Rising trends of dissolved organic matter in drinking-water reservoirs as a result of recovery from acidification in the Ore Mts., Czech Republic

The concentration of chemical oxygen demand (COD), a common proxy for dissolved organic matter (DOM), was measured at seven drinking-water reservoirs and four streams between 1969 and 2006. Nine of them showed significant DOM increases (median COD change +0.08 mg L⁻¹ yr⁻¹). Several potential drivers of these trends were considered, including air temperature, rainfall, land-use and water sulfate concentration. Temperature and precipitation influenced inter-annual variations, but not long-term trends. The long-term DOM increase was significantly associated with declines of acidic deposition, especially sulfur deposition. Surface water sulfate concentrations decreased from a median of 62 mg L⁻¹-27 mg L⁻¹ since 1980. The magnitude of DOM increase was positively correlated with average DOM concentration (R² = 0.79, p < 0.001). Simultaneously, DOM concentration was positively correlated with the proportion of Histosols within the catchments (R² = 0.79, p < 0.001). A focus on the direct removal of DOM by water treatment procedures rather than catchment remediation is needed.     

不同水分梯度下UV-B辐射对2个稻田土壤碳氮转化的影响

UV-B辐射对土壤碳氮转化的影响与土壤物理化学性质有关,为明确土壤水分状态对UV-B辐射的影响,以有机质含量不同的两个水稻土(有机质含量低的记为L,高的记为H)为研究材料,在室内研究了含水量为25%(W1)、50%(W2)和100%(W3)时,UV-B辐射对土壤总有机碳(TOC)、可溶性有机碳(DOC)、铵态氮(NH_4~+-N)、硝态氮(NO_3~--N)以及累积净矿化氮量的影响.结果表明:120 h后,与避光(对照,CK)相比,UV-B辐射显著降低了土壤TOC的含量(P0.05);UV-B辐射下,水分从低到高,L土壤的TOC分别降低了9.9%、4.5%和6.3%,H土壤降低了10.9%、5.6%和6.3%.但与对照相比,UV-B辐射却促使土壤DOC增加;且在UV-B辐射下水分为100%的处理中,土壤DOC含量高于25%和50%的处理,120 h时,L土壤的DOC分别增加了21.5%(W1)、9.4(W2)和26.3%(W3),H土壤分别降低了26.7%(W1)、14.2%(W2)和33.8%(W3).与对照相比,UV-B辐射使NH_4~+-N含量有所下降;且在UV-B辐射中,NH_4~+-N含量的变化幅度在不同水分条件下的整体表现为W1W2W3.较对照处理,UV-B辐射促进NO_3~--N的累积,NO_3~--N变化幅度在不同水分条件下的表现为:W1W3W2.24 h后与对照相比,UV-B辐射对土壤累积净矿化氮量有显著影响(P0.05),且UV-B辐射下累积净矿化氮量在不同水分之间差异显著(P0.05).这表明光降解在土壤有机质的稳定中扮演着重要角色,UV-B辐射会加速土壤有机碳的损失,影响土壤矿质态氮的转化,且水分不同,UV-B辐射对土壤碳氮转化的影响存在一定差异.     

DOC+CDPF对重型柴油车排放特性的影响

基于重型转毂试验平台对比研究国Ⅲ重型柴油车加装催化型连续再生颗粒捕集器(DOC+CDPF)前后的气态物及颗粒物排放性能,结果表明从市区循环、公路循环到高速循环,原车的CO、THC、CO_2及颗粒质量(PM)排放因子依次减小,NO_x及颗粒数量(PN)排放因子依次增大,颗粒数量浓度随粒径呈双峰分布并且以聚集态颗粒排放为主;加装DOC+CDPF后,各污染物排放因子均有所下降,且下降趋势从市区循环、公路循环到高速循环依次增大,从整个C-WTVC循环来看,CO排放因子下降70.36%,THC排放因子下降72.73%,CO_2排放因子下降17.00%,NO_x排放因子下降7.76%,PM、PN排放因子分别下降93.77%和98.91%,颗粒数量浓度随粒径仍呈双峰分布,但排放以核模态颗粒为主,并且聚集态峰值对应粒径减小.     

基于DOC+CDPF技术的公交车燃用生物柴油气态物道路排放特性

基于OBS-2200车载排放检测系统,试验研究并分析了催化型连续再生颗粒捕集器(DOC+CDPF)及生物柴油混合燃料B20(生物柴油体积占比20%)对国Ⅲ柴油公交车瞬态工况和稳态工况下气态物道路排放特性的影响.结果表明相较于B0(纯柴油),B20的一氧化碳(CO)、总碳氢化合物(THC)平均排放率偏低,其中,稳态工况下降幅分别为26.43%、10.44%,瞬态工况下降幅分别为22.78%、4.95%;二氧化碳(CO_2)和氮氧化物(NO_x)平均排放率偏高,其中,稳态工况下分别上升8.41%和8.26%,瞬态工况下分别上升7.15%、9.13%.相较于B0,DOC+CDPF对B20的CO和THC净化效果更为显著,其中,稳态工况下降幅分别达60.58%和79.92%,瞬态工况下,降幅分别达63.67%和82.57%.DOC+CDPF使用后,CO_2和NO_x的排放率略微下降.     

