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1.
Purpose Increases in dissolved organic carbon (DOC) concentrations have been reported in surface waters worldwide in the last 10 to
20 years. The causes behind these increases have been attributed to many factors, including climate change and decreasing
depositions of atmospheric sulphate (
\text SO42 - {\text{SO}}_4^{{{2} - }} ). Trends in DOC concentrations and their potential causal factors were examined in a network of 30 lakes lying in undisturbed
temperate and boreal catchments in the province of Quebec, Canada. 相似文献
2.
Recent studies have shown up to 6 % of rivers in England and Wales to be impacted by discharges from abandoned metal mines. Despite the large extent of impacts, there are still many areas where mine water impact assessments are limited by data availability. This study provides an overview of water quality, trace element composition and flux arising from one such area; the Yorkshire Pennine Orefield in the UK. Mine drainage waters across the orefield are characterised by Ca–HCO 3–SO 4-type waters, with moderate mineralization (specific electrical conductance: 160–525 μS cm ?1) and enrichment of dissolved Zn (≤2003 μg?L ?1), Ba (≤971 μg?L ?1), Pb (≤183 μg?L ?1) and Cd (≤12 μg?L ?1). The major ion composition of the waters reflects the Carboniferous gritstone and limestone-dominated country rock, the latter of which is heavily karstified in parts of the orefield, while sulphate and trace element enrichment is a product of the oxidation of galena, sphalerite and barite mineralization. Contaminant flux measurements at discharge sites highlight the disproportionate importance of large drainage levels across the region, which generally discharge into first-order headwater streams. Synoptic metal loading surveys undertaken in the Hebden Beck sub-catchment of the river Wharfe highlight the importance of major drainage levels to instream baseflow contamination, with diffuse sources from identifiable expanses of waste rock becoming increasingly prominent as river flows increase. 相似文献
3.
Cryogenic time-resolved laser-induced fluorescence spectroscopy was successfully used to identify uranium binding forms in selected German mineral waters of extremely low uranium concentrations (<2.0 μg/L). The measurements were performed at a low temperature of 153 K. The spectroscopic data showed a prevalence of aquatic species Ca 2UO 2(CO 3) 3 in all investigated waters, while other uranyl–carbonate complexes, viz, UO 2CO 3(aq) and UO 2(CO 3) 2 2?, only existed as minor species. The pH value, alkalinity (CO 3 2?), and the main water inorganic constituents, specifically the Ca 2+ concentration, showed a clear influence on uranium speciation. Speciation modeling was performed using the most recent thermodynamic data for aqueous complexes of uranium. The modeling results for the main uranium binding form in the investigated waters indicated a good agreement with the spectroscopy measurements. 相似文献
4.
Based on available literature data of [NO 2
−], steady-state [·OH], and ·OH generation rate upon nitrate photolysis in environmental aqueous samples under sunlight, the
steady-state [·NO 2], could be calculated. Interestingly, one to two orders of magnitude more ·NO 2 would be formed in photochemical processes in atmospheric water droplets compared to transfer from the gas phase. The relative
importance of nitrite oxidation compared to nitrate photolysis as an ·NO 2 source would be higher in atmospheric than in surface waters. The calculated levels of ·NO 2 could lead to substantial transformation of phenol into nitrophenols in both atmospheric and surface waters. 相似文献
5.
