The Boston Harbor Project, and large decreases in loadings of eutrophication-related materials to Boston Harbor

Boston Harbor, a bay-estuary in the north-east USA, has recently been the site of one of the largest wastewater infrastructure projects conducted in the USA, the Boston Harbor Project (BHP). The BHP, which was conducted from 1991 to 2000, ended over a century of direct wastewater treatment facility discharges to the harbor. The BHP caused the loadings of total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS) and particulate organic carbon (POC) to the harbor, to decrease by between 80% and 90%. Approximately one-third of the decreases in TSS and POC loadings occurred between 1991 and 1992; the remaining two-thirds, between 1995 and 2000. For TN and TP, the bulk of the decreases occurred between 1997 or 1998, and 2000.     

Water quality of a port in NW Mexico and its rehabilitation with swell energy

Ensenada Harbor is one of the most important ports of Mexico. Anthropogenic activities have affected the area over several decades, leading to the accumulation of contaminants in its sediments, which eventually are re-suspended into the water column. In spite of water treatment of the tributaries that discharge into the Ensenada Harbor, the water circulation patterns of the harbor, which consist of closed eddies in the northern and southeastern sector, favor the accumulation of those contaminants and hinder exchange with adjacent seawater. Samples collected in October of 2005 registered 63 μM total inorganic nitrogen and 280 mg/L of COD, confirming that this is a highly contaminated environment when compared with other water bodies of North America. Such concentrations can be lowered up to 80% by using a wave energy pumping system that demonstrates the possibility to gradually dilute these contaminants and rehabilitate the Ensenada Harbor.     

Caffeine in Boston Harbor seawater

Caffeine has been detected in Boston Harbor seawater with concentrations ranging from 140 to 1600 ng l(-1), and in Massachusetts Bay seawater at concentrations from 5.2 to 71 ng l(-1). Sources of caffeine appear to be anthropogenic with higher concentrations in the seawater of Boston's inner harbor and in freshwater sources to the harbor. Charles River water and Deer Island sewage treatment plant effluent, the two major sources of freshwater to the harbor, contained 370 and 6700 ng l(-1) of caffeine, respectively, in 1998. Sewage influent and effluent concentrations appear to be consistent with consumption estimates of caffeinated beverages for the Boston area and total organic carbon removal targets for treated sewage. Caffeine was inversely correlated to salinity in a transect from the mouth of Boston Harbor to Stellwagen Basin, indicating it may be a useful chemical tracer of anthropogenic inputs to marine systems.     

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides in water columns from the Pearl River and the Macao harbor in the Pearl River Delta in South China

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) were measured in suspended particles and dissolved phase from the Baiertang water column and the Macao water column samples as collected from the Guangzhou channel of the Pearl River and the Macao harbor, where the sediments were heavily contaminated with organic pollutants. Total OCPs concentration varies from 23.4 to 61.7 ng/l in Baiertang water column and from 25.2 to 67.8 ng/l in Macao column, while total PAHs concentration varies from 987.1 to 2878.5 ng/l in the Baiertang water column and from 944.0 to 6654.6 ng/l in the Macao column. The vertical distribution profiles of pollutants and the partition of pollutants between particles and dissolved phases indicate that the sediments in Baiertang act as an important source of selected pollutants, and the pollutants in water of this region were mainly originated from the release and re-suspension of contaminants residing in the sediments. The sediments in Macao harbor act as a reservoir for organochlorine pesticides, such as DDTs mainly introduced by river inflow from Xijiang and PAHs input by brackish water from the Lingdingyang estuary. Combustion of fossil fuels and petroleum input are the main sources of PAHs in the Macao water column, while combustion of fossil fuels and coal is responsible for the PAHs in the Baiertang water column. The ratios of DDT/(DDD+DDE) for the Macao water column samples demonstrate that such chemicals were input into this region in recent times.     

