Modelling recovery from soil acidification in European forests under climate change

A simple soil acidification model was applied to evaluate the effects of sulphur and nitrogen emission reductions on the recovery of acidified European forest soils. In addition we included the effects of climate change on soil solution chemistry, by modelling temperature effects on soil chemical processes and including temperature and precipitation effects on nitrogen uptake and on leaching. Model results showed a strong effect of the emission reduction scenarios on soil solution chemistry. Using the Current Legislation (CLE) scenario, the forest area in Europe with soil solution Al/Bc >1 mol mol^− 1 (a widely used critical limit) decreased from about 4% in 1990 to about 1.7% in 2050. Under Maximum Feasible Reductions (MFR), the exceeded area will be < 1% in 2050. In addition, the area where limits for the nitrate concentration in soils are violated is predicted to be smaller under MFR than under CLE. Using the most stringent criterion for nitrate ([NO₃] <0.3 mg l^− 1), the area with nitrate concentrations in excess of the critical limit is about 33% in 2050 under CLE, but only 12% under MFR. Recovery, i.e. attaining non-violation of the criterion, is also much faster under MFR than under CLE. Climate change leads to higher weathering rates and nitrogen uptake in the model, but positive effects on recovery from acidification are limited compared to current climate, and differences between the A1 and B2 climate change scenarios were small. Target loads for 2050 exist for 4% of the area for Al/Bc = 1 and for 12% of the area when using a criterion of ANC = 0 for the soil solution. In about 30% of the area where meaningful target loads exists, the computed target load is lower than the deposition under MFR, and thus cannot be attained with current emission abatement technologies.     

Removal of organic acids by activated sludges

Removal of coexisted volatile organic acids was studied using three kinds of activated sludges; treated with sewage, digested night soil and undiluted night soil at the plant scale and laboratrial experiment. Concentration of volatile fatty acids in sewage were too low to be detected, meanwhile 5–28 ppm of acetic acid were detected in influent of aeration tank of digested night soil treatment plant, and 1335–5340 ppm of acetic acid were detected in night soil. Removal rates of acetic acid were 35.9 mg g⁻¹ h⁻¹ by sewage activated sludge, 33.6 mg g⁻¹ h⁻¹ by digested night soil activated sludge and 16.9 mg g⁻¹ h⁻¹ by undiluted night soil activated sludge under coexisting volatile fatty acids. This difference depends on the number of bacteria in the activated sludge. Dissimilation percentage of acetic, propionic, butyric and valeric acids were similar results in these activated sludges.     

Climate variability and forecasting surface water recovery from acidification: modelling drought-induced sulphate release from wetlands

Climate-induced drought events have been shown to have a significant influence on sulphate (SO(4)(2-)) export from forested catchments in central Ontario, subsequently delaying recovery of surface waters from acidification. Field and modelling studies have demonstrated that water table drawdown during drought periods promotes oxidation of previously stored (reduced) sulphur (S) compounds in wetlands, with subsequent efflux of SO(4)(2-) upon re-wetting. Although climate-induced changes in processes are generally not integrated into soil-acidification models, MAGIC (Model of Acidification of Groundwater in Catchments) includes a wetland compartment that incorporates redox processes driven by drought events. The potential confounding influence of climate-induced drought events on acidification recovery at Plastic Lake, south-central Ontario (under proposed future S emission reductions) was investigated using MAGIC and two climate scenarios: monthly precipitation and runoff based on long-term means (average-climate scenario), and variable precipitation and runoff based on the past 20 years of observed monthly data (variable-climate scenario). The variable-climate scenario included several periods of summer drought owing to lower than average rainfall and higher then average temperature. Nonetheless, long-term regional trends in precipitation and temperature suggest that the variable-climate scenario may be a conservative estimate of future climate. The average-climate scenario indicated good recovery potential with acid neutralising capacity (ANC) reaching approximately 40 micromol(c)L(-1) by 2020 and 50 micromol(c)L(-1) by 2080. In contrast, the forecasted recovery potential under the variable-climate scenario was very much reduced. By 2080, ANC was forecasted to increase to 2.6 micromol(c)L(-1) from -10.0 micromol(c)L(-1) in 2000. Elevated SO(4)(2-) efflux following drought events (introduced under the variable-climate scenario) has a dramatic impact on simulated future surface water chemistry. The results clearly demonstrate that prediction of future water quality, using models such as MAGIC, should take into account changes or variability in climate as well as acid deposition.     

