The removal of dissolved humic acids and iron during estuarine mixing

The estuarine chemistry of dissolved humic acids was determined by carrying out both field and laboratory studies. These approaches were combined in an investigation of the Amazon estuary while laboratory mixing experiments were performed using filtered (0.45?0.001 μm) river water fractions of the Water of Luce (Scotland).The results demonstrate that a small fraction of river dissolved organic matter is preferentially and rapidly flocculated during estuarine mixing. This fraction is the high molecular weight component of dissolved humic acids (0.45?0.1 μm filtered). Approximately 60–80% of the dissolved humic acid in these rivers flocculates during estuarine mixing. This represents a removal of only 3–6% of river dissolved organic matter and is responsible for the non-conservative behaviour of dissolved humic acid in the Amazon estuary even though total dissolved organic carbon appears conservative.The salinity dependence with which humic acid flocculates in estuaries is similar to that of iron. This implies that both constituents may be removed from river water by a common mechanism of colloid flocculation.     

Dynamics of dissolved major (Na,K, Ca,Mg, and Si) and trace (Al,Fe, Mn,Zn, Cu,and Cr) elements along the lower Orinoco River

This study addresses the changes in dissolved major and trace element concentrations along the Orinoco River, including the mixing zone between the Orinoco and Apure Rivers. Water samples from the Apure and Orinoco Rivers were collected monthly in four sectors over a period of 15 months. Auxiliary parameters (pH, dissolved oxygen, conductivity, and temperature), total suspended sediments, dissolved organic carbon (DOC), and major (Na, K, Ca, Mg, and Si) and trace (Al, Fe, Mn, Zn, Cu, and Cr) element concentrations were measured in all sectors. The relative contribution of both rivers after the Apure–Orinoco confluence was determined using Ca as a tracer. Moreover, a mixing model was developed to determine whether dissolved species exhibit a conservative behavior during mixing. The results indicate that DOC is removed from waters during the Apure–Orinoco mixing, probably due to absorption of DOC on mineral phases supplied by the Apure River. Dissolved Na, Ca, and Mg behave conservatively during the mixing processes, and their concentrations are controlled by a dilution process. The anomaly in the temporal pattern of K in the Orinoco is caused by the input of biogenic K originating from the Apure River during the high‐water stage. The loss of dissolved Si during the low‐water stage can be explained by the uptake of Si by diatoms. Dissolved Mn, Zn, Al, and Fe showed a non‐conservative behavior during the Apure–Orinoco mixing. The removal of Mn and Zn from the dissolved phase can be explained by the formation of Mn‐oxyhydroxides and the scavenging of Zn onto Mn oxides. Dissolved Fe is controlled by redox processes, although the removals of Fe and Al due to the preferential adsorption of large organometallic complexes by mineral surfaces after the Apure–Orinoco confluence can affect the mobility of both elements during transport. The conservative behavior shown by Cu and Cr can be related to the tendency of both elements to be complexed with small organic colloids, which are not preferentially adsorbed by clays.     

Behaviour of hexachlorocyclohexane isomers and Zn,Cu and Cd in the freshwater-seawater mixing area

Dissolved and suspended concentrations of hexachlorocyclohexane isomers, α, γ and δ HCH, and Zn, Cu and Cd have been measured in the Napostá Grande stream, located in the Blance Bay area, Argentina, for the purpose of studying the behaviour of these compounds in the freshwater-seawater mixing zone. The aim was to establish the mobilization processes, according to their distribution over the dissolved and suspended forms, in order to obtain a better understanding of their impact on organochlorine and heavy metal levels in the marine environment. It is concluded that the compounds studied are removed from solution by suspended matter which is afterwards precipitated during the freshwater-seawater mixing process. Seawater and surface sediment concentrations of these pollutants for two sampling sites in Blanca Bay, Argentina, are also reported.     