Estimation of suspended sediment concentration based on bio-optical mechanism and HJ-1 image in Chaohu Lake

Synchronization experiment was conducted in June, 2009 to get Inherent Optical Properties (IOP) of water component in Chaohu Lake. Water bio-optical mechanism was studied combined with multispectral data of Environmental Satellite 1 (CCD), and then inversion models of total suspended matter (TSM), inorganic suspended matter (ISM) and organic suspended matter (OSM) concentration were built. The data indicated that: the absorption ratio of suspended particulate matter and CDOM to total were almost no change from band 1 to band 2 with about 85% and 9%, respectively. The ratio of pure water to total increased from 0.4% to 5.6%. Water reflectance in these two bands were influenced by absorption of three kinds of components: algae particles absorption surpassed non-algal particles in band 3, and so played an important role in total absorption with about 35.7%; the proportion of pure water absorption and particles matter backscattering both were 99% in band 4, so these two components decided the main inherent optical properties in band 4. The models of TSM and ISM concentration inversion based on band combination (band 3 + band 4)/(band 1 + band 2) were built, while OSM concentration was estimated by band 4/(band 1 + band 2) index. Inversed by image data, RE of TSM concentration between modeled and measured was 33.4%, and RMSE was 18.68 mg/L. RE of ISM and OSM concentration were 39.9% and 35.2% respectively. The inversion was more accurate when satellite-ground data were just in the same day. At this situation, RE of ISM concentration dropped to 25.4%, and that of TSM and OSM reduced to 26.5% and 26.8% as well.

     

Estimation of suspended sediment concentration based on bio-optical mechanism and HJ-1 image in Chaohu Lake

Synchronization experiment was conducted in June, 2009 to get Inherent Optical Properties (IOP) of water component in Chaohu Lake. Water bio-optical mechanism was studied combined with multispectral data of Environmental Satellite 1 (CCD), and then inversion models of total suspended matter (TSM), inorganic suspended matter (ISM) and organic suspended matter (OSM) concentration were built. The data indicated that: the absorption ratio of suspended particulate matter and CDOM to total were almost no change from band 1 to band 2 with about 85% and 9%, respectively. The ratio of pure water to total increased from 0.4% to 5.6%. Water reflectance in these two bands were influenced by absorption of three kinds of components: algae particles absorption surpassed non-algal particles in band 3, and so played an important role in total absorption with about 35.7%; the proportion of pure water absorption and particles matter backscattering both were 99% in band 4, so these two components decided the main inherent optical properties in band 4. The models of TSM and ISM concentration inversion based on band combination (band 3 + band 4)/(band 1 + band 2) were built, while OSM concentration was estimated by band 4/(band 1 + band 2) index. Inversed by image data, RE of TSM concentration between modeled and measured was 33.4%, and RMSE was 18.68 mg/L. RE of ISM and OSM concentration were 39.9% and 35.2% respectively. The inversion was more accurate when satellite-ground data were just in the same day. At this situation, RE of ISM concentration dropped to 25.4%, and that of TSM and OSM reduced to 26.5% and 26.8% as well.     

Environmental behavior of organotin compounds in the coastal environment of Xiamen, China

In 2006, organotins pollution were investigated in the coastal environment of Xiamen, China. Six species of organotin compounds including tributyltin, triphenyltin and their degradation compounds were quantified in the dissolved and particulate phases of the water, and in the sediment using GC-FPD. The concentrations of organotin compounds ranged from 2.2 to 160 ng (Sn) L(-1) dissolved in the water, 0.14-6.7 ng (Sn) L(-1) in suspended particulate matter and nd approximately 26 ng (Sn) g(-1) (dry weight) in the sediment. The highest concentration of total organotin or tributyltin in water was found in a shipyard and at a station near the inlet of the harbor, indicating fresh inputs of antifouling paints to Xiamen's coastal environment. Organotin speciation was performed on sediment cores to investigate contamination trends over the past ten years in the harbor. The results of (210)Pb dating indicated that Xiamen western harbor suffered contamination during 2000. The environmental behavior of organotins such as the enhancement of the microlayer, partitioning between water/suspended particulate matter and between water/sediment are also discussed in this paper.     

