Ji-Zhong Wang

Organochlorine pesticides and polychlorinated biphenyls in riverine runoff of the Pearl River Delta, China: assessment of mass loading, input source and environmental fate.

A large-scale sampling program was conducted to simultaneously collect water samples at the eight major riverine runoff outlets of the Pearl River Delta (PRD), South China to assess the importance of riverine runoff in transporting anthropogenic pollutants from terrestrial sources to the coastal ocean. The concentrations of Sigma21OCPs (sum of 21 OCP components) and Sigma20PCBs (sum of 20 PCB congeners) were 2.57-41.2 and 0.12-1.47 ng/L, respectively. Compositional distributions of DDTs suggested the possibility of new input sources in the study area, but contributions from dicofol seemed considerably low. The annual inputs of Sigma21OCPs and Sigma20PCBs were 3090 and 215 kg, with those of total HCHs and DDTs being 1110 and 1020 kg, respectively. A mass balance consideration indicated that riverine runoff is the major mode carrying OCPs from the PRD to the coastal ocean, and the majority of OCPs is further dissipated to open seas.

Sediment Records of Polycyclic Aromatic Hydrocarbons (PAHs) in the Continental Shelf of China: Implications for Evolving Anthropogenic Impacts

Sources, compositions, and historical records of polycyclic aromatic hydrocarbons (PAHs) in sediment cores collected from the Yellow Sea and the South China Sea were analyzed to investigate the influence of anthropogenic activities. The occurrence of PAHs was mainly derived from various combustion sources, especially the combustion of biomass and domestic coal. Uniform composition of sedimentary PAHs (52-62% of phenanthrene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[g,h,i]perylene) suggested air-borne mixtures intractable to degradation. The concentrations of the sum of 15 PAHs (16 priority pollutants designed by the United States Environmental Protection Agency minus naphthalene; designed as Σ(15)PAH) in Yellow Sea sediment cores were generally higher than those in the South China Sea. The profiles of Σ(15)PAH concentrations recorded in the sediment cores closely followed historical socioeconomic development in China. In general, Σ(15)PAH concentrations started to increase from the background pollution level posed by agricultural economy at the turn of 20th century. In addition, a Σ(15)PAH concentration reduction was observed during the Chinese Civil War (1946-1949) and Great Cultural Revolution (1966-1976), suggesting them as setbacks for economic development in Chinese history. Increasing PAH emissions as a result of increasing coal combustion associated with the rapid urbanization and industrialization since the implementation of the Reform and Open Policy (since 1978) accounted for the fast growth of Σ(15)PAH concentrations in sediment cores. The decline of Σ(15)PAH concentrations from subsurface maximum until sampling time was inconsistent with current-day economic development in China, and may possibly suggest emission reductions due to decreasing proportional use of domestic coal and increasing consumption of cleaner energies (natural gas and liquefied petroleum gas).

Polycyclic aromatic hydrocarbons (PAHs) in continental shelf sediment of China: Implications for anthropogenic influences on coastal marine environment

Sediments collected from the continental shelf of China, embracing Yellow Sea, inner shelf of the East China Sea (ECS), and the South China Sea (SCS), were analyzed for polycyclic aromatic hydrocarbons (PAHs). The concentrations of anthropogenic PAHs (Σ(18)PAH) were 27-224 ng/g dry weight, with an average of 82 ng/g. Sedimentary PAHs in the continental shelf off China were mainly derived from mixed residues of biomass, coal, and petroleum combustion. Fluvial transport and atmospheric deposition mainly accounted for sediment PAHs in the ECS inner shelf and Yellow Sea (and the SCS), respectively. Furthermore, statistically higher levels of Σ(18)PAH (28-224 ng/g; mean 110 ng/g) in the Yellow Sea sediment than in the SCS sediment (28-109 ng/g; mean 58 ng/g) were probably resulted from higher PAH emissions from coke industry and domestic coal combustion in North China than in South China.