Fe, Ni and Co variations in the metals of some antarctic chondrites

Nearly 4,000 Fe, Ni and Co analyses have been carried out on the metal phases of 12 Antarctic chondritic meteorites by means of the electron microprobe. H-group chondrites show relatively simple patterns of variation for these elements but L- and LL-group members show much more scatter in both Ni and Co concentrations. A single member of the CO3 group investigated shows some scatter in the concentrations and also much higher Co concentrations in the high-Ni (awaruite?) phase (1.25–2%) than in the coexisting kamacite (0.2–0.5%). Thus, analysis of the metal phases can provide not only a means of identifying the group to which a meteorite belongs, but also the possibility of distinguishing between individual chondrites from the same group.

The overall concentrations of Co in the metal particles in the different groups are considered to be related inversely to the abundance of metal grains in meteorites of these groups while the scatter is interpreted as reflecting characteristics inherited at the time of accretion. The absence of homogenisation of the concentrations of Fe, Ni and Co in the metal particles, even in so-called equilibrated chondrites, provides further evidence against the widely held notion that these meteorites have been involved in a high-temperature prograde metamorphism.     

Schwermetalle (Fe,Mn, Cd,Cr, Cu,Pb, Zn) im Pelagial des Bodensees (Obersee und Untersee) und des Greifensees

Monthly measurements were made over a one-year period to determine the heavy metals Fe, Mn, Cd, Cr, Cu, Pb and Zn in the vertical profiles of Lake Constance (Obersee and Untersee) and Greifensee, by means of atomic absorption spectrometry. Fe and Mn exhibited the usual cyclical fluctuations depending on redox conditions in the hypolimnion. For Cd, Cr, Cu, Pb and Zn no concentration patterns were noted that would show their dependency on seasonal and vertical stratifications.      

Geochemical processes controlling the relationship between Co,Mn, and Fe in early diagenetic deep-sea nodules

Early diagenetic manganese nodules from the northeast Pacific nodule belt and from the southeast Pacific (Peru Basin) show primary growth features of dendritic microtextures consisting of alternating laminae of crystalline 10-Åmanganate (A1 substance) and amorphous material which is composed of an intimate mixture of ferric hydroxide, silicate, and δ-MnO₂ (A2 substance). The formation of rhythmic sequences of A1 and A2 microlayers is explained by physico-chemical changes in the peneliquid sediment layer and in the microenvironment of the accreting nodule surface: (a) upward diffusion of Mn²⁺ in the interstitial water as a result of decay of organic matter and Mn mobilization; (b) oxidation of Mn²⁺ and formation of 10-Åmanganate in the upper part of the peneliquid sediment layer, leading to pH depression in the microenvironment of the nodule surface which decreases the mobility of silicate, resulting in formation of A2 layers; (c) restoration of pH and renewed precipitation of 10-Åmanganate.Based on data of 171 bulk analyses and on electron microprobe investigations, interelement relationships between Co, Mn, and Fe are pointed out. Fe and Co show a significant positive correlation (r = 0.84), while Mn and Co are poorly negatively correlated (r = ?0.21), assuming linear regression. The enrichment of Co within the amorphous A2 phase is attributed to specific surface adsorption and subsequent oxidation of Co²⁺ to Co³⁺ in the strong electric field of Si⁴⁺. Robust complexes of Co(III) and ≡ FeH₂SiO₄^? prevent most of the Co from being available for the 10-Åmanganate precipitation. Concerning the relation between Mn and Fe and Co respectively, the highest correlation coefficients are obtained using an inverse logarithmic regression. Under early diagenetic conditions, the concentration and precipitation of Mn²⁺ in the interstitial water depends on the redox gradient which is controlled by the amount of decomposing organic matter. The Nernst equation describes the relationship as a reciprocal logarithmic function. However, the quantities of colloidal ferric hydroxide and of dissolved silicate are not affected by variations of the redox potential. These different characteristics in the precipitation of Mn and the Fe- and Si-rich colloidal phase may cause the significantly negative logarithmic correlation of Mn versus Fe and Co, respectively.     