Quantifying the effects of forestry practices on the recovery of upland streams and lochs from acidification

Trends in long-term chemistry data are presented for 37 acidified upland streams and lochs, located in four areas (A, B, C and D) across Scotland, to provide a comparison between recovery rates of moorland catchments and forest catchments at different stages of the management cycle. For all sites, non-marine sulfate (nm-SO(4)) showed a significant decline in annual median concentrations, the greatest decline being in streams draining felled catchments, which showed a 50% greater decline than catchments with moorland or young, aggrading forests. A similar pattern was found for chloride (Cl) concentrations in Area C, which reflected the reduced interception of sea-salt aerosols following clearfelling. However, high elevation moorland sites in Area D also revealed significant declines in Cl while trends in aggrading forest sites in this area were insignificant. Alkalinity (ALK) and pH increased more at sites where felling had taken place than at moorland or young forest sites while aggrading forest catchments appeared to be most resistant to changes in pH and ALK. Associated with these acid-base changes was a corresponding decline in labile aluminium (Al-L) concentrations. The pattern of nitrate (NO(3)) change was especially affected by the timing of felling in forested catchments. Large negative trends in NO(3) at stream sites were associated with felling during the early part of the study period. This downward trend was further enhanced as NO(3) concentrations fell below pre-felling levels as the second rotation crop became established. Few forest sites showed significant increases in NO(3) due to felling in the latter part of the study period. Most moorland loch sites showed a small but significant increase in NO(3,) probably in response to similar increases in N deposition and/or climatic impacts. Dissolved organic carbon (DOC) increased significantly at both forest and moorland sites, however, the extent of these increasing trends appeared to be positively correlated with absolute DOC concentrations. Despite the complex response of streams and lochs during the various stages of the forest cycle, especially for NO(3), both forest and moorland catchments showed generally similar and rapid responses to reductions in S deposition. Nevertheless, forested sites are still more acid and have higher concentrations of toxic forms of Al than moorland sites. Although the proposed emission reductions in Europe are likely to result in a continuing decline in S and N loadings to catchments, the continuing policy of planting second rotation forests in these acidified catchments may, in the long-term, delay or halt chemical and biological recovery. However, in the short-term, any increase in the uptake of N deposition by aggrading forests should help to counteract the acidifying effects of a small increase in the interception of S and N compounds.     

Fate of organic matter during natural and anthropogenic lake acidification

In Groβer Arbersee, a cirque lake in the Bavarian Forest (Germany), the acidification chronology since the late-glacial period has been studied paleolimnologically, applying subfossil diatom assemblages. Distinct phases of acidification could be detected, both natural ones by post-glacial development of soils and vegetation in the catchment and anthropogenic ones by mineral acid depositions. Whereas the first phases were accompanied (and most probably caused as well) by increases in organic carbon contents, the recent phases are characterized by losses of organic carbon contents in the lake.

In various sensitive lakes in Central Europe the fate of organic carbon (measured as loss on ignition) is documented for the anthropogenic acidification period. In lowland as well as in high alpine lakes this process is accompanied by loss of organic carbon. These losses are by no means uniform. On the contrary, they range between 10 and 90% per drop of one pH-unit, in each lake calculated from estimated preacidification pH-conditions.     

Decreasing DOC trends in soil solution along the hillslopes at two IM sites in southern Sweden--geochemical modeling of organic matter solubility during acidification recovery

