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  Behavior of Cu, Zn, Pb, Ni and Mn   Behavior of Cu, Zn, Pb, Ni and Mn during mixing of freshwater with Caspian Sea water       A.R. Karbassia, J. Nourib*, Gh.R. Nabi Bidhendia, G.O. Ayazc       از تیتر این مقاله تعجب نکنید چون متن این مقاله مثل تیترش به زبان انگلیسیه.   من خودم از ترجمه اش عاجزم اما برای استفاده بقیه دانشجوها اینو تو سایت قرار می دم و خیلی خوشحال می شم اگه کسی این مقاله رو ترجمه کرده واسه قرار دادن ترجمه در این سایت به نام خودش بهمون خبر بده.   در ضمن از خواهرم برای اینکه از این دست مقالات رو در اختیارم قرار داده تشکر میکنم.   در ادامه مطلب می تونید مقاله رو ببینید       Behavior of Cu, Zn, Pb, Ni and Mn during mixing of freshwater with Caspian Sea water       A.R. Karbassia, J. Nourib*, Gh.R. Nabi Bidhendia, G.O. Ayazc       aGraduate Faculty of the Environment, University of Tehran, P .O .Box 14155-6135, Tehran, Iran   bDepartment of Environmental Health Engineering and Center for Environmental Research, Medical Sciences/University of Tehran, Tehran, Iran   Tel. +98(21) 8895-4914; Fax +98(21) 2010-8361, email: [email protected]   cDepartment of Environmental Science, Graduate School of the Environment and Energy, Science and Research Campus, IAU, Tehran, Iran       Received 30 September2006; Revised 22 May 2007; accepted ×××           Abstract             Behavior and flocculation of metals during estuarine mixing can significantly influence the chemical mass balance between rivers and seas or lakes. Present investigation describes the results of mixing of sample of filtered (0.45 μm) Caspian Sea water with filtered water sample taken from Babolrud River in 9 different salinity proportions. Flocculation of colloidal size fraction heavy metals was investigated on a series of mixtures with salinities water ranging from 1.5 to 9.5‰ during mixing of Babolrud River with the Caspian Sea water. The flocculation trend of Cu (77.9%)>Zn (74.6%)>Mn (64.97%)>Pb (38.2%)>Ni (12.2%) indicates that Cu, Zn, Pb and Mn have non-conservative behavior and Ni has relatively conservative behavior during estuarine mixing.  Highest flocculation of heavy metals occurs between salinities of 1.5 to 3.5‰.  Statistical analysis indicates that the flocculation of Cu is governed by pH and PO4. The flocculation rate of studied metals showed that the overall colloidal metal pollution loads can be reduced by various percentiles (ranging from as low as 12 to as high as 78%); during estuarine mixing.       Keywords: Behavior, flocculation, heavy metals, saline water, estuary             *Corresponding author.       ××× - ××× /$- See front matter © 2007 Elsevier B.V. All rights reserved.   doi: ×× - ××××/j.desal.2006. ××-×××   1. Introduction            During estuarine mixing, dissolved metals come into the particulate phase due to flocculation processes [3, 8 & 21].  Flocculation is enhanced by increased pH, turbulence, concentration of suspended matters, ionic strength and high algal concentration [15].  This investigation seem to be one of the only 3 such studies carried out in the southern coasts of the largest lake in the world – the Caspian Sea.  Moreover, other researchers have mainly focused on colloidal stability, surface properties, humic acids, salinity and pH [9-11, 19 & 22]. However not much information is available on recognition of dissolved metals flocculation processes during estuarine mixing of river waters with brackish lake waters [11-12 & 18].        The salinity of Caspian Sea waters ranges from 4 ppt in the northern parts to almost 13‰ in the southern parts.  Babolrud River has a length of 161 Km with a discharge of 560x106 m3/yr.  The catchments area of river is about 1659 Km2 with average precipitation of 765 mm/yr.        2. Materials and Methods        Freshwater samples were collected from the Babolrud River in a 25 liter clean polyethylene bucket on 12th Dec. 2005.  On the same day it was filtered through 0.45 μm Millipore AP and HA filters.  About one liter of filtered water was acidified with concentrated HNO3 to a pH of approximately 1.8 and stored in polyethylene bottles in a refrigerator prior to the analysis of dissolved metals.  