Cd, Cr, Cu, Ni and Pb in the water column and sediments of the Ob-Irtysh Rivers, Russia

Concentrations of Cd, Cr, Cu, Ni and Pb were determined in filtered water, suspended particulate matter, and bottom sediments from a 2000 km section of the Ob and Irtysh Rivers. Dissolved Cd, Cr, Cu and Ni concentrations are similar to, or higher than, results from other Russian Arctic and large world river-estuaries. Concentrations of Cd, Cr, Cu, Ni and Pb in suspended particulate matter are generally comparable to results from other Russian Arctic and large world rivers and estuaries. Comparison of trace metal ratios in crustal material and suspended particulate matter and bottom sediment suggests that the source of Cr, Cu and Ni is continental weathering. Particulate Cd and Pb are elevated relative to their crustal abundance, suggesting a source of these metals to the Ob-Irtysh in addition to continental weathering.     

Photosynthetic capability and Fe,Mn, Cu,and Zn contents in two Moraceae species under different phosphorus levels

The strong adaptability of Broussonetia papyrifera(L.) Vent. to low phosphorus(P) conditions can be attributed to the large amount of root-exuded organic acids and the high ef?ciency of P extraction. However,microelement contents are in?uenced by low-P stress, and their effects on the photosynthetic capability of B. papyrifera remain unknown. In this study, we investigated the effects of low-P treatment on net photosynthetic rate(P_N);chlorophyll a ?uorescence(ChlF) characteristics; and Fe,Mn, Cu, and Zn contents of B. papyrifera and Morus alba L. seedlings. Results show that B. papyrifera exhibited better photosynthetic capability under moderate P de?-ciency(0.125, 0.063, and 0.031 mmol/L P treatments),whereas the photosynthetic capability of M. alba decreased under moderate and severe P de?ciency(0.016 and0 mmol/L P treatments). Under moderate P de?ciency, the decrease in Cu and Zn contents in B. papyrifera was lower than that in M. alba. Under severe P de?ciency, a considerable decrease of photosynthetic capability in B. papyrifera and M. alba was associated with low Cu and Zn contents. The P N of the two Moraceae species exhibited a better correlation with Cu and Zn contents than with Fe or Mn content. P de?ciency could not only decrease cyclic photophorylation and photosynthetic ef?ciency, but could also affect the stability of thylakoid membrane structure and electron transport ef?ciency by in?uencing the contents of Cu or Zn, thereby affecting photosynthesis.     

Kinetic partitioning of Co,Mn, Cs,Fe, Ag,Zn and Cd in fresh waters (Loire) mixed with brackish waters (Loire estuary): experimental and modelling approaches

To simulate the behavior of radionuclides along a salinity gradient, in vitro sorption and desorption kinetics of Co, Mn, Cs, Fe, Ag, Zn and Cd were studied in Loire river water and the macrotidal Loire estuarine water over two different seasons. Partitioning between the dissolved phase and suspended solids were followed up over 100 h after adding radioactive tracers to freshly collected freshwater (sorption stage); this stage was followed by desorption in fresh and estuarine waters. A kinetic model describing the interactions between trace metals and particles under a salinity gradient was developed and calibrated. Among parameters and/or processes that control the fate and behavior of contaminated particles during their transfer in estuarine systems, this study shows that the speciation of trace metals is controlled by: (i) the chemical water composition: for all the elements except for Fe, desorption increased with salinity; however, the amplitude of such an effect strongly depended on the element and/or on the composition of the particulate phase (and consequently on the season); (ii) the possibility for a given element to form (or not) stable surface particle moieties such as oxides or inner-sphere complexes; (iii) the distribution of a given element among different types of sites characterised by different binding forces that can lead (or not) to re-adsorption processes after mixing of contaminated particles with uncontaminated water.Our model enabled the quantification of the contribution and the characteristic time of reactions that took place over short and long periods on the global partitioning between particulate and dissolved phases during sorption and desorption and to determine the extent to which these reactions were modified by the salinity.     

