Chemical and mineralogical forms of heavy metals in sediments at Langat River, Selangor

Langat River is one of the most important rivers in Selangor that caters drinking water sources for up to 1.2 million populations within the basin. In 2004, Langat River has been recognized as one of the Hydrology for the Environment, Life and Policy (HELP) river basin. An explanatory study was carried out at 22 sampling stations along the river. The sediment samples (0 – 20cm) were collected for metal speciation (Cd, Cu, Zn, As, Pb) using sequential extraction technique (SET) and analyzed via the inductively coupled plasma-mass spectrometry (ICP-MS). Parameters such as pH, Eh, electrical conductivity (EC), salinity, loss on ignition (LOI), cation exchange capacity (CEC) and particle size analysis (PSA) were also determined. The sediment mineralogy was determined using X - Ray diffraction (XRD). This study revealed that sediment was predominantly by Pb(150.29μg/g)>Cu(57.91μg/g)>As (37.40μg/g)>Zn (30.46μg/g)>Cd (0.061μg/g). There is a significant correlation among pH, Eh, EC, Ca2+, Cu, Zn, As with Pb at r=-0.234 - 0.354 (p<0.01). The associations among metals (Cd, Cu, Zn and As) © COPYRIGHT UPM ii with sediment characteristics variables were due to the factor that each variables poses towards the bioavailability of metals in the environment. The sediment mineralogy also played a significant role in controlling the fate of metal. The mineralogy that is dominant by quartz correlated with Zn, As and Pb at pCd>Zn>As>Pb in decreasing order. The association of Cu (94.61%) and Cd (64.80%) were described to be strongly attached with the non residual phase. This is contradicting with Zn (52.46%), As (66.43%) and Pb (92.21%) that accounted as the least mobile metals as a result of strong association with the residual phases. This suggests that Cu and Cd are more prone to the remobilization in the overlying water compared to Zn, As and Pb. The principal component analysis (PCA) exhibited salinity as the controlling factor in the river clusters separation. This is proven by the correlation of salinity with CEC, LOI, Na+, Ca2+, Mg2+, K+, Cd, Cu and Zn at PC1. This suggests that natural sources are the highest percentage of contribution (31.92%). The dendogram displayed stations LA 2, LA 3, LA 4, LA 5 and LA 8 as highly contaminated by Cu, Zn and As. This is supported by sediment quality guidelines (SQGs) that exhibited As as the most contaminated with 100% exceeding the permissible limits. Therefore, it is crucial to understand the interactions of specific metals in the sediment in order to controls the release, remobilization and absorption. These findings are expected to update the current status of the heavy metal pollution status as well as creating awareness concerning the security of the river water as a drinking water sources

Heart Rate Variability Recording System Using Photoplethysmography Sensor

Heart rate variability (HRV) is a physiological measurement that can help to monitor and diagnose chronic diseases such as cardiovascular disease, depression, and psychological stress. HRV measurement is commonly extracted from the electrocardiography (ECG). However, ECG has bulky wires where it needs at least three surface electrodes to be placed on the skin. This may cause distraction during the recording and need longer time to setup. Therefore, photoplethysmography (PPG), a simple optical technique, was suggested to obtain heart rate. This study proposes to investigate the effectiveness of PPG recording and derivation of HRV for feature analysis. The PPG signal was preprocessed to remove all the noise and to extract the HRV. HRV features were collected using time-domain analysis (TA), frequency-domain analysis (FA) and nonlinear time-frequency analysis (TFA). Five out of 22 HRV features, which are HR, RMSSD, LF/HF, LFnu, and HFnu, showed high correlation (rho > 0.6 and prho < 0.05) in comparison to standard 5-min excerpt while producing significant difference (p-value < 0.05) during the stressing condition across all interval HRV excerpts. This simple yet accurate PPG recording system perhaps might useful to assess the HRV signal in a short time, and further can be used for the ANS assessment

Geoaccumulation and distribution of heavy metals in the urban river sediment

Current study presents the application of chemometric techniques to comprehend the interrelations among sediment variables whilst identifying the possible pollution source at Langat River, Malaysia. Surface sediment samples (0-10 cm) were collected at 22 sampling stations and analyzed for total metals (48Cd, 29Cu, 30Zn, 82Pb), pH, redox potential (Eh), salinity, electrical conductivity (EC), loss on ignition (LOI) and cation exchange capacity (CEC). The principal component analysis (PCA) scrutinized the origin of environmental pollution by various anthropogenic and natural activities: four principal components were obtained with 86.34% (5 cm) and 88.34% (10 cm). Standard, forward and backward stepwise discriminant analysis effectively discriminate 2 variables (84.06%) indicating high variation of heavy metals accumulation at both depth. The cluster analysis accounted for high input of Zn and Pb at LA8, LA 10, LA 11 and LA 12 that mergers three (5 cm) and four (10 cm) into clusters. This is consistent with the contamination factor (Cf) that shows high Cd (LA 1) and Pb (LA 7, LA 8, LA 10, LA 11 and LA 12) contaminations at 5cm. These indicate that Pb and Zn are the most bioavailable metals in the sediment with significant positive linear relationship at both sediment depths. Therefore, this approach is a good indication of environmental pollution status that transfers new findings on the assessment of heavy metals by interpreting large complex datasets and predicting the fate of heavy metals in the sediment