花生壳活性炭对反渗透(RO)浓水的吸附特性

以花生壳活性炭对RO浓水进行吸附处理,利用傅立叶红外光谱(FTIR)和荧光光谱(EEM)研究花生壳活性炭对不同pH的RO浓水的吸附特性.结果表明,花生壳活性炭对溶解性有机碳(DOC)的吸附遵循准二级吸附动力学方程,特别是碱性条件下,DOC的吸附量随着pH的升高而降低.而且pH越高,达到吸附平衡的时间越长.通过FTIR光谱分析发现,活性炭的芳香结构吸收峰在吸附后红移至1630 cm-1,表明被吸附的有机物在该处有明显的特征吸收峰,而C—O和O—H官能团的吸收峰则因为钙离子等物质的吸附而显著降低.由EEM光谱分析可知,RO浓水的荧光物质主要由腐殖酸类腐殖质和富里酸类腐殖质组成,其荧光强度与DOC之间具有较好的线性相关性.     

Characteristics of mercury speciation in Minnesota rivers and streams

Patterns of mercury (Hg) speciation were examined in four Minnesota streams ranging from the main-stem Mississippi River to small tributaries in the basin. Filtered phase concentrations of methylmercury (MeHg), inorganic Hg (IHg), and dissolved organic carbon (DOC) were higher in all streams during a major summertime runoff event, and DOC was enriched with MeHg but not with IHg. Particulate-phase MeHg and IHg concentrations generally increased with total suspended solids (TSS) concentrations but the event data did not diverge greatly from the non-event data, suggesting that sources of suspended sediments in these streams did not vary significantly between event and non-event samplings. The dissolved fractions (filtered concentration/unfiltered concentration) of both MeHg and IHg increased with increasing DOC concentrations, but varied inversely with TSS concentrations. While MeHg typically constitutes only a minor portion of the total Hg (THg) in these streams, this contribution is not constant and can vary greatly over time in response to watershed inputs.     

Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites

Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at Gårdsjön increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20–62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.     

太湖典型草、藻型湖区有色可溶性有机物的吸收及荧光特性

2004年4月对太湖典型草、藻型湖区东太湖和梅梁湾有色可溶性有机物(CDOM)的吸收和荧光特性进行了研究.通过实验测定方法得到东太湖和梅梁湾CDOM的光谱吸收系数及其荧光值.结果表明,溶解性有机碳(DOC)的浓度在6.3～17.2 mg/L间变化,其均值为9.08±2.66 mg/L;CDOM在280 nm和355 nm的吸收系数分别为11.2～32.6 m^-1(平均值17.46m-1±5.75 m^-1)和2.4m～8.3 m^-1(平均值4.17 m^-1±1.47 m^-1);355 nm波长处CDOM的比吸收系数为0.31～0.64 L·(mg·m)^-1,平均值0.46L·(mg·m)^-1±0.08 L·(mg·m)^-1.355 nm的激发波长、450 nm的发射波长处的荧光值的变化范围0.50～3.91 nm^-1(平均值1.32nm-1±0.84 nm^-1).2类草、藻型湖区的DOC浓度、CDOM吸收系数、355 nm处荧光值均存在显著性差异,但CDOM比吸收系数和指数函数斜率则没有显著性差异,由此则反映了CDOM来源的一致性.CDOM的吸收系数与DOC浓度的相关性随波长的降低而增加,在短波部分存在明显的正相关.355 nm处的荧光值、DOC浓度与CDOM吸收系数存在如下显著性的正相关关系:F_n(355)=0.544(±0.035)a(355)-0.946(±0.152),DOC=1.537(±0.196)a(355)+2.683(±0.862).280～500 nm、280～360 nm、360～440 nm指数函数斜率分别为14.37μm^-1±0.73μm^-1、19.17μm-1±0.84μm^-1、13.38μm-1±0.82μm^-1.     

生物活性炭内吸附与生物降解协同去除有机污染物

本研究建立了一个确定BAC内2种机理去除有机物分配比例的试验方法.该方法以BAC进出水中溶解性有机碳（DOC）与可生物降解有机碳（BDOC）浓度变化作为评价参数,并利用此方法确定了臭氧投加量对2种去除机理的影响.臭氧化可以使BDOC浓度增加,臭氧投量为2～8mg/L时,BDOC增加0.12～0.54mg/L;BAC过滤使出水BDOC浓度降低为0.23～0.31mg/L.随着臭氧投量增加（2～8mg/L）,在BAC内生物降解作用去除有机物比例从46%增加到89%.     

三峡库区消落带典型草本植物淹水浸泡后可溶性有机碳的释放特征

三峡库区消落带出露时草本植被生长旺盛,每年9月底蓄水后植物被淹没并开始腐解,导致有机体分解释放大量可溶性有机碳(DOC),可能对水质产生负面影响.研究选取三峡库区消落带典型草本植物,通过室内模拟浸泡实验,测定上覆水中DOC浓度变化过程,计算其释放速率与通量,旨在查明消落带草本植物淹水后DOC的释放特征,为库区植被修复与管理提供基础数据.结果表明,几种典型草本植物浸泡后上覆水的DOC浓度变化反映出草本植物淹水后DOC释放呈先增后减,后期趋于平稳的变化过程,在15 d左右达到峰值,表明消落带草本植物淹水浸泡后DOC随植物腐解快速释放,随后释放基本稳定,几种典型草本植物的DOC释放过程符合动力学过程.草本植物浸泡后DOC的释放浓度(最大为苦蒿的486.88 mg·L-1±35.97 mg·L-1,最小为稗子的4.18 mg·L-1±1.07 mg·L-1)、释放量(最大为苦蒿的50.54 mg·g-1,最小为水蓼的6.51mg·g-1)存在显著差异,主要受植物基质的影响,特别是植物基质的C/N值.实验浸泡植物的DOC释放量与相应草本植物基质的C/N值呈显著线性关系.