Factors influencing concentrations of dissolved gaseous mercury (DGM) and total mercury (TM) in an artificial reservoir

The effects of various factors including turbidity, pH, DOC, temperature, and solar radiation on the concentrations of total mercury (TM) and dissolved gaseous mercury (DGM) were investigated in an artificial reservoir in Korea. Episodic total mercury accumulation events occurred during the rainy season as turbidity increased, indicating that the TM concentration was not controlled by direct atmospheric deposition. The DGM concentration in surface water ranged from 3.6 to 160 pg/L, having a maximum in summer and minimum in winter. While in most previous studies DGM was controlled primarily by a photo-reduction process, DGM concentrations tracked the amount of solar radiation only in winter when the water temperature was fairly low in this study. During the other seasons microbial transformation seemed to play an important role in reducing Hg(II) to Hg(0). DGM increased as dissolved organic carbon (DOC) concentration increased (p-value < 0.01) while it increased with a decrease of pH (p-value < 0.01).     

Mechanisms of enhanced mobilisation of trace metals by anionic surfactants in soil

Long-term applications of small concentrations of surfactants in soil via wastewater irrigation or pesticide application may enhance trace metal solubility. Mechanisms by which anionic surfactants (Aerosol 22, SDS and Biopower) affect trace metal solubility were assessed using batch, incubation and column experiments. In batch experiments on seven soils, the concentrations of Cu, Cd, Ni and Zn in the dissolved fraction of soils increased up to 100-fold at the high application rates, but increased less than 1.5-fold below the critical micelle concentration. Dissolved metal concentrations were less than 20% affected by surfactants in long-term incubations (70 days) up to the largest dose of 200 mg C kg⁻¹ soil. Leaching soil columns with A22 (100-1000 mg C L⁻¹) under unsaturated conditions increased trace metal concentrations in the leachates 2-4 fold over the control. Correlation analysis and speciation modelling showed that the increased solubility of metals upon surfactant application was more related to the solubilisation of soil organic matter from soil than to complexation of the metals with the surfactant. Organic matter from soil was solubilised in response to a decrease of solution Ca²⁺ as a result of Ca-surfactant precipitation. At environmentally relevant concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility.     

西南喀斯特流域土地利用对河流溶解无机碳及其同位素的影响

河流溶解无机碳(DIC)作为流域碳循环的重要部分一直备受关注,其稳定同位素(δ13CDIC)能够反映DIC来源和转化过程,而其受土地利用变化的影响的研究还较为缺乏.为了研究喀斯特河流水体DIC和δ13CDIC的影响因素,在典型喀斯特流域赤水河进行了河水样品采集与分析.赤水河流域上游主要分布碳酸盐岩而下游分布硅酸盐岩,且...     

青海湖流域有色可溶性有机物来源与特征分析

青海湖是我国最大的湖泊,该流域生态系统健康对维系青藏高原生态安全具有重要意义.关于我国青藏高原区内大型湖泊的有色可溶性有机物(CDOM)组成与来源研究甚少,对青海湖流域开展CDOM的来源及特征研究对该湖水质保护及填补空白区的研究具有重要意义.通过两次青海湖流域采样并结合三维荧光光谱-平行因子分析法(EEMs-PARAF...     

湿地垦殖对土壤微生物量及土壤溶解有机碳、氮的影响

对三江平原天然沼泽湿地及湿地垦殖后的农田、弃耕还湿地、人工林地等不同土地利用方式下表层土壤(0～10cm)的活性碳、氮组分:微生物量碳(MBC)、微生物量氮(MBN)、溶解有机碳(DOC)、溶解有机氮(DON)进行了研究.结果表明,天然小叶章沼泽湿地垦殖为农田后,表层土壤各活性碳、氮组分显著降低:MBC减少了63.8%～80.5%; MBN减少了56.3%～67.1%; DOC减少了43.1%～44.3%; DON减少了25.2%～56.1%.农田弃耕还湿和人工造林后表层土壤的活性碳、氮组分有明显恢复的趋势,各组分恢复到天然小叶章湿地土壤水平的36.1%～59.9%(MBC);46.7%～65.9%(MBN);67.0%～69.3%(DOC);81.2%～88.3%(DON),土地利用方式是影响土壤MBC、MBN、DOC、DON变化的重要因素;各土地利用方式表层土壤的DOC、DON、MBC、MBN呈显著的正相关关系,土地利用方式对表层土壤DOC的影响大于对DON的影响;各土地利用方式下土壤微生物可利用碳、氮的来源不同是影响DOC、DON与MBC、MBN相关性差别明显的主要原因.     

太湖梅梁湾有色可溶性有机物对光的吸收

探讨了太湖梅梁湾不同湖区有色可溶性有机物(CDOM)对光的吸收、光衰减系数的变化及与DOC浓度的关系、CDOM吸收对光衰减系数的贡献率以及指数函数曲线斜率S值.结果表明,不同类型湖区CDOM吸收系数差异明显,a_d(440)、a_d(320)的变化范围分别为1.22～2.58m^-1,6.24～10.69m^-1;DOC浓度最高值出现在梁溪河口,为12.74mg/L,最低值出现梅梁湾口,为6.87mg/L,大致呈由湾内向湾口逐渐递减的趋势;DOC与CDOM吸收系数在波长320nm以下存在显著性相关,波长320～700nm CDOM吸收对光衰减系数的贡献率在0.69%～60.9%间变化,400nm以下紫外短光部分贡献率均大于20%,空间上短波部分贡献率在河口区、五里湖比梅梁湾内及沿岸带要大;CDOM吸收的指数函数曲线斜率S在13.9～18.1m^-1间.     

