Variability of nitrate concentration in nitrogen-depleted subtropical surface waters

Recent improvements in the analytical determination of nitrate and nitrite allow measurements of nanomolar concentrations in nitrogen-depleted surface waters, revealing variability not previously observable. The new methods allow direct observation of net nitrate consumption and production measured as changes in nitrate concentration over time in incubated samples of seawater. We find that nitrate concentrations in nitrogendepleted surface waters show regional differences, and sometimes diel differences. The variability in nitrate concentration reflects differences in atmospheric inputs, in physical forcing, as well as in the biological processes of nitrate uptake and nitrification. Examples are shown from the Southern California Bight (1986–1987), the equatorial Pacific (February–March, 1988), and the eastern subtropical Atlantic (March–April, 1989).     

Nocturnal synthesis and diurnal degradation of phytoplankton biomass in surface waters

Natural populations of phytoplankton were collected near the Bay of Bourgneuf, France, in spring 1982, and were subjected to natural surface irradiance outdoors. They exhibited exponential growth on time scales of a week, but significant decreases in biomass indicators such as chlorophyll a and particulate nitrogen were observed during daytime. At night, these decreases were more than compensated by increases in the same biomass variables, which could double over 12 h of darkness. These features are characteristic of phytoplankton populations in surface waters which cannot escape high irradiances, and may be representative of situations in incubation bottles held at fixed depths near the surface. Under such conditions, a decrease in biomass during daytime should not necessarily be interpreted as irreversible damage unless growth measurements are carried out over the following night hours to check for possible recovery.     

The sea-skater Halobates micans: an open ocean bioindicator for cadmium distribution in Atlantic surface waters

Our knowledge of the horizontal distribution of heavy metals in the open ocean with time and space is still very incomplete. Complementary to chemical water analyses suitable biological indicator species may be used to fill this gap. The pleuston organism Halobates micans was collected from 1966 to 1987 at 151 sampling stations of the tropical and subtropical Atlantic Ocean. The cadmium data from more than 1000 individuals analysed display a chemicaloceanographic meaningful distribution in surface waters and compare favourably to primary production values. Chemical analysis of individual plankton species offer a new tool for a better understanding of geochemical cycling of heavy metals in the ocean.     

Monitoring and modeling pesticide fate in surface waters at the catchment scale

In this paper, a state-of-the-art is given of the current knowledge related to the occurrence and sources of pesticides in surface waters. An emphasis is put on sources and transport routes that contribute most to the pesticide loads found in river systems. Possible mitigation measures are described. Once pesticides have entered a river system, they are exposed to different physical, chemical and microbial processes which determine their fate. As mathematical models can describe the fate of pesticides in river systems and can be used for the control of environmental pollution and management of resources, an overview is given of available watershed and in-river water quality models able to predict pesticide concentrations in surface waters. Advantages and disadvantages of simple screening tools and complex watershed models are discussed. Finally, some recommendations are made concerning monitoring, modeling and their combined use in order to achieve the water quality goals set by the EU Water Framework Directive.     

Occurrence of pharmaceuticals and hormones in drinking water treated from surface waters

The levels of a wide variety of pharmaceuticals and hormones, in source and potable-water supplies of French drinking water treatment plants, were assessed. In surface waters, 27 of the 51 target compounds were determined at least once. Paracetamol, salicylic acid and carbamazepine were quantified in more than 80% of samples. The highest concentration of 71 ng/L was observed for paracetamol. Twelve other substances were widely found in the surface waters studied, contaminating between 33 and 80% of the samples. These compounds include analgesics, psychotropic drugs, antibiotics and beta-blockers consistent with the French consumption, as well as natural hormones (oestrone, progesterone and androgens) and synthetic progestatives. In drinking water supplies, 25 compounds were also present, salicylic acid being the most frequently detected. Carbamazepine and the β-blocker atenolol found at lower levels (maximum 2 ng/L), are also present in more than 30% of the contaminated drinking waters. The pharmaceuticals exhibit different reactivity towards the treatments, while progestagens and androgens seem resistant to most of them. The effectiveness of the treatments is discussed, as well as the consequences of the presence of all these compounds on human health. This is the first time that such a long list of compounds (51) is proposed to assessment, and consequently this study provides the first data on pharmaceuticals and steroids occurrences in French drinking waters and represents a basis for the assessment of risks for humans. Moreover, at the international level, this is the first time that so many substances are quantified in drinking water, due to the very low detection limits, especially in the case of the hormones.     