Occurrence and phase distribution of polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta, China

The occurrence and phase distribution of polycyclic aromatic hydrocarbons (PAHs) in waters at the eight riverine outlets of the Pearl River Delta (China) were examined based on a monthly sampling program from March 2005 to February 2006. The total concentrations of PAHs in the aqueous phase and suspended particulate matter (SPM) combined ranged from 55.5 to 522 ng/L, at the mid level of the global values in rivers and estuaries. No clear temporal and spatial trends of PAH concentrations were found. However, the concentrations of PAHs associated with SPM coincided with the monthly precipitation of Guangzhou, indicating the importance of atmospheric deposition. The PAHs found in the region were likely derived from a combined pyrolytic and petrogenic origin, as suggested by the molecular indices of PAHs. Normalized partition coefficient (K(oc)) between water and SPM was correlated with octanol-water partition coefficient (K(ow)) to understand the environmental behavior of PAHs.

Polycyclic aromatic hydrocarbons in upstream riverine runoff of the Pearl River Delta, China: An assessment of regional input sources

Water samples collected from upstream tributaries of the Pearl River Delta (PRD) and from locations within the PRD (South China) were analyzed for 27 polycyclic aromatic hydrocarbons (PAHs). Average concentrations (aqueous plus particulate) of total 27 PAHs (Σ(27)PAH), 16 priority PAHs designated by the United States Environmental Protection Agency (USEPA) except naphthalene (Σ(15)PAH), and the seven carcinogenic PAHs (Σ(7)PAH) classified by the USEPA were 260 ± 410, 130 ± 310, and 15 ± 12 ng/L, respectively. Riverine PAHs were predominantly generated from coal and vegetation combustion, coke production, vehicle exhausts, and petroleum residues, accounting for 28%, 25%, 22% and 21%, respectively, on average. Upstream riverine fluxes of Σ(27)PAH and Σ(15)PAH amounted to 38.9 and 12.9 tons/year, respectively. The net contributions of Σ(27)PAH and Σ(15)PAH from sources within the PRD were estimated at 21.4 and 21.0 tons/year, respectively.

Use of aliphatic hydrocarbons to infer terrestrial organic matter in coastal marine sediments off China.

Sediment samples from the marine systems along the coast of China, covering Yellow Sea, inner shelf of the East China Sea (ECS) and the South China Sea (SCS), were analyzed for n-alkanes and organic carbon. The concentrations of Σn-C(15-35) were 120-1680 ng g(-1) dry weight with an average of 560 ng g(-1). Short-chain n-alkanes (<C(21)) in Yellow Sea and the SCS were derived from mixed bacteria and planktonic sources, while those in the ECS inner shelf were mainly of planktonic sources. Long-chain n-alkanes (>C(21)) were mainly derived from terrestrial higher plants. Organic carbon deposited into Yellow Sea and Southeast Hainan within the SCS was mainly of terrestrial (13-110%; mean: 58%) and marine (48-110%; mean: 86%) sources, respectively. On the other hand, organic carbon accumulated in the SCS adjacent to the Pearl River Estuary was derived from both terrestrial and marine sources.

Persistent organic pollutants in coastal sediment off South China in relation to the importance of anthropogenic inputs

Surface sediments collected from the coastal region off South China were analyzed for persistent organic pollutants (POPs), including polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs). The concentrations of BDE-209, Σ(12)PBDE, Σ(15)PAH, Σ(7)PAH, and Σ(11)OCP were 0.22 to 26.3, 0.01 to 0.77, 13.9 to 271, 6 to 133, and 0.9 to 104 ng/g, respectively. The spatial distribution patterns of PBDEs and PAHs suggested that the eastern coastal region was slightly more contaminated than the western coast. In addition, the concentrations of dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDXs) were highly variable, with the highest level found at a site in Zhanjiang Bay, which might have been reflective of the impact of antifouling paints mainly used in boat maintenance in harbor areas. The predominance of BDE-209 in the study region was consistent with the usage pattern of penta-, octa-, and deca-BDEs in China, whereas sediment PAHs appeared to have been derived largely from coal or wood and petroleum combustion. Preliminary assessments indicated that terrestrial inputs, such as atmospheric transport and riverine runoff, may have been the major input pathways for PBDEs and PAHs, respectively, to accumulate in coastal sediment off South China. Conversely, residues of DDT-containing antifouling paints associated with shipping activities and boat maintenance accounted for most of the accumulated sediment DDTs.