In addition to direct photolysis studies, in this work the second-order reaction rate constants of pesticides imidacloprid (IMD) and ametryn (AMT) with hydroxyl radicals (HO●), singlet oxygen (1O2), and triplet excited states of chromophoric dissolved organic matter (3CDOM*) were determined by kinetic competition under sunlight. IMD and AMT exhibited low photolysis quantum yields: (1.23?±?0.07)?×?10–2 and (7.99?±?1.61)?×?10–3 mol Einstein?1, respectively. In contrast, reactions with HO● radicals and 3CDOM* dominate their degradation, with 1O2 exhibiting rates three to five orders of magnitude lower. The values of kIMD,HO● and kAMT,HO● were (3.51?±?0.06)?×?109 and (4.97?±?0.37)?×?109 L mol?1 s?1, respectively, while different rate constants were obtained using anthraquinone-2-sulfonate (AQ2S) or 4-carboxybenzophenone (CBBP) as CDOM proxies. For IMD this difference was significant, with kIMD,3AQ2S*?=?(1.02?±?0.08)?×?109 L mol?1 s?1 and kIMD,3CBBP*?=?(3.17?±?0.14)?×?108 L mol?1 s?1; on the contrary, the values found for AMT are close, kAMT,3AQ2S*?=?(8.13?±?0.35)?×?108 L mol?1 s?1 and kAMT,3CBBP*?=?(7.75?±?0.80)?×?108 L mol?1 s?1. Based on these results, mathematical simulations performed with the APEX model for typical levels of water constituents (NO3?, NO2?, CO32?, TOC, pH) indicate that the half-lives of these pesticides should vary between 24.1 and 18.8 days in the waters of the Paranapanema River (São Paulo, Brazil), which can therefore be impacted by intensive agricultural activity in the region. 相似文献
6.
The influences of HCO 3 ?, Cl ?, and other components on the UV/TiO 2 degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO 3 ?, Cl ?, NO 3 ?, and SO 4 2? in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3–7.3 and 3.2–6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO 2 loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO 3 ? in the UV/TiO 2/HCO 3 ? system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of ?CO 3 ? in the system. The results also showed that ?CO 3 ? likely induces a preferred ketonization pathway. Besides the inorganic anions HCO 3 ?, Cl ?, NO 3 ?, and SO 4 2?, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO 3 ? or Cl ? during UV/TiO 2 treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater. 相似文献
7.
Weathering of sulphide minerals produces a great variety of efflorescences of soluble sulphate salts. These minerals play an important role for environmental pollution, since they can be either a sink or a source for acidity and trace elements. This paper aims to characterise surface waters affected by mining activities in the Sierra Minera of Cartagena-La Union (SE, Spain). Water samples were analysed for trace metals (Zn, Cd, Pb, Cu, As and Fe), major ions (Na +, K +, Ca 2+ and Mg 2+) and anions (F ?, Cl ?, NO 3 ?, CO 3 2?, SO 4 2?) concentrations and were submitted to an “evaporation-precipitation” experiment that consisted in identifying the salts resulting from the evaporation of the water aliquots sampled onsite. Mineralogy of the salts was studied using X-ray diffraction and compared with the results of calculations using VISUAL MINTEQ. The study area is heavily polluted as a result of historical mining and processing activities that has produced large amount of wastes characterised by a high trace elements content, acidic pH and containing minerals resulting from the supergene alteration of the raw materials. The mineralogical study of the efflorescences obtained from waters shows that magnesium, zinc, iron and aluminium sulphates predominate in the acid mine drainage precipitates. Minerals of the hexahydrite group have been quantified together with minerals of the rozenite group, alunogen and other phases such as coquimbite and copiapite. Calcium sulphates correspond exclusively to gypsum. In a semiarid climate, such as that of the study area, these minerals contribute to understand the response of the system to episodic rainfall events. MINTEQ model could be used for the analysis of waters affected by mining activities but simulation of evaporation gives more realistic results considering that MINTEQ does not consider soluble hydrated salts. 相似文献
8.
