Polychlorinated biphenyls and polybrominated diphenylethers in soils from planted forests and adjacent natural forests on a tropical island

Comprehensive evaluation of environmental dimension reduction of multi-type islands: a sustainable development perspective

In recent years, the sustainable development of islands has attracted increasing attention from countries all over the world. An important prerequisite for promoting sustainable development is to understand the foundation and sustainable development potential of islands. Constructing index systems and models is an important means of evaluating the sustainability of islands. This study used factor analysis (FA) to construct an indicator system and set weights. Thirty-eight indicators were set from both natural and social directions to evaluate the sustainable development of seven typical islands in China. The FA removed the 10 indicators that were too relevant, and the 28 effective indicators were reduced into 9 main factors for evaluation. The results showed that the evaluation results are in line with the actual development of the island, which verifies the applicability of the model to different types of islands. The study also found that the changing trends of island social sustainability, tourism sustainability, ecological sustainability, resource sustainability, and economic sustainability are consistent. The value of fully balanced islands is higher than that of unbalanced or undeveloped islands. Among the seven islands, social islands have the highest total value, and ecological islands have the lowest total value.

Thermal treatment of decabrominated diphenyl ether in its highly contaminated soil in Taiwan

Polybrominated diphenyl ethers (PBDEs) were commonly used flame retardants in the world, while some of PBDEs have been listed as persistent organic pollutants (POPs). Decabrominated diphenyl ether (BDE-209) was the most commercially used PBDEs. A farm near the factory located in Northern Taiwan was highly contaminated with BDE-209. Since PBDEs in the contaminated soils can be uptake by crops shown in our previous studies and could be potentially consumed by humans, it is very important to establish a feasible treatment method for PBDE remediation in this contaminated farm. Thermal treatment of PBDEs in soil was studied. The initial concentration of BDE-209 in contaminated soil was 1.472 mg/kg. A series of thermal experiments under different operating conditions including various temperature (105, 150, 200, 250, 300, 350, 400 and 450 °C), holding time (10, 20 and 30 min), heating rate (5, 10, 20 and 40 °C/min), and soil amount (10, 100, 1000 and 2000 g) were investigated. The optimal heating conditions for thermal treatment of contaminated soil were heating at 450 °C for 30 min with a heating rate of 10 °C/min. Under this condition, the removal of BDE-209 in the different weights of contaminated soil was tested. The soils in the contaminated farm were tested to further evaluate the feasibility of remediating the on-site PBDE contaminated soil through thermal treatment, suggesting that the holding time was extended to 2 h for the field-scale contaminated soil. The results showed that BDE-209 had been removed to below the detection limit in on-site soil. This investigation is the first study using thermal treatment to remediate soils really contaminated with PBDEs.

Role of low-latitude forests in modulating forest filter effect on a continental scale: Long-term simulation on PCB-153 in Chinese forests

Forests are important compartments influencing the environmental fate of persistent organic pollutants (POPs). To illustrate the effect of forests on the regional cycle of POPs, a level IV fugacity fate and transport model coupled with a detailed dynamic-forest module was applied to simulate the long-term variations of PCB-153 in China, where forest coverage accounts for approximately one fifth of land area. In the scenarios with forests, atmospheric outflow from China was 69% of that in the scenario without forests due to the enhanced storage in soil, degradation, and leaching. Previous studies regarded high-latitude areas, such as the polar region and boreal forests, as environments capable of reducing mobility of PCB-153, and they act as sinks of POPs. This modeling result suggests that tropical and subtropical forests may also play a similar role despite high temperatures favoring volatilization. Unlike boreal forest, the low-latitude forests may reduce the overall lifetime of PCB-153 in China due to enhanced degradation in warmer and moist soils of the tropical and subtropical area. Given that approximately half of the global forests are located in tropical and subtropical regions, they can be important environments influencing the global geochemical cycle and distribution of POPs, hence deserving more scientific attention by modeling and empirical studies.

Assessment of persistent organic pollutants (POPs) in sediments of the Eastern Indian Ocean

The concentrations of persistent organic pollutants (POPs) in sediments from the Eastern Indian Ocean were analyzed by GC-MS/MS to explore the status of contamination, distribution and their potential sources and risk. The average (±SD) concentrations of total polycyclic aromatic hydrocarbons (∑₁₆PAHs), polybrominated diphenyl ethers (∑₁₀PBDEs), dechlorane plus (∑₂DP), organochlorine pesticides (∑₂₂OCPs) and polychlorinated biphenyls (∑₃₁PCBs) in sediments were 79,900 ± 31,400, 173 ± 62, 42 ± 24, 1051 ± 305 and 147 ± 24 pg g^-1 dw (or 11,200 ± 7200, 28 ± 26, 6 ± 6, 168 ± 121 and 24 ± 17 ng g^-1 organic carbon), respectively. The concentrations of POPs in sediments were generally at low to median levels compared to those recorded in other ocean sediments. Composition analyses suggest that PAHs originate from both petrogenic and pyrogenic sources, while dichlorodiphenyltrichloroethane (DDT) mainly comes from technical-DDT, hexachlorocyclohexane (HCH) from lindane, and chlordane from fresh inputs. The risk assessments show that the targeted chemicals except for chlordane and naphthalene in sediments do not pose potential biological effects to the organisms in the Eastern Indian Ocean. The present study contributes to the very rare data on PAHs, PBDEs, DP, OCPs and PCBs in the vast deep-ocean and will deepen our knowledge of the fate of POPs in ocean environments.

