (HI), the risk of groundwater pollution was evaluated. The K_d values obtained for soil samples were between 4.5?mL g^?1 (Oxic Argiudoll – HB) and 15.9?mL g^?1 (Typic Argiudoll – HA) and between 1.13 and 14.0?mL g^?1 for the different mineral fractions, whereas the K_oc values varied between 276 (Oxic Argiudoll – HB) and 462 (Typic Argiudoll – HA). According to the parameter GUS, only Oxic Argiudoll – HB presented leaching potential, and based on the LIX index this same soil presented the highest leaching potential. Some samples presented low LIX and GUS values, indicating no leaching potential, but none presented HI results indicative of hysteresis, suggesting weak bonds between diuron and the soil samples and, hence, the risk of groundwater pollution by diuron.     

2-n-丙基酚在模拟海水中的耗氧特性及降解动力学

以2-n-丙基酚为研究对象,分3个质量浓度系列研究其在人工模拟海水中的耗氧特性及降解过程.试验结果表明,在该模拟海水体系中,ρ(DO)呈现先下降后上升的趋势,ρ(DO)变化过程与2-n-丙基酚的生物降解过程密切相关,ρ(DO)最低值出现在2-n-丙基酚降解率达85%～90%的阶段.2-n-丙基酚在该体系中的生物降解反应符合一级反应动力学规律,其生物降解速率与2-n-丙基酚初始质量浓度有关.2-n-丙基酚初始质量浓度增加,生物降解速率下降,滞后期和半衰期也相应延长.      

Total Maximum Daily Load Criteria Assessment Using Monitoring and Modeling Data

Applications of Total Maximum Daily Load (TMDL) criteria for complex estuarine systems like Chesapeake Bay have been limited by difficulties in estimating precisely how changes in input loads will impact ambient water quality. A method to deal with this limitation combines the strengths of the Chesapeake Bay's Water Quality Sediment Transport Model (WQSTM), which simulates load response, and the Chesapeake Bay Program's robust historical monitoring dataset. The method uses linear regression to apply simulated relative load responses to historical observations of water quality at a given location and time. Steps to optimize the application of regression analysis were to: (1) determine the best temporal and spatial scale for applying the WQSTM scenarios, (2) determine whether the WQSTM method remained valid with significant perturbation from calibration conditions, and (3) evaluate the need for log transformation of both dissolved oxygen (DO) and chlorophyll a (CHL) datasets. The final method used simple linear regression at the single month, single WQSTM grid cell scale to quantify changes in DO and CHL resulting from simulated load reduction scenarios. The resulting linear equations were applied to historical monitoring data to produce a set of “scenario‐modified” DO or CHL concentration estimates. The utility of the regression method was validated by its ability to estimate progressively increasing attainment in support of the 2010 Chesapeake Bay TMDL.     

Development of the Chesapeake Bay Watershed Total Maximum Daily Load Allocation

Nutrient load allocations and subsequent reductions in total nitrogen and phosphorus have been applied in the Chesapeake watershed since 1992 to reduce hypoxia and to restore living resources. In 2010, sediment allocations were established to augment nutrient allocations supporting the submerged aquatic vegetation resource. From the initial introduction of nutrient allocations in 1992 to the present, the allocations have become more completely applied to all areas and loads in the watershed and have also become more rigorously assessed and tracked. The latest 2010 application of nutrient and sediment allocations were made as part of the Chesapeake Bay total maximum daily load and covered all six states of the Chesapeake watershed. A quantitative allocation process was developed that applied principles of equity and efficiency in the watershed, while achieving all tidal water quality standards through an assessment of equitable levels of effort in reducing nutrients and sediments. The level of effort was determined through application of two key watershed scenarios: one where no action was taken in nutrient control and one where maximum nutrient control efforts were applied. Once the level of effort was determined for different jurisdictions, the overall load reduction was set watershed‐wide to achieve dissolved oxygen water quality standards. Further adjustments were made to the allocation to achieve the James River chlorophyll‐a standard.     