Fractionation characteristics of rare earth elements(REEs) linked with secondary Fe,Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements(REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs(La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs(LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs(HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs.The substantial fractions of REEs in soils extracted byoxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile(10 %–30 %), which were similar to the mass fraction of Fe(10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.     

Metal (Al, Fe, Mn and Cu) distributions and origins of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Marmara Sea and the coast of Istanbul, Turkey

In this study, total metal (Al, Fe, Mn and Cu) and PAHs analyses have been done in the surface sediments. Sediment samples have been collected from seven parts of the Marmara Sea and the coast of Istanbul during 2009. Total Al, Fe, Mn and Cu contents vary between 1.8% and 5.4%; 1.1% and 2.8%; 122 and 259 μg g⁻¹; 27 and 416 μg g⁻¹, respectively. EF and CF values of Fe and Mn are lower than 1.5 and 1, respectively, in all the stations. Total PAH contents range between 135 and 6009 ng g⁻¹ in the surface sediments. The origin of PAHs has been found pyrolitic according to the Phe/Ant ratio in the all stations. Contrastingly, at K0, MKC and MY1 Stations, PAH origins have been observed petrogenic according to the Flu/Pyr ratio.     

Removal of As,Cd, Cu,Ni, Pb,and Zn from a highly contaminated industrial soil using surfactant enhanced soil washing

Surfactant enhanced soil washing (SESW) was applied to an industrial contaminated soil. A preliminary characterization of the soil regarding the alkaline-earth metals, Na, K, Ca and Mg took values of 2866, 2036, 2783 and 4149 mg/kg. The heavy metals As, Cd, Cu, Pb, Ni and Zn, had values of 4019, 14, 35582, 70, 2603, and 261 mg/kg, respectively. When using different surfactants, high removal of Cu, Ni and Zn were found, and medium removals for Pb, As and Cd. In the case of these three metals, tap water removed more than the surfactant solutions, except for the case of As.There were surfactants with average removals (this is, the removal for all the metals studied) of 67.1% (Tween 80), 64.9% (Surfacpol 14104) and 61.2% (Emulgin W600). There were exceptional removals using Texapon N-40 (83.2%, 82.8% and 86.6% for Cu, Ni and Zn), Tween 80 (85.9, 85.4 and 81.5 for Cd, Zn and Cu), Polafix CAPB (79%, 83.2% and 49.7% for Ni, Zn and As). The worst results were obtained with POLAFIX LO with a global removal of 45%, well below of the average removal with tap water (50.2%).All removal efficiencies are reported for a one step washing using 0.5% surfactant solutions, except for the case of mezquite gum, where a 0.1% solution was employed.     

Assessment of heavy metals/metalloid (As,Pb, Cd,Ni, Zn,Cr, Cu,Mn) concentrations in edible fish species tissue in the Pearl River Delta (PRD), China

The major aim of this study was to investigate heavy metal content of edible fish in the PRD. Eleven species of fish (consisting of 711 individuals) [catfish (Clarias fuscus), tilapia (Oreochromis mossambicus), grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mandarin fish (Siniperca kneri), snakehead (Channa asiatiea), black bass (Micropterus salmoides), mangrove snapper (Lutjanus griseus), star snapper (Lutjanu stellatus), snubnose pompano (Trachinotus blochii) and orange-spotted grouper (Epinephelus coioides)] were collected for the analyses of heavy metals. Overall concentrations (mg/kg, ww) in the fish muscles were: As (0.03–1.53), Pb (0.03–8.62), Cd (0.02–0.06), Ni (0.44–9.75), Zn (15.7–29.5), Cr (0.22–0.65), Cu (0.79–2.26), Mn (0.82–6.91). Significant level of Pb were found in tilapia at all locations. It is recommended that heavy metal concentrations in different fish species must be determined on a regular basis in the future so as to reduce human health risks from acute and chronic food intoxication.     

