Shapefile of processed results from surface carbon and nitrogen analysis of sediment grab samples, Long Island Sound mapping project Phase II

Sediment grab samples were taken in summer of 2017 and 2018 using a modified van Veen grab sampler. A sub-sample of the top two centimeters was stored in a jar. Dried and homogenized splits of the samples were sent to the Cornell Isotope Laboratory (COIL) to be analyzed for carbon and nitrogen concentrations as well as stable isotopic compositions. Total carbon (TC), total nitrogen (TN), and δ15N were determined on an aliquot of untreated, dried homogenized sediments. In order to accurately determine total organic carbon (TOC) and δ13C, removal of carbonate is necessary. This was achieved through sequential treatments of the sediments with dilute hydrochloric acid until no bubbling was observed. The acidified sediments were then rinsed in deionized water and re-dried. In the Cornell Lab the samples were analyzed using a NC2500 elemental analyzer interfaced with a Thermo Delta V isotope ratio mass spectrometer (IRMS). The data is presented here as an ESRI shapefile. There is an accompanying Excel spreadsheet. Funding was provided by the Long Island Sound Mapping Fund administered cooperatively by the EPA Long Island Sound Study and the Connecticut Department of Energy and Environmental Protection (DEEP).

本数据集的采样工作于2017年与2018年夏季开展，采用改良型范维恩抓斗采泥器（modified van Veen grab sampler）采集抓斗采泥样品。取样品表层2厘米的子样装入样品罐保存。将经干燥、均质化处理后的样品分样送至康奈尔同位素实验室（Cornell Isotope Laboratory, COIL），开展碳、氮浓度及稳定同位素组成分析。对未经处理的干燥均质沉积物等分试样，测定了总碳（total carbon, TC）、总氮（total nitrogen, TN）及δ15N值。为精准测定总有机碳（total organic carbon, TOC）与δ13C值，需移除样品中的碳酸盐组分。本研究通过逐次向沉积物中滴加稀盐酸直至无气泡产生，完成碳酸盐脱除操作。随后将经酸处理的沉积物用去离子水冲洗并重行干燥。在康奈尔同位素实验室中，研究人员采用NC2500元素分析仪与赛默飞Delta V同位素比值质谱仪（isotope ratio mass spectrometer, IRMS）联用系统对样品进行分析。本数据集以ESRI形状文件（ESRI shapefile）格式提供，并附带一份Excel电子表格。本研究得到由美国环境保护署（EPA）长岛海湾研究项目与康涅狄格州能源与环境保护部（Connecticut Department of Energy and Environmental Protection, DEEP）联合管理的长岛海湾绘图基金（Long Island Sound Mapping Fund）资助。