Assessment of As, Cd, Ni and Cr Contamination in Water, Sediments and Fish of Shahid Rajaie Dam, North Iran

 
Introduction
The pollution of the aquatic environment with heavy metals and trace elements has become a worldwide problem during recent years, because they are indestructible and most of them have toxic effects on organisms. Potentially toxic elements (PTEs) added to an aquatic system by anthropogenic and natural sources are distributed during their transport between different compartments of aquatic ecosystems, such as water, sediment and biota. The main goals of present study are: 1) determine concentrations of As, Cd, Ni and Cr in water and sediment as well as their accumulation in fish, 2) Evaluating contamination and toxicological factor in the river and lake dam sediments and 3) calculate monthly fish consumption limits for carcinogenic and noncarcinogenic health.
Materials & Methods
Study area
Shahid Rajaei dam is located in 40Km south of the Sari City, in the north part of Iran (Fig. 1) with 160 million cubic meters capacity and approximate catchment of 1244Km². It is constructed on Tajan River and its reservior is fed by Shirinrood and Sefidrood rivers (in the confluence of these rivers, Tajan river arise). It was designed to provide irrigation, drinking, and industrial water in the region. The main activities in this area are agriculture, crop irrigation, and dairy activities. The main human settlements are in upstream including Ferim, Afrachal, Ali-Abad, Sekuya villages with a total of more than 10000 habitants. Geological formations in the region in terms of lithology are mainly limestone, dolomitic limestone, sandstone, marl and shale (Fig. 1).
Sampling and analysis
For water quality assessment, 16 water samples were collected from the surface waters including 9 sites along the Shirinrood (Sh-1 to Sh-9) and 4 sites along Sefidrood (S-1 to S-4) rivers and 3 samples from Lake Dam (M-1 to M-3) during two periods (November 2012 and September 2013). The location of the sampling points is shown in Fig. 1. The samples were kept at 4°C prior to analysis. As, Cd, Ni and Cr were analyzed by ICP-MS in Westlab, Australia. 26 Sediment samples were collected from Sefidrood, Shirinrood rivers and dam lake, using a pre-cleaned stainless steel grab sampler for Lake samples (SR-7 to SR-15) and using a plastic scoop for river samples (SR-1 to SR-6 and SR-16 to SR-26) in October 2012. Figure 2 shows the location of the sampling points. The collected samples were immediately stored in polyethylene bags and air-dried in the laboratory at room temperature. Then, gravel and plant root were removed. The samples were passed through a 63 micron steel sieve. The concentrations of the constituent potentially toxic elements (PTEs) were measured at Zar Azma Laboratory (Iran) using ICP-MS methods. Fish samples, including two species Barbel and L. cephalus of Cyprinidae family, were collected from the Lake Dam. The fish samples were washed with deionized water, packed in polyethylene bags and kept at -20°C, then, transported on ice to the laboratory. As, Cd, Cr and Ni were analyzed by atomic absorption spectrometry.
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 1: Geological map of the study area and location of water sampling stations.                Fig. 2: Location of sediment sampling stations.
 
Discussion of Results and Conclusions
All water samples are Ca-HCO₃-SO₄ type. The average abundance order of PTEs for water samples in two periods are: Ni >Cr >As >Cd (Table 1). Concentrations of As, Cd, Cr and Ni in all the water samples are less than WHO and EPA standard. The average abundance order of PTEs for sediment samples are: Cr >Ni >As >Cd (Table 2).
 
 
Table 1 Concentration of PTEs (µg/l) and Major ions (mg/l) in water.             Table 2 The comparison of As, Cd, Cr and Ni concentration




 


Na⁺


Mg⁺⁺


Ca⁺⁺


HCO₃^-


Cl^-


SO₄^-


As


Cr


Cd


Ni




Average


19.0


5.3


66.4


200.2


20.9


65.7


0.39


2.2


0.11


7.73




Max


61.5


11.0


123.0


283.7


30.2


177.6


0.81


4.0


0.18


9.85




Min


11.3


3.3


55.0


161.7


12.9


33.2


0.01


1.0


0.07


2.80




WHO


30-60


-


-


-


250


250


10


50


3


20




EPA


50


150


200


-


250


250


10


100


3


-




     in sediment samples with sediment quality guidelines




PETS (mg/kg)


