[Distribution, seasonal variation and influence factors of dissolved inorganic arsenic in the Sanggou Bay].

The biogeochemical behavior of arsenic in the aquatic environment has already captured the attentions of scientists due to its complex forms and toxicity. Four cruises were carried out in April, August, October 2011 and January 2012 in the Sanggou Bay. The concentrations of total dissolved inorganic arsenic (TDIAs, TDIAs = [ As(5+] + [As(3+)]) and arsenite (As(3+)) were measured by Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS). The concentrations of TDIAs ranged from 3.4-12.4 nmol x L(-1) in April, 8.9-16.9 nmol x L(-1) in August, 14.7-21.3 nmol x L(-1) in October and 13.8-21.9 nmol x L(-1) in January. The concentrations of arsenite ranged from 0.3-2.1 nmol x L(-1), 0.4-3.8 nmol x L(-1), 1.8-4.0 nmol x L(-1) and 0.3-2.9 nmol x L(-1) during four cruises, respectively. The concentrations of TDIAs in spring and summer were lower than those in autumn and winter, and high values of TDIAs appeared in the bay-mouth and the coastal estuary. The concentrations of arsenite in spring and winter were lower than those in summer and autumn. The maximum As(3+)/TDIAs ratios appeared in summer. The mean value of TDIAs in the Sanggou Bay was (13.9 +/- 4.7) nmol x L(-1), which was lower than the national primary drinking in water Standards from USEPA and met the first grade water quality based on the environmental quality standards for surface water of China. It indicates that there is no obvious anthropogenic pollution. The concentrations of TDIAs in the Sanggou Bay were lower than those in the Ailian Bay and the Lidao Bay in spring and summer due to the different hydrological environments and terrestrial inputs. Riverine input, incursion of Yellow Sea and biological activities were the three main factors impacting the distribution of TDIAs in the Sanggou Bay, and the influence of aquaculture activities was particularly significant. The enrichment of arsenic by aquaculture may lead to potential ecological crisis and food safety problems, and need to be paid more attentions to ensure the sustainable development of aquaculture in the Sanggou Bay.

[Effects of calcification on respiratory quotient of cultured oyster Crassostrea gigas and its fouling animals].

Respiratory quotient (RQ) is one of the basic indices in physiology and energy metabolism of animals. When RQ is calculated, the amount of released CO2 is typically used directly. But for calcifying marine organisms, calcification which can affect dissolved inorganic carbon (DIC) content in the water may cause methodological error to some extent, if it is ignored. In this paper, RQ and O/N of cultured oyster Crassostrea gigas and 3 marine fouling animal species (Mytilus edulis, Ciona intestinalis, Styela clava) were measured in the respiratory chamber to discuss the effect of calcification in RQ determination. The results demonstrated that calcification rates of C. gigas and M. edulis were (56.37 +/- 14.85) and (17.95 +/- 7.21) micromol x g(-1) x h(-1), respectively. (3.72 +/- 0.80) and (1.48 +/- 0.14) mg x L(-1) DIC in the water were correspondingly decreased, which occupied about (60.9 +/- 7.6)% and (39.9 +/- 5.7)% of respired CO2, respectively. RQ values of 4 animals were C. gigas 1.38 +0.19, M. edulis 1.18 +/- 0.11, C. intestinalis 1.11 +/- 0.05 and S. clava 1.32 +/- 0.19, which agreed with the O/N values except C. intestinalis. Meanwhile, the uncorrected RQ values of C. gigas and M. edulis were 0.56 +/- 0.19 and 0.70 +/- 0.04, respectively, which were contrary to the O/N values. Therefore, it was obviously that calcification could result in a significant influence on the respiratory quotient by affecting water DIC concentration and should be accurately calculated in RQ measurement.

[Phosphate adsorption characteristics onto surface sediments from aquaculture area in Sungo bay].

Phosphate adsorption characteristics onto surface sediments from aquaculture area in Sungo bay were studied in laboratory simulating condition, and phosphate adsorption-desorption equilibrium mass concentration was also analyzed. The results showed that the process of phosphate adsorption onto sediments mainly occurred within 0.5 h, and attended to dynamic equilibrium after 6 h. Adsorption kinetics were fitted to modified Elovich model which can be expressed by Q = 85.536 + 35.512 lnt (R2 = 0.9602). Under low initial phosphate concentration condition, the adsorption isotherm curves were fitted to linear equation Q = 265.04c(e) - 7.46 (R2 = 0.965), while under high initial phosphate concentration condition, the adsorption isotherm curves were fitted to Langmuir equation (R2 = 0.989). The native adsorbed phosphorus was 7.46 microg/g and the maximum adsorption capacity was 769.23 microg/g. The phosphate adsorption-desorption equilibrium mass concentration was 0.028 mg/L, which indicated that the sediments played the source role in most time in this area based on the phosphate concentration in water body.

[Forms and bioavailability of phosphorus in surface sediments from Sungo Bay].

UNLABELLED: Forms and bioavailability of phosphorus in the sediments of eight sampling sites from Sungo Bay were analyzed by means of sequential extraction method (SEDEX). RESULTS: showed that: (1) The main form of total phosphorus (TP) in sediments was inorganic phosphorus (IP), which accounted for 73.33% and organic phosphorus (OP) was only the minor part. (2) Among different forms of inorganic phosphorus, calcium phosphorus (Ca-P) was the dominant forms, accounted for 45.22% of total phosphorus while organic phosphorus, adsorbed-phosphorus (Ads-P), iron-phosphorus (Fe-P) and detritus-phosphorus (Detr-P) was 26.67%, 9.92%, 4.74% and 13.46% respectively. (3) The correlation analysis among different phosphorus forms suggested that the concentrations and distribution of total phosphorus were mainly controlled by organic phosphorus (p < 0.05), while inorganic phosphorus was affected by calcium-phosphorus (p < 0.01). (4) Bioavailable phosphorus in sediments ranged from 358.05 microg/g to 448.39 microg/g and occupied 86.54% of the total phosphorus pool.