NITRATE LEVELS IN BELIZE’S RURAL DRINKING WATER

This study examined nitrate levels in Belize’s rural water supply with the aim to providing a baseline data for monitoring the concentration of nitrates as a means to preventing public health hazards. 2 water samples were conveniently collected from reservoirs, wells, vats and standpipes from 40 villages using plastic bottles. Plastic bottles were used to collect water samples from 43 water samples from 40 villages in all the districts of the country of Belize (Figure 5). 1000ml bottles were purchased from Bowen & Bowen Limited®, thoroughly rinsed with purified water, dried and used for water samples collection. Before sample collection, the bottles were also thoroughly rinsed with the respective water samples at the site of collection. 15 water samples were collected from reservoirs, 10 from wells, 3 from standpipes (boreholes) and 15 from vats (Figure 3). Water samples were also collected from each district in the country. 9 water samples were collected each from Belize and Toledo districts; 8 from Cayo; 5 each from Corozal and Stann Creek and 7 from Orange Walk. 2 water samples were collected from either a reservoir, a vat, a standpipe, a well or both depending on what is available in the village. Collected water samples were immediately transported to the laboratory of Belize Coastal Zone Institute and analyzed for nitrates. Water samples that were not immediately analyzed were filtered and refrigerated below 4o C till analyzed. Testing and Analysis was done according to USA EP for Nitrate-Nitrite Analysis Procedures as described. For quality assurance, each sample was analyzed twice and results statistically computed and presented. The one-way analysis of variance (ANOVA) test was performed to compare the sets of data obtained from different sites. The difference among mean analyzed by one way ANOVA was further analyzed using student t-test. A value of P≤ 0.05 was considered statistically significant. Data was presented as the arithmetic mean ± S.D. Estimated nitrates levels in water samples were compared with EPA’s acceptable safe drinking water levels and presented. Except for 4 water samples from 4 different sites, all other water samples analyzed were found to contain nitrates levels below 10mg/L. Nitrate levels above 10mg/L were seen in few samples in the northern part of the country probably due to agricultural activities in these areas. Belize’s rural drinking water contains low levels of nitrates except for a few villages that the levels exceeded the acceptable 10mg/L. Higher levels of nitrates detected in those villages need regular evaluation and monitoring to avoid public health issues as well as prevent harm to livestock.

本研究针对伯利兹农村供水系统中的硝酸盐水平展开调研，旨在建立硝酸盐浓度监测的基准数据，以此作为防范公共健康风险的手段。研究人员采用塑料瓶，从伯利兹全国40个村庄的水库、水井、储水大桶及竖管中便捷采集水样，共获取43份水样（图5）。所用1000ml塑料瓶购自Bowen & Bowen Limited®，先用纯化水充分冲洗并晾干后方用于水样采集；采样前，还需在采样现场用待采集的水样对塑料瓶进行二次冲洗。本次共从水库采集15份、水井10份、竖管（钻孔井）3份、储水大桶15份水样（图3）。同时，本研究从伯利兹所有行政区均采集了水样：伯利兹区与托莱多区各采集9份，卡约区8份，科罗萨尔区与斯坦克里克区各5份，奥兰治沃克区7份。每个村庄根据当地可获取的取水设施，从水库、储水大桶、竖管、水井中任选一处或两处采集2份水样。采集完成的水样随即被送往伯利兹海岸带研究所实验室进行硝酸盐含量检测；若无法立即开展检测，则需先经过滤处理，再置于4℃以下冷藏直至上机检测。本次检测与分析严格遵循美国环境保护署（US EPA）规定的硝酸盐-亚硝酸盐检测流程执行。为保障质量，每份水样均进行两次重复检测，结果经统计学计算后呈现。采用单因素方差分析（ANOVA）对比不同采样点获取的数据集，针对单因素方差分析得到的均值差异，进一步通过学生t检验进行分析；以P≤0.05作为具有统计学显著性的判定标准。数据以算术平均值±标准差（S.D.）的形式展示。将估算得到的水样硝酸盐浓度与美国环保署规定的安全饮用水限值进行对比后呈现结果。本次分析的水样中，仅来自4个不同采样点的4份水样硝酸盐浓度超过限值，其余所有水样的硝酸盐浓度均低于10mg/L。伯利兹北部区域的少数水样中检测到硝酸盐浓度超过10mg/L，推测与当地的农业活动有关。伯利兹农村饮用水整体硝酸盐浓度处于较低水平，仅少数村庄的水样硝酸盐浓度超出10mg/L的安全限值。针对这些村庄检出的高浓度硝酸盐，需开展定期评估与监测，以防范公共健康风险并避免对牲畜造成危害。