太湖水体遥感反演参数的空间异质性

空间异质性的存在,会导致水质参数遥感反演中的尺度效应,影响反演精度,因此通过分析水质参数空间异质性,对于选择适当分辨率的遥感影像,提高反演精度具有重要意义.通过2008年10月在太湖布置的3个样方,利用GIS地统计学原理和分形维数的方法,对水质遥感反演中的三要素浓度,包括叶绿素a(Chl.a)、总悬浮物(TSM)和溶解有机碳(DOC)的空间异质性及其可能产生的尺度效应进行了研究.结果表明:太湖水体的三要素浓度在不同样方单元中变异系数相差较大,存在着明显的尺度效应;三个样方内Chl.a变异函数曲线斜率在变程范围内变化都较为剧烈,分形维数较高,说明太湖水体Chl.a受到某种起主导作用的生态过程的影响和控制;Chl.a和TSM的空间结构比例都在90%左右,有较强的空间相关性,表明其空间异质性的产生主要是由于结构性因素引起的,随机性因素作用微弱;DOC空间结构比例较小,说明随机性因素对其空间异质性的产生起了主导作用.三个样方中Chl.a的变程分别为147.3m、129.3m和115.0m,TSM的变程分别为1131.7m、130.6m、149.1m,因此在遥感反演中可选择TM影像,选择5×5窗口,以150m×150m作为基本单元;而DOC的变程分别为34.3m、38.5m、26.4m,表明其自相关距离较小,建议直接选择分辨率为30m的TM影像,使实际测量值与遥感影像最小单元相对应,消除反演过程中的尺度效应带来的误差.该研究也表明,MODIS的像元尺寸(250、500、1000m)明显偏大,在太湖水体三要素反演过程中,由于空间异质性引起的尺度效应,会造成一定的误差.     

基于多时相主被动遥感的漓江水面监测与水质参数反演(2016—2020年)

以漓江流域为研究区域,以2016-2020年Landsat 8 OLI、GF-1、Sentinel-2A及Sentinel-1A逐月影像为数据源,选用归一化水指数(NDWI)、改进型归一化水指数(MNDWI)、增强型水体指数(EWI)、归一化差值池指数(NDPI)、后向散射系数(S)与主被动遥感加权指数(JQ)提取漓江水体信息,采用二类水体区域性近岸海域水色算法(C2RCC)、最大叶绿素指数(MCI)、双波段比值法(Double R)及叶绿素反射峰强度(ρchl)4种方式,反演漓江水体叶绿素a(Chl.a)与总悬浮物质(TSM)浓度.将漓江划分为278个基本评价单元,利用水面变化区域差异值(WDr)、河岸线发育系数(SDI)与水体信息变化动态度(K)等指标定量分析漓江上、中、下游枯水期和汛期的水文和水质信息的年内时空动态变化,得出以下结论:(1)主被动遥感加权指数JQ与NDPI指数的提取效果优于NDWI、MNDWI、EWI指数与后向散射系数,但与JQ指数相比,NDPI指数提取精度更高、可信度更强.(2)基于C2RCC算法反演的Chl.a浓度的均方根误差(RMSE)处于0.18~7.88 mg/m³之间,TSM浓度的RMSE为0.17~12.55 g/m³,可较好地反映漓江水质参数变化情况.(3)基本评价单元的划分可清楚地分析出上、中、下游地区水域水面宽度、水域面积、Chl.a与TSM浓度的连续变化情况,实测数据则依靠站点监测,所得结果较分散,无法进行连续性分析.(4)漓江5-10月降水较多、水体流动性强,大部分地区平均水面宽度在100~250 m范围内,水体富营养化程度低,水质较好,但2月水质最差,水体富营养化程度较高地区主要集中于上、中游的兴安县、灵川县等城镇居民区以及下游旅游开发区较多的兴坪镇.     