A laboratory study of the biogeochemical cycling of Fe,Mn, Zn and Cu across the sediment-water interface of a productive lake

Laboratory incubation experiments were carried out on sediment cores collected from Esthwaite Water, U.K., during April 1987, when the sediments displayed a characteristic surface (1.5 to 2 cm) oxide floc. The experiments were undertaken at 10°C, in the dark, under variable redox and pH conditions for periods of ~ 720 h (30 d). In some cases, realistic amounts of decomposing lake algae were added to simulate the deposition of an algal bloom. Pore waters and overlying waters were obtained from the incubated sediment cores at various time intervals and the samples analysed for pH and dissolved Fe, Mn, Zn and Cu by AAS. The results demonstrated that trace metal concentrations at the sediment-water interface can show rapid, pulsed responses to episodic events associated with controlling factors such as algal deposition and mixing conditions. The variations in dissolved Fe and Mn concentrations could generally be explained by their well known redox behaviour. Appreciable loss of Mn from solution under conditions of well-developed anoxia was consistent with adsorption of Mn²⁺ by FeS. Cu and Zn were both rapidly (24 h) released into solution during incubation of sediment cores prior to the development of anoxia in the overlying waters. Their most likely sources were the reductive remobilization of Mn oxides and the decomposition of organic matter. The addition of decomposing algae to a series of cores resulted in even higher interfacial dissolved concentrations of Cu and Zn, probably through acting as a supplementary source of the metals and through increased oxide dissolution. Switching from anoxic to oxic conditions also rapidly increased dissolved Cu and Zn concentrations, possibly due to their release during the oxidation of metal sulphides. The enhanced releases of dissolved Cu and Zn were generally short-lived with removal being attributed to the formation of sulphides during anoxia and to adsorption by Fe and Mn oxides under oxic conditions.     

Determination of Cu,Fe, and Ni in Spices after Preconcentration on Diaion‐HP 20 Resin as Their Zincon Complexes

In this work, a new separation–preconcentration method was developed for the determination of trace amounts of Cu(II), Ni(II), and Fe(III) by flame atomic absorption spectrometry (FAAS). Analytes were complexed by using zincon (2‐[2‐[alpha(2‐hydroxy‐5‐sulfophenylazo) benzylidene] hydrazino] benzoic acid sodium salt). The analyte ions were quantitatively adsorbed on a Diaion HP‐20 resin at pH 5. The retained metal ions on the resin were eluted by acetone. The analytical parameters such as pH of the sample, eluent type and volume, sample volume, and flow rates of the solution and the eluent were investigated. The influences of concomitant ions on the recoveries of the analytes were also examined. The instrumental detection limits for the analytes after application of the presented solid‐phase extraction procedure were in the range of 0.72–1.41 µg/L. The validation of the presented procedure was checked by analyzing certified reference material of SRM1515 Apple Leaves. The procedure was performed by analyzing some spice samples.     

大型水库分层期和混合期溶存温室气体空间变化及排放通量

水库作为温室气体的重要来源,对区域气候变化有不可忽略的影响。然而,目前对水库溶存温室气体的空间异质性及垂向特征的认知仍然欠缺。为了揭示水库分层期和混合期溶存温室气体空间特征及排放通量,也为厘清水库温室气体产生和排放的关键过程提供重要支撑。研究选择东北地区大型水库——汤河水库为对象,于2021年7—9月和10月(分别代表水库分层期和混合期)对水库不同位置(坝前、库中和库尾)开展溶存温室气体垂向分层监测。研究结果显示,水库CH₄排放通量变化范围为0.018～0.174 mmol/(m²·d),是大气CH₄的源,空间分布为库尾>库中>坝前;CO₂通量为-4.91～58.77 mmol/(m²·d),除分层期东支库尾,其余点位均表现为大气CO₂的源,空间分布为坝前>库中>库尾。时间上,分层期CH₄排放通量(0.071±0.044 mmol/(m²·d))高于混合期((0.027±0.008) mm...