酸性条件下红壤表面Pb反应动力学的能量特征

用自行设计的动力学装置研究了酸性条件下Pb在红壤表面的反应动力学能量特征.结果表明,酸性条件下,Pb吸附分为快反应和慢反应.用一级动力学方程拟合的Pb最大吸附量,随酸度增加显著下降,随温度升高提前达到平衡.用扩散速率常数计算的活化能(△E*)随酸度的增加而增加,Pb扩散需克服的能障加大;△H值为正,温度升高可促进Pb的扩散;AS值均为负,说明吸附反应使体系有序度增加.原液pH为4.5和5.6时,流出液的pH急剧下降;pH3.8和3.3时流入液比流出液的pH高,是由于土壤的缓冲作用和土壤表面质子化;当溶液中H+超过一定数量后,反应初期的H+消耗是快反应过程.H+对矿物的溶蚀成为速率控制步骤.     

Biogeochemical characterization of surface waters in the Aljustrel mining area (South Portugal)

Aljustrel mining area (South Portugal) is a part of the Iberian Pyrite Belt and encloses six sulfide mineral masses. This mine is classified of high environmental risk due to the large tailings’ volume and acid mine drainage (AMD)-affected waters generated by sulfides’ oxidation. The use of biological indicators (e.g., diatoms) revealed to be an important tool to address the degree of AMD contamination in waters. Multivariate analysis has been used as a relevant approach for the characterization of AMD processes. Cluster analysis was used to integrate the significant amount and diversity of variables (physicochemical and biological), discriminating the different types of waters, characterized by the high complexity occurring in this region. The distinction of two main marked phenomena was achieved: (1) the circumneutral-Na-Cl water type (sites DA, PF, BX, BF, RO, CB), expressing the geological contributions of the Cenozoic sediments of Sado river basin, with high diatom diversity (predominating brackish diatoms as Entomoneis alata); and (2) the acid–metal-sulfated water type (sites BM, JU, RJ, AA, MR, BE, PC, AF), reflecting both the AMD contamination and the dissolution of minerals (e.g., silicates) from the hosting rocks, potentiated by the extremely low pH. This last group of sites showed lower diatom diversity but with typical diatoms from acid- and metal-contaminated waters (e.g., Pinnularia aljustrelica). In addition to these two water types, this hierarchical classification method also allowed to distinguish individual cases in subclusters, for example, treated dams (DC, DD), with alkaline substances (lime/limestone), that changed the physicochemical dynamics of the contaminated waters.

     

Elemental composition of surface waters in the Antarctic Peninsula and interactions with the environment

The fast changes in chemical and biological properties of many coastal and inland waters in the last decades reflect the pressure of man on the environment. The surface waters of the Antarctic Peninsula, located far from industrial or populated areas, could eventually be used as background lines. Surface water samples were taken from five lagoons of King George Island, Antarctic Peninsula, and from the Kitiesh Lake. Sample pH and electrical conductivity were analysed in situ and in the laboratory, respectively. The dissolved fractions were analysed in 1997 and 1998. Total concentrations only for 1998 were determined in another fraction adjusted to pH 2. Aluminium, Ca, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sn, Sb, Ba, Bi, and Pb were quantified in all samples by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total and dissolved elemental concentrations were discussed considering the composition of particulate material suspended in the waters removed by streams or by water runoff, or from atmospheric aerosols. Concentrations of dissolved elements change from one lagoon to another. Total and dissolved elemental concentrations could be related to water movement by windstorms, to chemical mechanisms in water and/or to natural and anthropogenic atmospheric factors.     

