Critical loads of acidity for surface waters in China

Various types of partition coefficients have been used to facilitate the prediction of the concentration of pollutants in different phases in the environment. Many thousands of chemicals may exist in our environment which makes prediction work difficult or impossible due to a deficiency of knowledge of those unfamiliar compounds. In this study, the correlation between an octanol-water partition coefficient (Kow), water solubility (S) and a normalized soil/sediment partition coefficient (Koc) was investigated though the examination of 148 model chemicals. These model chemicals were classified into five major categories for easier adoption in future use. They are aliphatic compounds, aromatic compounds, pesticides, herbicides and polyaromatic hydrocarbons (PAH). Linear models are developed to correlate these partition coefficients in each category. The prediction of unfamiliar chemicals in the same category becomes possible if the fundamental properties of these chemicals (such as solubility) are previously known.     

A review of the calculation procedure for critical acid loads for terrestrial ecosystems

Target loads for acid deposition in the Netherlands, as formulated in the Dutch environmental policy plan, are based on critical load calculations at the end of the 1980s. Since then knowledge on the effect of acid deposition on terrestrial ecosystems has substantially increased. In the early 1990s a simple mass balance model was developed to calculate critical loads. This model was evaluated and the methods were adapted to represent the current knowledge. The main changes in the model are the use of actual empirical relationships between Al and H concentrations in the soil solution, the addition of a constant base saturation as a second criterion for soil quality and the use of tree species-dependant critical Al/base cation (BC) ratios for Dutch circumstances. The changes in the model parameterisation and in the Al/BC criteria led to considerably (50%) higher critical loads for root damage. The addition of a second criterion in the critical load calculations for soil quality caused a decrease in the critical loads for soils with a median to high base saturation such as loess and clay soils. The adaptation hardly effected the median critical load for soil quality in the Netherlands, since only 15% of the Dutch forests occur on these soils. On a regional scale, however, critical loads were (much) lower in areas where those soils are located.     

An evaluation of critical loads of soil acidity in areas of high sea salt deposition

The empirical and mass balance approaches to setting critical loads of acidity for mineral soils have been evaluated using field data from forest sites in Wales. Using the Simple Mass Balance Equation (SMBE) with Sitka spruce as the biological target, critical loads ranged between 2.3 and 9.8 keq H+ ha(-1) year(-1) compared to mapped empirical critical loads which ranged between 0.2 and 0.5 keq H+ ha(-1) year(-1). At all sites the empirical critical load was exceeded with respect to deposited sulfur acidity. There were no exceeded sites for the SMBE critical loads. The big differences between the two methods arise from the large ANC leaching term in the SMBE model which is determined by the relatively low (Ca + Mg + K)/Al(crit) ratio for Sitka spruce, compared to other conifers, and the influence of the large deposition of sea salt base cations. The low value of the (Ca + Mg + K)/Al(crit) ratio for Sitka spruce implies that it is tolerant of very acidic soil conditions, however, the ratio is based on the results of only one solution culture study and may thus be uncertain under field conditions. Large sea salt base cation deposition directly influences SMBE critical loads because the predicted soil water base cation concentrations permit large concentrations of hydrogen ions and aluminium (low ANC values) before the critical chemical limit is transgressed. Where weathering rates are low, critical ANC leaching (ANC(lecrit)) becomes the dominant term in the SMBE, with the counter intuitive result that the critical load becomes a linear function of sea salt base cation deposition. Thus the current formulation of the SMBE may not be appropriate for low weathering rate areas receiving large amounts of sea salt base cation deposition.     

K6型单层球面网壳弹塑性稳定极限承载力的杆件灵敏度分析

利用蒙特卡洛模拟技术以及基于Spearman秩相关系数的灵敏度分析方法,对工程常用的16种K6型单层球面网壳进行了参数分析.利用ANSYS进行了64000次双重非线性模拟运算并对计算结果进行了统计分析,得到了其弹塑性稳定极限承载力对于所有杆件的灵敏度值.总结了K6型单层球面网壳不同位置杆件对其弹塑性稳定极限承载力的影响规律,并对计算分析结果进行了验证.     

The fate of metals in Arctic surface waters. Method for defining critical levels.