福建省流域-近海溶解氧时空格局与低氧调控机制

溶解氧是衡量水环境质量和生态系统健康的关键参数,当前我国海岸带地区的低氧问题突出,但缺乏对流域-近海溶解氧时空格局与低氧调控机制的研究.基于2011~2020年福建省135个地表水（含河口）和66个近岸海域监测点位数据,系统分析了年际和季节两个时间尺度溶解氧的时空演变规律,选取低氧（溶解氧饱和度位于10%分位之内）站位数据,采用数理统计和随机森林模型分析方法,重点研究了河流、水库、河口和近海这4种类型水体的低氧特征及其调控机制.结果表明,溶解氧饱和度近海最高［（98.2±10.2）%］,河口最低［（79.2±17.9）%］.与"十二五"（2011~2015年）相比, "十三五" （2016~2020年）河流和水库的低氧检出频率有明显降低,但河口变化不大.统计有低氧检出的点位,河流和水库的多年平均低氧检出频率在秋季最高,河口在夏季最高.水库和河口低氧问题最为突出但机制不同,水库河段的低氧与夏季径流携带大量有机质输入、层化导致底层水持续耗氧、秋季混合上涌或通过大坝泄流有关,河口的低氧与污染输入、潮水顶托和还原性物质耗氧有关.需要建立系统治理与分区管控制度,进一步加强流域-近海污染控制有助于减缓水体富营养化和低氧问题.     

不同淹水环境下湖泊沉积物DOM的特征与来源

为揭示水位的空间差异对于湖泊沉积物溶解性有机质（DOM）特性的影响与作用途径,采用紫外可见光谱（UV-Vis）和三维荧光光谱结合平行因子分析（EEM-PARAFAC）,探究东洞庭湖不同淹水环境对沉积物DOM的组成与来源的影响.结果表明,DOM中类蛋白组分［类色氨酸C2与类酪氨酸C3,（72.95±8.94）%］高于类腐殖酸组分［C1,（27.05±8.94）%］.季节淹水下DOM具有更高的类蛋白组分和更低的类腐殖酸组分,而常年淹水下的DOM芳香性（SUVA₂₅₄）与疏水组分（SUVA₂₆₀）更高,在空间上表现为：湖中段>入湖段>出湖段,更有利于污染物迁移.通过对荧光参数FI （1.93）、BIX （0.91）和HIX （1.57）的计算发现,沉积物DOM具有内源为主和陆源较弱的混合特征.这可能受到人为输入与沉积物特性影响,季节淹水区沉积物裸露增强污水排放的直接作用,且黏粒和总氮（TN）含量与FI呈显著正相关,说明沉积物高营养成分和黏粒含量影响DOM的内源成分（FI>1.9）;而常年淹水区具有外来径流输入,pH和C/N与HIX和C1呈显著正相关,说明沉积物DOM由于常年淹水的碱性环境（pH>7.5）和径流输入比季节淹水区具有更高的陆源成分（HIX=1.38±0.57）.上述结果有助于揭示湖泊水文与人类活动过程中沉积物DOM对水质与污染响应的相关理论,为沉积物污染防治提供科学依据.     