Composition and flux of suspended organic matter in the middle and lower reaches of the Changjiang (Yangtze River) — impact of the Three Gorges Dam and the role of tributaries and channel erosion

To investigate the sources of particulate organic matter (POM) and the impact of Three Gorges Dam (TGD), two large lakes and erosion processes on determining the composition and flux of POM in low water discharge periods along the middle and lower Changjiang, suspended particulate samples were collected along the middle and lower reaches of the Changjiang (Yangtze River) in January 2008. Organic geochemistry of bulk sediment (particulate organic carbon, organic carbon to nitrogen molar ratio (C/N), stable carbon isotope (δ¹³C) and grain size) and biomarker of bulk sediment (lignin phenols) were measured to trace the sources of POM. The range of C/N ratios (6.4–8.9), δ¹³C (?24.3‰ – ?26.2‰) and lignin phenols concentration Λ8 (0.45 mg/100 mg OC‐2.00 mg/100 mg OC) of POM suggested that POM originated from the mixture of soil, plant tissue and autochthonous organic matter (OM) during the dry season. POM from lakes contained a higher portion of terrestrial OM than the mainstream, which was related to sand mining and hydropower erosion processes. A three end‐member model based on δ¹³C and Λ8 was performed. The results indicated that soil contributed approximately 50% of OM to the POM, which is the dominant OM source in most stations. POM composition was affected by total suspended matter (TSM) and grain size composition, and the direct OM input from two lakes and channel erosion induced OM. The lower TSM concentration in January 2008 was mainly caused by seasonal variations; the impact from the TGD in the dry season was relatively small. A box model indicated that more than 90% of the terrestrial OM transported by the Changjiang in January 2008 was from the middle and lower drainage basins. Channel erosion induced OM, and contributions from Poyang Lake were the major terrestrial OM sources in the dry season. Copyright © 2012 John Wiley & Sons, Ltd.     

基于高频次GOCI数据的太湖悬浮物浓度短期动态和驱动力分析

总悬浮物是水体中重要的光学敏感物质之一,很大程度上决定了水柱中光的吸收、散射和衰减,同时吸附营养盐、重金属和有毒有害物,对水体物质生物地球化学过程、沉积物埋藏动力和湖泊环境演化具有重要的意义.基于星地同步实验和静止水色成像仪GOCI(Geostationary Ocean Color Imager)构建了太湖悬浮物浓度估算模型,并分析了典型风浪过程中太湖悬浮物浓度短期动态变化过程.研究表明:对太湖水体悬浮物浓度较为敏感的波段为GOCI的第7波段(745nm)和第8波段(865 nm),悬浮物浓度与对应波段遥感反射率线性相关决定系数分别为0.72和0.55;基于GOCI第7波段的悬浮物浓度单波段遥感估算模型能较为准确地估算太湖的悬浮物浓度,模型相对均方根误差和平均绝对百分误差分别为28.3%和24.4%.通过研究典型风浪过程前后太湖悬浮物浓度变化发现其短期动态变化显著,风速、风向是悬浮物浓度短期动态变化的重要驱动因素,悬浮物浓度与风速呈正比,并随着风向扩散;高频连续GOCI影像结果显示悬浮物浓度短期动态变化对风浪扰动的响应有一定的滞后性,滞后时间为数小时到1天,悬浮物沉降与沉积物再悬浮的临界风速约为3.4 m/s.     