Gaseous nitrogen dioxide (NO 2) represents an oxidant that is present in relatively high concentrations in various indoor settings. Remarkably increased NO 2 levels up to 1.5 ppm are associated with homes using gas stoves. The heterogeneous reactions of NO 2 with adsorbed water on surfaces lead to the generation of nitrous acid (HONO). Here, we present a HONO source induced by heterogeneous reactions of NO 2 with selected indoor paint surfaces in the presence of light (300 nm?<? λ?<?400 nm). We demonstrate that the formation of HONO is much more pronounced at elevated relative humidity. In the presence of light (5.5 W m ?2), an increase of HONO production rate of up to 8.6?·?10 9 molecules cm ?2 s ?1 was observed at [NO 2]?=?60 ppb and 50 % relative humidity (RH). At higher light intensity of 10.6 (W m ?2), the HONO production rate increased to 2.1?·?10 10 molecules cm ?2 s ?1. A high NO 2 to HONO conversion yield of up to 84 % was observed. This result strongly suggests that a light-driven process of indoor HONO production is operational. This work highlights the potential of paint surfaces to generate HONO within indoor environments by light-induced NO 2 heterogeneous reactions. 相似文献
9.
Photocatalytic degradation of bisphenol A (BPA) in waters and wastewaters in the presence of titanium dioxide (TiO 2) was performed under different conditions. Suspensions of the TiO 2 were used to compare the degradation efficiency of BPA (20 mg L ?1) in batch and compound parabolic collector (CPC) reactors. A TiO 2 catalyst supported on glass spheres was prepared (sol–gel method) and used in a CPC solar pilot plant for the photodegradation of BPA (100 μg L ?1). The influence of OH·, O 2 ·?, and h + on the BPA degradation were evaluated. The radicals OH· and O 2 ·? were proved to be the main species involved on BPA photodegradation. Total organic carbon (TOC) and carboxylic acids were determined to evaluate the BPA mineralization during the photodegradation process. Some toxicological effects of BPA and its photoproducts on Eisenia andrei earthworms were evaluated. The results show that the optimal concentration of suspended TiO 2 to degrade BPA in batch or CPC reactors was 0.1 g L ?1. According to biological tests, the BPA LC 50 in 24 h for E. andrei was of 1.7?×?10 ?2 mg cm ?2. The photocatalytic degradation of BPA mediated by TiO 2 supported on glass spheres suffered strong influence of the water matrix. On real municipal wastewater treatment plant (MWWTP) secondary effluent, 30 % of BPA remains in solution; nevertheless, the method has the enormous advantage since it eliminates the need of catalyst removal step, reducing the cost of treatment. 相似文献
10.
Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THg d), DOC concentration and DOC composition, and UV 254 absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive correlation of THg d to DOC ( r2 = 0.87), but progressively stronger correlations of THg d with the hydrophobic acid fraction (HPOA) of DOC ( r2 = 0.91) and with UV 254 absorbance ( r2 = 0.92). The strength of the UV 254 absorbance-THg d relationship suggests that optical properties associated with dissolved organic matter may be excellent proxies for THg d concentration in these streams. Ease of sample collection and analysis, the potential application of in-situ optical sensors, and the possibility for intensive monitoring over the hydrograph make this an effective, inexpensive approach to estimate THg d flux in drainage waters. 相似文献
11.
Atrazine (1.1 mg · L ?1) and Dichlobenil (“DBN”) (4.3 mg · L ?1) were dosed in triplicates into the water of a compartimentalized pond. Maximum concentrations of the chemicals detected were 200 μg · L ?1 Atrazine and 4.2 mg · L ?1 DBN (on day 3 – 5 after dosing). Residues were monitored for 55 days, amounting to 60 μg Atrazine and 1.5 mg DBN per litre at the end of observation.O 2- and H +-concentrations were significantly lower for 35 and 30 days resp. in the treated water as compared to controls. The conductivity of the dosed water was significantly higher for at least 65 (DBN) and 120 days (Atrazine) than in the untreated compartments. Differences in phytoplankton abundance and diversity could be evaluated between controls and treated biotopes. 相似文献
12.
