Hydrocarbons compounds accumulated in the plants cells suppressed their photosynthesis by reducing the primary photochemical yield, electron transport capacity, the activity of release oxygen center and photosystem II. Meanwhile respiration of plants enhanced, compelling the increase of energy expenditures (Aksmann and Tukaj, 2008). Oil also could block the absorption of CO₂ and nutrients, leading to decrease chlorophyll a and reduce of primary productivity. Oil would destroy the cell structure and membrane system of plants and disturb the operation of anti-oxidation defense system, stop the synthesis of nucleic acid and protein, even inducethe cell abnormality and gene mutation (Bopp and Lettieri, 2007). Researches showed that oil would damage DNA structure or cause the DNA adduct formation of plant cells, prevent the replication of DNA, thus cells could not divide, leading to the augmentof cell size (Singh and Gaur, 1990). In addition to that petroleum hydrocarbons may affect the lipid structures within plant and other cells if they are not metabolized quickly (CCME, 2000). Gallegos et al. (2000) found that oil components can enter into the seed and disturb metabolic reactions or even kill the embryo and a reduction of biomass for plant species. Inhibition of plant growth can be caused by toxic effects of petroleum hydrocarbons. Small molecules of hydrocarbons can enter and pass cell membranes, leading to reduced membrane integrity or even to the death of the cell (Merkl, 2004). In this study we used two species from common aquatic plants as bio-indicators of pollution with hydrocarbons compounds and provided information on temporal and spatial variations of TPHs of these plants in the study area.

Plant samples were collected from Al-Kahlaa River during the period from October 2012 to November 2013. The samples were rinsed thoroughly with distilled water in the lab then were cut to small parts, dried, grounded and sieved using a 63μm metal sieve then placed in clean glass vial to become ready for analysis. The procedure of Grimalt and Oliver (1993) was used for the extraction of hydrocarbon compounds from plants samples. Spectrofluorometer was used to determine total petroleum hydrocarbons in plant samples. Simple thermometer with range from 0 to 100 °C graduated at 0.2 °C used to measure air and water temperature.

 

Classification of plant species (Al-Saadi and Al-Mayah, 1983)

Class: Angiospermae                                      Class: Angiospermae

Order: Ranales                                                 Order: Poales

Family :Ceratophyllaceae                               Family: Graminceae

Sp: Ceratophyllum demersum                       Sp: Paspalum pespaioides

 

Concentrations of TPHs µg/g d.w in C. demersum ranged from 5 to 11.92, from 6.02 to 12.106, from 19.73 to 58.97 and from 13.74 to 31.34 during winter, spring, summer and autumn respectively (Table 1), whereas in P. pespaioides ranged from 3.18 to 8.46, from 5.18 to 19.73, from 16.26 to 43.44 and from 14.09 to 46.03 during winter, spring, summer and autumn respectively (Table 2). The highest level of TPHs in aquatic plants was recorded during summer, while the lowest level was during winter in all stations. From these results, it can be observed that there is a difference in the concentrations of TPHs in different species of aquatic plants, these variations may be due to the different abilities of plants to accumulate or eliminate certain pollutants to the environment and the accumulation processes of pollutants may depend on some physical and chemical properties like pH, temperature, concentration of nutrients, salinity and dissolved oxygen (Thomas et al., 1984; Al-Saad, 1994), this perhaps explain the rather high concentration in some plants than others. Also a seasonal variation was noticed in the concentrations of TPHs in C. demersum and P. pespaioides, therefore the high concentrations in the two plants were recorded during summer followed by autumn and this may be attributed to the growth of plants during these seasons (Table 3). A positive significant correlation has been noticed (r= 0.764 and r= 0.717 at P< 0.01, Table 4) in C. demersum and (r= 0.673 and r= 0.650 at P< 0.01, Table 5) in P. paspaloides between TPHs and temperature (water and air, respectively), the same conclusions reached by Al-Saad (1994), Talal (2008), Al-Khatib (2008) and Abed Ali (2013) when working on some aquatic plants in Hor Al-Hammar, Hor Al-Howaiza and Euphrates river. In addition to that non-significant spatial variations in C. demersum species were observed, but there are a significant spatial variation especially between the results of P. pespaioides in treatment unit and reference stations in Table 5, the highest levels were recorded in treatment unit station while the lowest in reference station these differences in concentrations of TPHs in P. paspaloides may be due to the input of oil from vehicle maintenance (motor mechanic) as well as sewage discharge which reach to Al-Kahlaa River across treatment unit (Jazza, 2009). The decrease of their levels in control station is due to that it is located farther from the eminent anthropogenic pollution and also dilution factor since it lies on the end of Tigris River before entering Amara city about 25km.

