A non-parametric distance-based method using all available indicators for integrated environmental assessment – a case study of the Mid-Atlantic Region,USA

The paper presents a multivariate measure useful for integrated environmental assessments. It is a weighted distance measure applied to metric data but based on nonparametric statistical procedures. The proposed measure allows all environmental indicators to be used directly without any reduction in dimension (e.g. as in principal component analysis) nor losing variance while being able to tolerate possible non-normality of the indicators, as well as non-linear relationships among them. Results of the hypothetical example and the Mid-Atlantic case study show that the proposed measure is suitable and valuable for integrating multiple indicators into a single index, an important task in integrated environmental assessment.     

Significance of mangrove–mudflat boundaries as nursery grounds for the mud crab, Scylla paramamosain

Fisheries managers frequently try to protect juveniles in order to preserve stocks. Juveniles can be protected by either implementing changes designed to avoid catching immature animals (e.g. increasing mesh size or altering fishing techniques) or protecting nursery grounds. To prevent the capture of immature animals, an estimate of size at maturity is required as well as a knowledge of both fishing methods and the exact location of the nursery grounds. Strong demand for juvenile mud crabs to stock aquaculture ponds has resulted in development of fisheries targeting crabs of all sizes from instar 1 to mature individuals. Using five different fishing methods, different stages in the life cycle of Scylla paramamosain were followed for a period of 16 months in an estuarine population in the Mekong Delta, Vietnam. Mangrove habitat utilisation begins when crabs settle out from the plankton at instar 1 [modal internal carapace width (ICW), 0.5 cm] amongst the pneumatophores at the mangrove fringe. Increasingly larger crabs were found deeper into the mangrove but they were still living on the surface (modal ICW size class, 1.5 cm). As their size increases, the crabs either dig burrows (modal ICW size class, 4.5 cm) or they live in the sub-tidal zone, migrating into the mangrove with each tide to feed (modal ICW size class, 4.5 cm). Larger crabs were caught offshore (modal ICW size class, 12.5 cm) where females accounted for 60% of the catch although of these, only 63% were mature. Recruitment of early instars was continuous but peaked in December to February. Subsequent peaks in the catch rates of larger size classes indicated the development of a single cohort with an estimated growth rate of 2.0 cm ICW per month. On the basis of abdominal width, females were estimated to mature at 10.2 cm ICW although at 9.7 cm ICW, 50% of females had disengaged abdomens. Abdominal disengagement occurred in males at the slightly smaller size of 9.1 cm ICW. Allometric relationships between chela height and carapace width suggested 50% of males acquire mature chelae at 10.2 cm ICW. These results demonstrate the close linkage between early life stages of S. paramamosain and certain specific niches within mangrove habitats, with the main adult population found to be living sub-tidally at some distance from the mouth of the estuary. The study also highlights the special importance of the mangrove fringe, the border between the mangrove forest and the sea, an area which is particularly vulnerable to physical and anthropogenic impacts.     

Simulation of retention and transport of copper,lead and zinc in a paddy soil of the Red River Delta,Vietnam

Heavy metal (HM) contaminations in the topsoil around handicraft villages with non-ferrous heavy metal recycling in the Red River Delta can impose serious threats to the subsoil as well as to the groundwater quality. This feature is very important for paddy soils due to relatively high leaching rates and the dissolution of Fe–Mn oxides under reducing conditions which can accelerate the amount of HM translocated to the subsoil and groundwater.The transport of Cu, Pb and Zn in paddy soils was simulated by numerical modeling of non-equilibrium solute transport with an adaptation of the Hydrus-1D model. For the simulation, a water layer on the soil surface was included, from which HM can infiltrate into the soil depending on the soil hydraulic properties. Sorption coefficients, obtained from batch experiments were used as input data for the simulations. Calculated leaching rates were compared with the binding forms of HM in the samples.The simulations show that leaching rates decrease in the order: Zn > Cu > Pb. This order is confirmed by the results of sequential extractions. Under constant flooded conditions at a water table of 20 cm, Cu, Pb and Zn were estimated to reach the soil depth of 1 m within 470, 495 and 370 days, respectively, emphasizing that reactive pollutants can reach groundwater in a relatively short time. A change of the water layer from 1 to 30 cm can accelerate the leaching rate of HM up to 36%. The hard pan layer was observed to induce a hysteresis in hydraulic conductivity and slow down the movement of HM. Uncertainties in modeling arise as several parameters in the simulation can be determined only with significant errors. However, Hydrus-1D is a suitable tool for simulation of the transport of HM in paddy soils.     

Formation,antimicrobial activity,and biomedical performance of plant-based nanoparticles: a review

Environmental Chemistry Letters - Because many engineered nanoparticles are toxic, there is a need for methods to fabricate safe nanoparticles such as plant-based nanoparticles. Indeed, plant...     

A survey of parabens in aquatic environments in Hanoi,Vietnam and its implications for human exposure and ecological risk

Environmental Science and Pollution Research - Seven parabens including methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), iso-propylparaben (iPrP), butylparaben (BuP), benzylparaben...     

Energy crop as an environmentally sustainable reclamation option for post-mining sites: a life cycle assessment of cassava planting in Vietnam

Environmental Science and Pollution Research - Using post-mining areas for planting energy crops has emerged as a promising and sustainable reclamation solution due to its potential contributions...     

Characteristics and Bioactivities of Carrageenan/Chitosan Microparticles Loading α-Mangostin

Journal of Polymers and the Environment - This study attempted to develop carrageenan/chitosan based microparticles loading α-mangostin which was extracted from Vietnamese mangosteen skin. The...     

Site-specific bioaccumulation of polychlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins and polychlorinated dibenzofurans (PCDD/PCDFs) in mothers and their infants living in vicinity of Bien Hoa airbase,Southern Vietnam

Bien Hoa airbase is located in Dong Nai Province (Southern Vietnam). Several sites within the airbase are highly contaminated by Agent Orange/Dioxin, and thus, they are also commonly named as an Agent Orange/Dioxin hotpot. In the present study, 36 maternal milk samples were collected from primiparas who have lived at least 5 years in four wards, Buu Long, Quang Vinh, Trung Dung and Tan Phong, which are closed to Bien Hoa airbase in order to investigate the level and distribution of Agent Orange/Dioxin exposure in different local communities. The mean concentrations of PCDD/PCDFs in four investigated wards range from 6.4 to 13.6 pgTEQ/g lipid. The highest mean TEQ of PCDD/PCDFs was observed in Buu Long ward (13.6 pgTEQ/g lipid), followed by Tan Phong ward (12.3 pgTEQ/g lipid), and the lowest value was observed in Trung Dung ward (6.4 pgTEQ/g lipid). The mean concentration of 2,3,7,8-TCDD in Buu Long (7.6 pg/g lipid) was approximately 2–6 times higher than those in Tan Phong (3.9 pg/g lipid), Quang Vinh (2.3 pg/g lipid), or Trung Dung (1.2 pg/g lipid). These results imply site-specific exposure to PCDD/PCDFs in different local communities living around Bien Hoa airbase. The mean values of daily intake of dioxin estimated for the breast fed infants living in Buu Long, Quang Vinh, Trung Dung and Tan Phong were about 80, 37.5, 31.7 and 58 pg TEQ/kg bw/day, respectively.     

Synthesis and applications of carbon quantum dots derived from biomass waste: a review

Environmental Chemistry Letters - In the context of the circular economy and decreasing earth resources, waste should be converted into value-added materials such as carbon quantum dots, which are...