Assessment of aquatic wastewater pollution in a highly industrialized zone with sediment linear alkylbenzenes

Forty-five sediment samples collected from Dongjiang River, which drains one of the most industrialized and urbanized regions in South China, were analyzed for 19 linear alkylbenzene (LAB) components. The sample dry weight-based concentrations of total LABs (ΣLAB) ranged from 1.5 to 410 ng/g. Comparison of the relative abundances of n-dodecylbenzenes (or C(12) -LABs) and internal to external ratio (I/E) values in riverine sediment, wastewater, and sediment samples from the outfalls of paper mills, as well as three brands of domestic detergents obtained from the present and previous studies, implicated the occurrence of untreated wastewater in the sampling sites. Levels of ΣLAB were significantly linear correlated with those of total organic carbon (TOC) but not with those of polycyclic aromatic hydrocarbons. Multiple linear regression integrated principal component analysis indicated that 56% of LABs in wastewater in the study area were treated, but the extent of degradation of LABs was low. Finally, it is proposed that ineffective law enforcement and loopholes in the current regulations for wastewater discharge account for the substantial amount (44%) of untreated wastewater discharged in the study region.

APPLICATION OF MULTIPLE GEOCHEMICAL MARKERS TO INVESTIGATE ORGANIC POLLUTION IN A DYNAMIC COASTAL ZONE

Multiple geochemical markers, including aliphatic hydrocarbons (n-alkanes), linear alkylbenzenes (LABs), and polycyclic aromatic hydrocarbons (PAHs), were employed to relate sediment organic chemical pollution in the coastal zone off South China to socioeconomic development there. Concentrations of Σn-C(15-35) (n-alkanes with 15-35 carbon atoms), ΣLAB (sum of C(10) to C(13) LABs), and Σ(26) PAH (sum of 26 PAH compounds) ranged from 110 to 3,160, 11 to 160, and 26 to 600 ng/g, with medians of 730, 40, and 230 ng/g, respectively. Natural hydrocarbons were mainly derived from terrestrial higher plant waxes, and in minor amounts from aquatic plankton and bacteria. Compositions of LABs indicated that considerable amounts of poorly treated wastewater had been directly discharged or transported to the eastern and western coastal areas of Guangdong Province. In addition, anthropogenic hydrocarbons were derived largely from vehicular emissions and combustion of domestic coal and biomass and to a lesser extent from oil spills. Eastern and western coastal sediments contained higher levels of LABs but lower levels of PAHs than those of the Pearl River Estuary, a coastal area of the Pearl River Delta. This spatial pattern of organic pollution was consistent with chemical use patterns. The eastern and western regions of Guangdong Province are economically less developed than the Pearl River Delta region, where more domestic wastewater treatment plants have been built. However, greater amounts of energy are consumed in the latter region to produce more combustion-derived PAH contamination.

Occurrence and mass loadings of n-Alkanes in riverine runoff of the Pearl River Delta, South China: Global implications for levels and inputs†

Riverine runoff samples were collected monthly from March 2005 to February 2006 from the eight major outlets of the Pearl River Delta (PRD), South China, and analyzed to obtain the concentrations of n-alkanes in both the filtrate and particulate phases. The average concentrations of Sigma(C15-C34) (i.e., sum of C15 to C34 normal alkanes) ranged from 0.06 to 2.97 microg/L (mean, 0.64 microg/L) in filtrate samples and from 1.00 to 98.8 microg/g (average, 19.8 microg/g dry weight) in particulate samples. Compared to results from around the world, the levels of hydrocarbon compounds in the PRD were at the high end of the global range. Evaluation of compositional indices of n-alkanes indicated that petroleum-related sources are the main contributor of n-alkanes found in the PRD, with minor contributions from high plant wax. Regression analyses appeared to suggest that n-alkanes are transported into the aquatic environment of the PRD via various pathways, and the transport mechanisms also are considerably influenced by the complex hydrologic conditions in the PRD. The annual riverine input of Sigma(C15-C34) from the PRD to the coastal ocean was 360 tons/year, or the equivalent of approximately 8,800 tons/year of petroleum hydrocarbons. The emission of Sigma(C15-C34) from all sources in the PRD was estimated at 39,000 tons/year, or 2.4 g/day per capita. Overall, the PRD contributes approximately 0.2% of the annual global input of n-alkanes to the coastal oceans, similar to the contributions of polycyclic aromatic hydrocarbons, further indicating that the PRD has been a significant source of hydrocarbon contamination to the global coastal marine environment.