Human activities have increased anthropogenic CO2 emissions, which are believed to play important roles in global warming. The spatiotemporal variations of CO2 concentration and flux at fine spatial scales in aquaculture ponds remain unclear, particularly in China, the country with the largest aquaculture. In this study, the plot-scale spatiotemporal variations of water CO2 concentration and flux, both within and among ponds, were researched in shrimp ponds in Shanyutan Wetland, Min River Estuary, Southeast China. The average water CO2 concentration and flux across the water–air interface in the shrimp ponds over the shrimp farming period varied from 22.79?±?0.54 to 186.66?±?8.71 μmol L?1 and from ??0.50?±?0.04 to 2.87?±?0.78 mol m?2 day?1, respectively. There was no remarkable difference in CO2 concentration and flux within the ponds, but significantly spatiotemporal differences in CO2 flux were observed between shrimp ponds. Chlorophyll a, pH, salinity, air temperature, and morphometry were the important factors driving the spatiotemporal patterns of CO2 flux in the shrimp ponds. Our findings highlighted the importance and spatiotemporal variations of CO2 flux in the important coastal ecosystems. 相似文献
13.
The ozonation involved in drinking water treatment raises issues of water quality security when the raw water contains bromide (Br ?). Br ? ions may be converted to bromate (BrO 3 ?) during ozonation and some brominated disinfection by-products (Br-DBPs) in the following chlorination. In this study, the effects of ozone (O 3) dosage, contact time, pH, and Br ? and ammonia (NH 3-N) concentrations on the formation of BrO 3 ? and Br-DBPs have been investigated. The results show that decreasing the initial Br ? concentration is an effective means of controlling the formation of BrO 3 ?. When the concentration of Br ? was lower than 100 μg/L, by keeping the ratio of O 3 dosage to dissolved organic carbon (DOC) concentration at less than 1, BrO 3 ? production was effectively suppressed. The concentration of BrO 3 ? steadily increased with increasing O 3 dosage at high Br ? concentration (>900 μg/L). Additionally, a longer ozonation time increased the concentrations of BrO 3 ? and total organic bromine (TOBr), while it had less impact on the formation potentials of brominated trihalomethanes (Br-THMFP) and haloacetic acids (Br-HAAFP). Higher pH value and the presence of ammonia may lead to an increase in the formation potential of BrO 3 ? and Br-DBPs. 相似文献
14.
Boreal peatlands are substantial sources of isoprene, a reactive hydrocarbon. However, it is not known how much mosses, vascular plants and peat each contribute to isoprene emission from peatlands. Furthermore, there is no information on the effects of declining water table depth on isoprene emission in these naturally wet ecosystems, although water table is predicted to decline due to climate warming. We studied the relative contribution of mosses vs. vascular plants to isoprene emission in boreal peatland microcosms in growth chambers by removing either vascular vegetation or both vascular vegetation and mosses. The microcosms represented wet hollows and dry hummocks of a boreal ombrotrophic bog. A water table drawdown treatment was applied to the hollows with naturally high water table. The mean (±SE) isoprene emission from hummocks with intact vegetation, 30 ± 6 μg m ?2 h ?1, was decreased by over 90% with removal of vascular plants or all vegetation. Thus, our results indicate that vascular plants, in contrast to mosses, were the main source of isoprene in the studied peatland ecosystem. Water table drawdown also significantly decreased the emissions; the mean isoprene emission from hollows with intact vegetation, 45 ± 6 μg m ?2 h ?1, was decreased by 25% under water table drawdown. However, water table drawdown reduced net ecosystem carbon dioxide (CO 2) exchange more dramatically than isoprene emission. Isoprene emission strongly correlated with both CO 2 exchange and methane emission. In conclusion, isoprene emissions from peatlands will decrease, but the proportion of assimilated carbon lost as isoprene will increase, if the naturally high water table declines under the changing climate. 相似文献
15.
