Periodic density as an endpoint of customized plankton community responses to petroleum hydrocarbons: A level of toxic effect should be matched with a suitable time scale.

As an endpoint of community response to contaminants, average periodic density of populations (APDP) has been introduced to model species interactions in a community with 4 planktonic species. An ecological model for the community was developed by means of interspecific relationship including competition and predation to calculate the APDP. As a case study, we reported here the ecotoxicological effects of petroleum hydrocarbons (PHC) collected from Bohai oil field on densities of two algae, Platymonas subcordiformis and Isochrysis galbana, a rotifer, Brachionus plicatilis, and of a cladocera, Penilia avirostris, in single species and a microcosm experiment. Time scales expressing toxic effect increased with increasing levels of toxic effect from molecule to community. Remarkable periodic changes in densities were found during the tests in microcosm experiment, revealing a strong species reaction. The minimum time scale characterizing toxic effect at a community level should be the common cycle of population densities of the microcosm. In addition, the cycles of plankton densities shortened in general with increasing PHC, showing an evident toxic effect on the microcosm. Using APDP as the endpoint, a threshold concentration for the modeled microcosm was calculated to be 0.404 mg-PHC L-1. The APDP was found to be more sensitive and reliable than the standing crops of populations as the endpoint. This indicated that the APDP, an endpoint at the community level, could be quantitatively related to the endpoints at the population level, and led to the quantitative concentration-toxic effect relationship at the community level.

Polycyclic aromatic hydrocarbons in coastal rivers in Jiangsu Province, China: Spatial distribution, source apportionment and human impacts.

The ocean is the ultimate sink for all pollutants, rivers are important channels for land-based pollutants to enter the oceans. Riverine transport of polycyclic aromatic hydrocarbons (PAHs) to coastal seas in China poses environmental threats. This study examined the spatial and temporal distribution of PAHs in coastal rivers in Yancheng City in Jiangsu Province of China, with the aim of identifying their likely sources, concentrations, and influencing factors. Surface sediments were taken from the Xinyanggang River (XYR) and the Sheyang River (SYR). The concentrations of Æ©16PAHs in river sediments were measured on average 477.05 ng/g dry weight (dw), with values varying from 2.18 to 6351.42 ng/g, indicating a moderate pollution level, with a dominance of high molecular weight (HMW) PAHs. The XYR exhibited significantly higher PAHs concentrations compared to the SYR. The key sources of PAHs were vehicle emissions (47.87%), coal and natural gas combustion (35.07%). Geographically weighted regression and redundancy analysis linked PAHs pollution to distinct land use patterns and socioeconomic indicators, highlighting urban land as the major contributor, driven by high urbanization and industrialization (70.91%). In XYR, industrial activities and transport emissions were major contributors, while in SYR, agricultural activities predominantly influenced PAHs pollution. Urgent mitigation strategies are needed to reduce PAHs pollution in river sediments, mitigating ecological and human risks associated with these contaminants.

Trace elements in surface sediments from Xinyanggang River of Jiangsu Province, China: Spatial distribution, risk assessment and source appointment.

The Xinyanggang River in Yancheng City, one of the essential rivers entering the Yellow sea, has imported abundant pollutants to the coast of Jiangsu Province. Trace elements (Cr, Ni, Cu, Zn, As, Rb, Sr, Mo, Pb, Th, U, Sc, Ga, Se, Zr, Nb, and Sn) in surface sediments in the Xinyanggang River were measured to analyze the spatial distribution, risk assessment, and source appointment. The results showed that the parts of 17 trace elements presented high average values in river sediments, such as Zr (309.19 mg/kg), Sr (182.72 mg/kg), Zn (77.67 mg/kg), and Cr (70.63 mg/kg). Compared with some coastal rivers, the Xinyanggang River was polluted by certain trace elements, such as Cr, Zn, and As. Based on the analysis of the enrichment factor (EF), the contamination factor (CF), the pollution load index (PLI), and the geoaccumulation index (Igeo), trace elements in sediments showed unpolluted to moderate contamination and mild to moderate enrichment. Among them, Zn, Pb, and Sn were highly polluted. The multivariate analysis, the principal component analysis-multiple linear regression (APCS-MLR) model, and the Unmix model identified four contributing trace element sources. Cr, Th, U, Se, Zr, and Nb originated from manufacturing industries and hydrodynamic transport erosion. Ni, Rb, Sc, and Ga were attributed to natural source. Cu, Zn, Mo, Pb, and Sn were contributed from mixed sources including industrial wastewater and transportation emissions. As and Sr were associated mainly with mixed sources of agriculture and combustion. These four sources of metals accounted for 22.5 %, 5.7 %, 15.3 %, and 11.1 % by using the APCS-MLR model, whereas 22.9 %, 39.7 %, 17.5 %, and 19.9 % by using the Unmix model, respectively.