Based upon studies in the industrially developed Arctic region, Russian Kola, here we discuss the fate of metals in high latitude surface water. Mainly, attention is paid to the priority pollutants from copper-nickel smelters. The influence of accompanying processes, such as acidification and eutrophication, on metal behavior is considered. The dramatic situation for fauna of Arctic latitudes is illustrated: (i) during the snow-melt, due to the pulse of ionic metal forms; and (ii) during the long polar winter in lower water layers, due to the involvement of a wide spectrum of metals in the redox-cycle under eutrophication and oxygen deficiency. Here we identify fish pathologies, which are related to the influence of metals. Generalizing the data on metal behavior, an original approach to define the integrated impact dose of metals--a toxicity index--has been developed. It presents a visualization of the integrated toxicity index for surface waters of the Russian Kola (based on the data for a 460-lake survey). As shown, there is a risk of fish diseases, due to both airborne contamination by metals and an indirect leaching by acid runoff over almost 30% of the area of the Russian Kola. For the Arctic region, polar winter stress syndrome will be repeatedly significant. During the polar night, as well as the spring, the vulnerability of the Arctic biota to toxic impact is higher. The accompaniment of water metal-pollution by two or more stressors would occur simultaneously, thereby multiplying the risk that it could develop.     

Humic acid adsorption and surface charge effects on schwertmannite and goethite in acid sulphate waters

In acid conditions, as in acid mine drainage waters, iron oxide particles are positively charged, attracting negatively charged organic particles present in surrounding natural waters. Schwertmannite (Fe8O8(OH)6SO4) and goethite (alpha-FeOOH) are the most typical iron oxide minerals found in mine effluents. We studied schwertmannite formation in the presence of humic acid. Further, surface charge and adsorption of humic acid on synthetic schwertmannite and goethite surfaces in pH 2-9 and in humic acid concentrations of 0.1-100 mg/L C were examined. Schwertmannite did precipitate despite the presence of humic acid, although it contained more sulphate and had higher specific surface area than ordinary schwertmannite. Specific surface area weighted results showed that schwertmannite and goethite had similar humic acid adsorption capacities. Sulphate was released from schwertmannite surfaces with increasing pH, resulting in an increase in specific surface area. Presence of sulphate in solution decreased the surface charge of schwertmannite and goethite similarly, causing coagulation. In acid conditions (pH 2-3.5), according to the zeta potential, schwertmannite is expected to coagulate even in the presence of high concentrations of humic acid (< or = 100 mg/L C). However, at high humic acid concentrations (10-100 mg/L C) with moderate acid conditions (pH>3.5), both schwertmannite and goethite surfaces are strongly negatively charged (zeta potential < -30 mV) thus posing a risk for colloid stabilization and colloidal transport.     

Limestone neutralization of acid waters in the presence of surface precipitates

Acid waste waters are usually treated by means of lime in order to meet pH requirements for discharge. Considerable saving may be achieved using limestone in neutralization processes.The feasibility of limestone neutralization processes also in those cases where precipitates form both on the reactive surface and in the liquid bulk as pH rises has been evaluated.Experiments were carried out with a well mixed tank reactor contacting limestone with acid solutions containing iron (III) sulphate and sulphuric acid. Analyses for calcium and iron (III) concentrations as well as for CO₂ desorption rate for their changes with time and continuous recording of pH were carried out during each run.The results show that neutrality can be achieved within a few minutes providing the operation conditions ensure a continuous removal of precipitates from the reacting surface.A critical comparison with previous results concerning a similar system containing AlCl₃ and HCl emphasizes the phenomenological differences between the two systems.The kinetic model for limestone dissolution in acid solutions previously developed has been successfully applied to the system studied.     