An indoor/outdoor monitoring programme of PM 10 was carried out in two sports venues (a fronton and a gymnasium). Levels always below 50 μg m ?3 were obtained in the fronton and outdoor air. Due to the climbing chalk and the constant process of resuspension, concentrations above 150 μg m ?3 were registered in the gymnasium. The chalk dust contributed to CO 3 2? concentrations of 32?±?9.4 μg m ?3 in this sports facility, which represented, on average, 18 % of the PM 10 mass. Here, the carbonate levels were 128 times higher than those registered outdoors. Much lower concentrations, around 1 μg m ?3, were measured in the fronton. The chalk dust is also responsible for the high Mg 2+ concentrations in the gym (4.7?±?0.89 μg m ?3), unfolding a PM 10 mass fraction of 2.7 %. Total carbon accounted for almost 30 % of PM 10 in both indoor spaces. Aerosol size distributions were bimodal and revealed a clear dependence on physical activities and characteristics of the sports facilities. The use of climbing chalk in the gymnasium contributed significantly to the coarse mode. The average geometric mean diameter, geometric standard deviation and total number of coarse particles were 0.77 μm, 2.79 cm ?3 and 28 cm ?3, respectively. 相似文献
16.
This study revealed a dual pathway for the degradation of tris(1-chloro-2-propanyl) phosphate (TCPP) by zero-valent iron (ZVI) and persulfate as co-milling agents in a mechanochemical (MC) process. Persulfate was activated with ZVI to degrade TCPP in a planetary ball mill. After milling for 2 h, 96.5% of the TCPP was degraded with the release of 63.16, 50.39, and 42.01% of the Cl?, SO42?, and PO43?, respectively. In the first degradation pathway, persulfate was activated with ZVI to produce hydroxyl (·OH) radicals, and ZVI is oxidized to Fe(II) and Fe(III). A substitution reaction occurred as a result of the attack of ·OH on the P–O–C bonds, leading to the successive breakage of the three P–O–C bonds in TCPP to produce PO43?. In the second pathway, a C–Cl bond in part of the TCPP molecule was oxidized by SO4·? to carbonyl and carboxyl groups. The P–O–C bonds continued to react with ·OH to produce PO43?. Finally, the intermediate organochloride products were further reductively dechlorinated by ZVI. However, the synergistic effect of the oxidation (·OH and SO4·?) and the reduction reaction (ZVI) did not completely degrade TCPP to CO2, resulting in a low mineralization rate (35.87%). Moreover, the intermediate products still showed the toxicities in LD50 and developmental toxicant. In addition, the method was applied for the degradation of TCPP in soil, and high degradations (>?83.83%) were achieved in different types of soils. 相似文献
17.
Purpose Gamma ray irradiation is considered as an effective way to degrade diclofenac. However, due to the extensive coexisting substances
in natural waters, the use of gamma ray irradiation for degradation is often influenced by multiple factors. The various factors
that affect degradation efficiency, such as initial diclofenac concentration, initial pH, and the concentration of the additives
including H 2O 2 (·OH radical promoter), CH 3OH (·OH radical scavenger), thiourea (·OH, H·, and e aq− scavenger), humic acid, and NO 3− (coexisting substances in natural waters), are investigated. Furthermore, possible intermediate products are identified and
corresponding transformation pathways are proposed. 相似文献
18.