磁性氧化铁/桑树杆生物炭的制备及其对砷污染土壤溶解性有机碳和砷形态的影响

以桑树杆为原料,制备了原始桑树杆生物炭（M-BC）及磁性氧化铁/桑树杆生物炭（Fe-BC）并对其进行表征.通过土壤培养实验,研究了3个温度下炭化制备的Fe-BC和M-BC在不同培养时间对土壤浸出液溶解性有机碳（DOC）和土壤砷（As）形态等的影响.结果表明：①Fe-BC负载的铁氧化物主要为Fe₃ O₄,且有磁性,主要官能团有C＝O双键、O—H键、C—O键和Fe—O键;Fe-BC-400、Fe-BC-500和Fe-BC-600的pH_zpc分别为8.92、8.74和9.19,比表面积分别为447.412、482.697和525.708 m² ·g^-1.②土壤浸出液中ρ（DOC）随着M-BC和Fe-BC炭化温度的升高而分别降低11.6~315.6 mg ·L^-1和78~365.6 mg ·L^-1,土壤浸出液中DOC浓度与土壤电导率（EC）值呈负相关;在培养第35 d,添加Fe-BC-600的土壤浸出液中As浓度比对照组土壤浸出液中的降低了55.96%.土壤浸出液中As浓度与DOC浓度相关性不显著.③添加Fe-BC的土壤有效态As占比均低于对照组的,在培养第35 d时,Fe-BC-600可使土壤有效态As占比降低39.21%.④在培养第35 d时,添加M-BC的土壤残渣态As含量减少了17.76%~49.11%,添加Fe-BC-600的土壤残渣态As占比增加了80%.Fe-BC-600最有利于降低土壤溶液DOC浓度,提高残渣态As含量,从而降低土壤As生物有效性.研究可为磁性氧化铁/生物炭在砷污染土壤修复提供理论依据.     

2013—2020年泸沽湖溶解氧随时间变化规律及主要影响因素分析

泸沽湖坐落于川滇交界处,是中国典型高原淡水湖泊。对泸沽湖水质的客观评价对于其规划保护及保护成效评估极为重要。鉴于溶解氧常常成为决定泸沽湖水质类别的唯一关键指标,在综合分析泸沽湖2013—2020年连续8年水环境主要指标变化的基础上,着重分析了溶解氧随季节、年际等的变化情况及其主要影响因素。结果表明,溶解氧浓度及饱和率存在明显的季节和年际波动。其中:溶解氧浓度一般是在春季升至全年最高,夏季末降低,并在秋冬季维持低位;溶解氧饱和率则是夏秋季节最高,冬季最低。溶解氧浓度的季节变化与水温显著负相关,而溶解氧饱和率的季节变化和水温、pH显著正相关;溶解氧浓度及饱和率的年际变化与水质主要指标均不存在显著相关关系。受高海拔低气压影响,虽然采取了大气压和温度补偿校准,但泸沽湖溶解氧浓度仍不易达到Ⅰ类水质标准限值(7.5 mg/L);而优良的水质加之茂盛的水生植被使得其溶解氧饱和率长期处于较高水平,可以达到Ⅰ类标准限值(90%)。因此,在自然环境特征类似于泸沽湖的水质优良高原湖泊,优先以饱和率作为溶解氧的评价指标更为合理。     

重庆雪玉洞地下河溶解态脂肪酸来源解析及变化特征

为研究岩溶地下河中溶解性有机质来源及变化特征,2014年11月1日和11月8日分别对重庆丰都雪玉洞地下河入口(Site 1)及出口(Site 2)进行取样,利用气相色谱气质联用仪(GS-MS)对样品中溶解态脂肪酸的组分进行定量分析.结果表明,Site1和Site2溶解态脂肪酸平均浓度分别为1698和4419 ng·L~(-1),地下河出口处溶解态脂肪酸浓度明显高于地下河入口处;各采样点中溶解态脂肪酸组成以低碳数饱和直链脂肪酸(C≤20:0)为主要组成部分,其次为单不饱和脂肪酸;结合主成分分析(PCA)表明,雪玉洞地下河水中DOM主要来源于土壤中细菌、真菌等微生物,其次为洞外地表河流中DOM向雪玉洞地下河水中的输入.另外,洞内游客的旅游活动对地下河水中DOM的来源影响明显.     

金属负载活性炭催化剂的稳定性研究

通过预处理、浸渍处理、改性液后处理等方式,研究开发出具有电化学反应性能的系列金属负载活性炭催化剂.分别将未改性和改性后的系列金属负载活性炭用于不同pH值下多种高浓度有机废水处理.试验结果表明,改性后的载铜及载铁活性炭催化剂经催化氧化反应后,处理出水中Cu2+离子和Fe2+离子的溶出量均可减少90％以上,苯胺及苯酚废水中COD的去除率可达50％～95％.大大提高了金属负载活性炭催化剂的稳定性,提高了催化剂的使用寿命,降低了废水处理成本.