Monitoring of trifluoroacetic acid concentration in environmental waters in China

It is critically important and extremely meaningful to determine the concentration of TFA in the environmental water in China. This will create background reference for the effects of analyzing the extensive employment of the substitutes to CFCs in China. In this paper a set of analytical methods was described for use in monitoring of trifluoroacetic acid (TFA) concentration of environmental waters including collecting, pre-treatment measures, preserving, concentrating and derivatization of samples from different kinds of environmental waters. The GC with electrical capture detector (ECD) and headspace auto sampler were used in the analysis. The lowest detection limit of the instrument is 0.0004 ng methyl trifluoroacetic acid (MTFA), and the lowest detected concentration with the method is 3.0 ng/ml TFA. TFA collected in various environmental water samples (including rainfall, inland surface water, ground water, and waste water) from nine provinces and autonomous regions in China have been determined by applying the analytical methods created and defined in this work. The results indicate that the concentrations of TFA in nine rainfalls and three snowfalls through the period from 2000 to 2001 ranged from 25 to 220 ng/l, the TFA concentration in the inland surface water samples ranged from 4.7 to 221 ng/l, the concentration of TFA in groundwater samples collected in Beijing was 10 ng/l, and the TFA concentration in coastal water samples ranged from 4.2 to 190.1 ng/l.     

Uncertainties in critical loads and target loads of sulphur and nitrogen for European forests: Analysis and quantification

An analysis of the uncertainties in critical loads and target loads of sulphur (S) and nitrogen (N) for 182 European forest soils was carried out using the Very Simple Dynamic (VSD) model. The VSD model was calibrated with a Bayesian approach using prior probability functions for model parameters based on literature data, data from 200 Dutch forest sites and from simulated denitrification rates from a detailed ecosystem model. The calibration strongly improved the fit of the model to observed soil and soil solution concentrations, especially for pH and base saturation. Calibration also narrowed down the ranges in input parameters. The uncertainty analysis showed which parameters contribute most to the uncertainty in the critical loads and target loads. Base cation weathering and deposition and the parameters describing the H-Al equilibrium in the soil solution determine the uncertainty in the maximum critical loads for S, CL_max(S), when based on the aluminium to base cation (Al/Bc) criterion. Uncertainty in CL_max(S) based on an acid neutralizing capacity (ANC) criterion is completely determined by base cation inputs alone. The denitrification fraction is the most important source of uncertainty for the maximum critical loads of N, CL_max(N). N uptake and N immobilisation determine the uncertainties in the critical load for N as a nutrient, CL_nut(N). Calibration of VSD reduced the uncertainty: the coefficient of variation (CV) was reduced for all critical loads and criteria. After calibration, the CV for CL_max(S) was below 0.4 for almost all plots; however for CL_max(N) high values occurred for plots with high denitrification rates. Model calibration also improved the robustness of target load estimates: after calibration, no target loads were needed in any of the simulations for 40% of the plots, with the uncalibrated model there was a positive probability for the need of a target load for almost all plots.     

Calculating critical loads for acidification for five forested catchments in China using an extended steady state function

The critical load concept has become widely accepted as an important theoretical basis for establishing effective acid deposition control strategies. In the critical load calculations, the influence of variation in base cation (BC) deposition, which plays an important role in mitigating acidification, was seldom considered. In this manner, high uncertainty and over-estimation might be caused in those areas where current BC deposition is very high and of significant anthropogenic origin since anthropogenic deposition can change due to human activity. In this study, an extended sulfur(S)-nitrogen (N)-BC function based on the Steady State Mass Balance (SSMB) method is applied to calculate the critical loads for five sampled catchments in southern China under variable S, N, and BC deposition. The ceiling of S deposition (when N deposition is zero; CL(max)(S)) under current BC deposition varies from 4.5 to 10.8 keq ha(-1) yr(-1) among the five catchments, and the ceiling of N deposition (when S deposition is zero; CL(max)(N)) varies from 23.2 to 54.5 keq ha(-1) yr(-1). A 75% reduction in BC deposition is estimated to cause a 46%-86% decrease of CL(max)(S) and 45%-81% decrease of CL(max)(N). The critical loads for acidification are not exceeded in any of the five catchments under the current base cation deposition, despite extremely high S deposition in some places. However, if the BC deposition decreases to 25% of current while S remains unchanged, critical loads will be exceeded at all sites except one. A sensitivity analysis confirms that the long-term future BC deposition is among the most important parameters to the uncertainty of critical load, together with the dose-response relationship between ecosystem health and soil solution chemistry.     