Cr


Ni


As


Cd




Max


81.05


57.31


10.80


0.80




Min


46.55


27


2.30


0.20




Average


68.13


37.85


7.40


0.41




PEL


90.00


36


17


3.53




Average/PEL


0.76


1.05


0.44


0.12




TEL


37.30


18


5.90


0.60




Average/TEL


1.83


2.10


1.25


0.69




ERM


370


51.60


70


9.60




Average/ERM


0.18


0.73


0.11


0.04




ERL


81


20.90


8.20


1.20




Average/ERL


0.84


1.81


0.90


0.34




 
 
 
 
 
 
 
The enrichment factor (EF), base of average shale were calculated with equation 1.
 
Where [M]= total trace element concentration measured in sediment sample (mg/kg) and [Sc]= total concentration of scandium as the reference element (mg/kg ). Enrichment factor value for As, Ni and Cr is 2 that reveals moderate contamination (Fig. 3)
 
Fig. 3: Box diagram of enrichment factor for PTEs in Sediment samples.
 
The comparison of selected elements concentration in sediment samples with sediment quality guidelines indicate that the average concentration of As, Cr and Ni in the present sediments is higher than threshold effect level (TEL). Nickel shows higher concentration than probable effect level (PEL) and effect range low (ERL) values (Table 2). These sediments based on PELQ (equation 2) and ERMQ (equation 3) calculations, for Cr, As, Ni and Cd indicate slightly toxic.
 
Where M_i is the concentration of element i in sediments, ERM_i and PEL_i the guideline values for the element i and n the number of metals
The average abundance order of PTEs contents in Barbel fish is similar to water samples, while for L. cephalus fish is Cr >Ni >Cd >As. Chromium reveal higher concentration than WHO standard (0.15 mg/kg) in both fish species, while Ni content in Barbel fish is higher than WHO standard (0.4 mg/kg).
To estimate the public health risk of exposure PTEs through fish consumption, the CR_lim for either carcinogenic (equation 4) or noncarcinogenic (equation 5) health effects, were calculated.
 
Where CR_lim =maximum allowable fish consumption rate (kg/d)
ARL = maximum acceptable individual lifetime risk level (unit-less)
BW = consumer body weight (70kg)
C_m =measured concentration of chemical contaminant m in fish (mg/kg)
CSF = cancer slope factor (mg/kg-d)
RfD = oral reference dose (mg/kg-d)
Equation (6) was used to convert daily consumption limits, in kilograms, to meals consumption limits over a given time period (month) as a function of meals size
 
Where CR_mm = maximum allowable fish consumption rate (meals/mo)
T_ap=time averaging period (365.25 d/12 mo = 30.44 (d/mo))
MS = meals size (0.227 kg fish/meals)
The RfD values, CSF values, allowable Monthly fish consumption for As, Cd, Ni and Cr are summarized in Table 3.
Based on CR_mm value, maximum allowable Barbel and L. cephalus fishes consumption for carcinogenic health of As is two meals per month (Approximately 0.5 kg).
 
Table 3 Monthly fish consumption limits for carcinogenic and noncarcinogenic health endpoints and other parameters of PTEs in fish species




Fish species


PTEs


C_m


RfD


CSF


Noncancer


cancer




CR_lim


CR_mm


CR_lim


CR_mm




Barbel


As


0.0325


0.0003


1.5


0.65


87


0.01


2




Cd


0.018


0.001


NA


3.89


521


-


-




Ni


1.44


0.02


NA


0.97


130


-


-




Cr


1.39


0.02


NA


1.01


135


-


-




Leuciscus cephalus


As


0.035


0.0003


1.5


0.6


80


0.01


2




Cd


0.04


0.001


NA


1.75


235


-


-




Ni


0.065


0.02


NA


21.54


2888


-


-




Cr


0.91


0.02


NA


1.54


206


-


-