Distribution and source of black carbon in coastal river sediments around Haizhou Bay, Eastern China: implications for anthropogenic inputs.

It is crucial to investigate the distribution and origin of black carbon (BC) in the environment for evaluating human inputs and developing pollution control strategies. This study analyzed BC in coastal river sediments from Haizhou Bay, Eastern China. The concentrations (dry weight) of the BC, char, soot, and total organic carbon (TOC) in coastal river sediments flowing into Haizhou Bay were 0.11-4.68, 0.06-4.24, 0.04-0.70, and 0.15-2.29 mg/g, respectively. Char and soot accounted for 38.54-90.70% and 9.30-61.46% of BC, with an average of 68.95% and 31.05%, respectively. The results show that the spatial variation of char was markedly presented in river sediment (108.27%), followed by that of BC (89.25%), TOC (58.69%), and soot (55.85%). The BC was mainly distributed in the Shawang River and the Shiliang River, soot was distributed primarily in the Shawang River, and char was mainly distributed in the Shiliang River. This finding supports the presence of anthropogenic activity sources in coastal rivers. The grey correlation analysis results show that industrial and agricultural activities greatly influenced BC emissions, as the influence degree of four socio-economic variables on BC contamination decreased as follows: regional total production value, population density, total agricultural production value, and total industrial production value. The char/soot ratio, an index to discriminate the source of BC contamination in sediments, was found to range from 0.63 to 9.75 with an average of 2.75. The result indicates that BC in Haizhou Bay was contributed from mixed sources including transportation emissions, fossil fuel combustion, and biomass combustion. The study demonstrates that BC could be an effective indicator for the degree and spatial distribution of organic pollutants in coastal river sediments.

Pollution, risks, and sources of heavy metals in sediments from the urban rivers flowing into Haizhou Bay, China.

The Haizhou Bay in eastern China, for a long time, is seriously polluted with heavy metals (HMs) due to intensive anthropic pressure. The river runoff is the dominant pathway of HM transport in the coastal region. However, the information on HM pollution in coastal rivers flowing into Haizhou Bay was still limited, and potential risks and possible sources raised by HMs in this area were neglected up to now. To fully understand the distribution and ecological risks of sediments in seven rivers along the bay, surface sediments were collected and seven HMs (Cr, Mn, Ni, Cu, Zn, Cd, and Pb) were investigated. The results showed that HM concentrations generally met the primary standard criteria of China (marine sediment quality), except for Cu and Zn. On the other hand, Zn and Cu tended to exhibit probable adverse biological effects in the Shawang River comparison with some sediment quality guidelines (SQGs). Moreover, the enrichment factor and geo-accumulation index demonstrated that there was no or slight contamination to be found for Cr, Mn, Ni, Cu, Zn, and Pb and moderate pollution for Cd. The contamination factor (Cfi), integrated contamination degree (CF), modified degree of contamination (mCd), and modified pollution index (MPI) revealed individual metal contamination in localized areas. In these river sediments, the potential ecological risk (RI) was low to moderate, except Cd posted a considerable ecological risk because of its high enrichment. Furthermore, the Shawang River and Linhong River were seriously polluted with HMs among seven rivers. These results provided a new direction for controlling HM pollution in Haizhou Bay which suggested substantial measures should be implemented to alleviate the potential risk of HMs, to these rivers sediments.

Source apportionment of heavy metals in sediments of the urban rivers flowing into Haizhou Bay, Eastern China: using multivariate statistical analyses and Pb-Sr isotope fingerprints.

