With the acceleration of industrialization and urbanization, increasing attention has been paid to the problem of heavy metal pollution in mangroves and its ecological restoration. Urban mangroves can be used to measure the impact of human activities on the urban ecological environment because mangroves are sensitive to human activities. However, studies on the evaluation of heavy metal elements in urban mangroves are still limited. Consequently, this study selected the urban mangroves in a central commercial area of Zhanjiang Bay as a case study to investigate the content and distribution of the heavy metals (Co, V, Cu, Pb, Ni, As, Cd, and Hg) in mangrove surface sediments. Risk levels and possible sources of heavy metals were evaluated based on multivariate statistical analysis methods and pollution indices. The results showed that the average concentrations of heavy metals for Co, V, Cu, Pb, Ni, As, Cd, and Hg were 2.91, 29.96, 18.24, 20.07, 7.86, 5.0, 0.20, and 0.09 mg/kg, respectively. Cd, Cu, and Hg were most prominent within the Zhanjiang Bay mangrove sediments, whereas other metals showed a low contamination factor of therm. Cd displayed a high potential ecological risk followed by Hg and Cu. The sampling site, the sewage outlet sampling site, exhibited the highest pollution degree followed by the surrounding area of the sewage outlet sampling site. Those polluted heavy metals could arise from anthropogenic sources, including domestic sewage and automobile exhaust emission. Correlation analysis between the heavy metals and physicochemical properties indicated that fine particles and organic matter play a key role in controlling heavy metal enrichment.

The offshore of Leizhou Peninsula (LP, China), which contains unique ecosystems such as mangroves, seagrass beds, and coral reefs, is an environmentally sensitive area. For this reason, the levels of aliphatic hydrocarbon including biomarkers (hopanes, steranes) in the offshore seafloor sediments were analyzed in terms of their composition, distribution, and input sources and aimed to evaluate the extent of possible petroleum hydrocarbon contamination in the sediments of coastal areas. The total aliphatic hydrocarbons (TAH) fraction, the content of total n-alkanes (nC₁₄–nC₃₇) (∑n-alkanes), and content of hopane + sterane are in the range of 13.76–99.53, 1.22–8.33, and 0.02–0.23 μg/g dw, respectively. The presence of unresolved complex mixture (UCM) hydrocarbons hump and petrogenic steranes and hopanes in these seafloor sediments suggest that petrogenic sourced hydrocarbon inputs were present. The stations on the peninsula’s southwest side had the lowest values of UCM/resolved aliphatic compounds (UCM/R) and UCM/n-alkanes. These findings suggest that seafloor sediments from the southwest offshore of the peninsula were likely contaminated by recently inputted petroleum hydrocarbons. The presence of relatively high ∑n-alkanes content in seafloor sediments from southwest offshore of the LP, combined with relatively low natural n-alkane ratios (NARs), indicates an increased influence of petrogenic hydrocarbons. The elevated levels of recent petrogenic hydrocarbon contamination in the sediments from the LP’s southwestern offshore were likely related to petroleum exploitation in the Beibu Gulf’s Maichen and Wushi sags.

Mangrove ecosystems effectively sequester heavy metals, making their sediment distribution and ecological risk assessment vital for coastal protection. This study focuses on the mangrove forests on both sides of the Donghai Island embankment in Huguang Town, Zhanjiang Bay, analyzing the content, spatial distribution, and potential ecological risks of heavy metals (Cu, Zn, Cd, Pb, Cr, As, Hg) in surface and vertical sediment profiles through systematic sampling. The results show higher, more uniform heavy metal concentrations inside the bay, with Cd, Cr, and As showing significant accumulation, while outside, levels are lower but with Pb and As at sites like DW-Z-1 and DW-Z-4 nearing Class I Marine Sediment Quality Guideline limits. Vertically, concentrations inside the bay increase with depth due to long-term pollution, geoaccumulation and potential ecological risk indices, Cd emerges as the primary pollutant, posing a high risk (Er Class 3) inside the bay (RI Class 2) and a low to moderate risk outside. Pollution sources inside stem from industrial, urban, and aquaculture inputs, while tidal dynamics and mangroves pose purification mitigate risks outside. This study underscores Cd control needs and supports the ecological conservation of Zhanjiang Bay.

The oil–oil and oil–source rock correlations, also termed as geochemical correlations, play an essential role in the construction of petroleum systems, guidance of petroleum exploration, and definition of reservoir compartments. In this study, the problems arising from oil–oil and oil–source rock correlations were investigated using chemometric methods on oil and source rock samples from the WZ12 oil field in the Weixinan sag in the Beibuwan Basin. Crude oil from the WZ12 oil field can be classified into two genetic families: group A and B, using multidimensional scaling and principal component analysis. Similarly, source rocks of the Liushagang Formation, including its first, second, and third members, can be classified into group I and II, corresponding to group B and A crude oils, respectively. The principle geochemical parameters in the geochemical correlation for the characterisation and classification of crude oils and source rocks were 4MSI, C₂₇Dia/C₂₇S, and C₂₄ Tet/C₂₆ TT. This study provides insights into the selection of appropriate geochemical parameters for oil–oil and oil–source rock correlations, which can also be applied to other sedimentary basins.