上海大气氮湿沉降的污染特征

为探讨上海大气氮湿沉降的污染特征,采集了2007年11月至2008年10月上海雨水样品,分析了大气氮湿沉降浓度,探讨了上海大气湿沉降氮通量及上海市区,市郊和远郊大气氮湿沉降的时空污染特征.结果表明:(1)上海市区、市郊和远郊大气氮湿沉降质量浓度平均值分别为2.96、2.31、2.21 mg/L.从上海大气湿沉降总体来看,大气氮湿沉降劣V类、V类的超标率分别达到51.09%和13.87%.推断大气氮湿沉降的主要来源是机动车辆所排放的大量氮氧化物.(2)除冬季外,其余季节上海市区大气氮湿沉降浓度均大于市郊和远郊;市区和远郊大气氮湿沉降浓度均在秋季最大,市郊大气氮湿沉降浓度在春季最大.(3)上海大气年氮湿沉降通量为78.42 kg/hm~2,同其他区域相比较,属于世界上高氮沉降区域.(4)上海大气月氮沉降通量与月平均降雨量呈显著的线性正相关(p<0.05),说明上海大气氮湿沉降通量主要受降雨量的影响.     

邯郸市大气氮干湿沉降通量及其特征

为研究大气降尘对土壤、水体等环境介质中氮的贡献,在邯郸市区设置3个大气干湿沉降采样点,并进行了为期1年的监测。根据监测数据分析了氮干湿沉降通量、氮形态及随季节的变化。结果显示,监测期内3个采样点的全年平均氮干沉降通量为385.2kg/km~2,湿沉降通量为2 292.5kg/km~2,总沉降通量为2 677.7kg/km~2。氮沉降以湿沉降为主,占总沉降通量的85.6%。氮湿沉降通量与降雨量线性相关(R~2=0.87),各采样点的降雨量和氮湿沉降主要集中在4—8月。氮干沉降与降尘量均随季节变化,总的来说冬春季开始增长,夏季降低,到了初秋又开始增长,并在10月达到峰值。不论是干沉降还是湿沉降,各监测点氮形态都是以有机氮为主,硝酸盐氮次之,氨氮所占比例最低。     

城市湖泊总磷对干湿沉降和地表径流污染的响应研究

随着对水污染的深入治理，干湿沉降、地表径流等面源污染逐步成为城市湖泊最重要的污染源之一。通过对武汉市东湖流域连续4个月干湿沉降和2场次地表径流的监测，分析了湖泊水体总磷(TP)对干湿沉降和地表径流污染的响应。结果表明，东湖湿沉降TP累积通量远大于干沉降TP累积通量，这可能与降水的洗尘作用有关；低强度降雨地表径流TP质量浓度为0.74～1.59 mg/L,高强度降雨地表径流TP质量浓度为0.95～5.82 mg/L,初期地表径流TP浓度大于后期地表径流；湖泊TP浓度变化与风速、湿沉降TP通量、降雨量紧密相关，当降雨量小于20 mm时，风速是造成湖泊中TP变动的主要因素之一，当降雨量超过20 mm时，湖泊TP变化与湿沉降TP通量变化较为一致。点源污染防治与大气污染治理、城市道路清洁、城市绿化、沉水植物生态恢复等的协调治理，将是未来城市湖泊TP污染防治的重要途径。     

珠江口大气氮磷干湿沉降通量及其污染特征

为准确核定入海污染负荷和系统实施入海污染物总量控制,观测了珠江口地区大气氮磷的干湿沉降通量,并分析了其时空变异规律、化学组成特征以及主要的影响因素。结果显示,珠江口地区大气总氮和总磷的平均月沉降通量分别约为299.00、4.12kg/km2,其中湿沉降通量占总沉降通量的60%以上。干沉降和湿沉降通量均表现出明显的时空变异规律,前者的季节性变化主要受农业活动氮磷挥发的影响,而后者与年内降雨量分布以及季风作用下降雨云团来源的关系更为密切;沉降负荷的空间分布规律基本与不同区域受人类活动影响的特点相一致。由于不同污染来源和季风气候的影响,氮沉降化学组成的季节差异特征也较为明显,氨氮在秋冬季沉降中所占的比例明显高于春夏季,而有机氮则与之相反。     