The rest of filtered waters were also kept in refrigerator.  On the same day, Caspian Sea water was collected approximately 20 Km away from the coast to ensure that the sample was not diluted by river water (salinity=13‰).  Filtered river water and sea water were mixed together at room temperature in 9 proportions yielding salinities 1.5 to 9.5‰.  They were kept for 24 hours with occasional stirring.  The resulting flocculants were collected on 2.5 Cm diameter Millipore membrane filters (type HA, Pore size: 0.45 μm).  Millipore filters were digested by 5 ml concentrated HNO3 overnight.  The concentrations of Cu, Zn, Ni, Pb and Mn were determined by AAS (Philips model PU-9004).  Procedural blanks and duplicates were run with the samples in a similar way.  The inner standards in determination were obtained by dilution of single concentrated standards purchased from Merck Company. The accuracy of analysis was about ±5% for all elements in dissolved and flocculants phases.  Salinity, pH and electrical conductivity (Ec) of water samples were measured by Siemens multi-channel portable apparatus.  Nitrates, phosphates and sulfates were measured by photometer (model 8000) in accordance with ASTM procedure (2003).  Total Dissolved organic carbon (DOC) of water samples were measured by TOC meter (Shimatzu model TOC-VCSH-3000a).  Total hardness (TH) was determined titrimetrically.  Cluster analysis was carried out according to the Weighted Pair Group (WPG) method [4].   3. Results and Discussions        Table 1 shows concentrations of Cu, Zn, Pb, Ni and Mn found in flocculants at various salinities as well as fresh river water. The concentration of total dissolved organic carbon (DOC) in the river water is about 2.4 mg/L that increase to 51.3 mg/L at salinity of 9.5‰ (Table 2). Such an increase is suggestive of marine carbon source in the estuarine zone. Other parameters such as SO4 and total hardness (TH) show similar trend as DOC does. The increasing trend of SO4 is mainly due to redox conditions that prevail in the Caspian Sea [18]. The concentration of total nitrogen (NT) increases at low salinities (1.5 to 2.5‰) and sharply decreases at salinity of 3.5‰. Generally, concentration of NT is more in saline waters than fresh water in the area of study.        During estuarine mixing, flocculation processes may not occur as shown in Table 1. In fact, at the very first stages of mixing of river water with lake water, some of the colloidal metals ooze out of the freshwater in the form of flocculants [18 & 22]. Thus, at the later stages of mixing (i.e. higher salinities) freshwater is impoverished in base metals and fewer flocculates form (Table 2).  We, therefore, do not discuss on the data of Table 1 as they are indicative of laboratory conditions/setup. In other words during laboratory mixing, a constant amount of fresh water is mixed up with various proportion of seawater.  The values presented in Table 2, are actually derived from Table 1 by subtracting the concentrations of flocculates at a specific salinity from the prior steps.  In this way, the flocculate quantity is not calibrated to the very first concentration of the metals in the river water [12]. According to data shown in Table 2, the maximal removal of Cu, Zn and Mn occur between salinities of 1.5 to 3.5‰ while Ni removal is confined to salinity ranges of 1.5 and 9.5‰.  Lead shows similar pattern as Ni at salinities of 3.5 and 8.5‰.   The variation in the maximal removal of the studied metals may be due to destabilization of dissolve metals, corresponding to the different stages of mixing with seawater and a decrease in their negative net charge [1]. The flocculation rates of studied metals in Babolrud River are in the following order:              Cu (77.9%)>Zn (74.6%)>Mn (64.97%)>Pb (38.2%)>Ni (12.2%)            Thus, rapid flocculation in the earlier stages of mixing freshwater with lake water (salinity of 1.5 to 3.5‰) occurs that is in accordance with the findings of other researchers [2 & 7]. Interestingly, reports from other rivers flowing into southern coasts of the Caspian Sea show that Pb and Ni undergo minimum flocculation when compared with Cu, Zn and Mn [12]. However, a near conservative behavior of Ni is in conflict with the nearby estuaries [18]. It is widely accepted that dissolved organic carbon (DOC) represent a dynamic component in the interaction between geo-sphere, biosphere and hydrosphere.  