Temporal and spatial surveys of polybromodiphenyl ethers (PBDEs) contamination of soil near a factory using PBDEs in northern Taiwan

Polybrominated diphenyl ethers (PBDEs), previously commonly used as flame retardants, should be monitored in the environment since some are listed as persistent organic pollutants. A contaminated site near a northern Taiwan factory using decabrominated diphenyl ether (deca-BDE) was identified based on a vegetable PBDEs monitoring project in 2013. The subsequent spatial and temporal survey of that contaminated site shows the contamination ingredients in soils were close to ones used by the factory, indicating that contamination was from the factory, possibly through an exhaust vent. The average concentration of deca-BDE in the main contaminated soil was 615 μg/kg d. w. (dry weight) soil in 2015, slightly decreasing to 604 μg/kg d. w. soil in 2016, increasing to 844 μg/kg d. w. soil in 2017, and then slightly decreasing to 670 μg/kg d. w. soil in 2018. The slight change of deca-BDE and the minor change in low brominated congener level indicate a low degradation rate. The contamination of peripheral sites was around 5000 μg/kg d. w. soil for one PBDEs sampling site that was higher than those around or within the main contaminated farm, indicating serious pollution. Concentrations of PBDEs in different soil depths show that depth 2-15 cm accounted for the greatest PBDEs accumulation, indicating that deca-BDE pollution had been present over time and transported into deeper soil. There can be PBDEs uptake by crops consumed by humans, as shown in our previous studies, so continuous monitoring of PBDEs in this site is important and treatments should be established urgently.

Accumulation and fate processes of organochlorine pesticides (OCPs) in soil profiles in Mt. Shergyla, Tibetan Plateau: A comparison on different forest types

Previous work documented that forest plays an important role in the deposition of persistent organic pollutants (POPs) in the southeast Tibetan Plateau (TP) due to the "forest filter effect". However, forest types in the southeast TP are entirely different and the influence on POPs fate and forest filter effect by different forests remains unclear. This study focused on the distribution and transfer of organochlorine pesticides (OCPs) in soil of different forest types (quercus, birch, fir, and spruce dominated forests) in Mt. Shergyla, southeast TP under similar environmental and meteorological conditions. Total levels of ∑HCHs, ∑DDTs and HCB in soils ranged from < LOD to 2.25 ng/g dry weight (dw), < LOD-10.2 ng/g dw, and < LOD-0.95 ng/g dw, respectively. Concentrations of OCPs in humus layers were significantly higher than those in mineral layers in the four forest types. Relatively higher ∑DDTs concentrations were found in soil profile of broadleaved birch forest, while higher concentrations of ∑HCHs and HCB were found in soil profile of coniferous fir forest, and the same trend was observed in fresh leaf samples. Air-to-ground fluxes and mobility of OCPs in the four forest types were also evaluated. Relatively higher fluxes were found in fir forests than in other forest types, suggesting that fir forest could be more effective to transfer OCPs from the air into soil in the southeast TP. The findings in this study would be helpful for improving model simulation of POPs fate in different forest ecosystem.

Bioaccumulation and cycling of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in three mangrove reserves of south China

Total 22 organochlorine pesticides (OCPs) compounds and 31 polychlorinated biphenyls (PCBs) congeners in mangrove sediments and tissues (leaf, branch, root and fruit) of nine species from three Mangrove Reserves of China were studied. The mean concentrations of total DDTs, HCHs, OCPs and PCBs in sediments were 2.84, 0.06, 3.84 and 0.17 ng g^-1 dw, while those in tissues were 1.85, 0.22, 9.43 and 1.61 ng g^-1 dw, respectively. The elevated OCPs and PCBs levels in mangrove leaves may be caused by atmospheric sedimentation. The biota sediment accumulation factor (BSAF) values of both OCPs (mean: 3.4) and PCBs (mean: 9.9) are generally larger than one, implying mangroves' bioaccumulation and their ability to intercept pollutants. The BSAFs of PCBs in mangrove tissues were negatively correlated with the PCB congener's octanol-water partition coefficients (K_OW, R = 0.58, n = 31, p < 0.001), suggesting that lower chlorinated CB congeners are more bioaccumulative in mangroves. In order to better understanding the fate of these organochlorine compounds, the cycling (including the standing accumulation, the annual absorption, the annual net retention, the annual return, and the turnover period) of OCPs and PCBs in the Mangrove Reserves were estimated, and the results indicated that mangroves are playing important roles in retaining OCPs and PCBs.