重庆西部农业区大气沉降特征及其对地表的影响

从2009年4月至2010年4月,在重庆西部农业区采集了50个大气干、湿沉降样品,分别测试干、湿沉降样品中K、Ca、Mg、N、P、S、Fe、As、Cd、Cr、Cu、Hg、Ni、Zn、Pb、B、Mo、Mn 18种元素的含量,计算各元素的年沉降通量。研究发现,重庆西部农业区各元素年沉降通量均低于重庆主城区和成都经济区。采用富集因子分析得出,S、Cd、N、Pb、P、Hg、Mo、Zn、Cr、As明显受人为活动影响,其中S、Hg、As、Pb是典型的燃煤元素,Cd、Cr、Zn主要来源于工业排放、汽车尾气等,N、P与农业施肥密切相关。相关性分析表明,大气沉降输入Hg引起土壤中Hg含量显著增加,大气沉降输入S引起地表水中SO2-4浓度显著升高。     

西安市城区持久性有机污染物的干湿沉降

为了确定大气干湿沉降中持久性有机污染物的主要特征及干、湿沉降对大气中污染物去除的相对贡献,选择西安市城区为研究对象,于2014年4—10月在东、西、南、北各区域的一环路和二环路均设采样点,共采集了302个大气干、湿沉降样品。降雨样品经过液液萃取,降尘样品经过超声萃取,使用气相色谱法测定了36种POPs的含量,仅PCB157未检出。结果表明,干、湿沉降样品POPs沉降通量分别为458.78 kg/a和1846.90 kg/a,其中的多环芳烃(PAHs)、多氯联苯(PCBs)和有机氯农药(OCPs)分别占总量的47%~77%、16%~42%和5%~12%。就POPs的空间分布而言,南郊北郊东郊西郊,大气中POPs主要由燃油污染贡献。就POPs的存在特征而言,降雨降尘径流,湿沉降是大气环境中POPs的主要排除方式。经SPSS分析晴天数、TOC与POPs的相关性得到r0.7,因此晴天数和TOC是大气中POPs干湿沉降的主要影响因素。     

太湖西岸水质变化趋势及主要驱动因子

基于2009—2015年太湖西岸10个监测断面的8个水质指标数据,采用季节性Kendall检验法对其指标的浓度变化趋势进行分析,并用主成分分析法结合相关分析评价历年水质状况,分析影响太湖西岸水质的主要驱动因子。结果表明:(1)2009—2015年太湖西岸COD下降趋势显著,DO非显著上升,电导率、高锰酸盐指数、BOD5、氨氮、TP和TN均表现为高度显著下降趋势。(2)主成分分析从原始信息中提取出两个主成分,共解释了73.645%的结果,分别代表水质氮磷营养盐和有机污染。综合得分表明,2009—2015年太湖西岸水质呈逐年改善趋势。水质污染在空间上表现为北部向南部递减的趋势。(3)相关分析表明,氨氮和COD是影响该区域水质的主要驱动因子。     

南宁市郊空气和大气干湿沉降物中多环芳烃的污染特征

采用空气被动采样器和大气干湿采样器分夏、冬季采集大气及其干湿沉降物样品,利用气相色谱-质谱联用仪测定16种多环芳烃(PAHs)优先控制污染物。结果表明:冬、夏季大气干湿沉降物中PAHs的平均值分别为581.06、174.59ng/(m2·d),冬季PAHs的组成以2～3环PAHs为主,夏季以4～6环PAHs为主;冬、夏季空气中PAHs的平均值分别为149.16、168.70ng/d,均以2～3环PAHs为主。大气干湿沉降物PAHs的沉降通量时空变化为:冬季,商住文教混合区农业区工业区;夏季,工业区农业区商住文教混合区;冬季大于夏季3.3倍。空气PAHs沉降通量的时空变化为:冬季,工业区商住文教混合区农业区;夏季,农业区工业区商住文教混合区;冬季略低于夏季。     

积雪中氮、磷污染物浓度及其垂直分布特征

分别于2014、2015年采集合肥市区两场典型降雪雪样,对地面积雪按每层1cm进行分层收集,同时采集整体雪样,测定雪样中TN、氨氮、TP和COD。采用一次线性方程对积雪层自下而上方向上对污染物浓度进行趋势拟合。结果表明:(1)积雪层中TN和氨氮按自下而上的方向浓度的线性变化趋势为逐层递减的变化趋势,而TP和COD在积雪中的垂直变化特征不明显。(2)2014、2015年合肥市区两场降雪积雪中的氮、磷污染物主要以TN污染为主,分别为《地表水环境质量标准》(GB 3838—2002)Ⅲ类和劣Ⅴ类水平。与中国其他地区的湿沉降相比,合肥市区降雪积雪中氮、磷污染物浓度基本相近。     

