We evaluated the anthropogenic forcing and exceedance probability of arsenic vulnerability in the Quaternary Alluviums of the Mid-Gangetic Plain through the coupled application of hydrogeochemical analyses, inverse modelling, probability analyses, kriging, bivariate and multivariate statistical analysis (MVA). Fifty-seven groundwater samples (total 171) each were collected during the pre-monsoon (April 2015), monsoon (July 2015) and post-monsoon (January 2016). Seasonal cyclicity of ion exchange and reverse ion exchange was observed, with the former being common during pre-monsoon while the latter was dominant during post-monsoon. PHREEQC modelling showed the involvement of the agrochemicals such as calcium nitrate and calcium phosphate and other isolated incidences of chemical usage like bleaching powder as well as the probability of wet deposition of the anions like SO₄²⁻ and NO₃⁻. Kriging-based arsenic mapping revealed that rainfall recharge-led dilution plays the most dominant role in its mobilization. Owing to natural recharge in the alluvium plain, the exceedance probability of arsenic concentration above 5 μg L⁻¹ falls drastically from more than 0.8 in the pre-monsoon to 0.5 during the post-monsoon. Study implies that pre-monsoon pumping of groundwater must be regulated in combination with proper disposal of pH and ORP affecting chemicals so that the high natural recharge should not significantly induce arsenic mobilization. Further, we recommend that vulnerability estimation should not be based solely on the present scenarios but must include the features of probable exceedance and saturation status of groundwater in this belt. We put forward a comprehensive model to explain the operative processes governing arsenic mobilization.

我们通过水文地球化学分析，逆模型，概率分析，克里格法，双变量和多变量统计分析（MVA）的联合应用，评估了中古冈平原第四纪冲积层中人为强迫的砷脆弱性和超标概率。在季风前（2015年4月），季风（2015年7月）和季风后（2016年1月）分别收集了57个地下水样本（共171个）。观察到离子交换和反向离子交换的季节性周期性，前者在季风前很常见，而后者在季风后很明显。₄ ^2-和NO ₃ ^- 。基于克里格法的砷测绘表明，降雨补给导致的稀释在其动员中起最主要的作用。由于冲积平原的自然补给，砷浓度超过5μgL ^-1的超标概率从季风前的超过0.8急剧下降到季风后的0.5。研究表明，必须对季风前的地下水泵送进行控制，并适当处理影响化学品的pH值和ORP，这样才能保证较高的自然补给不会显着诱导砷的迁移。此外，我们建议脆弱性估算不应仅基于当前情景，而应包括该带中地下水可能超标和饱和状态的特征。我们提出了一个综合模型来解释控制砷动员的操作过程。