During the summertime of 2007/2008, carbon dioxide (CO 2) and methane (CH 4) fluxes across air–water interface were investigated in the littoral zones of Lake Mochou and Lake Tuanjie, east Antarctica, using a static chamber technique. The mean fluxes of CO 2 and CH 4 were ?70.8 mgCO 2 m ?2 h ?1 and 144.6 μgCH 4 m ?2 h ?1, respectively, in the littoral zone of Lake Mochou; The mean fluxes were ?36.9 mgCO 2 m ?2 h ?1 and 109.8 μgCH 4 m ?2 h ?1, respectively, in the littoral zone of Lake Tuanjie. Their fluxes showed large temporal and spatial dynamics. The CO 2 fluxes showed a significantly negative correlation with daily total radiation (DTR) and a weakly negative correlation with air temperature and water temperature, indicating that sunlight intensity controlled the magnitude of CO 2 fluxes from the open lakes. The CH 4 fluxes significantly correlated with local air temperature, water table and total dissolved solids (TDS), indicating that they were the predominant factors influencing CH 4 fluxes. Summertime CO 2 budgets in the littoral zones of Lake Mochou and Lake Tuanjie were estimated to be ?152.9 gCO 2 m ?2 and ?79.7 gCO 2 m ?2, respectively, and net CH 4 emissions were estimated to be 312.3 mgCH 4 m ?2 and 237.2 mgCH 4 m ?2, respectively. Our results show that shallow, open, alga-rich lakes might be strong summertime CO 2 absorbers and small CH 4 emitters during the open water in coastal Antarctica. 相似文献
19.
The effects of elevated CO 2 on metal species and mobility in the rhizosphere of hyperaccumulator are not well understood. We report an experiment designed to compare the effects of elevated CO 2 on Cd/Zn speciation and mobility in the rhizosphere of hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii grown under ambient (350 μl l ?1) or elevated (800 μl l ?1) CO 2 conditions. No difference in solution pH of NHE was observed between ambient and elevated CO 2 treatments. For HE, however, elevated CO 2 reduced soil solution pH by 0.22 unit, as compared to ambient CO 2 conditions. Elevated CO 2 increased dissolved organic carbon (DOC) and organic acid levels in soil solution of both ecotypes, but the increase in HE solution was much greater than in NHE solution. After the growth of HE, the concentrations of Cd and Zn in soil solution decreased significantly regardless of CO 2 level. The visual MINTEQ speciation model predicted that Cd/Zn–DOM complexes were the dominant species in soil solutions, followed by free Cd 2+ and Zn 2+ species for both ecotypes. However, Cd/Zn–DOM complexes fraction in soil solution of HE was increased by the elevated CO 2 treatment (by 8.01 % for Cd and 8.47 % for Zn, respectively). Resin equilibration experiment results indicated that DOM derived from the rhizosphere of HE under elevated CO 2 (HE-DOM-E) (90 % for Cd and 73 % for Zn, respectively) showed greater ability to form complexes with Cd and Zn than those under ambient CO 2 (HE-DOM-A) (82 % for Cd and 61 % for Zn, respectively) in the undiluted sample. HE-DOM-E showed greater ability to extract Cd and Zn from soil than HE-DOM-A. It was concluded that elevated CO 2 could increase the mobility of Cd and Zn due to the enhanced formation of DOM–metal complexes in the rhizosphere of HE S. alfredii. 相似文献
20.
以模拟污水处理厂污泥厌氧消化液为处理对象,进行磷酸钙沉淀除磷小试实验,考察了不同Ca/P物质的量比下碳酸根(CO2-3)对磷酸钙沉淀反应回收磷的影响;利用扫描电镜(SEM)、X射线衍射仪(XRD)和傅里叶变换红外光谱(FTIR)对沉淀产物进行表征。结果表明,磷酸钙沉淀反应是一个快速过程,CO2-3的存在并未改变这一显著特征。磷酸钙沉淀反应过程中,CO2-3的存在降低了磷的去除率,改变了沉淀物形貌、结构和组分;实验设定范围内,磷酸钙的过饱和度越高,越难形成晶体态羟基磷灰石((Ca5(PO4)3OH,HAP);当pH值为9.0,Ca/P比为1.67时,CO2-3取代HAP晶格中的PO3-4,形成碳磷灰石(CHAP);当pH值为9.0,Ca/P比为3.33和5.01时,CO2-3和PO3-4之间竞争,形成碳酸钙(CaCO3);增大Ca/P能有效提高磷的去除率,降低CO2-3对磷酸钙沉淀反应的抑制作用,但综合考虑实际效果,选择Ca/P比为3.33作为适宜的反应条件。 相似文献
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