风浪扰动对太湖梅梁湾水体总磷变化的驱动模式研究

风浪扰动下的底泥再悬浮是浅水湖泊水体底泥内源性磷向水体释放的关键驱动因子。水体总磷(TP)受底泥内源磷释放过程影响频繁波动。基于风浪扰动强度与底泥悬浮物(SS)浓度定量关系模型,采用太湖原位未扰动柱状底泥开展水体底泥再悬浮过程模拟研究,分别模拟在小风(搅拌强度100～125 r/min)、大风(搅拌强度200～220 r/min)模式下底泥内源释放过程,探究风浪扰动对太湖梅梁湾水域TP浓度波动的贡献。结果表明,风浪扰动显著增加(P<0.01)了水体SS,小风与大风下水体SS均值分别增加了80.9%与360.8%,但随着扰动周期的延长,风浪扰动的效果会削弱。不同风浪扰动强度下水体TP均呈先上升后下降趋势。小风下水体TP为0.08～0.20 mg/L;大风下水体TP为0.09～0.34 mg/L。与对照组相比,小风组水体TP浓度呈现显著下降的趋势(P<0.05),而大风组水体TP浓度则表现为显著上升的趋势(P<0.01)。此外,大风持续扰动增加了水体TP浓度,但效果不显著(P>0.05)。风浪扰动致使0～3 cm底泥内的TP含量有所提高,底泥表面氧化还原条件的改变是...     

The impact of nitrogen deposition on acid grasslands in the Atlantic region of Europe

A survey of 153 acid grasslands from the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is changing plant species composition and soil and plant-tissue chemistry. Across the deposition gradient (2-44 kg N ha⁻¹ yr⁻¹) grass richness as a proportion of total species richness increased whereas forb richness decreased. Soil C:N ratio increased, but soil extractable nitrate and ammonium concentrations did not show any relationship with nitrogen deposition. The above-ground tissue nitrogen contents of three plant species were examined: Agrostis capillaris (grass), Galium saxatile (forb) and Rhytidiadelphus squarrosus (bryophyte). The tissue nitrogen content of neither vascular plant species showed any relationship with nitrogen deposition, but there was a weak positive relationship between R. squarrosus nitrogen content and nitrogen deposition. None of the species showed strong relationships between above-ground tissue N:P or C:N and nitrogen deposition, indicating that they are not good indicators of deposition rate.     

Determination of atmospheric nitrogen input to Lake Greenwood, South Carolina: part 2--Gaseous measurements and modeling

The Reedy River branch of Lake Greenwood, SC, has repeatedly experienced summertime algal blooms, upsetting the natural system. A series of experiments were carried out to investigate atmospheric nitrogen (N) input into the lake. N was examined because of the insignificant phosphorus dry atmospheric flux and the unique nutrient demands of the dominant algae (Pithophora oedogonia) contributing to the blooms. Episodic atmospheric measurements during January and March 2001 have shown that the dry N flux onto the lake ranged from 0.9 to 17.4 kg N/ha-yr, and on average is caused by nitric acid (HNO3; 31%), followed by nitrogen dioxide (NO2; 23%), fine ammonium (NH4+; 20%), coarse nitrate (NO3-; 16%), fine NO3 (5%), and coarse NH4+ (5%). Similar measurements in Greenville, SC (the upper watershed of the Reedy River), showed that the dry N deposition flux there ranged from 1.4 to 9.7 kg N/ha-yr and was mostly caused by gaseous deposition (40% NO2 and 40% HNO3). The magnitude of this dry N deposition flux is comparable to wet N flux as well as other point sources in the area. Thermodynamic modeling showed low concentrations of ammonia, relative to the particulate NH4+ concentrations.     

Preliminary measurements of summer nitric acid and ammonia concentrations in the Lake Tahoe Basin air-shed: implications for dry deposition of atmospheric nitrogen

Over the past 50 years, Lake Tahoe, an alpine lake located in the Sierra Nevada mountains on the border between California and Nevada, has seen a decline in water clarity. With significant urbanization within its borders and major urban areas 130 km upwind of the prevailing synoptic airflow, it is believed the Lake Tahoe Basin is receiving substantial nitrogen (N) input via atmospheric deposition during summer and fall. We present preliminary inferential flux estimates to both lake surface and forest canopy based on empirical measurements of ambient nitric acid (HNO3), ammonia (NH3), and ammonium nitrate (NH4NO3) concentrations, in an effort to identify the major contributors to and ranges of atmospheric dry N deposition to the Lake Tahoe Basin. Total flux from dry deposition ranges from 1.2 to 8.6 kg N ha-1 for the summer and fall dry season and is significantly higher than wet deposition, which ranges from 1.7 to 2.9 kg N ha-1 year-1. These preliminary results suggest that dry deposition of HNO3 is the major source of atmospheric N deposition for the Lake Tahoe Basin, and that overall N deposition is similar in magnitude to deposition reported for sites exposed to moderate N pollution in the southern California mountains.     