Urban river runoff carrying various anthropogenic sources of heavy metals (HMs) is the most important input pathways for HM pollutions in the coastal region, apportioning sources of environmental pollutants is key to controlling coastal HM pollution. In the study, surface sediments were collected from seven urban rivers flowing through Lianyungang City and discharging into Haizhou Bay, Eastern China. The concentrations of HMs of the river sediments were, in mg/kg (mean value ± standard deviation): Mn (550 ± 227) > Zn (67 ± 61) > Cr (33 ± 12) > Ni (21 ± 8.5) > Cu (16 ± 7.6) > Pb (15 ± 5.6) > Cd (0.11 ± 0.06), which were slightly to moderately polluted. As important outlets for municipal and industrial sewages, the Shawang River and Linhong River were the most polluted. Based on the multivariate statistical analysis, HMs were attributed to anthropogenic source (industrial, domestic, and agricultural discharges) and natural source (soil parent materials and atmospheric deposition). Based on isotope source apportionment, Pb was mainly from natural source, exhausts of leaded gasoline vehicles, and coal combustion, with the mean contributions of 39.3%, 23.7%, and 37.0%, respectively, and Sr originated from natural source and anthropogenic source, with mean contributions of 31.8% and 68.2%, respectively. Pb-Sr isotopes illustrated that anthropogenic inputs were the dominant source for HMs in urban river sediments flowing into Haizhou Bay, and the isotope tracing results make up the discriminating deficiency of the multivariate statistical analysis.

Contamination Evaluation and Source Identification of Heavy Metals in the Sediments from the Lishui River Watershed, Southern China.

Seven heavy metals (Cr, Mn, Co, Ni, Cu, Zn, Pb) were measured in surface sediments from the Lishui River watershed, an area with increased soil erosion in China. The mean concentrations of heavy metals were 61.20 mg/kg (Cr), 757.15 mg/kg (Mn), 9.39 mg/kg (Co), 25.31 mg/kg (Ni), 22.84 mg/kg (Cu), 91.66 mg/kg (Zn), and 40.19 mg/kg (Pb), respectively. The spatial distribution of heavy metals was site-specific, exhibiting a remarkably high level in the sampling stations with intense agricultural activities (Lixian) and industrial activities (Jinshi). Contamination indexes including contamination factor, pollution load index, nemerow multi-factor index, potential ecological risk index, and human health risk were used to assess the pollution degree of the river sediments. The results indicated the pollution degree of heavy metals decreased in the order of Mn>Pb>Zn>Cr>Cu>Ni>Co. Heavy metals resulted in non-pollution to moderate pollution, with low ecological risk and an acceptable carcinogenic risk caused by Cr and Ni for children and adults. Person's correlation analysis and principal component analysis, coupled with cluster analysis, revealed that the sediments from the Lishui River were mainly influenced by two sources. Cr, Co, Ni, and Cu were mainly derived from natural sources, while Mn, Zn, and Pb originated from agricultural and industrial activities, mining, and vehicular traffic.

Emission of primary microplastics in mainland China: Invisible but not negligible.

Primary microplastics are mostly produced as part of the daily plastic product use. The emission process is often invisible but poses potential ecological hazards. Thus, primary microplastics deserve public attention. Due to China's huge population base and its rapid economic development, primary microplastics emissions are of both regional and global significance. This study is the first to establish the emission inventory of primary microplastics in mainland China. It was estimated that the primary microplastic waste from mainland China amounts to 737.29 Gg, and one-sixth of this amount entered the aquatic environment in 2015. The highest proportion of this waste was attributable to tire dust and synthetic fiber, accounting for 53.91% and 28.77% of the total respectively, in mainland China. The primary microplastics emissions mainly depend on the population, followed by the level of economic development. It was roughly estimated that 538 g of microplastics is produced by each person in China. At the grid scale, the spatial difference in the total primary microplastics emissions in mainland China primarily depends on the population density distribution and transportation network. We studied the entire life cycle of several sources of microplastics, from production to discharge into the aquatic environment. We suggested different control measures under different nodes. Increasing microplastics treatment in sewage treatment plants should be a short-term viable way to achieve some measure of reduction in their entry to the environment in mainland China. Our research can not only raise public awareness about primary microplastics, but can also guide the development of environmental policies to reduce plastic pollution.