Numerous studies report increased concentrations of dissolved organic carbon (DOC) during the last two decades in boreal lakes and streams in Europe and North America. Recently, a hypothesis was presented on how various spatial and temporal factors affect the DOC dynamics. It was concluded that declining sulphur deposition and thereby increased DOC solubility, is the most important driver for the long-term DOC concentration trends in surface waters. If this recovery hypothesis is correct, the DOC levels should increase both in the soil solution as well as in the surrounding surface waters as soil pH rises and the ionic strength declines due to the reduced input of SO₄²⁻ ions. In this project a geochemical model was set up to calculate the net humic charge and DOC solubility trends in soils during the period 1996-2007 at two integrated monitoring sites in southern Sweden, showing clear signs of acidification recovery. The Stockholm Humic Model was used to investigate whether the observed DOC solubility is related to the humic charge and to examine how pH and ionic strength influence it. Soil water data from recharge and discharge areas, covering both podzols and riparian soils, were used. The model exercise showed that the increased net charge following the pH increase was in many cases counteracted by a decreased ionic strength, which acted to decrease the net charge and hence the DOC solubility. Thus, the recovery from acidification does not necessarily have to generate increasing DOC trends in soil solution. Depending on changes in pH, ionic strength and soil Al pools, the trends might be positive, negative or indifferent. Due to the high hydraulic connectivity with the streams, the explanations to the DOC trends in surface waters should be searched for in discharge areas and peat lands.     

Mutagenicity and organic solute recovery from water with a high-volume resin concentrator

The high-volume sampler achieves an average 70% organic removal with four 1150 ml columns, from a 100–2001, waste-water or potable water sample pumped at 200 ml min⁻¹ and 8000–10,000 kN m⁻². Sample elution yields composite resin concentrates which are mutagenic to Salmonella typhimurium strains TA98 and TA100. No mutagenicity is observed in concentrator effluents or in blanks between samples. The main advantage of the resin concentrator is in savings of time and solvent for a large sample volume. Recoveries of spikes of compounds taken from the EPA priority pollutant list are reported.     

Vulnerability of organic acid tolerant wetland biota to the effects of inorganic acidification

Inland waterbodies are often naturally acidic but are these ecosystems pre-adapted to inorganic acidification e.g., by acid sulfate soils (ASS)? We conducted a controlled mesocosm experiment with inorganically acidified wetland water and wetland sediment replicates to pH 3 from a naturally acidic (pH 3.9, conductivity = 74 µS cm^− 1) wetland in south-western Australia. Following acidification, dissolved organic carbon and nitrogen declined, and chlorophyll a dropped to zero. Inorganic acidification mobilised metals from sediment sods with increased water concentrations of Cu, Fe, Mn, Ca, Mg and Al. Acidification showed no significant effect on diatom assemblage. Nonetheless, greatly reduced abundance and diversity of grazing zooplankton was observed. Macroinvertebrates generally showed abundance decreases, although filterer-collector taxa increased. Decreased primary production reduced functional diversity and consumer biomasses. These results suggest likely impact to ecosystem functioning of low pH, weakly-buffered and stained wetlands if exposed to inorganic acidification.     

Pilot scale mineralization of organic acids by electro-Fenton process plus sunlight exposure

The viability of the electro-Fenton degradation of aqueous solutions of benzoic acid, 2,4-dichlorophenoxyacetic acid and oxalic acid has been studied at 20 A using a pilot flow reactor containing an anode and an oxygen diffusion cathode, both of 100 cm(2) section. Pollutants were preferentially oxidized by hydroxyl radicals formed in solution from reaction of Fe(2+) with electrogenerated H(2)O(2), allowing mineralization of benzoic acid and 2,4-D. For oxalic acid no electrochemical mineralization was observed. After electrolysis, samples of the different effluents were exposed to sunlight (Helielectro-Fenton process) and almost complete mineralization was reached after ca. 30-50 min without additional cost. Effects of parameters such as electrolysis time, pH and solar irradiation time on the process efficiencies were studied.     

Separation of selective organic acids from wastewater through a polyol supported liquid membrane

Pesticide toxicity databases usually include data on pure chemicals (active ingredients). Technical pesticides formulations, however, are mixtures with adjuvants as applied to fields/crops. Two formulations of the same pesticide can differ in their environmental fate and their toxicity. This work presents the evaluation of the toxicity of the dinitroaniline herbicide, pendimethalin by simultaneous analysis of its respiration rate and generation of a membrane potential (Δ Ψ) in rat liver mitochondria. Chromatography grade pendimethalin (8.2·10^?5 ‐ 5.47·10^?4 M or 23 – 154 ppm) caused lower enhancement of the mitochondrial respiration and decrease of the Δ Ψ than technical grade pendimethalin (Stomp), i.e. the mixture of pure ingredient and adjuvant(s). These effects are comparable to those of 2,4‐dinitrophenol. Pure and technical grade pendimethalin acts as an uncoupler of oxidative phosphorylation in mitochondria (enhances respiration and diminishes Δ Ψ). These data conflict with the statement, presented in the US EPA manual Recognition and Management of Pesticides Poisonings, that pendimethalin does not act as an uncoupler of oxidative phosphorylation.     

