Efficient microwave degradation of humic acids in water using persulfate and activated carbon

Environmental Chemistry Letters - Humic acids are complex mixtures of organic molecules of different sizes, molecular weights and functional groups such as phenols, carboxyls, quinones and amino...     

Groundwater contamination evolution in the Guadiamar and Agrio aquifers after the Aznalcóllar spill: assessment and environmental implications

In 1998, the Agrio and Guadiamar rivers underwent an enormous environmental disaster caused by the rupture of the Aznalcóllar tailings dam and the release of 6 hm³ of pyrite sludge and acidic water. Both rivers run over recent alluvial materials which form a small-sized aquifer which is however important because underground water feeds the flow of the rivers. This work analyzes the state of groundwater 10 years after the spill. Before the dam failure, this aquifer was already contaminated in the zone nearest to the mine, to which the impact of the spill was added. Contamination levels in the alluvial aquifer of the Agrio River have decreased remarkably. However, they are still important, with acidic pH values and high concentrations of toxic elements (maximum values of 16 mg/L of Zn and 15 mg/L of Al). There are also important levels of contamination in the Guadiamar alluvial area closest to the mine, as well as in specific zones located further south. The concentration of toxic elements is mainly controlled by pH. The evolution of contaminant levels show a sharp decrease after the first years following the spill, followed by a subsequent stabilization. It is necessary to take measures for the recovery of the aquifer because, otherwise, groundwater will continue contributing contaminants into the Agrio and Guadiamar rivers.     

Iron, cadmium, and chromium in seagrass (Thalassia testudinum) from a coastal nature reserve in karstic Yucatán

The management of protected areas in karstic regions is a challenge because flooded cave systems form there and provide underground hydrological conducts that may link different zones. As a consequence, affectations to the protected areas can possibly occur as a consequence of human activities in remote areas and may therefore pass undetected. Thus, the monitoring of possible contaminants in these regions is becoming imperative. In this work, we analyze the concentration of essential (iron) and non-essential metals (cadmium and chromium) in the seagrass Thalassia testudinum that grows in Yalahau Lagoon, located in a near-to-pristine protected area of the Yucatán Peninsula, close to the rapidly developing touristic belt of the Mexican Caribbean. Salinity and silicate patterns show that Yalahau is an evaporation lagoon, where groundwater discharge is important. High iron (>400 μg/g), cadmium (>4 μg/g), and chromium (≈1 μg/g) concentrations were found in the area of highest groundwater input of the lagoon. High levels (5.1 μg/g) were also found near the town dump. In the rest of the sampling sites, metal concentrations remained near to background levels as estimated from other works. Temporal changes of concentrations in the seagrass tissues show also a local input and an input from the groundwater that could provoke an environmental problem in the Yalahau Lagoon in the near future.     

Spectral trend of vegetation with rainfall in events of El Niño-Southern Oscillation for Atlantic Forest biome,Brazil

This study aimed to analyze the spectral trend of vegetation with rainfall in El Niño-Southern Oscillation events (ENSO) in the Atlantic Forest, Brazil. Monthly rainfall data were collected from 85 conventional meteorological stations (EMC), data from the Enhanced Vegetation Index 2 (EVI2) and ENSO events (El Niño, La Niña, and Neutral) in the period from 2001 to 2013. Afterwards, state cluster analysis was performed using the results of non-parametric tests. The Mann-Kendall (MK) non-parametric test did not identify a trend pattern in rainfall distribution in the Atlantic Forest. The results for EVI2 by state and region showed that the trend is decreasing in the Northeast Region, except for the states of Alagoas and Pernambuco. Southeast region showed an increasing trend of EVI2 (except for Rio de Janeiro and São Paulo), while the South region showed a decreasing trend. In the Midwest, the trend was significantly decreasing. In the prognosis elaborated for the future, the regions with significant declines of the vegetation were the Northeast and Midwest. This study shows that the Atlantic Forest in some regions of Brazil has been suffering from the growing urbanization process and there is a trend of soil degradation.     

色谱、光谱及联用技术在多农药残留检测中的应用

介绍了国内外多农药残留检测的发展状况,综述了色谱法、光谱法、色谱-质谱联用技术、色谱-光谱联用法、多维气相色谱技术的特点及在多农药残留检测中的应用,指出多农药残留检测在今后的农药残留检测中将占据主导地位.     