Frequency Domain Response at Pacific Coast Harbors to Major Tsunamis of 2005–2011

Tsunamis waves caused by submarine earthquake or landslide might contain large wave energy, which could cause significant human loss and property damage locally as well as in distant region. The response of three harbors located at the Pacific coast (i.e. Crescent City Harbor, Los Angeles/Long Beach Port, and San Diego Harbor) to six well-known tsunamis events generated (both near-field and far-field) between 2005 and 2011 are examined and simulated using a hybrid finite element numerical model in frequency domain. The model incorporated the effects of wave refraction, wave diffraction, partial wave reflection from boundaries, entrance and bottom energy dissipation. It can be applied to harbor regions with arbitrary shapes and variable water depth. The computed resonant periods or modes of oscillation for three harbors are in good agreement with the energy spectral analysis of the time series of water surface elevations recorded at tide gauge stations inside three harbors during the six tsunamis events. The computed wave induced currents based on the present model are also in qualitative agreement with some of the reported eye-witness accounts absence of reliable current data. The simulated results show that each harbor responded differently and significantly amplified certain wave period(s) of incident wave trains according to the shape, topography, characteristic dimensions and water depth of the harbor basins.     

Environmental behavior of organotin compounds in the coastal environment of Xiamen,China

In 2006, organotins pollution were investigated in the coastal environment of Xiamen, China. Six species of organotin compounds including tributyltin, triphenyltin and their degradation compounds were quantified in the dissolved and particulate phases of the water, and in the sediment using GC-FPD. The concentrations of organotin compounds ranged from 2.2 to 160 ng (Sn) L⁻¹ dissolved in the water, 0.14–6.7 ng (Sn) L⁻¹ in suspended particulate matter and nd ∼ 26 ng (Sn) g⁻¹ (dry weight) in the sediment. The highest concentration of total organotin or tributyltin in water was found in a shipyard and at a station near the inlet of the harbor, indicating fresh inputs of antifouling paints to Xiamen’s coastal environment. Organotin speciation was performed on sediment cores to investigate contamination trends over the past ten years in the harbor. The results of ²¹⁰Pb dating indicated that Xiamen western harbor suffered contamination during 2000. The environmental behavior of organotins such as the enhancement of the microlayer, partitioning between water/suspended particulate matter and between water/sediment are also discussed in this paper.     

太湖沉积物再悬浮模拟方法

由于风浪对浅水湖泊底泥的强烈扰动作用,底泥再悬浮的生态效应研究成为目前国际研究热点之一.但方法的缺乏极大地限制了有关底泥再悬浮环境效应的深入研究.本研究应用一种新的沉积物再悬浮装置,模拟了太湖南部长兜港水域不同风浪影响下悬浮物的垂向分布,获得水柱总悬浮物量(T)与扰动频率(n)的定量关系:T=19.77×exp(n/2.61)-71.7.结合现场实测风情下的水柱总悬浮物量,建立了室内水动力条件、水柱总悬浮物量和现场风情的定量关系.研究2004年10月至2005年10月太湖全年代表性小风、中风及大风与再悬浮装置的扰动频率对应关系,估算了小风、中风和大风常规风情引起的总悬浮物量分别为159、230、425 g/m2.结果表明,模拟获得的太湖悬浮物垂向分布规律与现场状况较为接近,是目前较为适用的浅水水体沉积物再悬浮模拟方法.     

巢湖西湖心底泥蓝藻对水体蓝藻生物量的贡献

2018年10月-2019年10月对巢湖西湖心水体浮游藻类群落结构以及水体和底泥蓝藻生物量进行了月度调查.结果表明:巢湖西湖心浮游藻类的主要优势种属为微囊藻属、席藻属、十字藻、卵形隐藻和鱼腥藻属.蓝藻优势种属在5-10月为微囊藻属,11-12月为鱼腥藻属,1-4月为席藻属.巢湖水体和底泥蓝藻生物量峰值分别出现在9月和2月,水体蓝藻的衰亡下沉会导致底泥蓝藻生物量的上升.巢湖蓝藻主要分布在水体,底泥蓝藻生物量相对较低,单位面积水柱与底泥蓝藻生物量6月的比值大于100,在11-3月相对较低,最低值小于2.底泥蓝藻主要分布在底泥表层0～2 cm.通过安装原位捕获器,监测了蓝藻在西巢湖湖心水柱和底泥中的垂直迁移过程和通量.结果表明:11月和2月蓝藻有明显从水柱向底泥迁移的过程;底泥蓝藻全年向水体的静态迁移量都很低,而动态迁移在11月和6月出现两个峰值,主要受底泥蓝藻生物量和再悬浮的影响.本研究结果表明削减巢湖西湖心底泥种源的最佳时期为10月至来年2月,但是由于底泥蓝藻生物量远远小于水柱蓝藻生物量,底泥蓝藻向水体复苏迁移的通量也较低,即使削减了底泥种源,也不能有效降低水体蓝藻生物量.     

