No abstract

Nonpoint source pollution from agricultural runoff which contains hazardous agrochemicals like pesticides and fertilizers threatens water bodies, posing a serious danger to aquatic ecosystems and drinking water resources. Use of agrochemicals in rice cultivation has rapidly increased in the last few decades in Sri Lanka. It has been reported that many agrochemicals contain toxic trace elements like As, Cd, Pb, Zn, Cu, Ni, Cr, Al, etc. To reduce the harmful effect of heavy metal contain-ing agrochemicals, the Government of Sri Lanka has banned the use of several toxic agrochemicals in recent years. In this context, this study was conducted after posing these restrictions to assess the occurrence of heavy metals in surface water bodies in rice cultivation areas in Trincomalee district, Sri Lanka. Ninety-three (n = 93) sample locations were randomly selected for collection of water, before and after applying agrochemicals to rice fields. This include areas from rural farm-ing communities having endemic (Padavi Sripura DS) and non-endemic (Kanthala DS and Seruvila DS) Chronic Kidney Disease of unknown etiology (CKDu). Mean and standard error of mean of As, Cd, Pb, Cu and Zn concentrations (µg/L) before and after applying agrochemicals were as {0.048 ± 0.038 and 6.220 ± 0.912}, {0.014 ± 0.013 and 0.371 ± 0.192}, {not detected and 4.421 ± 0.712}, {1.583 ± 0.397 and 1.262 ± 0.165} and {not detected and 6.403 ± 0.366}, respectively. Findings revealed that concentrations of As, Cd, Pb and Zn were significantly different (p < 0.001) before and after the application of agrochemicals. However, the observed heavy metal concentrations were far below the permissible levels for irrigation water set by Food and Agriculture Organization and United States Environmental Protection Agency, ambient water quality set by Central Environmental Authority, and drinking water quality set by World Health Organization. In addition, analyzed heavy metal concentrations in surface water samples from CKDu endemic areas were not significantly different from those from non-endemic areas (p < 0.05). To our knowledge, this is the first report of heavy metal analysis after government ban of agrochemicals. Therefore, continuous detailed research is required to fully comprehend the behavior of agrochemicals in surface water bodies in Sri Lanka.

No abstract

Eichhornia crassipes is considered the worst aquatic weed in the world as it has become a serious threat to the environment and biodiversity hence eco-friendly utilization of this hydrophyte is needed and important. Enhancement of agricultural production to cater for increased food demand is a global challenge which is aggravated by climate change and scarcity of water. Superabsorbent materials have been developed to improve water retention in soil but majority of superabsorbent are synthetic based and non-biodegradable. Therefore, this study is aimed at developing an eco-friendly superabsorbent from E. crassipes in a cost-effective manner and assess its efficacy on improved water retention in soil. E. crassipes was collected from tank nearby Faculty of Applied Sciences, Wayamba University of Sri Lanka and petiole was treated with potassium hydroxide (KOH) followed by microwave irradiation in which reaction conditions were optimized to obtain maximum water absorption and swelling capacity. Prepared superabsorbent was characterized using Fourier Transform Infrared Spectroscopy (FTIR), XRD and scanning electron microscopy (SEM) techniques. Efficacy of the superabsorbent on improved water retention was assessed using normal loam soil. The superabsorbent showed a maximum swelling index of 1276% at KOH concentration of 0.1 moles/l which is attributed to highly porous structure, presence of hydrophilic functional groups in cellulose and hemicellulose, increased number of surface hydrophilic functional groups during the KOH activation process and carboxymethyl cellulose created during microwave irradiation. Water absorption capacity of the superabsorbent is greatly influenced by KOH concentration, reaction time, microwave power and exposure time. Water retention studies in soil showed that superabsorbent has capacity to retain water for 27 days with a slow rate of water evaporation whereas soil samples without superabsorbent showed a high rate of water evaporation retaining water only for 15 days. Findings of this study disclose an innovative method for development of an eco-friendly superabsorbent from E. crassipes in a cost-effective manner excluding toxic chemical reagents which can be used for improved water retention in soil effectively for climate change resilient sustainable agriculture.