IntroductionPakistanonce a water surplus country, is now in the list of water deficit countries. Wateravailability is decreasing drastically from 1299m3 in 1996-1997 to11,00m3 in 2006 and it will be decreased to about 700m3in the near 2025.
Therefore, most of the people rely on the non-conventionalwater resources i.e. Industrial waste water,for irrigation practices (Ghulam Murtaza and Munir H.
Zia). Irrigation withwaste water may result in a number of benefits and can change the soilchemistry as well. Potential beneficial changes may be, increase in availablephosphorus, potassium, nitrogen and organic carbon when compared with soil treatedwith clean irrigation water (36 in Agarwal). In many cases irrigation withwaste water resulted in increased growth, yield and plant constituents as well(2 in agarwal). Dueto uninterruptedly increasing population, very large amount of waste water isproduced on daily basis from houses, markets and as well as from industries (4in 30-36). By reusing this huge amount of water for agricultural irrigationpurpose will result in less dependence on freshwater resources. (2 in 30-36).
Waste water pollution is now a major problem which should be handled at ourfirst priority to stop the depleting freshwater resources (3 in 30-36). Lactuca sativaL. belongs to largest family of an angiosperms, Asteraceae. It is mostimportant leafy vegetable which is exclusively used as a salad but some varietiesare also cooked. (Zahr). Lettuce is a cool season crop and grows best intemperature range of 73oF at day time and 45oF at night.Silt loams and sandy soils are the best soil for growing lettuce.
Onemajor threat associated with the use of waste water is the accumulation ofheavy metals by plants (44 in agarwal). Therefore this study was carried out toevaluate the effect of waste water on morphological and physiologicalcharacters of lettuce (Lactuca sativa L.).
It is hypothesized that proper ratioof waste water and freshwater may result in vigorous growth and high yield withlow heavy metal accumulation. Moreover, by filtering the waste water with biofilter may result in a waste water with low potential threat to heavy metalaccumulation as well. Materials and MethodsArea of StudyThisexperiment was carried out in PMAS Arid Agriculture University Rawalpindi(33.6492° N, 73.0815° E) to access the impacts of industrial waste water (LaiStream, Rawalpindi) on morphological, biochemical and physiological propertiesof two varieties of Lactuca sativa L.namely L. sativa var.
Iceberg andBoston. This experiment wasconducted in pots with dimeter of 14″ length and 8″of width. F1 generationplants of two lettuce varieties were provided by the National agricultureresearch council Islamabad. In each potfour seedlings were transplanted and properly watered at transplantation time.Experiment was conducted in totally randomized block design and all thetreatments were in three replicates. Watering was done thrice in a week. Plantswhich were given well water were taken as control.
Detail of the treatment isgiven in the table. Sampling of WastewaterWastewaterwas collected from the I-9 industrial area of Islamabad. All the industrial anddomestic wastewater of I-8 and I-9 area is drained into this stream.
A compostsample was taken and brought into the experimental sight. Waste water was thenfiltered with the help of biofilter for further treatments. Sampling was madetwo times during the study, first at start of the experiment and secondly after25 days of sowing. Collected wastewater was analyzed for its physico-chemicalproperties in the lab. Parameter Value ISI Standards pH 8.02 5.5-9.0 Total solids (mg l-1) 6380 – Total dissolved solids (mg l-1) 6180 2100 Total suspended solids (mg l-1) 200 100 Hardness (mg l-1) 1130 600 Chlorides (mg l-1) 1350 1000 Table 1.
Some physio-chemicalproperties of wastewater sample from Lai stream S.no Row Treatments 1 To 100% irrigation water (Control) 2 T1 75% IW+ 25% WW 3 T2 50%IW+ 50%ww 4 T3 25% IW + 75% WW 5 T4 100 % Wastewater 6 T5 75% IW + 25% FW 7 T6 50% IW + 50% FW 8 T7 25% IW+ 75%FW Table 2. Treatments of thewastewater and filtered water Parameters Value ISI standards Copper 0.
