الوحدة العضوية في القصيدة العربية قديما وحديثا

The issue of harmony and unity in the Arabic criticism and poem is of prime concern, which gained the great importance in modern criticism; as various critiques are of the different opinions regarding its existence, significance, applications and concepts even; in both ancient Arabic criticism and modern poetry. The present study will investigate to find out its roots in the ancient Arabic criticism and poetry; and to prove its references in modern Arabic criticism and poetry while indicating how this issue is kept alive by contemporary poets.

Use of Biochar to Decrease Heavy Metals Uptake in Vegetables, Irrigated With Wastewater

Wastewater is being used frequently in urban and semi urban areas of the world to irrigate vegetables (30% of total wastewater), fodder and food crops. It contains a vast variety of organic and inorganic pollutants along with high concentrations of plant nutrients. Among inorganic pollutants, heavy metals (HM) are of major concerns because of their persistence, toxicity and non-biodegradable nature. The concentrations of toxic metals especially cadmi-um (Cd), chromium (Cr) and lead (Pb) have reached to phytotoxic levels in vegetables irrigat-ed with wastewater in Pakistan. Further, these toxic metals enter the food chain by the con-sumption of contaminated food crops, especially vegetables, and cause many diseases in hu-man beings. The use of biochar as a low-cost biosorbent is an emerging and promising tech-nology for remediation of HM contaminated wastewater and soil. High surface area, wide range of pH, high CEC, long term stability and presence of oxygen-containing functional groups are the properties of biochar, which make it suitable for remediation of HM contami-nated wastewater and soil through various mechanisms, i.e. sorption, altering pH, changing the redox state of the HM, complexation and precipitation of metals. Biochar also has the ability to improve soil nutritional properties along with remediation of HM contaminated soil. This study was based on the hypothesis that use of biochar may decrease the HM uptake in vegetables that are irrigated with wastewater. In a laboratory study, four different biochars were produced by using two feedstocks (green waste and popular twigs) and two pyrolysis temperatures (350 and 650°C). The biochars were characterized on the basis of their nutri-tional, chemical, proximate, molar ratio and oxygen-containing functional groups. The low pyrolytic temperature (350°C) produced biochar from both green waste and popular twigs feedstocks that had better chemical properties (i.e. high CEC) and nutritional properties of N, P and K content as well as contained high concentration of oxygen-containing functional groups as compared with the high pyrolytic temperature (650°C) pro-duced biochar. These four types of produced biochars were also tested to check their effec-tiveness for remediation of HM spiked water and soil. Maximum removal and immobilization of HM (Pb, Cd and Cr) from water and soil were measured by using low pyrolytic tempera-ture produced biochars (i.e. green waste biochar produced at 350°C (GWB350°C) and popu-lar twigs biochar produced at 350°C (PTB350°C)). These two biochars were further evaluat-ed to determine the best rate of biochars on the basis of maximum immobilization and remov-al of HM from soil irrigated with wastewater and from wastewater collected from Chukara Farm, Faisalabad. It was concluded that the 2.0% (w/w) and 4 g L-1 rates of selected biochars for soil and water, respectively, showed maximum immobilization and removal of HM. The main mechanisms for this remediation of HM polluted soil and water was at-tributed to improved soil chemical properties including increased soil CEC and organic car-bon content, enhanced soil microbial biomass carbon and biochar characteristics (i.e. high concentration of oxygen-containing functional groups and high CEC). The addition of bio-char in soil also improved the soil nutritional properties in that it increased total N, available P and extractable K concentrations in soil along with remediation of HM. In a final pot experi-ment study, spinach was grown as a test crop to evaluate the impact of biochar on HM con-centration, and growth, yield and quality of spinach produced when irrigated with wastewater at different fertilizer rates. Results revealed that maximum yield of wastewater irrigated spinach having good nutritious value and health safety standards related to HM was obtained when biochar was directly added soil under 50% of recommended fertilizer dose as compared with irrigation with biochar treated wastewater. Further, among biochar types, the GWB350°C showed significantly better results as compared with the PTB350°C. The overall conclusion from this study was that direct addition of low pyrolytic temperature- produced biochar applied to soil at a rate of 2.0% (w/w) reduced the fertilizer dose needed and gave maximum yields while significantly reducing concentrations of HM in vegetables.