Pesticides in Portuguese surface and ground waters

Pesticides used in Portuguese agricultural areas have been found in surface and ground waters. In the surface water collected in three river basins from 1983 to 1999, insecticides and herbicides were detected from the monitored pesticides, particularly atrazine, chlorfenvinphos (Z+E), alpha- and beta-endosulfan, lindane, molinate and simazine, reaching the maximum values, respectively, of 0.63, 31.6, 0.18 microg/L (alpha-endosulfan), 0.18 microg/L (beta-endosulfan), 0.24, 48 and 0.3 microg/L. In the ground water collected from the wells of seven agricultural areas from 1991 to 1998, several monitored herbicides were detected: alachlor, atrazine, metolachlor, metribuzine and simazine, reaching the maximum concentration values of 13, 30, 56, 1.4 and 0.4 microg/L, respectively. The herbicides more frequently detected were atrazine (64%), simazine (45%) and alachlor (25%). Other than these, the monitored pesticides can be present in Portuguese surface and ground waters. Therefore, to improve the analytical conditions, the use of multiresidue methods and automated techniques are desirable in future work.     

动力敏感性结构风荷载全阶概率分析方法

高层建筑主体结构设计风荷载受来流风速的方向性影响较为明显,传统风荷载估算方法偏于保守。为此,提出一种考虑风向的风荷载全阶概率分析方法,基于可靠度理论将单风向的风荷载概率分布表达成风荷载效应系数极值和来流风速极值的概率分布函数。为了计入结构动力敏感性的影响,基于风洞试验获得的结构气动力数据,通过对结构动力响应分析,将风荷载效应系数极值的概率分布参数表达成来流风速的函数,进而结合各个风向的风荷载概率分布数据,给出了动力敏感性结构具有一定保证率的风荷载。最后,将所提方法的计算结果与蒙特卡洛模拟方法和传统方法的计算结果进行了详细对比。结果表明,本文方法计算结果与蒙特卡洛方法模拟结果吻合较好,传统的最不利荷载法和风向折减方法计算结果过于保守。     

Modeling copper partitioning in surface waters

Suspended particulate matter from the surface waters of the Susquehanna, Christina and Brandywine Rivers was collected by tangential flow filtration to study copper partitioning. Copper adsorption increased with an increase of suspended particles and decreased with low pH values or with an increase of dissolved organic matter. Effects of particulate organic matter on copper distribution between suspended particulate and solution phases were studied using modified aluminum oxide. An increase of particulate organic matter enhanced copper adsorption. Copper adsorption per mass of particulate organic carbon was similar for the different sources of suspended particles. A model, based on copper adsorption on particles and complexation with dissolved organic matter, was developed to assess copper partition coefficient as a function of the easily measurable water quality parameters: pH, alkalinity, dissolved organic carbon and particulate organic matter. The partitioning model was calibrated on pH edge data using suspended particles collected from the three rivers. The model was verified using partitioning data as a function of dissolved organic matter. The model adequately describes the system containing natural suspended solids collected from the surface waters.     

Perfluorinated compounds in surface waters and WWTPs in Shenyang, China: mass flows and source analysis

Concentrations of 10 perfluorinated chemicals (PFCs) were investigated in the Hun River (HR), four canals, ten lakes, and influents and effluents from four main municipal wastewater treatment plants (WWTPs) in Shenyang, China. Mass flows of four main PFCs were calculated to elucidate the contribution from different sections of the HR. Overall, perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were the major PFCs in the HR, with ranges of 2.68-9.13 ng/L, and 2.12-11.3 ng/L, respectively, while perfluorooctane sulfonate (PFOS) was detected at lower levels, ranging from 0.40 to 3.32 ng/L. The PFC concentrations in the HR increased after the river passes through two cities (Shenyang and Fushun), indicating cities are an important contributor for PFCs. Mass flow analysis in the HR revealed that PFC mass flows from Fushun are 1.65-5.50 kg/year for C6-C8 perfluorinated acids (PFCAs) and 1.29 kg/year for PFOS, while Shenyang contributed 2.83-5.18 kg C6-C8 PFCAs/year, and 3.65 kg PFOS/year. The concentrations of PFCs in four urban canals were higher than those in the HR, with the maximum total PFCs of 240 ng/L. PFOA and PFOS showed different trends along these canals, suggesting different sources for the two PFCs. Total PFCs in ten lakes from Shenyang were at low levels, with the greatest concentration (56.2 ng/L) detected in a heavily industrialized area. The PFC levels in WWTP effluents were higher than those in surface waters with concentrations ranging from 18.4 to 41.1 ng/L for PFOA, and 1.69-3.85 ng/L for PFOS. Similar PFC profiles between effluents from WWTPs and urban surface waters were found. These results indicate that WWTPs are an important PFC source in surface water. Finally, we found that the composition profiles of PFCs in surface waters were similar to those in tap water, but not consistent with those in adult blood from Shenyang. The calculation on total daily intake of PFOS by adults from Shenyang showed that the contribution of drinking water to human exposure was minor.     