21 0.05-1.5 Chromium 2.03 0.05 Nickel 1.59 <0.01 Zinc 0.
46 5.0 – 15.0 *ISI standards No. 2490 (1974)Table 3. Heavy metals concentration (mg l-1) in industrialwastewater samples Lai Stream RawalpindiSoil AnalysisCompositesoil sample was collected after harvesting and stored in a plastic bottle forfurther analysis. The soil sample was analyzed for different physico chemicalproperties like pH, EC, total organic content etc.
Texture Bulk density (g cc-1) pH Organic matter (%) CaCO3 (%) E.C. (dS m-1) Heavy metals (ppm) Loamy 1.40 7.
20 0.53 0.60 1.
60 Zn Cu Ni Cr 0.26 0.72 0.18 0.
12 E.C. = Electrical conductanceTable 4: Physico-chemical properties of alluvial soil before sowing Resultsand DiscussionLeaf Chlorophyll Content: Withincrease in wastewater concentration upto 50%, leaf chlorophyll contentsincreased and then decreased with further increase in wastewater concentration.Also Iceberg variety was more effected than Boston (Table 5). Naaz and S.N.Pandey (2009) and Jenkins etal. (1994) observed that plant irrigated by wastewater had darker greencolor than control and had lower chlorophyll contents when concentration wasincreased beyond 50%.
When bio-filtered was applied, chlorophyll contentsincreased but similar pattern was observed. Table5.Chlorophyll Contents after treatment with wastewater Leaf Area: Byincreasing wastewater to irrigational water ratio to 50%, leaf area wasincreased, but it then rapidly decreased when exposed to 75% and 100%wastewater (Table 6).
When bio-filtered water was applied, it was observed thatleaf area increased by 8% in Boston and 13% in Iceberg. Alizade et al. (2001) reported that wastewaterincreased leaf width in maize (Zea mays).Wastewater contains a great number of essential nutrients for increasing plantleaf area. Table6. Leaf area after treatment with wastewater Root Fresh weight: Rootfresh weight increased with increase in wastewater concentration in bothvarieties upto 50% and then decreased upto 100% concentration.
Wastewatercontains essential nutrients increasing cell volume and turgor so leaf weightincreases (Jalali et al., 2010). Byexposing the plants to bio-filtered water, relative weight increased indicatingthe removal of some nutrients by bio-filter (Table 7). Table7.
Root fresh weight after exposure to wastewater Shoot Fresh Weight: Increasein shoot fresh weight was observed when exposed upto 50% concentration in bothvarieties but it then decreased when exposed to higher concentration.Wastewater contains essential nutrients increasing cell volume and turgor soleaf weight increases (Jalali et al.,2010). By exposing the plants to bio-filtered water, relative weight increasedindicating the removal of some nutrients by bio-filter (Table 8). Table8. Shoot fresh weight after wastewater treatment Root Length: Plantirrigated with wastewater shown considerable root elongation upto 50% concentrationand then it decreased upto 100% concentration in both varieties.
When they wereirrigated with bio-filtered water root length increased sufficiently then untreatedwastewater (Table 9). Table9. Effect of wastewater on Root length Shoot Length: Plantirrigated with wastewater shown considerable shoot elongation upto 50% concentrationand then it decreased upto 100% in both varieties. The retardation in growth and development oftoxicity symptoms in plants could be attributed due to high uptake of heavymetals and their accumulation in plant parts (Pandey, 2006).Whenthey were irrigated with bio-filtered water shoot length increased sufficientlythen untreated wastewater (Table 10).
Table10. Effect of wastewater on Shoot length ConclusionThis study concluded that wastewater ofLai stream is not suitable for irrigational purposes without filtration as itcontains high concentration of heavy metal, and it may enter human food chain,if plants are directly irrigated with this water. Lactuca sativa L. was found to be affected by the undilutedwastewater and produced visible symptoms of toxicity indicating its sensitivenature to pollution thus can be used in phytoremediation studies.