Elemental distribution and source analysis of atmospheric aerosols from Meycauayan, Bulacan, Philippines.

One of the industrialized cities in the Philippines is Meycauayan, Bulacan. This study reports the elemental distribution and source apportionment in eight varying land cover-land use type sampling points located along the Marilao-Meycauayan- Obando Rivers System. Elemental analysis was conducted using a scanning electron microscope coupled with energy dispersive x-ray. Cu, Pb, Zn, Cr, Mn, As, Cd, Co, Fe, Ni, Ti, and V concentrations were determined using Inductively Coupled Plasma Mass Spectrometry, and Hg concentrations by Mercury analyzer. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and Pearson's r correlation were used to analyze different sources of heavy metals and its corresponding land use-land cover type. The aerosol samples showed the presence of heavy metals Pb and Hg, elements that were also detected in trace amounts in the water measurements. Concentrations of heavy metals such as Cu, Fe, Pb, Zn, V, Ni, and As found in the atmospheric aerosols and urban dusts were attributed to anthropogenic sources such as residential, commercial and industrial wastes. Other source of aerosols in the area were traffic and crustal emissions in Meycauayan. Using HCA, there are 3 clusters observed based on the similar sets of heavy metals: (1) AQS1 (Caingin), AQS2 (Banga), and AQS8 (Malhacan); (2) AQS3(Calvario), AQS4 (Camalig), and AQS5(Langka); (3) AQS1(Sto Nino-Perez), and (AQS7) (Sterling). These groups are related based on different land use setting such as residential/commercial, agricultural, and commercial/industrial areas. Our study recommends the need to address heavy metal pollution in Meycauayan in support to the ongoing implementation of laws and regulations by the local and private sectors.

Ecological and health risks from heavy metal sources surrounding an abandoned mercury mine in the island paradise of Palawan, Philippines.

A recent survey that determined heavy metal concentrations in an abandoned Hg mine in Palawan, Philippines, found the occurrence of Hg with As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Tl, V, and Zn. While the Hg originated from the mine waste calcines, the critical knowledge about the origin of the other heavy metals remains unknown. This study assessed the ecological and health risks from heavy metal pollution surrounding the abandoned Hg mine. Principal component analysis (PCA) showed that the abandoned mine and natural sources (i.e., local geology) are the two main contributors of heavy metal pollution. Historically, the mine waste calcines (retorted ore) were used as construction material for the wharf and as land filler for the adjacent communities. There is highly strong ecological risk associated with the heavy metals: Ni, Hg, Cr, and Mn contribute 44.3%, 29.5%, 10.7%, and 8.9% to the potential ecological risk index (RI), respectively. Hazard index (HI) exceeded 1 for both adults and children in all the sampling locations, implying non-carcinogenic adverse effects. The total cancer risk over a lifetime (LCR) also exceeded the threshold limit of 10-4 for both adults and children, contributed mainly by Cr (91.8%) and As (8.1%). By combining the results of the PCA and risk assessments, a clear link between heavy metal source apportionment to ecological and health risks was established. It was estimated that the abandoned mine contributed to most of the ecological and health risks for people living near the wharf that was built using the calcine, as well as the nearby Honda Bay. The findings of this study are expected to help policy makers develop regulations that will safeguard the ecosystem and the general public from the damaging impacts of heavy metals from the abandoned mine.

Transport of toxic metals in the bottom sediments and health risk assessment of Corbicula fluminea (Asiatic clam) collected from Laguna de Bay, Philippines.

Laguna de Bay, the 3rd largest lake in Southeast Asia, is the most significant source of freshwater fish in the Philippines. With decades of unregulated discharge of industrial, domestic, and agricultural wastewaters into the lake, this study investigates the apportionment of heavy metals from the bottom sediments and its impact on the toxicity of Corbicula fluminea (Asiatic clam), a popular food item in the markets. The sediment samples from the western part of the lake contained higher Cd, Cu, Pb, and Zn and lower As and Cr concentrations compared to the eastern part. There were positive correlations for As, Cr, Cu, Pb, and Zn and negative correlations for Cd and Ni concentrations noted between sediments and C. fluminea. Human health risk associated with the consumption of C. fluminea collected from Laguna de Bay was attributed to the following heavy metals: Cu > As > Zn > Cd > Pb > Cr > Ni. Interestingly, the observed trend in toxicities of the shellfish was consistent with the transport phenomenon of heavy metals facilitated by the counterclockwise direction of the bottom current. This study strongly suggests the re-evaluation of the waste management plan in the industrial zones and policies regulating the sale of the shellfish harvest.

Analysis of the copper removal kinetics of the Philippine giant bamboo (Dendrocalamus asper) in hydroponics.

Copper is the third most utilized metal and is a versatile resource with multiple beneficial uses, but it may also become toxic to aquatic life in excess amount. Thus, there is a need to develop methods to reduce the copper contamination in the environment, particularly in bodies of water. Phytoremediation using Dendrocalamus asper may offer an environment-benign and potentially effective method for copper removal though its effectiveness may take several years to materialize for this technology to become cost-effective. By growing D. asper in synthesized contaminated water and analyzing the change in the copper content of the substrate via atomic absorption spectrophotometry, the removal was found to be optimal at 20 ppm Cu and pH 5. The rate of removal was found to have an order of 2.71 and a kinetic constant of 0.0013 ppm-1.71 day-1. With this, it may be possible to estimate the treatment length of phytoremediation given an initial level of copper contamination and a target concentration.

Phytoremediation potential and copper uptake kinetics of Philippine bamboo species in copper contaminated substrate.

The phytoremediation potential of three bamboo species, i.e. Bambusa merilliana, Bambusa blumeana, and Dendrocalamus asper, were evaluated for their total Cu uptake ability in hydroponics. Dendrocalamus asper proved to be the most efficient in terms of Cu phytoremediating potential with a constant positive uptake of 80 µM in a contaminated substrate and a bioconcentration factor of 50.57. Copper accumulation was found to concentrate the most in the roots compared to the amount translocated in the shoots. Analysis of the Cu uptake of D. asper roots at varying concentrations of Cu contamination (40, 80 and 120 µM) allowed for the fitting of the kinetics of Cu uptake and removal with existing kinetic models. The rate of copper removal per mass of plant was the best for the 0th order model in the 80 µM solution with an R2 of 0.954 and rate constant of 3.136 mg-kg-1d-1. The accumulation of Cu within the roots on day 7 (7d) followed the Michaelis-Menten model with an R2 of 0.970. The Michaelis-Menten constant (KM) was 4.87 mg/L and maximum accumulation velocity (Vmax) was 66.26 mg Cu-kg-1-day-1. Results suggest that D. asper is a potential hyperaccumulator plant that can be used in clean-up of domestic and industrial wastes present along river systems in the Philippines.