Mercury photoreduction and photooxidation in lakes: Effects of filtration and dissolved organic carbon concentration

Mercury is a globally distributed, environmental contaminant. Quantifying the retention and loss of mercury is integral for predicting mercury-sensitive ecosystems. There is little information on how dissolved organic carbon(DOC) concentrations and particulates affect mercury photoreaction kinetics in freshwater lakes. To address this knowledge gap,samples were collected from ten lakes in Kejimkujik National Park, Nova Scotia(DOC: 2.6–15.4 mg/L). Filtered(0.2 μm) and unfiltered samples were analysed for gross photoreduction, gross photooxidation, and net reduction rates of mercury using pseudo first-order curves. Unfiltered samples had higher concentrations(p = 0.04) of photoreducible divalent mercury(Hg(II)RED)(mean of 754 ± 253 pg/L) than filtered samples(mean of 482 ± 206 pg/L);however, gross photoreduction and photooxidation rate constants were not significantly different in filtered or unfiltered samples in early summer. DOC was not significantly related to gross photoreduction rate constants in filtered(R~2= 0.43; p = 0.08) and unfiltered(R~2= 0.02; p = 0.71) samples; DOC was also not significantly related to gross photooxidation rate constants in filtered or unfiltered samples. However, DOC was significantly negatively related with Hg(Ⅱ)_(RED) in unfiltered(R2= 0.53; p = 0.04), but not in filtered samples(R~2= 0.04;p = 0.60). These trends indicate that DOC is a factor in determining dissolved mercury photoreduction rates and particles partially control available Hg(Ⅱ)_(RED) in lake water. This research also demonstrates that within these lakes gross photoreduction and photooxidation processes are close to being in balance. Changes to catchment inputs of particulate matter and DOC may alter mercury retention in these lakes and could partially explain observed increases of mercury accumulation in biota.     

Subtropical urban turfs: Carbon and nitrogen pools and the role of enzyme activity

Urban grasslands not only provide a recreational venue for urban residents, but also sequester organic carbon in vegetation and soils through photosynthesis, and release carbon dioxide through respiration, which largely contribute to carbon storage and fluxes at regional and global scales. We investigated organic carbon and nitrogen pools in subtropical turfs and found that dissolved organic carbon(DOC) and dissolved organic nitrogen(DON)were regulated by several factors including microbial activity which is indicated by soil enzymatic activity. We observed a vertical variation and different temporal patterns in both soil DOC, DON and enzyme activities, which decreased significantly with increasing soil depths. We further found that concentration of soil DON was linked with turf age. There were correlations between grass biomass and soil properties, and soil enzyme activities. In particular, soil bulk density was significantly correlated with soil moisture and soil organic carbon(SOC). In addition, DOC correlated significantly with DON. Significant negative correlations were also observed between soil total dissolved nitrogen(TDN) and grass biomass of Axonopus compressus and Zoysia matrella. Specifically, grass biomass was significantly correlated with the soil activity of urease and β-glucosidase. Soil NO3-N concentration also showed negative correlations with the activity of both β-glucosidase and protease but there were no significant correlations between cellulase and soil properties or grass biomass. Our study demonstrated a relationship between soil C and N dynamics and soil enzymes that could be modulated to enhance SOC pools through management and maintenance practices.     

水培植物生态槽对低C/N污水的脱氮研究

选用某污水处理厂的二沉池出水[(TN主要以硝态氮(NO3--N)形式存在)作为研究对象,采取水培植物生态槽进行脱氮试验,着重研究了NO3--N的反硝化过程.结果表明, NO3--N与COD均得到有效去除;生态槽厌氧区水力停留时间(HRT)为10~18h,系统水力负荷为1.33m3/(m3×d),不投外加碳源时,空槽运行NO3--N去除率为10.80%;种植能分泌溶解性有机碳(DOC)的凤眼莲使NO3--N去除率升至15.89%;而硫自养反硝化过程使NO3--N去除率提高至37.80%;投加葡萄糖时,TN与NO3--N的去除率分别达到87.20%和93.21%,出水浓度分别降到2.2,1.04mg/L.     

Impact of Lime and Ash Applications on Soil Solution Chemistry of an Acidified Podzolic Soil

Soil solution samples were taken from two sites (Horröd and Hasslöv) in the south part of Sweden to evaluate how soil solution chemistry responded to different treatmentswith dolomite and wood ash. At Horröd, samples were taken four years after application of wood ash, 4.28 ton ha^-1 and dolomite, 3.25 ton ha^-1. At Hasslöv dolomite, 3.45 ton ha^-1 and 8.75 ton ha^-1 was applied and samples were taken 15 yr later. It was found that treatment with dolomite at one site (Hasslöv) resulted in higher pH values (<2 pH units) and higher nitrification. It was also found at this site that the total Al and the inorganic Al concentrations decreased with dolomite treatment. The Ca, Mg, DOC, Fe, SO₄ ^2- and Cl^- concentrations, mainly in the topsoil, were found to be higher at both sites, following dolomite treatment; Ca and Mg concentrations were 2–8 times higher (<820 M) than in controls (<70 M). Wood ash was found to have less impact. The PO₄ concentration in the O2 horizon at Hasslöv decreased due to dolomite-treatment. ANOVA (Analyse of Variance) and PLS (Partial Least Square) were used to evaluate the data from the two sites.