| Cadmium（Cd）mainly pollutes the water environment,which is ranked as the top among the 12 hazardous chemicals of global significance proposed by the United Nations Environment Programme.Unlike organic pollutants,cadmium in water environment cannot be degraded by aquatic organisms,but will accumulate in aquatic organisms and gradually enrich through the food chain,which will then cause many problems such as aquatic products quality and safety hazards,water environment pollution and human health.Therefore,the pollution and harm of cadmium to water environment and aquatic organisms has caused wide attention throughout the world.Based on a review of the current status and enrichment rules of cadmium in crustacean aquatic organisms and previous studies,it is found that the cadmium accumulation is specific to swimming crabs.However,there are few studies on the distribution characteristics and dietary exposure risks of cadmium in different edible tissues of swimming crabs,and the occurrence forms of cadmium in organisms are rarely reported.In this study,a typical aquatic crustacean in the East China Sea was taken as the research object.Based on the inductively coupled plasma mass spectrometry method,the differences of cadmium accumulation in different edible tissues of swimming crabs and the effects of cooking mode（steaming）on the redistribution of cadmium in edible tissues of swimming crabs were respectively explored.At the same time,dietary exposure risk assessment of fresh edible tissue and steamed edible tissue was carried out respectively,and the evaluation results could provide reference for consumers to consume swimming crabs.In addition,the occurrence forms of cadmium in edible tissues of swimming crabs were investigated by high performance liquid chromatography tandem inductively coupled plasma mass spectrometry（HPLC-ICP/MS）.The main research results are as follows:（1）The distribution characteristics and enrichment rules of cadmium in the edible tissues of swimming crabs（mainly harvested from the East China Sea）in Shanghai were analyzed.Meanwhile,heavy metal pollution assessment and dietary exposure risk assessment were carried out in view of the differences of cadmium accumulation in different edible parts of swimming crabs.A total of 78 crabs were collected from local markets in eight administrative districts,including Yangpu District,Pudong New District and Baoshan District of Shanghai,and the claw,leg and body muscle were isolated as the white meat group,while the hepatopancreas and gonads were isolated as the brown meat group.The cadmium content of these edible parts was determined and analyzed by inductively coupled plasma mass spectrometry.The results showed that cadmium was the highest in brown meat（1.260-16.303 mg/kg）and in white meat（0.005-0.542 mg/kg）,showing a distribution trend of body muscle>leg muscle>claw muscle.In addition,the results of pollution index（Pi）showed that only the forceps muscle was at a low level of pollution,while other edible tissues were contaminated to varying degrees.The health risk assessment based on EDI,THQ and TCR indicated that the consumption risk of swimming crabs in Shanghai was low,but the cadmium accumulation in brown meat parts of swimming crabs and the potential carcinogenic risk need further attention and scientific evaluation.（2）Based on the research results in（1）,in order to study the effect of processing process on the content of cadmium in the edible parts of swimming crabs,the variation rule and redistribution characteristics of cadmium in various parts of swimming crabs were explored by the common traditional cooking mode（steaming）,and the dietary exposure risk of swimming crabs after steaming was assessed.The redistribution characteristics of cadmium in edible tissues of swimming crabs during steaming were studied by a three-part experiment design.The results showed that cadmium was transferred from brown meat of swimming crabs to leg muscle during steaming,and the concentration of cadmium in steamed leg muscle was nearly 10 times higher than that in raw leg muscle,while there was little difference in the concentration of cadmium in forceps muscle before and after steaming.At the same time,a scientific and reasonable explanation was given from the perspective of physiological structure of swimming crabs and the chemical morphological changes of cadmium during steaming.In addition,the results of dietary exposure risk assessment based on target hazard quotient（THQ）and target cancer risk（TCR）showed that the consumption of white meat of swimming crabs brought no risk,but the potential carcinogenic risk of steamed brown meat of swimming crabs in this study was higher than that of fresh meat,which should be paid attention to.（3）Based on the research results and discussion in（2）,10 mmol/L Tris-HCl was selected as the extraction agent and the extraction temperature was set at 20℃through comparison and optimization of pretreatment methods on the premise of not destroying the cadmium morphology in the edible tissue of the crab.Cadmium was extracted from the edible tissues of swimming crabs under the extraction time of 1 h.Under these conditions,the extraction rates of cadmium from brown meat and muscle were 91.15%,88.63%and 68.92%,respectively.C18 liquid chromatography column was used to separate the cadmium form,and cysteine-bound cadmium（Cys-Cd）and inorganic cadmium ion standard solution were prepared,combined with high performance liquid chromatography tandem inductively coupled plasma mass spectrometry（HPLC-ICP-MS）to conduct qualitative analysis of the cadmium form in each sample.Based on the retention time of cadmium morphology in standard solution and the range of molecular weight reported in relevant literature,it was concluded that Cys-Cd,metallothionein cadmium（MT-Cd）and Cd2+are mainly contained in edible tissues of swimming crabs,and the other chemical forms needs further study.Since the toxicological effects of different forms of cadmium are different,and the forms of cadmium in swimming crabs may change with the degree of freshness and processing,further attention and research are needed on the changes of the forms of cadmium in swimming crabs and the corresponding risk assessment,so as to provide theoretical basis for the relevant departments to propose a more scientific safe limit value of cadmium..In this study,the distribution characteristics and dietary risks of cadmium in swimming crabs were described,as well as the characteristics of cadmium redistribution in different edible tissues during the steaming process,and the occurrence forms were explored,which could provide reference for the morphological identification and quantitative analysis of cadmium in crustacean aquatic products as well as toxicological studies of different forms of cadmium.It can also promote the research on the mechanism of cadmium accumulation in crustaceans such as swimming crabs.At the same time,it is of great significance for the comprehensive understanding of the safety risks brought by cadmium as a heavy metal pollutant to the environment,aquatic product safety and human health,and also provides basic data support for the effective supervision and control of aquatic product safety risks caused by cadmium. |
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