Nitrogen content, 15N natural abundance and biomass of the two pleurocarpous mosses Pleurozium schreberi (Brid.) Mitt. and Scleropodium purum (Hedw.) Limpr. in relation to atmospheric nitrogen deposition

The suitability of the two pleurocarpous mosses Pleurozium schreberi and Scleropodium purum for assessing spatial variation in nitrogen deposition was investigated. Sampling was carried out at eight sites in the western part of Germany with bulk deposition rates ranging between 6.5 and 18.5 kg N ha(-1) yr(-1). In addition to the effect of deposition on the nitrogen content of the two species, its influence on 15N natural abundance (delta15N values) and on productivity was examined. Annual increases of the mosses were used for all analyses. Significant relationships between bulk N deposition and nitrogen content were obtained for both species; delta15N-values reflected the ratio of NH4-N to NO3-N in deposition. A negative effect of nitrogen input on productivity, i.e. decreasing biomass per area with increasing N deposition due to a reduction of stem density, was particularly evident with P. schreberi. Monitoring of N deposition by means of mosses is considered an important supplement to existing monitoring programs. It makes possible an improved spatial resolution, and thus those areas that receive high loads of nitrogen are more easily discernible.     

Can the foliar nitrogen concentration of upland vegetation be used for predicting atmospheric nitrogen deposition? Evidence from field surveys

The deposition of atmospheric nitrogen can be enhanced at high altitude sites as a consequence of cloud droplet deposition and orographic enhancement of wet deposition on hills. The degree to which the increased deposition of nitrogen influences foliar nitrogen concentration in a range of upland plant species was studied in a series of field surveys in northern Britain. A range of upland plant species sampled along altitudinal transects at sites of known atmospheric nitrogen deposition showed marked increases in foliar nitrogen concentration with increasing nitrogen deposition and altitude (and hence with decreasing temperature). For Nardus stricta L., Deschampsia flexuosa (L.) Trin., Calluna vulgaris (L.) Hull, Erica cinerea L. and Hylocomium splendens (Hedw.) Br. Eur. on an unpolluted hill, foliar nitrogen increased by 0.07, 0.12, 0.15, 0.08 and 0.04% dry weight respectively for each 1 kg ha(-1) year(-1) increase in nitrogen deposition. Most species showed an approximately linear relationship between foliar nitrogen concentration and altitude but no trend with altitude for foliar phosphorus concentration. This provided evidence that the tissue nutrient status of upland plants reflects nutrient availability rather than the direct effects of climate on growth. However, differences in the relationship between foliar nitrogen concentration and atmospheric nitrogen deposition for N. stricta sampled on hills in contrasting pollution climates show that the possibility of temperature-mediated growth effects on foliar nitrogen concentration should not be ignored. Thus, there is potential to use upland plant species as biomonitors of nitrogen deposition, but the response of different species to nitrogen addition, in combination with climatic effects on growth, must be well characterised.     

Atmospheric deposition and canopy exchange processes in heathland ecosystems

The aims of the present study were to determine canopy exchange processes and to quantify total atmospheric deposition of sulphur and nitrogen in heathland. The study was carried out in dry inland heath vegetation, dominated by Calluna vulgaris, in two nature reserves in the eastern part of the Netherlands. Atmospheric deposition was determined with throughfall-stemflow measurements, adapted for low vegetation. Throughflow measurements (sum of throughfall and stemflow) in artificial Calluna canopies showed co-deposition of SOx and NHy upon heathland vegetation. In the real Calluna canopy, a significant part of the deposited ammonia/ammonium was directly assimilated by the Calluna shoots, especially in wet periods. The concentrations of potassium, calcium and magnesium in throughflow, after passage through the Calluna canopy, increased significantly compared with bulk precipitation. The amount of cations lost from the canopy were in good agreement with the observed ammonium uptake by the Calluna. A field experiment demonstrated that losses of the above-mentioned cations can be doubled by application of ammonium sulphate. It was shown that interception deposition is an important component of the atmospheric deposition of sulphur and nitrogen upon Calluna heathland; bulk precipitation amounted to only c. 35-40% of total atmospheric input. Total atmospheric deposition of sulphur and nitrogen in the investigated heathlands was 1.5-2.1 (27-33 kg S ha(-1) yr(-1)) and 2.1-3.1 kmolc ha(-1) yr(-1) (30-45 kg N ha(-1) yr(-1)), respectively. It is concluded that the present atmospheric nitrogen deposition is a continuous threat for the existence of heathlands in Western Europe.     