Supreme双管喉罩与气管插管在妇科腹腔镜手术麻醉中的比较

目的:比较Supreme双管喉罩与气管插管在妇科腹腔镜手术麻醉中的应用效果。方法:择期妇科腹腔镜手术患者60例,按照随机双盲原则分为Supreme双管喉罩组(S组)和气管插管组(T组),经静脉麻醉诱导后,记录两组插入喉罩(导管)成功率、肺通气情况;记录插入前(T_1)、插入即刻(T_2)、插入后2 min(T_3)、拔除喉罩(拔管)前(T_4)、拔除即刻(T_5)、拔除后3 min(T6)的HR、SBP、DBP;监测气道峰压(Pmax)、气道平台压(Pmean)、Sp O2、PETCO2;苏醒期躁动、术后呛咳、咽喉痛、声嘶等并发症。结果:两组患者的年龄、身高、体重、手术时间、麻醉时间、拔管(罩)时间比较,差异均无统计学意义(P>0.05);两组插入成功率均为100%;诱导前后两组SBP、DBP和HR比较,差异均无统计学意义(P>0.05);与T组比较,S组置入喉罩或拨除喉罩后,即在T_2、T_3、T_5、T6时HR较慢,SBP、DBP较低,差异均有统计学意义(P<0.05);两组Pmax、Pmean、PETCO2值各时点比较,差异均无统计学意义(P>0.05);与T组比较,S组苏醒期呛咳、术后声嘶、咽喉痛发生率均较低,差异均有统计学意义(P<0.05);S组胃管放置顺利,成功率为100%,气道密封压(25±4)cm H2O,两组均未发生返流、误吸。结论:妇科腹腔镜手术中Supreme双管喉罩可以达到与气管插管相同的安全有效的通气效果,并且对血流动力学影响小,不良反应少。     

Cleaning strategies for flux recovery of an ultrafiltration membrane fouled by natural organic matter

One of the most common problems encountered in water treatment applications of membranes is fouling. Natural organic matter (NOM) represents a particularly problematic foulant. Membranes may be fouled by relatively hydrophilic and/or hydrophobic NOM components, depending on NOM characteristics, membrane properties, and operating conditions. To maximize flux recovery for an NOM-fouled ultrafiltration membrane (NTR 7410), chemical cleaning and hydraulic rinsing with a relatively high cross-flow velocity were investigated as cleaning strategies. The modification of the membrane surface with either an anionic or a cationic surfactant was also evaluated to minimize membrane fouling and to enhance NOM rejection. Foulants from a hydrophobic NOM source (Orange County ground water (OC-GW)) were cleaned more effectively in terms of permeate flux by acid and caustic cleanings than foulants from a relatively hydrophilic NOM source (Horsetooth surface water (HT-SW)). An anionic surfactant (sodium dodecyl sulfate (SDS)) was not effective as a cleaning agent for foulants from either hydrophobic or hydrophilic NOM sources. High ionic strength cleaning with 0.1 M NaCl was comparatively effective in providing flux recovery for NOM-fouled membranes compared to other chemical cleaning agents. Increased cross-flow velocity and longer cleaning time influenced the efficiency of caustic cleaning, but not high ionic strength cleaning. The membrane was successfully modified only with the cationic surfactant; however, enhanced NOM rejection was accompanied by a significant flux reduction.     