Microbial populations in surface films and subsurface waters: Amino acid metabolism and growth

Sea surface microlayer (film) and subsurface microbial populations (biomass and activities) were studied in the Damariscotta (Maine) estuary in May and September, 1987. Dissolved free and combined amino acids (DFAA, DCAA), bacterial numbers, microbial ATP, bacterial and microbial DNA synthesis (via³H-thymidine and³H-adenine), and amino acid (³H-glutamic acid) metabolism were measured. DFAA and DCAA were typically enriched in the surface microlayers relative to surface waters, although utilization of glutamic acid was usually more rapid in subsurface waters, as was incorporation of thymidine. Bacteria represented 12 to 40% of the microbial biomass as determined by ATP, except during microalgal blooms in the microlayer. Bacteria were generally not enriched in the surface films, although ATP usually was enriched. Rain input appeared to deplete population densities but stimulated population activities. Two stations which contained similar microbial populations (as estimated by bacterial counts, chlorophylla and ATP) showed very different microbial activities, apparently due to the effects of a substantial rainstorm on one of the stations. The bacterially-dominated processes utilizing thymidine and glutamic acid were enhanced approx five-fold after the rain. Autotrophic carbon production increased approx two-fold, while total microbal community DNA synthesis (as estimated by adenine incorporation into DNA) increased nearly tenfold. The observations of this study indicate that surface microlayers in the temperate waters off the coast of Maine contain highly active heterotrophic and autotrophic populations. The microbial community responds rapidly to changes in nutrient and dissolved organic matter concentrations resulting from both seasonal and temporal effects, including rain and runoff.     

自然水体生物膜有机组分对Cd2+的吸附特征

室内模拟研究了长春南湖水生物膜中有机组分即胞外聚合物、微生物非活性细胞和微生物活性细胞对Cd^2＋的吸附特征及其影响因素。结果表明：3种有机组分对Cd^2＋的吸附过程分为快速和慢速阶段，达到吸附平衡的时间分别为360、100和100min；Cd^2＋的吸附最均在pH为6h达到最佳；在实验所选温度范围内，胞外聚合物在30℃时对Cd^2＋的吸附量最大．而温度对Cd^2＋在微生物非活性细胞和活性细胞的影响不显著；Cd^2＋在3种有机组分上的吸附均符合Langmuir和Freundlish热力学方程，吸附能力为胞外聚合物〉微生物非活性细胞〉微生物活性细胞。在有Pb^2＋共存的条件下，Langmuir和Freundlish热力学方程仍然适合描述3种有机组分对Cd^2＋的热力学吸附过程，但Cd^2＋的吸附量和饱和吸附最均减小。     

Genetic diversity of aerobic anoxygenic photosynthetic bacteria in open ocean surface waters and upper twilight zones

Aerobic anoxygenic phototrophic bacteria (AAPB) represent a widespread mixotrophic bacterial group in marine ecosystems. Here we investigated AAPB genetic diversity in the surface waters and upper twilight zones of the central Pacific, Atlantic, and Indian oceans by amplifying an AAPB marker gene (pufM, encoding photosynthetic reaction center small subunit) directly from bacterioplankton community DNA. Phylogenetic and statistical analysis of 267 pufM partial sequences in six clone libraries revealed a high diversity pattern in open ocean AAPB communities. Various AAPB subgroups belonging to Alpha- and Gamma-proteobacteria were found in both surface and upper twilight zone waters. In most samples, subgroups in which no pure culture was isolated as yet were predominant. By sampling a wide size range of bacterioplankton (0.22–200 μm) and introducing nested PCR to amplification, we retrieved abundant pufM fragments (136 sequences in 37 OTUs) directly from upper twilight zone samples. AAPB populations in upper twilight zones covered major subgroups found in surface waters and had a slightly lower diversity, higher dominance, and lower GC and GC₃ contents in pufM genes than those in surface AAPB populations. These diversity data combined with previous BChl.a data in upper twilight zones support the hypothesis that AAPB may be present below euphotic zones based on the speculation that AAPB can utilize the dim light in twilight zones as a supplement to energy supply in their heterotrophic lives.     

