曝气和pH对城市污染河道底泥氮形态的影响

以城市重污染河道表层沉积物为研究对象,采用模拟实验方法,探讨了不同曝气方式(水曝气和泥曝气)、上覆水初始pH(自然状态pH=7和pH=11)对城市污染河道底泥氮形态的影响。结果表明:采用水曝气+pH11方式对城市重污染河道上覆水、间隙水中总氮去除率分别为70.03%和44.66%;泥曝气+pH7方式对上覆水、间隙水、底泥中氨氮去除率分别为94.31%、84.07%和68.29%;底泥pH与上覆水总氮浓度呈正相关(p<0.05);泥曝气+pH11方式使底泥含水率、烧失率明显升高,继而影响各形态氮在泥水系统中的赋存,其中底泥吸附态氨氮含量与底泥含水率呈显著负相关(p<0.01),间隙水可溶态氨氮浓度与底泥烧失率显著正相关(p<0.01)。     

电解法去除重污染河水中的磷

近年来,河流污染严重,严重影响了社会的发展,治理河水污染成为目前急需解决的问题。研究了石墨-铁板电极电解法对城市内河中重污染水体中磷去除的可行性;分析了静置时间、电解时长、初始磷浓度、电压、pH及极板间距对电解法除磷效果的影响,确定了电解法处理重污染水体的最佳运行参数,比较了电解法处理实际河水和模拟河水的TP去除效果。结果表明,重污染河流水体中的磷在较短时间内可以得到去除,在静置时间为3 h,电压为10 V,极板间距为1.5cm,pH保持在中性或弱酸性,电解时长在10~15 min时,TP去除率达到90%以上。同时,在最佳运行条件下,电解法处理实际河水效果较好。     

Characteristics of single atmospheric particles in a heavily polluted urban area of China: size distributions and mixing states

To investigate the chemical composition, size distribution, and mixing state of aerosol particles on heavy pollution days, single-particle aerosol mass spectrometry was conducted during 9–26 October 2015 in Xi’an, China. The measured particles were classified into six major categories: biomass burning (BB) particles, K-secondary particles, elemental carbon (EC)–related particles, metal-containing particles, dust, and organic carbon (OC) particles. BB and EC-related particles were the dominant types during the study period and mainly originated from biomass burning, vehicle emissions, and coal combustion. According to the ambient air quality index, two typical episodes were defined: clean days (CDs) and polluted days (PDs). Accumulation of BB particles and EC-related particles was the main reason for the pollution in Xi’an. Most types of particle size were larger on PDs than CDs. Each particle type was mixed with secondary species to different degrees on CDs and PDs, indicating that atmospheric aging occurred. The mixing state results demonstrated that the primary tracers were oxidized or vanished and that the amount of secondary species was increased on PDs. This study provides valuable information and a dataset to help control air pollution in the urban areas of Xi’an.

Graphical abstract

     

Agricultural ammonia emissions inventory and spatial distribution in the North China Plain

An agricultural ammonia (NH₃) emission inventory in the North China Plain (NCP) on a prefecture level for the year 2004, and a 5 × 5 km² resolution spatial distribution map, has been calculated for the first time. The census database from China's statistics datasets, and emission factors re-calculated by the RAINS model supported total emissions of 3071 kt NH₃-N yr⁻¹ for the NCP, accounting for 27% of the total emissions in China. NH₃ emission from mineral fertilizer application contributed 1620 kt NH₃-N yr⁻¹, 54% of the total emission, while livestock emissions accounted for the remaining 46% of the total emissions, including 7%, 27%, 7% and 5% from cattle, pigs, sheep and goats, and poultry, respectively. A high-resolution spatial NH₃ emissions map was developed based on 1 × 1 km land use database and aggregated to a 5 × 5 km grid resolution. The highest emission density value was 198 kg N ha⁻¹ yr⁻¹.     