Compared performances of different algorithms for estimating annual nutrient loads discharged by the eutrophic River Loire

Good estimates of pollutant fluxes are required for Earth systems sciences and water quality management. The gradual accumulation of water quality data records over the past few decades has increased the value of these data for examining long‐term trends. On many major rivers, however, infrequent sampling of most pollutants makes flux estimates and their analysis difficult. This paper explores the performance of different methods for estimating nutrient fluxes. The objective is to assess the accuracy (bias) and precision (dispersion) of annual nutrient fluxes based on monthly sampling, which is the frequency with which 80% of French water quality surveys have been carried out since 1971. The study is based on a data set of nutrient concentrations surveyed at high frequency during a 5 year pilot study (1981–85) at the Orléans station in the middle reaches of the River Loire, France. The mean specific fluxes were 641 (nitrate‐N), 96 (total‐P) and 37 kg year⁻¹ km⁻² (orthophosphate‐P). For each year, the data set was then ‘resampled’ by randomly simulating 12 sampling dates. 100 simulated monthly samplings were generated, upon which seven estimation methods were tested. The evaluations indicate that, when concentrations of specific substances in large rivers exhibit seasonal variation, a simple method based on linear interpolation between samples taken at approximately monthly intervals is advocated. With the monthly sampling interval, the precision (confidence level of 95%) of annual nutrient fluxes obtained by the appropriate methods was 13% for nitrates, 20% for total‐P, 26% for orthophosphates, and 34% for particulate‐P. The frequency of water quality surveys required to obtain an annual nutrient flux with 10% precision was around 15 days for nitrate, 10 days for orthophosphate‐P and total‐P, and about 5 days in the case of particulate‐P. Copyright © 2004 John Wiley & Sons, Ltd.     

澜沧江梯级筑坝下水体氮磷分布特征及其形成机制

水库建设改变了河流水文情势及物质迁移转化过程,从而影响水环境质量。为探究梯级筑坝影响下河流氮、磷的空间分布特征及其形成机制,以澜沧江为研究对象,于2016年和2021年分别开展了沿程水环境监测,对比分析水体中氮、磷及其形态浓度在水库建成前后的变化及沿程分布特征,探究氮、磷变化及其沿程分布的主控因子和影响机制。结果表明：由于河流建库蓄水淹没的土地释放大量土壤有机氮,新建水库段(2021年)水体总氮(TN)浓度相比于建库前(2016年)显著上升;由于建库后水流流速减缓而促进颗粒态磷沉降,水体总磷(TP)浓度显著下降。此外,河流建库蓄水后原自然河道的水环境特征改变且利于沉积物磷的释放,筑坝后水体磷酸盐(PO₄^3--P)占生物可利用磷(Bio-P)的比例显著上升。受沿程土地利用的影响,从上游到下游水体TN浓度总体上逐渐升高,而水体TP浓度由于水库的截留效应逐渐降低。筑坝增加的水力停留时间为水库氮、磷转化提供了有利条件,主要表现为溶解性无机氮以硝态氮为主转变为以氨氮为主;同时,Bio-P中PO₄^3--P的占比...     