Distributions of polycyclic aromatic hydrocarbons in surface waters, sediments and soils of Hangzhou City, China

Ten polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in 17 surface water samples and 11 sediments of four water bodies, and 3 soils near the water-body bank in Hangzhou, China in December 2002. It was observed that the sum of PAHs concentrations ranged from 0.989 to 9.663 microg/L in surface waters, from 132.7 to 7343 ng/g dry weight in sediments, and from 59.71 to 615.8 ng/g dry weight in soils. The composition pattern of PAHs by ring size in water, sediment and soil were surveyed. Three-ring PAHs were dominated in surface waters and soils, meanwhile sediments were mostly dominated by four-ring PAHs. Furthermore, PAHs apparent distribution coefficients (K(d)) and solid f(oc)-normalized K(d) (e.g. K(oc)= K(d) / f(oc)) were calculated. The relationship between logK(oc) and logK(ow) of PAHs for field data on sediments and predicted values were compared. The sources of PAHs in different water bodies were evaluated by comparison of K (oc) values in sediments of the river downstream with that in soils. Hangzhou section of the Great Canal was heavily polluted by PAHs released from industrial wastewater in the past and now PAHs in sediment may serve as sources of PAHs in surface water. PAHs in Qiantang River were contributed from soil runoff. Municipal road runoff was mostly contributed to West Lake PAHs.     

Aromatic amines in surface waters of The Netherlands

The results of a monitoring program with respect to aniline, chloroanilines, dichloroanilines and 2- and 4-methylaniline in Dutch rivers are presented. The results cover the year 1979. The aromatic amines were determined individually after bromination using a specific gas chromatographic method. Aniline, 2-, 3- and 4-chloroaniline, 3,4-dichloroaniline and 4-methylaniline had the highest frequencies of occurrence in the river Rhine and its tributaries. Aniline was found in the highest concentrations (up to 12 μg l⁻¹).The results of a sampling trip by boat in 1974 made along the river Rhine from Rheinfelden in Switzerland to Rotterdam in the Netherlands are also given. The sums of aromatic amines and their derivatives were determined colorimetrically.     

Occurrence of herbicide oxadiazon in surface waters and tap water

Occurrence of oxadiazon, 2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ²-1,3,4-oxadiazolin-5-one, in surface waters and tap water was investigated. At the Tonda Reservoir site, oxadiazon residue was usually detected. The maximum concentration was observed in August. After that, the concentrations gradually reduced. At the Higashitani, Nishitani and Murasaki River sites, high concentrations of oxadiazon residue were immediately detected after beginning of rice seedling transplantation, and rapidly reduced. The residue levels were between 0.001 and 1.953 ppb. However, oxadiazon residue at the Onga River site was detected over a long period in comparison with other river sites, and also observed in May. The concentration of oxadiazon residue in tap water was ranged about 3–23% of that in raw water.     