Evaluation of effluent toxicity and ambient toxicity in a polluted lowland river

The impact of an industrial effluent containing high loads of calcium, cadmium, lead chloride and sulphate, on a river ecosystem was assessed using a combination of an effluent toxicity test, an ambient toxicity test and an ecological survey. Only this combination of techniques made it possible to discriminate between the effects of the discharge and those of the background pollution. Each of the individual techniques detected essential effects which the other failed to reveal. With the physical and chemical measurements, important increases of several components were measured at all sampling sites downstream of the discharge. With the ecological survey, however, no large changes in water quality could be determined at the sampling sites, due to the high degree of pollution present upstream of the discharge. Reproduction of Daphnia magna, exposed to sublethal effluent dilutions, was followed over two generations. The offspring of the first generation were shown to have an increased sensitivity to the effluent, compared to the first generation that was born from previously unexposed mothers. Besides the toxicity of the effluent, the acute and chronic toxicity of its main component, CaCl(2), was also determined. The results of the CaCl(2)-tests and toxicity data from literature for the suspected toxicants were transformed to Toxic Units (TU). Using the sum of the TUs we investigated the possibility of predicting effluent toxicity to Daphnia magna. Effluent toxicity was under-estimated by calculating the sum of the TUs of the individual components. Dilution of the effluent to a level at which the measured toxicant concentrations comply with European regulations still showed significant effects on Daphnia reproduction.     

Evaluation of polluted urban river water quality: a case study of the Xunsi River watershed,China

Environmental Science and Pollution Research - Urbanization has caused severe negative impacts on intra-urban river water bodies. In this paper, 22 physicochemical parameters were measured at 20...     

Tolerance to trichlorophenols in microorganisms from a polluted and a pristine site of a river

The effect of 2,4,5- and 2,4,6-trichlorophenol on the microbiota from a polluted and a pristine site of a river was studied. Bacterial metabolic activity measurements by epifluorescence microscopy showed that the polluted site contained more metabolically active cells than the pristine site. Total culturable bacterial counts and tolerant bacterial counts from both sites were not affected by incubation (for up to 5 days) with 200 ppm of chlorophenols. However, the incubation with 500 ppm of 2,4,5-trichlorophenol prevented detection of total and tolerant bacterial counts in the pristine site, and inhibited tolerants in the polluted site. None of 250 bacterial colonies directly isolated from these samples was able to grow on chlorophenols. However, bacteria able to grow on 2,4,6-trichlorophenol, were obtained by enrichment of water and sediments samples.     

Prioritisation of organic contaminants in a river basin using chemical analyses and bioassays

Region-specific contaminant prioritisation is an important prerequisite for sustainable and cost-effective monitoring due to the high number of different contaminants that may be present. Surface water and sediment samples from the Sava River, Croatia, were collected at four locations covering a 150-km-long river section characterised by well-defined pollution gradients. Analysis of contaminant profiles along the pollution gradients was performed by combining toxicity screening using a battery of small-scale or in vitro bioassays, which covered different modes of action, with detailed chemical characterisation based on gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). A large number of contaminants, belonging to different toxicant classes, were identified in both analysed matrices. Analyses of water samples showed that contaminants having polar character occurred in the highest concentrations, while in sediments, contributions from both non-polar and amphiphilic contaminants should be taken into account. Estimated contributions of individual contaminant classes to the overall toxicity indicated that, besides the classical pollutants, a number of emerging contaminants, including surfactants, pharmaceuticals, personal care products and plasticizers, should be taken into consideration in future monitoring activities. This work demonstrates the importance of the integrated chemical and bioanalytical approach for a systematic region-specific pollutant prioritisation. Finally, the results presented in this study confirm that hazard assessment in complex environmental matrices should be directed towards identification of key pollutants, rather than focusing on a priori selected contaminants alone.     

Retrospective analysis of the age at death in two heavily polluted and two unpolluted Russian towns

Mean age at death during 1981-1999 was recorded in four small industrial towns located in the Kola Peninsula, north-western Russia. Two of these towns (Nikel and Monchegorsk) are heavily contaminated by sulphur dioxide and toxic metals (primarily Ni, Cu, Cd) emitted by large nickel-copper smelters; two other towns (Apatity and Polyarnye Zori) are nearly unpolluted. The results did not support the hypothesis that human life span is significantly shorter in the contaminated communities; moreover, mean age at death was lowest in Polyarnye Zori, the town not polluted by either sulfur dioxide or heavy metals but located close to the nuclear power plant. It seems that the impact of hazards other than pollution (both social and environmental), which are common for the populations of the investigated towns, shorten the life span so much that the contribution of pollutants to the decline in life expectancy cannot be detected. However, the relative importance of the life-shortening diseases associated with pollution may increase with the (expected) improvement of the quality of life.     