Vertical changes of POC flux and indicators of early degradation of organic matter in the South China Sea

Tie-series sediment trap materials at different water depths and surface sediments in northern and central South China Sea (SCS) were analyzed for organic carbon, amino acids, amino sugars and carbohydrates. Results show that particulate organic carbon (POC) is mainly derived from marine plankton, only 1.4%–1.6% of primary production sinks into deep SCS water column and less than 0.22 % of primary production ultimately reaches the sediments. The ranineralization and dissolution of organic matter as well as the compositional alterations of organic matter mixtures may mainly take place in the upper few hundred meters of water column, deep carbonate (opal) lysocline zones, and interface layers between sediments and water column, rather than in mid-waters. The organic geochemical parameters such as (T ^aa +T ^sug )OC%, AA/AS, Gluam/Galam, Arom. AA/non-prot. AA, ASP/b-ALA, Glu/g-ABA decrease from living marine plankton (or planktonic shells), to settling particulate matter and to sediments suggesting that they appear to be gad early degraded indicators of organic matter. Project supported by the National Natural Science Foundation of China (Grant No. 49776297). Cruises financially supported by State Oceanic Administration and German Federal Ministry of Research and Technology.     

Phosphorus Forms and Their Changes in Water of Three Subalpine Lakes in Italy

Total phosphorus and its main forms: dissolved mineral, dissolved organic, particulate organic and particulate mineral in the vertical water column of three subalpine lakes of various types in Italy, has been estimated during the winter-vernal season. The range of variation in the phosphorus content in these waters was as follows: total phosphorus 16 ± 2860 μg/1 PO₄, dissolved mineral phosphorus 4 ± 1040 μg/l PO₄, dissolved organic phosphorus 1 ± 160μg/l PO₄, particulate organic phosphorus 0 ± 290 μg/l PO₄ and particulate mineral phosphorus 1 ± 100 μg/l PO₄, Generally the content of total phosphorus and dissolved mineral phosphorus (phosphates) increased with the degree of eutrophy with the depth and with the progress of the vernal season towards the summer stagnation time. The amount of phosphates increased in water with the depletion of oxygen, both in the verical water column and with the progress of stagnation time. The amounts of dissolved organic phosphorus decressed with the depth of the vertical water column whereas the dissolved mineral phosphorus increased. The development of the particulate organic phosphorus stratification in the vertical water column was clearly visible in the eutrophic lake. The quantities of total phosphorus and its main component, dissolved mineral phosphorus, decreased evidently from January to May in all three lakes, mostly in the eutrophic lake. The reason of this decrease is sorption by lake sediments and to a certain degree sedimentation of phosphorus sorbed by ferric hydroxide. The increase of dissolved mineral phosphorus and that of total phosphorus in the vertical water column and with the progress of summer stagnation had as a reason the liberation of phosphorus from sediments, and not so much decomposition of sedimentating plankton or dissolved organic phosphorus. The share of single (mean) values of phosphorus forms in the total phosphorus was as follows: In the oligotrophic lake the share of particulate mineral phosphorus was extremely high in March (21% of the total), probably because of the inflow of the melting waters from the drainage area. The development of vertical stratification in waters of three subalpine Italian lakes at the end of the vernal season (May) indicates the quantitative prevailing of dissolved mineral phosphorus with its increase with the depth and domination of dissolved organic phosphorus in the trophogenic zone.     

Ecological risk assessment of trace metal accumulation in sediments of Veraval Harbor,Gujarat, Arabian Sea

In this study, different types of indices were used to assess the ecological risk of trace metal contamination in sediments on the basis of sediment quality guidelines at Veraval Fishery Harbor. Sediment samples were collected from three sectors in pre-, post-, and monsoon seasons in 2006. Trace metal concentrations were higher in the inner sector during post-monsoon, and it showed the highest statistical significance (p < 0.01) among the stations. Pollution load index was higher than unity, indicating alternation by effluent discharge from industries. Enrichment factor and geo-accumulation index showed that Cd, Pb, and Zn were enriched in the northern part of the harbor and Pb had accumulated in the harbor sediment. The ecological risk assessment index revealed that Ni, Zn, and Pb were higher than the effect range median values, indicating their potential toxicity to the aquatic environment in the Veraval Harbor. Hence, the harbor is dominated by anthropogenic activities rather than natural process.