Precipitation recovery of boron from wastewater by hydrothermal mineralization

It is well known that boric acid exhibits various toxic effects on plant, animal and human beings even at very low concentrations. Thus, the development of boron-removal technique from wastewater has been intensively investigated. In this study, a new hydrothermal treatment technique was developed to recover boron as recyclable precipitate Ca(2)B(2)O(5).H(2)O from aqueous solutions. As a result, it was found that the hydrothermal treatment using calcium hydroxide as a mineralizer converted boron in the aqueous media effectively into calcium borate, Ca(2)B(2)O(5).H(2)O. In the optimal hydrothermal condition, more than 99% of boron was collected from the synthetic wastewater of 500 ppm. Thus, the present hydrothermal treatment in the presence of calcium hydroxide is recommended as one of the effective techniques to recover boron from aqueous media.     

CO_2酸化海水淡化水接触式矿化研究

针对海水淡化水存在着较强的腐蚀性且缓冲能力低等问题,开展了采用CO2酸化淡化水后溶解方解石的矿化实验,研究了CO2通量、水力停留时间、温度及跌宕对海水淡化水的矿化水质影响。结果表明,在CO2与淡化水的体积比为1/5,水力停留时间为15 min,温度为33℃时,矿化后的海水淡化水的Ca2+含量达到37 mg/L以上,Ca CO3碱度达到67 mg/L以上,矿化后的淡化水经过跌宕能大幅提高其p H值,使最终矿化出水水质具有很好的稳定性。     

Cosorption of organic contaminants from water by hexadecyltrimethylammonium-exchanged clays

The characteristics of organoclays as sorbents for neutral organic contaminants (NOCs) in aqueous systems containing multiple solutes were evaluated by measuring the sorption of trichloroethylene on hexadecyltrimethylammonium (HDTMA) exchanged illite and smectite in the absence and presence of carbon tetrachloride, nitrobenzene and ethyl ether. Trichloroethylene partitioned into HDTMA-derived phases present on the external surfaces of the clay particles manifesting type III isotherms. Carbon tetrachloride functioned to increase the solvency of the external HDTMA phase, and hence enhanced sorption of trichloroethylene. Nitrobenzene solvated HDTMA resulting in a more vertical orientation of the C-16 alkyl chains and interlayer expansion. This rendered the interlamellar region of HDTMA-smectite accessible for trichloroethylene sorption, and nitrobenzene sorption simultaneously increased the solvency of HDTMA phase for trichloroethylene. Ethyl ether sorption suppressed the uptake of trichloroethylene by decreasing the solvency of HDTMA phase for trichloroethylene. Sorption of trichloroethylene also facilitated sorption of carbon tetrachloride and nitrobenzene. The results suggest that multiple organic compounds generally produce a synergistic effect on the uptake of NOCs from water by HDTMA-clays, and support multiple mechanisms controlling the sorption process.     

Nutrient removal and recovery from wastewater by ion exchange

After about 500 cycles have been continuously performed on a laboratory pilot plant, ion exchange resins have proved to be an effective means to treat municipal secondary effluents to prevent eutrophication in the receiving water bodies. Clinoptilolite, a natural zeolite, and Kastel A 510, a strong base anion resin with adsoptive properties, act selectively to remove ammonium and phosphate ions, at the same time affording filtration and adsorption of the wastewater. NaCl at sea-water concentration is used as resin regenerant. After the recovery of products of fertilizing value, as MgNH₄PO₄ and NH₄ NO₃, from the eluates, the latter can be recycled.     

Effect of short-chain organic acids on the enhanced desorption of phenanthrene by rhamnolipid biosurfactant in soil-water environment

This study investigated the effect of short-chain organic acids on biosurfactant-enhanced mobilization of phenanthrene in soil-water system. The desorption characteristics of phenanthrene by soils were assessed in the presence of rhamnolipid and four SCOAs, including acetic acid, oxalic acid, tartaric acid and citric acid. The tests with rhamnolipid and different organic acids could attain the higher desorption of phenanthrene compared to those with only rhamnolipid. Among the different combinations, the series with rhamnolipid and citric acid exhibited more significant effect on the desorption performance. The removal of phenanthrene using rhamnolipid and SCOAs gradually increased as the SCOA concentration increased up to a concentration of 300 mmol/L. The effects of pH, soil dissolved organic matter and ionic strength were further evaluated in the presence of both biosurfactant and SCOAs. The results showed that the extent of phenanthrene desorption was more significant at pH 6 and 9. Desorption of phenanthrene was relatively lower in the DOM-removed soils with the addition of biosurfactant and SCOAs. The presence of more salt ions made phenanthrene more persistent on the solid phase and adversely affected its desorption from contaminated soil. The results from this study may have important implications for soil washing technologies used to treat PAH-contaminated soil and groundwater.     