Temporal variations of benthic diatom community and its main influencing factors in a subtropical river, China

Benthic diatoms are the main component in many aquatic ecosystems such as streams, creeks and rivers, and they function as important primary producers and chemical modulators for other organisms in the ecosystems. In this study, the composition of benthic diatoms was investigated and further explored the primary physicals and chemicals affecting their temporal variations in the upper Han River, China. There were seasonal variations in physical and chemical variables in waters over the sampling period of 2007–2010. Water temperature (t), chemical oxygen demand, total nitrogen, dissolved organic carbon (DOC), silica and fluoride were much higher in the high flow season (i.e., July or August) than these in the base flow season. Three species Achnanthidium minutissimum (composed of 10.7 % of the total diatom abundance), Achnanthidium pyrenaicum (11.9 %), and Achnanthidium subatomus (12.7 %) accounting for more than 5 % of the total diatom abundance were persistently dominant in all seasons, while the other two prostrate and motile species including Eolimna minima and Nitzschia dissipata also dominant in the base flow season. The species richness always peaked in autumn with significant difference with summer (p?<?0.01), and density of benthic diatom varied and peaked in April. Analyses indicated that the temporal variation in benthic diatom communities was strongly related to t, nitrogen, organic pollutants (indicated by COD and DOC), and hydrological regime. The research will expand the understanding of water chemistry monitoring, and improve watershed- scale management and conservation efforts in the upper Han River, China.     

Height growth of different European Scots pine Pinus sylvestris L. Provenances in a heavily polluted and a control environment

Results are presented of height measurements and degree of needle injury on five-year-old plants of Scots pine (Pinus sylvestris L.) growing near a phosphate fertiliser plant that emits SO(2) and fluorides. The populations of Scots pine represented in this experiment originate from 11 countries and were substantially differentiated in height growth and extent of needle necroses. Those populations which grew most rapidly were found to be the most sensitive to pollutant injury. The least productive provenances from the north of the range (Sweden, USSR) are at the same time characterized by lowest decline in height growth, lowest mortality and least extensive necroses. It is proposed that gene banks be established for the best genotypes likely to be eliminated in the heavily polluted conditions of Poland today.     

Mass balance modelling of contaminants in river basins: a flexible matrix approach

A novel and flexible approach is described for simulating the behaviour of chemicals in river basins. A number (n) of river reaches are defined and their connectivity is described by entries in an n x n matrix. Changes in segmentation can be readily accommodated by altering the matrix entries, without the need for model revision. Two models are described. The simpler QMX-R model only considers advection and an overall loss due to the combined processes of volatilization, net transfer to sediment and degradation. The rate constant for the overall loss is derived from fugacity calculations for a single segment system. The more rigorous QMX-F model performs fugacity calculations for each segment and explicitly includes the processes of advection, evaporation, water-sediment exchange and degradation in both water and sediment. In this way chemical exposure in all compartments (including equilibrium concentrations in biota) can be estimated. Both models are designed to serve as intermediate-complexity exposure assessment tools for river basins with relatively low data requirements. By considering the spatially explicit nature of emission sources and the changes in concentration which occur with transport in the channel system, the approach offers significant advantages over simple one-segment simulations while being more readily applicable than more sophisticated, highly segmented, GIS-based models.     

Water and nitrate fluxes at a forest site in the North Tyrolean Limestone Alps

The water balance for the site Mühleggerköpfl in the North Tyrolean Limestone Alps has been established to a soil depth of 50 cm. The evaporation amounts to 42% and deep percolation is 58 % of the precipitation. The surface runoff was negligible and therefore the according nitrate fluxes as well. Soil water analysis revealed mean nitrate concentrations of 3 to 15 mg NO₃ L⁻¹, depending on soil depth. The nitrate concentrations at 50 cm soil depth and the associated percolation rates led to NO₂ ⁻N outputs of 15.9 kg NO₃ ⁻N ha⁻¹ in the year 1999 and 7.9 kg NO₃ ^∼N ha⁻¹ in the year 2000.

     

Ammonia emissions from different pig production scales and their temporal variations in the North China Plain

ABSTRACT

Pig production systems in China are shifting from small to industrial scale. Significant variation in housing ammonia (NH₃) emissions can exist due to differences in diet, housing design, and management practices. However, there is a knowledge gap regarding the impacts of farm-scale in China, which may be critical in identifying hotspots and mitigation targets. Here, continuous in-situ NH₃ concentration measurements were made at pig farms of different scales for sows and fattening pigs over periods of 3–6 days during two different seasons (summer vs. winter). For the sow farms, NH₃ emission rates were greater at the small farm (summer: 0.52 g pig^?1 hr^?1; winter: 0.21 g pig^?1 hr^?1) than at the large farm (summer: 0.34 g pig^?1 hr^?1; winter: 0.12 g pig^?1 hr^?1). For the fattening pig farms, NH₃ emission rates were greater at the large farm (summer: 0.22 g pig^?1 hr^?1; winter: 0.16 g pig^?1 hr^?1) than at the small farm (summer: 0.19 g pig^?1 hr^?1; winter: 0.07 g pig^?1 hr^?1). Regardless of farm scale, the NH₃ emission rates measured in summer were greater than those in winter; the NH₃ emission rates were greater in the daytime than at the nighttime; a positive relationship (R² = 0.06–0.68) was established between temperature and NH₃ emission rate, whereas a negative relationship (R² = 0.10–0.47) was found between relative humidity and NH₃ emission rate. The effect of farm-scale on indoor NH₃ concentration could mostly be explained by the differences in ventilation rates between farms. The diurnal variation in NH₃ concentration could be partly explained by ventilation rate (R² = 0.48–0.78) in the small traditional farms and by emission rate (R² = 0.26–0.85) in the large industrial farms, except for the large fattening pig farm in summer. Overall, mitigation of NH₃ emissions from sow farms should be a top priority in the North China Plain.

