Tanveer Adyel

Health Risk Assessment of Pesticide Residues via Dietary Intake of Market Vegetables from Dhaka, Bangladesh

The present study was designed to assess the health risk of pesticide residues via dietary intake of vegetables collected from four top agro-based markets of Dhaka, Bangladesh. High performance liquid chromatography with a photo diode array detector (HPLC-PDA) was used to determine six organophosphorus (chlorpyrifos, fenitrothion, parathion, ethion, acephate, fenthion), two carbamate (carbaryl and carbofuran) and one pyrethroid (cypermethrin) pesticide residues in twelve samples of three common vegetables (tomato, lady’s finger and brinjal). Pesticide residues ranged from below detectable limit (<0.01) to 0.36 mg/kg. Acephate, chlorpyrifos, ethion, carbaryl and cypermethrin were detected in only one sample, while co-occurrence occurred twice for fenitrothion and parathion. Apart from chlorpyrifos in tomato and cypermethrin in brinjal, all pesticide residues exceeded the maximum residue limit (MRL). Hazard risk index (HRI) for ethion (10.12) and carbaryl (1.09) was found in lady’s finger and tomato, respectively. Rest of the pesticide residues were classified as not a health risk. A continuous monitoring and strict regulation should be enforced regarding control of pesticide residues in vegetables and other food commodities.

Stormwater nutrient attenuation in a constructed wetland with alternating surface and subsurface flow pathways: Event to annual dynamics

Among different Water Sensitive Urban Design (WSUD) options, constructed wetlands (CWs) are widely used to protect and support downstream urban waterways from stormwater nutrients. This analysis assessed the nutrient attenuation ability of a novel CW in Western Australia that combined multiple alternating surface flow (SF) and laterite-based subsurface flow (SSF) compartments within a parkland context to improve the urban landscape and amenity. The CW was designed to maximise nutrient reduction despite experiencing a large range of hydrologic conditions, from low transit time nutrient-rich pulses during the wet periods to prolonged low to zero flow conditions during the dry periods. The CW design was further complicated by the possibility of ungauged water inputs after wet antecedent conditions, seasonal macrophyte senescence and a recirculation system to maintain flow during the dry periods. From analysis of data over a range of time scales, we determined that overall the CW attenuated up to 62% total nitrogen (TN) and 99% total phosphorus (TP) loads during dry weather conditions, and 54-76% TN and 27-68% TP during episodic flow pulses. N species attenuation was dominant in the SF compartments, while P species were attenuated mostly within the SSF compartments. Nutrient accumulation in the sediments, and above and below ground biomass of the macrophytes were found to increase during the early stages of operation, suggesting the system reached equilibrium within four years. Further, by comparing trends in nutrient attenuation within the context of diel changes in high frequency oxygen data from different compartments, it was demonstrated that changes in dissolved oxygen were related to changes in nutrient concentration across the CW, although interpretation of this was complicated by changing hydro-climatological conditions. The implementation of this CW concept in a highly seasonal Mediterranean climate demonstrates that urban liveability and environmental health can both be improved through careful design.

Storm event-scale nutrient attenuation in constructed wetlands experiencing a Mediterranean climate: A comparison of a surface flow and hybrid surface-subsurface flow system

Among different Water Sensitive Urban Design options, constructed wetlands (CWs) are used to protect and restore downstream water quality by attenuating nutrients generated by stormwater runoff. This research compared the nutrient attenuation ability during a diverse population of storm events of two CWs: (a) a hybrid CW with multiple alternating surface flow (SF) and laterite-based subsurface flow (SSF) compartments, and (b) a single stage SF CW. Within-storm variability, nutrient concentrations were assessed at 2 to 3-h intervals at both the main inlet and outlet of each CW. Dissolved oxygen concentrations of the surface waters were also monitored at 10-min intervals using high frequency in situ sensors. Nutrient loads into the CWs were observed to be higher when a high rainfall event occurred, particularly after longer antecedent dry conditions. Longer hydraulic retention times promoted higher attenuation at both sites. However, the relative extent of nutrient attenuation differed between the CW types; the mean total nitrogen (TN) attenuation in the hybrid and SF CW was 45 and 48%, respectively. The hybrid CW attenuated 67% total phosphorus (TP) loads on average, while the SF CW acted as a net TP source. Periodic storm events transitioned the lentic CW into a lotic CW and caused riparian zone saturation; it was therefore hypothesized that such saturation of organic matter rich-riparian zones led to release of TP in the system. The hybrid CW attenuated the released TP in the downstream laterite-based SSF compartments. Diel oxygen metabolism calculated before and after the storm events was found to be strongly correlated with water temperature, solar exposure and antecedent dry condition during the pre-storm conditions. Furthermore, the SF CW showed a significant relationship between overall nutrient load attenuation and the change in oxygen metabolism during the storm perturbation, suggesting oxygen variation could be a useful proxy indicator of CW function.

Reuse Feasibility of Electrocoagulated Metal Hydroxide Sludge of Textile Industry in the Manufacturing of Building Blocks

During the last decade, the growing load of sludge from textile industries, the top foreign exchange earning sector of Bangladesh, is a common nuisance to environmental system and community health. The present study was aimed to minimize the environmental impact from the disposal of Electrocoagulated Metal Hydroxide Sludge (EMHS) by using it as a partial substitute of clay in the manufacturing of construction material like building blocks (BBs). Different batches of normal and pressurized building blocks (NBBs and PBBs, resp.) were prepared using up to 50% EMHS with clay and then fired at a particular temperature. EMHS proportion in the mixture and firing temperature were two key factors determining the quality of BB. BB did not show any deformation or uneven surfaces at any of the examined firing temperature. At higher firing temperature and EMHS proportion, more weight loss and shrinkage of BB were noticed. Higher compressive strength and lower water adsorption were found at lower EMHS content and higher firing temperature. It was explored that NBB and PBB with 20 and 30% EMHS in clay, respectively, and fired at 1050 °C would be usable for nonloading applications; namely, ornamental bricks, decoration purposes, and fence of garden.