Abed Ali S.T., 2013, Seasonal and situational changes to hydrocarbons concentrations and n-alkane origin to samples from water, sediments and biota in Euphrates river near Al-Nasiriya city. MSc thesis college of science, university of Thi-Qar .127p. In Arabic.  

 

Aksmann A. and Tukaj Z., 2008, .Intact anthracene inhibits photosynthesis in algal cells: a fluorescence induction study on Chlamydomonas reinhardtii cw92 strain, Chemosphere 74 (1) 26–32.

 

Al-Khatib, and F.M.H., 2008, Determination the concentration, origin and distribution of hydrocarbons compounds in water, sediments and some biota of Hor Al-Howaiza, south of Iraq and their sources. PhD. thesis, College of Science, University of Basrah. 228P. In Arabic.

 

Al-Saad H.T., 1994, Distribution of Petroleum hydrocarbon in aquatic plant of Hor Al-Hammar marsh of Iraq. Mar. Mesopot .9(2): 313-321.

 

Al-Saadi H. A, and A. A Al-Mayah, 1983, Aquatic plants of Iraq. Cent. Arab. Gulf. Studies Pub. Basrah University (in Arabic).

Bopp S.K. and Lettieri T., 2007. Gene regulation in the marine diatom Thalassiosira pseudonana upon exposure to polycyclic aromatic hydrocarbons (PAHs), Gene 396 (2) 293–302.

 

CCME, 2000, Canada-Wide Standards for Petroleum Hydrocarbons (PHCs) in Soil: Scientific Rationale, CCME

 

Gallegos M. M. G, Gomez T. A.G., Gonzales L. G., Montes O. G., Yanez L.Y., Zermeno J.A. and Gutierrez R. M., 2000, Diagnostic and resulting approached to restore petroleum-contaminated soil in a Mexican tropical swamp. Water Sci. Technol. 42, 377.

 

Grimalt J. O., and Oliver J., 1993, Source input elucidation in aquatic systems by factor and principal component analysis of molecular marker data. Anal. Chem. Acta., 278 : 159 – 176 .

 

Jazaa S.H., 2009, A study of physical, chemical and bacteriological properties of water of Al-Kahlaa river in maysan governorate /Iraq .M. Sc thesis. college of science. university of Basrah .67pp.

 

Merkl N., Schultze K. R. & Infante C., 2004. Phytoremediation in the tropics-the effect of crude oil on the growth of tropical plants. Biorem. J. 8, 179.

 

Singh, A.K., and Gaur J.P., 1990, Effects of petroleum oils and their paraffinic, asphaltic, and aromatic fractions on photosynthesis and respiration of microalgae, Ecotoxicol. Environ. Safety 19 (1) 8–16.

Talal A. A., 2008, A study for the seasonal and regional variations of hydrocarbon levels and origin of n–alkanes in water, sediments and some species of Biota in Hor Al-Hammar Marshes. PhD thesis, college of science, University of Basrah. 166 p. In Arabic.

 

Thomas, W., Ruhling A., and Simon H.,1984, Accumulation of Air born pollutants (PAHs, Chlorinated hydrocarbons heavy metals) in various plant species and humans. Environ. Pollut. 36: 295-310.