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Two sediment cores were collected from Dianchi Lake, a plateau lake in Southwest China, to study the temporal trends and to investigate the sources of sedimentary deposited polycyclic aromatic hydrocarbon. The ΣPAH16 concentration in the two sediment cores ranged from 172.5 to 2244.8 ng/g and from 211.4 to 1777.8 ng/g, with mean values of 1106.2 and 865.1 ng/g, respectively. Three temporal trends for the ΣPAH16 concentration and the composition of PAHs in Dianchi Lake all showed three typical changing stages: (1) slight changes in deeper segments before the 1950s; (2) a rapid increase in PAH concentrations between the 1960s and 1990s; and (3) a slight reduction from the 1990s onward. These trends differ from those observed in developed countries due to differences in the timing of industrialization and urbanization processes. According to the results of the molecular ratios and principal component analysis, the PAH deposition was dominated by coal combustion, wood combustion, and vehicle emissions before and after the 1960s, respectively.

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Abstract:In situ measured values of particulate organic carbon (POC) in Taihu Lake and remote sensing reflectance observed by three satellite courses from 2014 to 2015 were used to develop an near infrared-red (NIR-Red) empirical algorithm of POC for the Moderate Resolution Imaging Spectroradiometer (MODIS-Aqua) satellite image. The performance of the POC algorithm is highly consistent with the in situ measured POC, with root mean square error percentage (RMSPs) of 38.9% and 31.5% for two independent validations, respectively. The MODIS-derived POC also shows an acceptable result, with RMSPs of 53.6% and 61.0% for two periods of match-up data. POC from 2005 to 2007 is much higher than it is from 2002 to 2004 and 2008 to 2013, due to a large area of algal bloom. Riverine flux is an important source of POC in Taihu Lake, especially in the lake's bank and bays. The influence of a terrigenous source of POC can reach the center lake during periods of heavy precipitation. Sediment resuspension is also a source of POC in the lake due to the area's high dynamic ratio (25.4) and wind speed. The source of POC in an inland shallow lake is particularly complex, and additional research on POC is needed to more clearly reveal its variation in inland water.

Abstract. We examined the relationship between, and variations in, particulate organic carbon (POC) and particulate organic nitrogen (PON) based on previously acquired ocean and inland water data. The latitudinal dependency of POC ∕ PON is significant between 20 and 90∘ N but weak in low-latitude areas and in the Southern Hemisphere. The mean values of POC ∕ PON in the Southern Hemisphere and Northern Hemisphere were 7.40±3.83 and 7.80±3.92, respectively. High values of POC ∕ PON appeared between 80–90 (12.2±7.5) and 70–80∘ N (9.4±6.4), while relatively low POC ∕ PON was found from 20 (6.6±2.8) to 40∘ N (6.7±2.7). The latitudinal variation of POC ∕ PON in the Northern Hemisphere is much stronger than in the Southern Hemisphere due to the influence of more terrestrial organic matter. Higher POC and PON could be expected in coastal waters. POC ∕ PON growth ranged from 6.89±2.38 to 7.59±4.22 in the Northern Hemisphere, with an increasing rate of 0.0024 km from the coastal to open ocean. Variations of POC ∕ PON in lake water also showed a similar latitude-variation tendency of POC ∕ PON with ocean water but were significantly regulated by the lakes' morphology, trophic state and climate. Small lakes and high-latitude lakes prefer relatively high POC ∕ PON, and large lakes and low-latitude lakes tend to prefer low POC ∕ PON. The coupling relationship between POC and PON in oceans is much stronger than in inland waters. Variations in POC, PON and POC ∕ PON in inland waters should receive more attention due to the implications of these values for the global carbon and nitrogen cycles and the indeterminacy of the relationship between POC and PON.

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