Froude scaling limitations in modeling of turbidity currents

The scaling problem associated with the modeling of turbidity currents has been recognized but is yet to be explored systematically. This paper presents an analysis of the dimensionless governing equations of turbidity currents to investigate the scale effect. Three types of flow conditions are considered: (i) conservative density current; (ii) purely depositional turbidity current; and (iii) mixed erosional/depositional turbidity current. Two controlling dimensionless numbers, the Froude number and the Reynolds number, appear in the non-dimensional governing equations. When densimetric Froude similarity is satisfied, the analysis shows that the results would be scale-invariant for conservative density current under the rough turbulent condition. In the case of purely depositional flows, truly scale-invariant results cannot be obtained, as the Reynolds-mediated scale effects appear in the bottom boundary conditions of the flow velocity and sediment fall velocity. However, the scale effect would be relatively modest. The Reynolds effect becomes more significant for erosional or mixed erosional/depositional turbidity currents as Reynolds-mediated scale effects also appear in the sediment entrainment relation. Numerical simulations have been conducted at three different scales by considering densimetric Froude scaling alone as well as combined densimetric Froude and Reynolds similarity. Simulation results confirm that although the scaling of densimetric Froude number alone can produce scale-invariable results for conservative density currents, variations occur in the case of turbidity currents. The results become scale invariant when densimetric Froude and Reynolds similarities are satisfied simultaneously.     

Optimum ridge-to-furrow ratio in ridge-furrow mulching systems for improving water conservation in maize (Zea may L.) production

Environmental Science and Pollution Research - Water-saving cultivation techniques have been attracting increased attention worldwide. Ridge-furrow mulching system (RFMS), as a prospective...     

纳米TiO2-石墨烯光催化剂的水热合成及其光催化性能

以钛酸四正丁酯和石墨为原料,通过水热法制备了锐钛矿型为主的纳米TiO2复合光催化剂（纳米TiO2-石墨烯）,并采用XRD,FTIR,FESEM,TEM技术对其进行了表征。通过紫外光照射降解溶液中的罗丹明B（RhB）研究了TiO2-石墨烯的光催化活性,分析了初始罗丹明B质量浓度、催化剂加入量、溶液pH和催化剂使用次数等影响降解效果的因素。实验结果表明：在初始RhB质量浓度为20 mg/L、溶液pH为7.10、催化剂加入量为1.000 g/L的条件下,紫外光照射30 min时,纳米TiO2-石墨烯对RhB的降解率高达98.69%,明显高于纳米TiO2的44.69%;纳米TiO2-石墨烯稳定性较强,可多次重复使用。     

Investigation of pharmaceutical metabolites in environmental waters by LC-MS/MS

Pharmaceuticals, once ingested, are commonly metabolized in the body into more polar and soluble forms. These compounds might not be completely removed in the wastewater treatment plants and consequently being discharged into the aquatic ecosystem. In this work, a multi-class sensitive method for the analysis of 21 compounds, including 7 widely consumed pharmaceuticals and 14 relevant metabolites, has been developed based on the use of UHPLC-MS/MS in selected reaction monitoring (SRM) mode. The method was validated in six surface waters (SW) and six effluent wastewaters (EWW) at realistic concentration levels that can be found in waters. The optimized method was applied to the analysis of different types of water samples (rivers, lakes and effluent wastewater), detecting nearly all the parent compounds and metabolites investigated in this work. This fact illustrates that not only pharmaceuticals but also their metabolites are commonly present in these types of waters. Analytical research and monitoring programs should be directed not only towards parent pharmaceuticals but also towards relevant metabolites to have a realistic overview of the impact of pharmaceuticals in the aquatic environment.     

渗滤液耦合矿化垃圾制备甲烷氧化菌菌液

利用甲烷氧化菌菌液增加材料中甲烷氧化菌的数量,可以得到高甲烷氧化率的填埋场甲烷生物氧化覆盖材料。研究发现,渗滤液原水和渗滤液处理尾水均能促进甲烷氧化菌的生长,可利用渗滤液耦合矿化垃圾混合培养制备甲烷氧化菌菌液用于填埋场甲烷减排。填埋龄长的渗滤液原水有着较好的培养效果,得到的菌液在4 d内最高甲烷氧化速率达到2.68 mL/h,超过甲烷氧化菌培养液(nitrate minimal salt medium,NMS)的实验结果。渗滤液中总氮、无机碳、总有机碳和Ni元素的含量对甲烷氧化菌的培养过程影响较大,适用于甲烷氧化培养的渗滤液应满足:总氮1 400 mg/L,总有机碳55 mg/L,Ni元素0.4 mg/L,总磷含量较高。