Implications: The present study firstly examined the farm-scale effect of ammonia emissions in the North China Plain. Of all farms, the sow farm was identified as the greatest source of ammonia emission. Regardless of farm scale, ammonia emission rates were observed to be higher in summer. Ammonia concentrations were mostly higher in the large industrial farms partly due to lower ventilation rates than in the small traditional farms.     

High concentrations and dry deposition of reactive nitrogen species at two sites in the North China Plain

Atmospheric concentrations of major reactive nitrogen (N_r) species were quantified using passive samplers, denuders, and particulate samplers at Dongbeiwang and Quzhou, North China Plain (NCP) in a two-year study. Average concentrations of NH₃, NO₂, HNO₃, pNH₄⁺ and pNO₃⁻ were 12.0, 12.9, 0.6, 10.3, and 4.7 μg N m⁻³ across the two sites, showing different seasonal patterns of these N_r species. For example, the highest NH₃ concentration occurred in summer while NO₂ concentrations were greater in winter, both of which reflected impacts of N fertilization (summer) and coal-fueled home heating (winter). Based on measured N_r concentrations and their deposition velocities taken from the literature, annual N dry deposition was up to 55 kg N ha⁻¹. Such high concentrations and deposition rates of N_r species in the NCP indicate very serious air pollution from anthropogenic sources and significant atmospheric N input to crops.     

受污染城市河道沉积物磷吸附特征及其影响因素

采集了典型受污染城市河道——陕西省新河不同季节的沉积物,研究其磷吸附特征及影响因素,并考察其缓冲外源污染的能力,评估其磷释放风险。结果显示,沉积物平均粒径在秋季小于夏季和春季,pH为7.64~8.88;沉积物总磷 (TP) 为870~2 173 mg·kg⁻¹;计算了沉积物磷富集系数,明确了新河部分点位为重度污染类型。吸附动力学研究结果表明：0~2 h沉积物对磷的吸附量在正负之间波动;2~4 h吸附量迅速增加,吸附速率也达到了峰值;之后吸附量增加趋势变缓,并在48 h达到平衡。绘制吸附等温线,可知沉积物的磷吸附-解吸平衡质量浓度 (EPC₀) 为0.39~2.21 mg·L⁻¹,高于同时段上覆水中磷的质量浓度,具有释放风险;磷最大缓冲容量MBC和Freundlich常数K_F呈现秋季>>夏季>春季的规律;经D-R模型拟合,绝大多数样品的吸附能为8.45~11.18 kJ·mol⁻¹,说明吸附机制为离子交换。相关性分析结果表明,沉积物的磷吸附速率常数与钙的相对含量呈显著相关 (P<0.05) 。EPC₀与沉积物的总磷和易释放态磷含量呈显著相关 (P<0.01) ,与沉积物平均粒径和有机质显著相关 (P<0.05) ,与pH显著相关 (P<0.05) 。本研究结果可为受污染城市河道治理提供参考。     

A review of the export of carbon in river water: fluxes and processes

This review summarizes data on exports of carbon from a large number of temperate and boreal catchments in North America, Europe and New Zealand. Organic carbon losses, usually dominated by dissolved organic matter, show relatively little variation, most catchments exporting between 10 and 100 kg C ha(-1) yr(-1). Inorganic carbon exports occur at a similar rate. However, a lack of information on the flux of particulate organic carbon and dissolved CO2 is highlighted, particularly for rivers in Europe. Processes regulating the flux of organic carbon to streams and its subsequent fate in-stream are reviewed, along with the effects of land use and acidification on these processes. The size of the global riverine flux of carbon in relation to the global carbon cycle and the possible effects of environmental change on the export of carbon in rivers are considered.