Conservative DOC behavior is reported during estuarine mixing in Beaulieu Estuary, England [17]. A linear decrease in DOC over salinity range of 17 to 28‰ is reported for Bristol Channel [14]. However, in the present study consistent linear DOC increase with increase in salinity is noticed (Table 2) that is indicative of non-terrigenous DOC.  Aquatic fulvic acids accounts for 50 to 80% of the total amount of DOC in coastal waters [13]. Interestingly high relationship amongst DOC, Ec and TH with salinity of Caspian Sea water is observed (Fig. 2) that is indicative of influence of sea water as a controlling mechanism for these parameters in the estuarine zone.  Cluster analysis (Fig. 2) shows that pH and S‰ do not govern the flocculation of Zn, Ni, Pb and Mn.  It is evident that pH controls Cu flocculation in the area of study.  Interestingly, PO4 shows meaningful similarity coefficient with pH and Cu. Further investigations are needed to know as what sea water constituents have more effect on the flocculation processes of metals.  The processes that are responsible for removing dissolved PO4 at high concentrations encountered in Babolrud estuary include precipitation of apatite (calcium phosphate), vivianite (ferrous phosphate) and magnesium-ammonium phosphate are theoretically possible but not have been identified in situ or in laboratory experiments simulating estuarine conditions [6 & 18]. Finally, considering the concentrations of dissolved metals in Babolrud river water [Cu(20.8 μg/l), Zn(85 μg/l), Pb(22 μg/l), Ni(40.15 μg/l) and Mn(19.7 μg/l)] and mean discharge of river (560x106 m3/yr.), the mean annual discharge of dissolved Cu, Zn, Pb, Ni and Mn into the Caspian sea via this river would be 11.60, 47.60, 12.32, 22.48 and 11.03 tons/yr., respectively.  However, results of present study show that 77.9, 74.6, 38.2, 12.2 and 64.97% of dissolved concentrations of Cu, Zn, Pb, Ni and Mn respectively, flocculates during estuarine mixing.  Therefore, the mean annual discharge of dissolved Cu, Zn, Pb, Ni and Mn from Babolrud River into the Caspian Sea would reduce from 11.6 to 2.57, 47.6 to 12.10, 12.32 to 7.62, 22.48 to 19.74 and 11.03 to 3.87 tons/yr., respectively.       4. Conclusion        The results showed that Cu, Zn, Pb, Ni and Mn flocculate at salinities of 1.5 to 9.5‰.  The maximum removal is at lower salinities (1.5 to 4.5‰) for Cu, Zn and Mn but Pb and Ni flocculation occur at salinities of 3.5 & 8.5 and 1.5 & 9.5, respectively. Dissolved organic carbon, total hardness, electrical conductivity, SO4, NT and PO4 do not play any role in flocculation processes of Cu, Zn, Pb, Ni and Mn.  Flocculation of Cu is controlled by pH and PO4. Statistically, salinity does not play significant role in the flocculation of metals.  Besides, pH is controlling Cu only. Thus, other constituents of seawater (than salinity) might be involved in flocculation processes.  The flocculation rate of studied metals showed that the overall colloidal metal pollution loads can be reduced by various percentiles (ranging from as low as 12 to as high as 78%); during estuarine mixing of the Babolrud river water with the Caspian Sea water.  This statement not only proves the important role of the flocculation processes of colloidal metals in natural self purification of estuarine zone, but also points out the ecological importance of estuarine processes. While a part of geochemical cycle of a few heavy metals is quantified in this study; more detailed studies such as sediment water interactions that have significant influences on the behavior of metals are needed.       References   [1]    S.R. Aston and R. 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Acta Oceanologica Sunica.,  6 (1987) 567-576.       منبع:     www.ake.blogfa.com     منبع:     www.ake.blogfa.com     منبع:     www.ake.blogfa.com