Removal of non-biodegradable organic matter from landfill leachates by adsorption

Leachates produced at the La Zoreda landfill in Asturias, Spain, were recirculated through a simulated landfill pilot plant. Prior to recirculation, three loads of different amounts of Municipal Solid Waste (MSW) were added to the plant, forming in this way consecutive layers. When anaerobic digestion was almost completed, the leachates from the landfill were recirculated. After recirculation, a new load of MSW was added and two new recirculations were carried out. The organic load of the three landfill leachates recirculated through the anaerobic pilot plant decreased from initial values of 5108, 3782 and 2560 mg/l to values of between 1500 and 1600 mg/l. Despite achieving reductions in the organic load of the leachate, a residual organic load still remained that was composed of non-biodegradable organic constituents such as humic substances. Similar values of the chemical oxygen demand (COD) were obtained when the landfill leachate was treated by a pressurised anoxic-aerobic process followed by ultrafiltration. After recirculation through the pilot plant, physico-chemical treatment was carried out to reduce the COD of the leachate. The pH of the leachate was decreased to a value of 1.5 to precipitate the humic fraction, obtaining a reduction in COD of about 13.5%. The supernatant liquid was treated with activated carbon and different resins, XAD-8, XAD-4 and IR-120. Activated carbon presented the highest adsorption capacities, obtaining COD values for the treated leachate in the order of 200mg/l. Similar results were obtained when treating with activated carbon, the leachate from the biological treatment plant at the La Zoreda landfill; in this case without decreasing the pH.     

Phosphorus recovery from dairy manure wastewater by fungal biomass treatment

Polyphosphate accumulating fungi was cultured to remove and recover the excessive phosphorus from dairy manure wastewater (DMW). The microbial treatment removed 83.9% of phosphorus in 20‐fold diluted DMW by the fungal biomass in 12 h. At the meantime, 33.6% of chemical oxygen demand, 46.5% of total nitrogen, and 89.4% of total ammonia nitrogen were removed as well. At seventh reuse batch, the cells could still remove 50.4% of phosphorus from the diluted wastewater. The average phosphorus removal efficiency in seven reuse batches was calculated as 62.1%, the nitrogen‐to‐phosphorus ratio in DMW increased from 3.6 : 1 to 6.3 : 1. With the treatment, DMW will be more suitable for farmland irrigation, with the better nutritional ratio to support crop growth, and it will help mitigate phosphorus pollution to water bodies caused by over‐applied phosphorus in the farmland.     

Selective optimization in thermophilic acidogenesis of cheese-whey wastewater to acetic and butyric acids: partial acidification and methanation

For partial acidogenesis of cheese-whey wastewater, a set of experiments were carried out to produce short-chain volatile fatty acids (VFA) in laboratory-scale continuously stirred tank reactors (CSTR). The maximum rate of acetic and butyric acid production associated with simultaneous changes in hydraulic retention time (HRT), pH, and temperature was investigated, in which the degree of acidification of the whey to the short-chain VFAs was less than 20% of the influent chemical oxygen demand (COD) concentration. Response surface methodology was successfully applied to determine the optimum physiological conditions where the maximum rates of acetic and butyric acid production occurred. These were 0.40-day HRT, pH 6.0 at 54.1 degrees C and 0.22-day HRT, pH 6.5 at 51.9 degrees C, respectively.The optimum conditions for acetic acid production were selected for partial acidification of cheese-whey wastewater because of a higher rate in combined productions of acetic and butyric acids than that at optimum conditions for butyric acid production. A thermophilic two-phase process with the partial acidification followed by a methanation step was operated. Performance of the two-phase process was compared to the single-phase anaerobic system. The two-phase process clearly showed a better performance in management of cheese-whey wastewater over the single-phase system. Maximum rate of COD removal and the rate of methane production in the two-phase process were, respectively, 116% and 43% higher than those of the single-phase system.