Exposure and risk assessment of zinc in Japanese surface waters

In recent years, due to concerns on the potential effects of zinc on aquatic biota, zinc is receiving particular attention from regulatory agencies. A comprehensive exposure and risk assessment of zinc in Japanese surface waters was conducted to provide a scientific basis for developing realistic risk reduction measures for zinc. Emissions from corrosion contribute approximately 37% of the total zinc emissions to surface water in Japan. The zinc concentration distributions estimated using 12 years of monitoring data from 2075 sites by a maximum likelihood method indicated that the mean concentrations have gradually declined. The threshold concentrations (HC5 and PHC5) derived from organism- and population-level species sensitivity distributions were estimated to be 27 and 107 μg/L for total zinc, respectively. The risk characterization identified that during 1991-2002, 14.5-26.8% of the monitoring sites likely exceeded the HC5, whereas only 0.7-3.5% likely exceeded the PHC5. Evaluation of the effect of stormwater runoff to zinc concentrations in a river showed that zinc concentrations in river water increased significantly from roadway drainage flowing into the river. The cost-effectiveness analyses demonstrated that enforcement of the zinc national effluent standard may be effective at a certain level for public water areas in Japan; however, the degree of the effectiveness is highly dependent on the characteristics (e.g., sources and background) of the watersheds. An emissions and exposure assessment along with cost-effectiveness analysis is crucial for developing realistic and appropriate ecological risk management of zinc. The zinc RAD in Japan illustrated that in any “state-of-the science” method used, some degree of ecological risk from zinc can be observed in some Japanese water environments. On the other hand, zinc is a beneficial material for human industrial activities. Because zinc is an element, its role in industrial activities would be difficult to be substituted by other metals with less toxicity. In addition to improving science-based risk assessment methodologies which often focus on the toxicological perspectives, it is important to develop a more robust framework considering a trade-off between a damage in ecosystem and a benefit in human activities. Zinc can be a role model for it.     

Calculation and mapping of critical loads of sulfur and nitrogen in Flanders, Belgium

Up to now, critical loads calculations for the Flemish Region were based on European background data of surrounding countries. A first attempt has been made to calculate and map critical loads for forest ecosystems in Flanders using available site-specific information. Values of current deposition were used to calculate and map exceedances. The lowest critical loads for acidification (697 eq ha(-1)year(-1)) occur in the Campine and the north of Limburg where ecosystems largely consist of coniferous forests on poor sandy soils. The dominance of coniferous forest types in the Campine is also responsible for low critical load values for eutrophication (between 536 and 971 eq ha(-1)year(-1)). In 75% of the receptor points that have been considered an exceedance of the critical load for acidification is noted, primarily in areas with high SO2 and NOx depositions, such as the north of the provinces East and West Flanders and Antwerp. The critical load for eutrophication is exceeded in all points considered. Exceedances are particularly high in coniferous forests in West Flanders, and in the north of the provinces of Antwerp and Limburg, where especially NHx depositions amount to high values. Data needed for the calculation of critical loads are still sparse in Flanders, e.g. for: (1) weathering rates of soil minerals; (2) interception and evaporation of forest ecosystems; and (3) uptake of N and basic cations by vegetation. This supplementary information will contribute to a further refining of the calculated critical loads, which constitute indispensable information in developing an emission abatement policy.     

Load duration effects in wood members and connections order statistics and critical loads

Load duration behavior, arising from creep-rupture, is one of the most significant effects distinguishing wood materials from other structural materials. The phenomenon of creep-rupture has been widely studied over the past two decades. Recent experimental programs have focused on duration-of-load (DOL) effects in full-size lumber and a number of different cumulative damage models have been proposed. These models have been used in reliability analyses that take into account the stochastic nature of the loading process to evaluate appropriate load duration adjustment factors for use in design. More recently, the stochastic damage accumulation process itself has been investigated. This has resulted in proposals for simplified cumulative damage analyses and the re-emergence of the ‘killer pulse’ concept for load duration effects in wood. Other recent studies have focused on evaluating analogous load–time effects in mechanical connections in wood. While the mechanisms in connections are recognized as different from those in wood members, the treatment of time effects in design are (at least at the present time) similar. With the tendency toward engineered design of wood structures subject to natural hazards loadings, such as wind and seismic loads, load duration effects in both the primary framing members and the structural connections may be of particular importance. The evolution of the new LRFD standard for wood provides a good opportunity to re-visit this important issue. This paper will briefly review DOL research, with particular emphasis on the work used as the basis for the time effects factors in the LRFD standard, and describe some recent work in (a) a simplified approach to cumulative damage analysis using order statistics, and (b) load–time effects in simple wood connections. It is shown that reliability analyses including DOL behavior can be performed more simply (efficiently) using an order statistics approach or even a simple FORM analysis. Thus, it may be possible to evaluate load duration factors for design without having to perform complex stochastic cumulative damage analyses.