Lichen-based critical loads for atmospheric nitrogen deposition in Western Oregon and Washington Forests, USA

Critical loads (CLs) define maximum atmospheric deposition levels apparently preventative of ecosystem harm. We present first nitrogen CLs for northwestern North America’s maritime forests. Using multiple linear regression, we related epiphytic-macrolichen community composition to: 1) wet deposition from the National Atmospheric Deposition Program, 2) wet, dry, and total N deposition from the Communities Multi-Scale Air Quality model, and 3) ambient particulate N from Interagency Monitoring of Protected Visual Environments (IMPROVE). Sensitive species declines of 20-40% were associated with CLs of 1-4 and 3-9 kg N ha⁻¹ y⁻¹ in wet and total deposition. CLs increased with precipitation across the landscape, presumably from dilution or leaching of depositional N. Tight linear correlation between lichen and IMPROVE data suggests a simple screening tool for CL exceedance in US Class I areas. The total N model replicated several US and European lichen CLs and may therefore be helpful in estimating other temperate-forest lichen CLs.     

Deposition of fixed atmospheric nitrogen and foliar nitrogen content of bryophytes and Calluna vulgaris (L.) Hull

Atmospheric deposition of fixed nitrogen as nitrate and ammonium in rain and by dry deposition of nitrogen dioxide, nitric acid and ammonia has increased throughout Europe during the last two decades, from 2-6 kg N ha(-1) year(-1) to 15-60 kg N ha(-1) year(-1). The nitrogen contents of bryophytes and the ericaceous shrub Calluna vulgaris have been measured at a range of sites, with the objective of showing the degree to which nitrogen deposition is reflected in foliar plant nitrogen. Tissue nitrogen concentrations of herbarium bryophyte samples and current samples of the same species collected from the same sites were compared. No significant change in tissue nitrogen was recorded at a remote site in north-west Scotland where nitrogen inputs are small (< 6 kg N ha(-1) year(-1)). Significant increases in tissue N occurred at four sites ranging from 38% in central Scotland to 63% in Cumbria where nitrogen inputs range from 15 to 30 kg N ha(-1) year(-1). The relationships found between the estimated input of atmospheric nitrogen and the tissue nitrogen content of the selected bryophytes and Calluna at the sites investigated were found to be generally linear and fitted the form N(tissue) = 0.62 + 0.022 N(dep) for bryophytes and N(tissue) = 0.83 + 0.045 N(dep) for Calluna. There was thus an increase in total tissue nitrogen of 0.02 mg g(-1) dry weight for bryophytes and 0.045 mg g(-1) dry weight for Calluna for an increase in atmospheric nitrogen deposition of 1 kg ha(-1) year(-1). The lowest concentrations were found in north-west Scotland and the highest in Cumbria and the Breckland heaths of East Anglia, both areas of high atmospheric nitrogen deposition (30-40 kg N ha(-1) year(-1)). The implications of increased tissue nitrogen content in terms of vegetation change are discussed. Changes in atmospheric nitrogen deposition with time were also examined using measured values and values inferred from tissue nitrogen content of mosses. The rate of increase in nitrogen deposition is not linear over the 90-year period, and the increases were negligible over the period 1880-1915. However, during the period 1950 to 1990 the data suggest an increase in nitrogen deposition of 2 kg N ha(-1) every 10 years.     

Preliminary study of phosphorus runoff and drainage from a paddy field in the Taihu Basin

An investigation into phosphorus runoff and drainage from a paddy field was carried out at Changshu Agricultural Ecological Station of CAS during the year 2000. According to the preliminary study, some results indicated: (1) Total phosphorus (TP) content of regular irrigation water was 19 times higher than TP content of P0 (zero rate of P fertilization) stand water. This indicates that paddy fields are a potential source of phosphorus pollution by runoff and drainage into the Taihu Lake Basin (TLB); (2) During the first 10 days after phosphate fertilizer application, the TP concentration of stand water in the paddy field was very high, therefore this was the high risk period for Taihu Lake phosphorus contamination; (3) Four mathematical models of P losses from a paddy field in the TLB are developed. These are based on data for the year 2000, but they will be improved as more data is acquired in future years.