Mercury in surface waters of a macrotidal urban estuary (River Adour, south-west France)

Surface waters were collected in the River Adour estuary (south-western France) during different sampling periods from 1998 to 2001 in order to investigate the phase distribution and speciation of methylmercury (MeHg⁺). Although a high variability is observed, significant higher average concentrations of total MeHg⁺ (dissolved and particulate) are measured during the warm seasons, at 4.40±8.18 pM and 3.90±1.87 pM for July 1998 and September 1999, compared with the winter seasons, with concentrations at 0.99±2.85 pM and 1.00±1.75 pM for February 1998 and February 2001, respectively (one-tailed t-test, P=0.01). The seasonal variations are explained with enhanced bacterial activity during summer and sedimentation/resuspension phenomena. Additionally, signi-ficant longitudinal variations of the MeHg⁺ concentrations are observed. The highest levels in both dissolved and particulate fractions are found within the downstream urban estuarine area. This can be explained by the high methylation potential of the sediments, but direct anthropogenic inputs of MeHg⁺ from specific discharge points cannot be neglected. Biogeochemical factors like phytoplankton biomass and salinity also show a relationship with MeHg⁺ partitioning in the surface waters of the Adour estuary.     

电子废弃物拆解地水体多溴联苯醚分布特征

为了解和比较广东贵屿电子废弃物拆解地和珠三角城市地区水体中多溴联苯醚的种类、含量及分布特征,于2011年9月在广东贵屿周边地区和广州采集了20个地下水、7个地表水和4个珠江水,用反相C18萃取小柱提取净化后,利用气相色谱-质谱法测定了样品中的8种多溴联苯醚（PBDEs）。研究结果表明：贵屿地区地下水中PBDEs浓度总体上较高,总质量浓度范围为2.54~71.74 ng·L-1,平均为22.97 ng·L-1,各类PBDEs的检出率为25%~95%。三溴联苯醚（BDE28）、四溴联苯醚（BDE47）、五溴联苯醚（BDE99和BDE100之和）、六溴联苯醚（BDE153和BDE154之和）、七溴联苯醚（BDE183）和十溴联苯醚（BDE209）的质量浓度分布分别为nd~0.64、nd~18.43、nd~25.26、nd~13.92、nd~9.06和nd~15.60 ng·L-1。从物种上来看,分别源于四溴、五溴和十溴联苯醚产品的BDE47、BDE99和BDE209是贵屿地区地下水样中的优势同系物。通过比率P=（BDE47＋BDE99）/BDE209研究发现：低溴代联苯醚比高溴代联苯醚更易被地表径流迁移转换进入到地下水中。贵屿地区地表水中PBDEs的质量浓度范围为3.41~63.83 ng·L-1,平均总质量浓度为19.38 ng·L-1,稍低于当地地下水中PBDEs的平均总质量浓度,PBDEs的组成以高溴代的BDE209为特征,与世界其他水体研究结果相比,可以发现贵屿地区的地表水中PBDEs的平均总质量浓度明显偏高,说明该地区的地表水受到较严重的PBDEs污染,必须引起足够的重视。珠江水中PBDEs的总质量浓度范围为3.48~20.84 ng·L-1,平均为10.39 ng·L-1,表明近年来珠江水体中PBDEs污染有逐渐恶化的趋势。     

Nitrogen assimilation by phytoplankton and other microorganisms in the surface waters of the central North Pacific Ocean

Assimilation rates of ¹⁵N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and 1 spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 g-at. N m^-3 day^-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range 1 to 8 g-at. N m^-3 day^-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.     

A distance dependent contagion function for vector-based data

Landscape pattern is of primary interest to landscape ecologists and landscape metrics are used to quantify landscape pattern. Metrics are commonly defined and calculated on raster-based land cover maps. One metric is the contagion, existing in several versions, e.g., unconditional and conditional, used as a measure of fragmentation. However, mapped data is sometimes in vector-based format or there may be no mapped data but only a point sample. In this study a definition of contagion for such cases is investigated. The metric is an extension of the usual contagion, based on pairs of points at varying distances and gives a function of the distance. In this study the extended contagion is calculated for vector-based delineated real landscapes and for simulated ones. Both unconditional and conditional contagions are studied using two classification systems. The unconditional contagion function was decreasing and convex, with upper and lower limits highly correlated to the Shannon diversity index, thus carrying only area proportion information. The spatial information lies in the speed by which the function converges to the lower limit; using a proxy function this can be expressed by a single parameter b, with high values for fragmented landscapes. No proxy function was found for the conditional contagion, for which only qualitative information was found. The extended contagion is applicable both in patch mosaic models of landscapes and in gradient-based models, where landscape characteristics change continuously without distinct borders between patches. The extended contagion can be useful in sample based surveys where there no map of the entire landscape is available.     

