Polycyclic aromatic hydrocarbons in sediment cores from the Dashiwei Tiankeng reach in the Bailang underground river, South China

Abstract

Sediment cores from the Dashiwei Tiankeng reach of the Bailang underground river were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of total PAHs ranged from 35.34 to 280.17 ng/g (mean 107.65 ng/g), and the concentrations of benzo[a]pyrene ranged from 1.78 to 175.74 ng/g (mean 35.94 ng/g). Analyses on molecular markers inferred that the PAHs were sourced mainly from wood and coal combustion before 1998, but there were obvious petroleum and petroleum combustion inputs after 1999. The PAHs profile indicated that the Bailang underground river was polluted by two major events. One was steel smelting in the 1950s, and the other was rapid economic development in the 1990s. The relationship between the PAHs and the sediment organic matter (SOM) in the profile was negative. Factors that impacted the SOM contents in sediment core included vegetation, agriculture crops, wood and fossil fuel burning, and soil erosion caused by construction. The sediment cores from the Bailang underground river reflected the economic development of the region.

A Quantitative Analysis of Factors Influencing Organic Matter Concentration in the Topsoil of Black Soil in Northeast China Based on Spatial Heterogeneous Patterns

“…The SOM content of black soil is affected by many natural and anthropogenic factors. They include soil type [4][5][6], topography [7,8], climate [9][10][11], vegetation [12][13][14][15], land use [16][17][18], and so on. The different soil types lead to different soil nutrient losses, which lead to different accumulation of SOM.…”

Source, Partition and Ecological Risk of Polycyclic Aromatic Hydrocarbons in Karst Underground River Environment, Southern China

“…Table 4 shows that the main ring number of sediments in the Moshui River, the Three Gorges Reservoir Area (Chongqing section), the Beijiang River and the Bailang underground river in Dashiwei were the same as that in the study area, and the main ring number of sediments in the other areas was a low-middle ring. In terms of concentrations, the concentrations of PAHs in the sediments in the study area were lower than those in the surface sediments of Fenhe River [33], Moshui River [34], Hun River [35] and Songhua River [36], similar to those in the Three Gorges Reservoir area (Chongqing section) [37], and much higher than those in the sediments of the Beijiang River [38], Sanya River [39], Yangtze River (Wuhan section) [40], Laolongdong underground river [41] and Bailang underground river of Dashiwei [42]. In conclusion, the level of PAHs' pollution in sediments in the study area was at a moderate level.…”

Karst tiankengs as refugia for indigenous tree flora amidst a degraded landscape in southwestern China

“…A refugium refers to an area in which climate and vegetation have remained relatively unchanged while areas surrounding it have changed markedly 37 . In contrast to the arid, degraded landscape outside the tiankengs, the humid microclimate inside them sustained a rich flora because of the underground river system in the cone karst area 10 , 27 and the relatively isolated habitat deep inside the earth. Unlike the traditional refugium concept, which describes plant diversity as having survived from the widespread Pleistocene glaciers on the earth 37 , tiankengs are oases amidst the degraded karst landscape.…”

“…Due to tiankengs’ inaccessibility, the studies that have been conducted are limited to general scientific surveys, geological investigations, and touristic explorations 12 , 25 . A few studies on plant resources, Chinese traditional herbs 13 , 26 , and soil pollution monitoring 27 – 29 have recently been reported, but we know little of the composition, diversity, and structure of the “underground” vegetation inside the tiankengs. Our preliminary report on the forest community structure and diversity in Liuxing Tiankeng from this area 8 may be the first published report on the ecological analysis of the forest community inside a tiankeng.…”