A time-dependent model of nutrient distribution in continental shelf waters

A time dependent, vertical plane mathematical model of nitrate distribution in Onslow Bay, North Carolina, is developed using similarity theory and conventional numerical techniques. Inputs of nitrate into Onslow Bay are the result of Gulf Stream intrusions (Atkinson et al., 1980) and this forcing is included as a boundary condition for this system. Advective and diffusive processes provide the mechanisms for transport of nitrate in Onslow Bay. The time dependence of the resulting nitrate fields is determined by the rate of phytoplankton removal of nitrate.Nondimensional numbers, arising from model formulation, indicate the relative importance of various processes included in the model. Two nondimensional numbers, H and P, and the nondimensional ratio, P/H, indicate interactions of physical processes. Importance of the biological terms is determined by a third nondimensional number, A. Model results are compared to nitrate data collected in Onslow Bay, North Carolina during an intrusion.     

Thymidine incorporation as a measure of heterotrophic bacterioplankton production in marine surface waters: Evaluation and field results

To assess bacterioplankton production in the sea, we have developed a procedure for measuring growth based on incorporation of tritiated thymidine into DNA; the accuracy of this procedure was tested under a variety of laboratory and field conditions. By autoradiography, we have found that for all practical purposes our technique is specific for the nonphotosynthetic bacteria and that virtually all of the active bacteria (one-third or more of the total countable bacteria) take up thymidine. We also measured (1) the intracellular isotope dilution of thymidine assessed by parallel experiments with labeled phosphorus, and (2) DNA content of natural marine bacteria (0.2 to 0.6 m size fraction); a conversion factor derived from these data permitted estimation of production from thymidine incorporation results. A very similar conversion factor was independently derived from the empirical relationship between thymidine incorporation and growth of natural bacterioplankton under controlled conditions. Combined results show that this technique, which can be performed rapidly and easily at sea, provides good estimates of production. Data from Southern California Bight waters, which contain oligotrophic as well as moderately eutrophic regions, show that average bacterioplankton doubling times, like those of the phytoplankton, are on the order of a few days, with fastest growth at depths just below those of greatest phytoplankton abundance. Offshore bacterial production is roughly 5 to 25% of the primary production; thus, at a 50% assimilation efficiency, the bacterioplankton would consume 10 to 50% of the total fixed carbon.     

Biosorbents for solid-phase extraction of toxic elements in waters

Some trace metals are highly toxic for the environment. There is therefore a need for reliable methods for the determination of metals at trace levels. To this end, new sample pretreatment methods such as separation, preconcentration and speciation prior to the determination of metal ions have developed rapidly. Biosorption has become a major tool for solid-phase extraction methods. This review covers selected biosorbents such as algae, bacteria, filamentous fungi and yeasts, as new sorbents used in the solid-phase extraction of metal ions from various water sample matrices. A survey of the literature over 2004-2014 shows possible applications of selected new sorbents available for use in trace metal analysis in waters using solidphase extraction. We highlight the preconcentration of the toxic elements prior to their determination by atomic spectrometry.     

基于RBF神经网络的鄱阳湖表层水体总悬浮颗粒物浓度遥感反演

为进一步提高湖泊总悬浮颗粒物浓度遥感反演的准确性,引进适应复杂非线性映射的RBF神经网络模型,以鄱阳湖通江湖体为例进行了实证分析,根据实测水体悬浮颗粒物浓度和MODIS遥感数据,对遥感数据进行预处理,建立了RBF神经网络悬浮颗粒物浓度反演模型,神经元个数为8个,误差性能目标值为0.001,对悬浮颗粒物浓度进行反演。研究结果表明,验证样本相关系数R2=0.956 8,均方根误差RMSE=0.54。利用神经网络模型反演水悬浮颗粒物浓度是有效的,其反演结果优于非线性回归模型的结果。